Network Working Group                                      R. R. Stewart
INTERNET-DRAFT                                                  Motorola                                                    Q. Xie
                                                                Motorola
Expires
                                                                 T. Bova
                                                               S Hussain
                                                           T Krivoruchka
                                                                R. Revis
                                                                   Cisco

expires in six months                                       1                                      April 19 1999

           MULTI_NETWORK DATAGRAM TRANSMISSION PROTOCOL
                 <draft-ietf-sigtran-mdtp-03.txt>
                <draft-ietf-sigtran-mdtp-04.txt>

Status of This Memo

This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups.  Note that other groups may also distribute
working documents as Internet-Drafts.

The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt

The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.

Abstract

This Internet Draft discusses an experimental call control signaling
transport protocol, namely the Multi-network Datagram Transmission
Protocol (MDTP), that is intended to provide fault-tolerant reliable/unreliable reliable
data transfer between communicating processes entities over IP networks [1].

MDTP is proposed as an application-level protocol which is designed
with a high emphasis on supporting redundant networks and transparent
fault management. MDTP also gives the application user a great degree of timing
control and configuration flexibilities. flexibilities in order to meet the stringent
time constraints often found in telephony signaling protocols. The
motivation of developing MDTP is to establish a framework for
supporting Internet-based high reliability real-time commercial
applications such as signaling and call control for Internet
telephony.

Stewart & Xie                                                  [Page  1]

                        TABLE OF CONTENTS

1.  Introduction..............................................3  Introduction
     1.1 Multi-network Datagram Transmission Protocol.........3 Design Requirements of MDTP
     1.2 Interfaces to MDTP...................................4
     1.3 Operation of MDTP....................................5 MDTP
2.  Design Principles.........................................5
3.  Header Format.............................................6
     3.1  MDTP Header Datagram Format Description.......................9
     3.2 Notes on Multicast
     2.1 Header format....................12
4. Field Descriptions
     2.2 Data Field
3.  Transmission Initialization..............................12
     4.1 Normal Initialization...............................12
     4.2 Multiple Network Addresses..........................14
     4.3 Initialization Collision............................15
     4.4 Re-initialization...................................16
     4.5 Link rotation.......................................16
5.
     3.1 Endpoint Association Initialization
       3.1.1 Choice of Tag Value
     3.2 Data Field Format of Initiation Datagrams
     3.3 Initialization Collision
     3.4 Association Re-initialization
4.  Reliable Transfer Mode...................................17
     5.1 of Datagrams
     4.1 Timer Control.......................................19
     5.2 Management Rules
       4.1.1 Link Rotation
     4.2 Gap Acknowledgments.................................21
     5.3 Acknowledgment for Missing Datagrams
     4.3 Congestion Control..................................23
     5.4 Control
       4.3.1 Sending with Window Control
       4.3.2 Window Length Adjustment
       4.3.3 Flow Control using In-Queue Information
       4.3.4 T3-send Timer Adjustment with RTT
     4.4 Sequence Number Reset...............................26
     5.5 Retransmission Reset
     4.5 Datagram Re-transmission
       4.5.1 Re-transmission on Multiple Networks.................27
       5.5.1 Randomization of the T3-Send timer at resend ...28
     5.6 Termination of an Endpoint..........................28
     5.7 Endpoint Drain......................................29
     5.8 Advisory Acknowledgments...........................29
     5.9 Redundant networks
     4.6 RTT Measurement.....................................30
     5.10 Measurement
       4.6.1 RTT Datagram Header Format
       4.6.2 Measure RTT
     4.7 Link Heart Beat Ack.....................................32
     4.8 Advisory Acknowledgment
     4.9 Termination of an Association
     4.10 Draining of an Association
5. Interface with upper level protocols
6.  Unreliable Transfer Mode.................................33
     6.1 Ordered reception..................................34 Suggested MDTP Protocol Parameter Values
7.  Reliable flows...........................................35
     7.1 Initiating a flow...................................36
     7.2 Flow acknowledgments................................37
     7.3 Flow session closing................................41 Acknowledgments
8.  Mixed Mode Data Transmission.............................42 Author's Addresses
9. References
Appendix A: Stream-based Reliable and Ordered Delivery
     A.1 Stream Initiation
     A.2 Stream Termination
     A.3 Stream Datagram Transfer
       A.3.1 Header Format in Stream Datagrams with User Data
       A.3.2 Transmission of Stream Datagrams
       A.3.3 Extended Stream Ack
     A.4 Other Issues with Stream Transfer
Appendix B: Bundled Messages.........................................43
     9.1 Message Transfer
     B.1 Format of Bundled Datagram..........................44
     9.2 Datagram
     B.2 Bundled Transfer....................................45
10. Datagram Transfer
Appendix C: Fragmented Messages......................................46
11. Non-protocol Datagrams...................................47
12. Broadcast and Multicast..................................48
     12.1 Multicast/Broadcast Initialization.................48
     12.2 Transmission of Broadcast Datagrams................48
     12.3 Transmission of Message Transfer
Appendix D: Multicast Datagrams................49
     12.4 Reset of the Datagram Transfer
     D.1 Multicast Datagram Sequence Number....50
13. Interface with upper level protocols.....................51
13.1 Init.MDTP primitive.....................................52
13.2 Send.Data primitive.....................................52
13.3 Receive.Data primitive..................................52
13.4 Data.Arrive notification................................53
13.5 Send.Failure notification...............................53
13.5 Link.Status.Change notification.........................53

Stewart & Xie                                                  [Page  2]

13.6 Communication.Lost notification.........................53
14. Suggested Timer and Protocol Parameter Values............54
15. Acknowledgments.........................................54
16. Author's Addresses.......................................54
17. References...............................................55 Header Format
     D.2 Transmission of Multicast Datagrams
Appendix E: Unreliable Delivery
     E.1 Ordered Unreliable Delivery

1.  Introduction

This Internet Draft discusses an experimental protocol, namely the
Multi-network Datagram Transmission Protocol (MDTP), that (MDTP). The intention of
developing MDTP is intended to provide fault-tolerant reliable/unreliable a fault-tolerant, real-time reliable
data transfer mechanism between communicating processes endpoints over IP
networks [1].

MDTP is proposed as an application-level protocol which is designed
with a high emphasis on supporting redundant networks and transparent
fault management. MDTP also gives the application user a great degree of timing
control and configuration flexibilities. flexibilities in order to meet the stringent
time constraints often found in telephony signaling protocols. The
motivation of developing MDTP is to establish a framework for
supporting Internet-based high reliability real-time commercial
applications such as signaling and call control for Internet
telephony.

This document describes the functional interface and the details
necessary

MDTP is also designed to implement MDTP.

1.1 Multi-network Datagram Transmission Protocol (MDTP)

The Multi-network Datagram Transmission Protocol (MDTP) presented be scalable in
this Internet Draft is designed order to meet support different
signaling transport requirements for different interfaces in a
telephony network.

For example, the transportation of signaling protocols such as PRI
ISDN may not require redundant links, and hence only a subset of MDTP
will need to be implemented.  On the other hand, redundant networks
may be mandated when transporting SS7 signaling messages amongst
different components in a carrier-grade telephony core network.  In
such cases, the transparent support for redundant networks, load
sharing, and fault management defined in MDTP become essential and
likely need to be fully supported in an implementation.

Many of the fundamental concepts that have made TCP such a useful
protocol are reused in MDTP, and some of the advantages of UDP are
also merged into the design. This has lead to a highly effective,
robust protocol for fault tolerant data communications.

This document describes the functional interface and the details
necessary for implementing MDTP. The main body of this document
contains the minimal set of functionalities of MDTP that must be
implemented. In the Appendices, a set of additional MDTP functions,
such as reliable stream, multicast, message bundling, message
fragmentation, are defined. Those additional functionalities are
optional to implementation.

1.1 Design Requirements of MDTP

The following critical are some of the design requirements common of MDTP, in order to
make MDTP capable of supporting real-time call control environments employing
which potentially may employ redundant networks:

A) A process High communication fan-out: an endpoint may need to be in
   simultaneous communication with hundreds or thousands of endpoints
   performing various call processing functions. These endpoints may
   be codec converters, SS7 to IP translation applications, or, in the
   case of mobile networks, data selector and combiner applications.

B) A process Stringent timer control: an endpoint needs to have a very fine
   control over the timing for delivering a datagram. The timing
   should be easily adjusted depending on the message type and the
   destination. For example, after a few seconds of non-delivery the
   call which the message is about may not exist anymore.

C) A process Support redundant links: an endpoint communicating with a peer
   should be able to take advantage of the redundant networks in a
   transparent way. This means that the application or upper level layer
   protocols need not to be involved in the network fault
   management. Instead, when network failure occurs the transmission protocol MDTP should be
   able to automatically re-route the out-bound datagram to the
   alternate

Stewart & Xie                                                  [Page  3] network (if one exists) without intervention from the
   application.

D) Datagrams Orderly delivery: datagrams may arrive out of order, or may arrive
   in duplicate copies. This is especially true in a if redundant network
   environment. The transmission protocol networks
   are used. MDTP should be strong enough to properly handle both
   situations with little intervention from the upper level protocol layer protocols
   or application.

To accomplish applications.

F) Support stream sequencing: on the above objectives we have defined demand of the upper layer
   protocols or applications, MDTP should be able to reside in
user-space, i.e., it is not intended support sequenced
   delivery with regard to be implemented as a module in
an operating system. This gives each individual stream, i.e., the application or upper level
protocols that use MDTP outstanding flexibility in controlling delay caused
   by the
timing loss and other operational characteristics for the data
transmissions.

MDTP is also made multi-network aware. This means that if more than
one path exists between two endpoints (such as redundant LANs), MDTP
will take advantage retransmission of the multiple networks by automatically
switching to the alternate LAN if the a datagram delivery becomes
unavailable or inefficient (e.g., too many re-transmissions) on the
current LAN. The ability to handle multiple networks by MDTP can also
greatly facilitate the implementation of various traffic balancing
schemes in the application or upper level protocols.

In the redundant network setting, out-of-order or duplicate datagrams
are proven to should be most harmful during MDTP transmission initiations and
re-initiations. To cope with the problem, MDTP utilizes a very
efficient tag mechanism isolated to guard against out-of-order or duplicate
datagrams.

MDTP assumes that a UDP-like [2] transport protocol is available at
   only the
operating system level for data transport. We have successfully
implemented and tested MDTP over UDP and Sun Microsystem's CLTS
transport layers.

Comparing stream to traditional TCP [3], MDTP design which the datagram belongs. This is more tuned towards particularly
   important in some call control applications, where a
special set loss of applications, that is the time critical fault tolerant
applications using redundant LANs. It is not designed to replace TCP
as a general purpose transmission protocol.
   message should only affect the call whom the message belongs to.

1.2 Interfaces to MDTP

MDTP interfaces with the

The application programs or higher level upper layer protocols interface with MDTP
through a set of function calls. Due to primitives (see section 5. for details).

Towards the fact networks, it is assumed that a UDP-like data transport
protocol will provide the interface between MDTP
is an application level protocol, these calls and the operating
system. No special interfaces or changes are not executed within
the operating system, but within the user process (i.e., in the user
space). The application or higher level protocols pass data to MDTP by
making calls to MDTP, which then enqueues the data for transmission.
When data arrives, MDTP will distribute the data to the application or
higher level protocols via mechanisms predefined by the application.
The application also has an interface to change the operational mode
of an MDTP endpoint and the default operational mode of the MDTP
endpoint. The default operational mode is used in the absence of any

Stewart & Xie                                                  [Page  4]

specific direction from the application. More details on the MDTP
interface to the upper level protocol/application can be found in
section 13.

As noted above, it is assumed that a UDP-like data transport protocol
will provide the interface between MDTP and the operating system. No
other special interfaces or changes are assumed assumed within the
operating system, all queuing and internal pseudo-connection endpoint association information is are
maintained inside MDTP endpoint.

1.3 Operation of layer.

2.  MDTP Datagram Format

MDTP operates in three different modes.

   A) Reliable transfer mode
   B) Unreliable transfer mode
   C) Raw UDP transfer mode

The two ends in a communication connection can operate in different
modes with respect to each other, with the exception of inserts the raw UDP
mode. For example, if two endpoints A and B are communicating with
each other. Endpoint A may be sending information to B in reliable
transfer mode, while B, on following protocol header at the other hand, may be sending information
to A in unreliable transfer mode. All communications from A to B will
be acknowledged by B, but A will not need to acknowledge data received
from B.

Raw UDP transfer is used when one beginning of the endpoints every
user datagram. The integer fields shall be transmitted in communication
does not support MDTP. This allows compatibility with non-MDTP
endpoints. Two MDTP capable endpoints are also allowed to engage in
communications in raw UDP transfer mode. However, both sides will have
to be in raw UDP mode once one of them indicates to use raw UDP
transfer mode.

MDTP also provides a bundling option for both the reliable and
unreliable transfer modes. This allows each side to hold the data
before transmission for some period of time, so that small datagrams
can be combined and sent in a single larger datagram to improve
network utilization efficiency.

2.  Design Principles

One of the major objectives which dictates the design of MDTP is to
provide a data transmission protocol that transparently supports highly
fault tolerant implementations. To accomplish this, provisions for two
endpoints engaging in communication to use multiple networks is
essential. MDTP is therefore designed to yield the best fault
tolerance when the application shares the load over multiple network
connections.

In cases of failed original transmission, MDTP provides the ability of
attempting retransmissions using an alternate network connection even

Stewart & Xie                                                  [Page  5]

when the upper level protocol or the application is completely
ignorant of the existence of the alternate route.

Many of the fundamental concepts that have made TCP such a useful
protocol are reused, and some of the advantages of UDP are also merged
into the design of MDTP. This has lead to a highly effective, robust
protocol for fault tolerant data communications.

3.  Header Format

MDTP inserts at the beginning of every datagram a header. This header
is composed of various flags and integers. The integers are always kept
in network byte order. The following table illustrates the common
MDTP header overlay. Note that one tick mark represents one bit
position. network byte
order.

                         MDTP Header Format - Non Multicast

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  MDTP Protocol Identifier 1                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 MDTP Protocol Identifier 2                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Acknowledgment Number (Seen)              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Sequence Number (Send)                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        Data Size   Version     |    Part              Flags            |      Of   In Queue    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Flags      |     Mode      |   Version     |   In Queue
   |               |N N W I F R D A|B A M S W R R B F G U|               |
   |               |O O I S I E T A C|R C U H N E E U T L A N|               |
   |
   |G               |M B N B R S M T K|O K L U R 1 2 N C O R R|               |               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   \                                                               \
   /                             data                              /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Stewart & Xie                                                  [Page  6]
                 MDTP Header Format - Multicast Format

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 MDTP Protocol Identifier 1                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 MDTP Protocol Identifier 2                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                Acknowledgment Number (Seen)                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                   Sequence Number (Send)                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        Data Size              |    Part       |      Of       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Flags      |     Mode      |   Version     |   In Queue    |
   |N N W I F R D A|B S W R R B G U|               |               |
   |O O I S I E A C|R H N E E U A N|               |               |
   |G B N B R S T K|O U R 1 2 N R R|               |               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  Multicast To Transmit address                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             Multicast From - senders base address             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   \                                                               \
   /                             data                              /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                   MDTP

2.1 Header Format - RTT Ack

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Field Descriptions

    MDTP Protocol Identifier 1                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 MDTP Identifier: 32 bits

      This shall be a fixed long value of 0xf7873072. The receiver
      shall always verify this Protocol Identifier 2                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Acknowledgment Number (Seen)              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Sequence Number (Send)                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        Data Size              |    Part       |      Of       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Flags      |     Mode      |   Version     |   In Queue    |
   |N N W I F R D A|B S W R R B G U|               |               |
   |O O I S I E A C|R H N E E U A N|               |               |
   |G B N B R S T K|O U R 1 2 N R R|               |               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  Transparent Time Int-1                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  Transparent Time Int-2                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Stewart & Xie                                                  [Page  7]
                   Flow Initiate/Close Message

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 MDTP Protocol Identifier 1                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 MDTP Protocol Identifier 2                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Acknowledgment Number (Seen/flow num)       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Sequence Number (Send)                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        Data Size              |    Part       |      Of       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Flags      |     Mode      |   Version     |   In Queue    |
   |N N W I F R D A|B S W R R B G U|               |               |
   |O O I S I E A C|R H N E E U A N|               |               |
   |G B N B R S T K|O U R 1 2 N R R|               |               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           Ack Flow (opening)  |        Ack datagram number    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                   Flow Extended Acknowledgment

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 MDTP Protocol Identifier 1                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 MDTP Protocol Identifier 2                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           Ack Flow (Seen)     |        Ack datagram number    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Number of flow Acks                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        Data Size              |    Part       |      Of       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Flags      |     Mode      |   Version     |   In Queue    |
   |N N W I F R D A|B S W R R B G U|               |               |
   |O O I S I E A C|R H N E E U A N|               |               |
   |G B N B R S T K|O U R 1 2 N R R|               |               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           Ack Flow (Seen)     |        Ack datagram number    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   \                                                               /
   /                 one for each 'Number of flow Acks'            \
   \                                                               /
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           Ack Flow (Seen)     |        Ack datagram number    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Stewart & Xie                                                  [Page  8]

3.1 MDTP Header Format

    MDTP Protocol Identifier 1: 32 bits

      This is a fixed long value of 0xf7873072.

    MDTP Protocol Identifier 2: 32 bits

      This is a fixed long value of 0x17074012. MDTP Protocol
      Identifier 1 and 2 are jointly examined to determine a received
      datagram is an MDTP protocol datagram.

    Acknowledgment Number (or Seen): 32 bits

      If the flag ACK is set this value is the next sequence number
      that the sender of this datagram expects to receive from the
      receiver of this datagram.

      However, during initialization negotiation, multicast and
      broadcast transmissions, this field will have special meanings
      (see 4 and 11).

    Sequence Number (or Send): 32 bits

      If DAT flag is set, this value represents the sequence number of
      the first data octet that follows this header. Otherwise, this
      value will be the sequence number of the first octet of the next
      data unit that will be sent.

      However, during initialization negotiation, multicast and
      broadcast transmissions, this field will have special meanings
      (see 4 and 11).

    Part: 8 bits

      This value represents the Part number of a fragmented message. The
      first fragment of a message is always part '0'.

    Of: 8 bits

      This value represents the total number of fragments in a
      fragmented message. The valid range for this value is from '1'
      to '255'. For broadcast and multicast datagrams this value is
      set to '1' to indicate that no fragmentation should occur.

    Data Size: 16 bits

      This value represents, in number of octets, the size of the data
      field that follows this header in the current datagram.

    Flags: 8 bits

      NOG - No Guaranteed delivery. This bit is used in negotiation

Stewart & Xie                                                  [Page  9]
      and is set to indicate that the sender does not wish to use
      reliable delivery. When this bit has been set in negotiation,
      the receiver should prevent its application from putting
      communication with this endpoint in reliable mode.
      In normal data transfer (after the initiate sequence) this
      bit should be set to 0, except when responding to a  RTT Ack
      request.

      NOB - No Bundling. This bit is used  in negotiation and
      is set to indicate that the sender does not wish to perform of
      bundling or un-bundling of datagrams. When this bit has been set
      in negotiation, the receiver should prevent its application from
      putting communication with this endpoint in bundled mode.
      In normal data transfer this bit should be set to 0, if this
      bit is set to 1 then this message is part of a flow.

      WIN - Window Up. This bit is set by the sender of this datagram
      to indicate that the sender needs the receiver to acknowledge on
      previously received datagrams before it can send more datagrams.

      ISB - Is Bundled. This bit is set by the sender to indicate that
      this datagram is bundled. This bit should never be set if during
      negotiation either end set the NOB bit.

      FIR - First Datagram. This flag is set to indicate that this is a
      negotiation datagram.

      RES - Reset Sequence Number. This bit is set to indicate that the
      sequence number is being reset. The sequence number should be reset
      whenever the sending count is greater than 0x7fffffff.

      DAT - Data Present. This bit is set to indicate that, following
      this header, application data is present in this datagram.

      ACK - Acknowledge. This bit is set to indicate that the sender is
      acknowledging receipt of the specified Acknowledgment Number.

    Mode: 8 bits

      BRO - Broadcast. This bit is set to indicate a broadcast or
      multicast datagram. When this bit is set, bit SHU, WNR, BUN, and
      GAR are not used and should be set to '0'. This datagram is a
      multicast datagram if the UNR bit is also set. Otherwise, this
      datagram is a broadcast datagram.

      SHU - Shutdown. This bit is set when the sender initiates its
      closing procedure and indicates to the receiver that the sender
      is no longer a valid destination.	If the UNR bit is set in
      conjunction with the SHU bit, an incomplete shutdown is
      specified. After an incomplete shutdown, the receiver can still
      re-establish the communication with the sender by re-initiating
      with the sender (see 5.7).

      WNR - Window Up Response. This bit is set in the acknowledgment
      reply to a Window Up flag.

      RE1 - This bit will represent one of two things. If the GAR
      bit is set to one, then setting the RE1 bit indicates to the
      receiver that the sender is requesting a advisory ACK. This
      is normally sent in a datagram when 1/2 of the current window
      has been sent. If this bit is set to 0 (when the GAR bit is
      set) then the sender is NOT requesting a advisory ACK.
      If the UNR bit is set then the RE1 bit is set than the receiver
      is requested to order the datagrams (if more than one have
      not been read). If the receiver has already delivered a datagram
      of higher sequence, then the receiver should discard lower number
      sequence datagrams that arrive late.

      RE2 - This bit will represent one of two things. If the GAR
      bit is set to one, the DAT bit is set to 0 and the ACK bit is
      set to 1 then this is a ACK with a Round Trip Time Request
      format. This also identifies the RTT Ack header format it
      in place. If the UNR bit is set to 1 and DAT bit is set to 0,
      then this datagram is used in a implementation specific way but
      carries no data. The datagram can be safely ignored and discarded.

      BUN - Bundled Mode. This bit is set to indicate that bundled
      mode is in effect for the sender. This bit should never be set
      if during negotiation either endpoint set the NOB flag.

      GAR - Guaranteed Mode. This bit is set to indicate that the
      reliable mode is in effect for the sender, i.e., the sender
      expects an acknowledgment. This bit should never be set if
      either endpoint set the NOG flag during negotiation.

      UNR - Unreliable Mode. This bit is set to indicate that
      unreliable mode is in effect for the sender and the sender does
      not expect an acknowledgment. This bit has special meanings if
      BRO or SHU bit is set (see above).

    Version: 8 bits

      This field represents the version number of the MDTP
      protocol. If these bits are set to 1, then the sender does
      not support Round Trip Time (RTT) calculation or Heart
      Beat of reliable protocol. If these bits are set to 2 then
      this version does support RTT and Heartbeat. If the Version
      is set to 3 then the sender/receiver supports reliable flows.

    In Queue: 8 bits

      This field contains the number of messages the sender has on its
      incoming queue, waiting to be read by the application. This gives
      the receiver an indication of the flow control conditions within
      the sender.

The message header is always followed by the data field. If there is
less than 4 octets of application data to send with the datagram, the
data field of the datagram should be padded with all '0' to make it
four (4) octets.  The padded all '0' octets, if there is any, are not
counted in the Data Size.

The maximal Data Size for a single MDTP datagram is the MTU size of
the underlying transport protocol (e.g., UDP) minus the MDTP header
size that is twenty four (24) octets. The combination of the maximal
'Of' value, which is 255, and the maximal Data Size will determined
the maximal size of a single message that the MDTP can send or
receive.

3.2 MDTP Multicast Header Format

The multicast header format is identical to the standard MDTP header
format, as discussed above, except for the following extensions.

Multicast To Transmit address - This is the multicast address, in
network byte order, that the sender transmitted the data to. The
receiver can use this information for internal tracking purposes.

Multicast From - This is the base address (address 0 in the initiate
message, see below) of the sender. Since a multicast sender may not
have gone through the initiate procedures this address is the base
reference that the receiver is to use to lookup the sender. This
network byte order address should be used to reference any internal
cache rather than the arriving network from address.

4.  Transmission Initialization

4.1 Normal Initialization

Before the first data transmission can take place from one endpoint
(A) to another endpoint (Z), the two endpoints will need to complete
an initialization process.

The initialization process consists of the following steps.

A) Endpoint A should first send an initiation datagram, while
   withholding the application data from transmission.

   Endpoint A                                          Endpoint Z
   [Header Flags=FIR|RES
	   Mode=options
	   Seen=0,Send=Tag_A] ----------------------->
   (Start T1-init timer)
   (Enter Tag_A-lock mode)

   The initiation datagram is identified by setting FIR and RES bits in
   the Flags field. No user data should be carried in the initiation
   datagram.

   The Endpoint A should fill in the appropriate options, e.g., BUN,
   GAR, or UNR, in the Mode field to indicate the transmission type it
   has chosen. It may also use NOB and NOG bits in the Flags field to
   specify to whether or not its peer is allowed for bundling or
   reliable transfer mode.

   The Seen field will be set to '0', but an initiation tag, Tag_A,
   generated by Endpoint A, will be carried in the Send field, as
   shown in the above diagram. If re-initializations are needed
   between two endpoints subsequently (see 4.3), a different tag with
   a unique value should be used for each re-initialization.

   After sending the initiation datagram, Endpoint A shall start T1-init
   timer and enter a Tag_A-lock mode.

   During the Tag_A-lock mode, Endpoint A will wait for the initiation
   Ack datagram with the Seen value set to Tag_A. Any other incoming
   datagrams from Endpoint Z, except for new initiation datagrams,
   will be discarded. The arrival of new initiation datagrams during the
   Tag_A-lock mode indicates an initialization collision that will be
   discussed in 4.3.

   If T1-init timer expires, the same initiation datagram will be
   retransmitted and the timer restarted. This will be repeated
   Max.Init.Retransmit times before Endpoint A considers Endpoint Z
   unreachable and optionally reports the failure.

B) Upon the receipt of the above initiation datagram from Endpoint A,
   Endpoint Z should respond immediately with an initiation Ack as shown
   below:

   Endpoint A                                 Endpoint Z
                                              [Header Flags=FIR|RES|ACK
					       Mode=Options
				   /---------- Seen=Tag_A,Send=Tag_Z]
				  /           (Enter Tag_Z-lock mode)
   (Cancel T1-init timer)<-------/

   The initiation Ack datagram is specified with FIR, RES, ACK bits set
   to '1' in the Mode field. Similarly, Endpoint Z will specify its
   preferred transmission mode and type by setting proper bits in the
   Mode and Flags fields.

   In addition, in the out-bound initiation Ack datagram, Endpoint Z
   should set the Seen field to Tag_A and supply its own initiation
   tag, Tag_Z, in the Send field.

   Once the initiation Ack is transmitted, Endpoint Z should enter the
   Tag_Z-lock mode. In the Tag_Z-lock mode Endpoint Z will ignore any
   incoming initiation Ack datagrams and also discard any other incoming
   datagram whose Seen field is not equal to Tag_Z, except for new
   initiation datagrams.

   If a new initiation datagram is received when Endpoint Z is in
   Tag_Z-lock mode, Endpoint Z will acknowledged the initiation datagram
   only when the tag carried in the Send field matches Tag_A previously
   recorded by Endpoint Z. Otherwise, Endpoint Z will send an initiation
   datagram with Send field set to Tag_Z back to Endpoint A to elicit an
   initiation Ack.

C) After transmitted the initiation Ack, Endpoint Z can start
   transmitting datagrams with user data. However, the Seen field in the

   first out-bound datagram with user data must be set to Tag_A.

D) Upon the receipt of the initiation Ack with Seen equal to Tag_A,
   Endpoint A can start transmitting datagrams with user data. However,
   the first datagram with application data transmitted by Endpoint A
   should have the Seen value set to Tag_Z, which is obtained from the
   initiation Ack.

   Endpoint A                                     Endpoint Z
   {first app message}
   [Header Flags=ACK|DAT
	   Mode=options
	   Seen=Tag_Z,Send=1]
	   [data field]   -----------\
				      \
				       \-------> (Leave Tag_Z-lock mode)

E) Upon the receipt of the first datagram with user data from Endpoint
   A and with the Seen value set to Tag_Z, Endpoint Z should leave the
   Tag_Z-lock mode.

F) Similarly, upon the receipt of the first datagram with user data
   and the Seen value set to Tag_A from Endpoint Z, Endpoint A
   should leave the Tag_A-lock mode.

The upper level protocol or application can predefine a set of default
transmission modes, which will be used by the endpoint for
initialization. However, it should be pointed out that the
transmission modes between two endpoints are allowed to change on a
datagram by datagram basis, as been illustrated in later chapters.

4.2 Multiple Network Addresses

In order to support multiple networks, both endpoints need to have
knowledge of all network addresses available to each other. This
information needs to be passed to the other end during the
initialization. The data field of the initiation and initiation Ack
datagrams is used for this purpose.

Depending on the underlying network configuration, the data field will
be filled in one of the two following ways:

A) If the sending endpoint of the initiation or initiation Ack
datagram does not have access to multiple networks, the data field
will be set to the pad value of 4 octets of '0's.

B) If the sending endpoint has access to multiple networks (for
example two redundant LANs), the first 4 octets of the data field will
be an unsigned long integer (in network order) specifying how many
networks the endpoint has access to. Following these 4 octets will be
a list of network addresses. Each address begins with a header of 4
octets followed by the actual address. The first 2 octets of the
header is an unsigned integer indicating the size of the actual
address. The next 2 octets of the header is the type of the address.

For an IPv4 address, the address header will have the size set to 8
and the type set to AF_INET (2). Of the 8 octets used by the actual
IPv4 address, the first 4 octets will contain the IP address (in
network order) of the path. The next two octets will contain the UDP
port number (in network byte order). The last two octets will be
padded with 0's.

The data field of the initiation or initiation Ack datagram from an
endpoint with access to two IPv4 networks would look the following:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Number of Networks = 2                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Size of address=8       |    Type of Address=AF_INET (2)|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             IP Address of Network 1 = 0x88b68108              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Port = 52212          |      Padding = 0              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Size of address=8       |    Type of Address=AF_INET (2)|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             IP Address of Network 2 = 0x0a100001              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Port = 52212          |      Padding = 0              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Any data following the initiate network list can be ignored. Implementations
are at option to use additional data sent in subsequent locations for
implementation specific data exchanges. No user data, however, is allowed
to be transported in this datagram.

4.3 Initialization Collision

If both endpoints attempt to initialize the communication at about the

same instance, a collision will occur. In a collision each endpoint
will receive an initiation datagram from the other side after it
transmitted its own. Both sides must acknowledge the initiation
datagram in the normal procedure as described in 4.1

The following is an example of initialization collision:

Endpoint A                                          Endpoint Z
[Header Flags=FIR|RES                          [Header Flags=FIR|RES
	Mode=options                            Mode=options
        Seen=0,Send=Tag_A] --------\   /-----   Seen=0, Send=Tag_Z]
(Start T1-init timer)               \ /        (Start T1-init timer)
                                     /
                                    / \
                                   /   \
[Header Flags=FIR|RES|ACK  <------/     \
        Mode=options		         \---> [Header Flags=FIR|RES|ACK
        Seen=Tag_Z,Send=Tag_A]----\             Mode=options
                                   \ /-------   Seen=Tag_A,Send=Tag_Z]
                                    \
                                   / \-------> (Cancel T1-init timer)
(Cancel T1-init timer)     <------/

..
[Header Flags=ACK|DAT
	Mode=options
        Seen=Tag_Z,Send=1] ------------------>
                                               ..
                                               [Header Flags=ACK|DAT
                                                Mode=options
			   <-----------------   Seen=Tag_A,Send=1]

4.4 Re-initialization

An endpoint is allowed to re-initialize an established communication.

In the case of re-initialization, the endpoint which initiates the
re-initialization (i.e, the initiator) should use a tag different
from the one used in the previous initialization. The initiator should
follow the standard initialization procedure as stated in 4.1.

Upon the arrival of the initiation datagram, the peer of the initiator
should also follow the procedure stated in 4.1 to respond. Note that
any outstanding flows that were open are considered closed once
re-initialized.

4.5 Link Rotation

When multiple networks exist between two communicating endpoints,
every time the application transmits a datagram, the MDTP
implementation MUST keep track of which network the transmission was
sent on (if more than one network exists) in the MDTP protocol variable
'last.sent.intf'. If the user does not specifically override rotation,

each send should be rotated in a round robin fashion amongst all
available networks and the protocol variable 'last.sent.intf' should
be updated to indicate which interface was used last. The MDTP
implementation should consider the rules defined in "5.5
Retransmission on Multiple Networks" to consider if a network is
"available"

The MDTP implementation MUST allow a user to override this rotation
defeating MDTP's rotation upon each send.

5.  Reliable Transfer Mode

Reliable transfer mode is indicated if the sending endpoint sets the
GAR option on the current datagram.

If the sending endpoint was previously transmitting in unreliable mode
(by setting UNR bit in each previous datagram), the receiver must
reset its Seen counter to the Send value of this current datagram
upon receiving it.

The following example illustrates both piggy-backed and non-piggy-backed
acknowledgments with both ends transmitting in reliable mode:

Endpoint A                                      Endpoint Z
{App sends 3 messages}
[Header Flags=DAT|ACK
	Mode=GAR
	Part=0,Of=1
        Seen=1,Send=1,Size=100]-------------> (Start T2-receive timer)
(Start T3-send timer)

[Header Flags=DAT|ACK
	Mode=GAR
	Part=0,Of=1
        Seen=1,Send=101,Size=100]----------->
(Restart T3-send timer)

[Header Flags=DAT|ACK
	Mode=GAR
	Part=0,Of=1
        Seen=1,Send=201,Size=100]----------->
(Stop and restart T3-send timer)

                                              {Timer T2 expires}
                <---------------------------- [Header Flags=ACK
                                              Mode=0
                                              Part=0,Of=0
                                              Seen=301,Send=1]

(cancel T3-send timer)
..
{App sends 1 message}
[Header Flags=DAT|ACK
	Mode=GAR
	Part=0,Of=1
        Seen=1,Send=301,Size=100]-----------> (Start T2-receive timer)
(Start T3-send timer)

                                              {App sends 1 message}
                                              (cancel T2-receive timer)
                <---------------------------- [Header Flags=DAT|ACK
                                               Mode=GAR
                                               Part=0,Of=1
                                               Seen=401,Send=1,Size=45]
                                               (Start T3-send timer)
(cancel T3-send timer)
(Start T2-receive timer)
..
{Timer T2 Expires}
[Header Flags=ACK
Part=0,Of=0
        Seen=46,Send=401]------------------> (cancel T3-send timer)

In the above example, the first series of 3 messages of 100 octets each
are sent by Endpoint A. The messages are unbundled in this example,
i.e., each message will be transmitted in a single datagram. Endpoint
A starts its send timer T3 after sending the first datagram, and each
subsequent send will stop and restart before it proceeds
      any further in interpreting the send timer T3, extending header fields.

    Version: 8 bits

      This field represents the
life version number of the send timer. Endpoint Z upon receiving the first datagram
starts MDTP protocol
      (value TBD).

    Flags: 16 bits

      NOM - shall be set to 1 (reserved for fragmentation, see
      Appendix C)

      NOB - shall be set to 1 (reserved for bundling, see Appendix B)

      WIN - Window Up. This bit is set by the receive timer T2. When timer T2 in Endpoint Z expires,
Endpoint Z transmits an Ack. Upon receipt sender of this Ack by Endpoint A,
it stops timer T3 and discards datagram
      to indicate that the first 3 sender needs the receiver to acknowledge on
      previously received datagrams (held before it can send more datagrams.

      ISB - shall set to 0 (reserved for
possible retransmissions).

After the first three messages were transmitted successfully, the bundling, see Appendix B)

      FIR - First Datagram. This flag is set to indicate that this is a
      Initiation datagram.

      RTM - normally set to 0 (used for Link Heart Beat and RTT
      measurement, see sections 4.6 and 4.7)

      DAT - Data Present. This bit is set to indicate that, following
      this header, application at Endpoint A sends another message of 100 octets.  After
sending data is present in this datagram, Endpoint A starts timer T3 again.  Upon
receipt of datagram.

      ACK - Acknowledge. This bit is set to indicate that the datagram, Endpoint Z starts Timer T2.  Before
Endpoint Z's T2 timer expires, sender is
      acknowledging the application at Endpoint Z sends a
message reception of 45 octets the specified Acknowledgment Number.

      MUL - shall be set to Endpoint A. 0 (reserved for multicast, see Appendix D)

      SHU - Shutdown. This causes Endpoint Z to cancel bit is set when the T2 timer sender initiates its
      closing procedure and indicates to piggyback an Ack on the out-bound datagram being
transmitted to Endpoint A. After receiver that the transmission, Endpoint Z then
starts its T3 timer.  Upon receipt of this datagram Endpoint A
cancels its T3 timer (since all data it has sent sender
      is acknowledged), and
starts no longer a receive timer T2. At the expiration of the T2 timer Endpoint
A acks the receipt of valid destination. If the last datagram from Endpoint Z.  This Ack
causes Endpoint Z to cancel its T3-send timer.

It UNR bit is very important to notice set in
      conjunction with the above example that SHU bit, an incomplete shutdown is
      specified. After an incomplete shutdown, the
acknowledgments to receiver can still
      re-establish the received datagrams are always delayed communication with the sender by timer
T2. re-initiating
      with the sender (see 4.7).

      WNR - Window Up Response. This delay gives bit is set in the receiving endpoint acknowledgment
      reply to a window Window Up flag.

      RE1 - normally set to piggyback the

Acks onto subsequent datagrams traveling in the opposite direction,
thus 0 (used for advisory ACK, see section 4.8)

      RTC - normally set to avoid sending the Acks in separate datagrams.

5.1 Timer Control

The basic rules 0, (used for timer control are as follows: RTT, see section 4.6)

      FLO - shall be set to 0 (reserved for reliable stream, see
      Appendix A) When all outstanding datagrams are acknowledged, the T3-send timer

      GAR - shall be stopped, if one is running.

B) When a datagram with application data (i.e., with DAT flag set) is
   received, the endpoint set to 1 (reserved for unreliable mode, see
      Appendix E)

      UNR - shall start a T2-receive timer if no timer is
   running.

C) Upon be set to 0 (reserved for unreliable mode see
      Appendix E)

    In Queue: 8 bits

      This field contains the expiration number of the T2-receive timer, the endpoint shall
   ack to messages the sender all the un-acked data it has received.

D) When a datagram with application data is sent out, on its
      incoming queue, waiting to be read by the sending
   endpoint shall start a T3-send timer. If application. This
      gives the T3-send timer is already
   running, receiver an indication of the endpoint shall first stop flow control conditions
      within the old T3 timer and then
   start a new one. sender.

    Acknowledgment Number (or Seen): 32 bits

      If the T2-receive timer flag ACK is set this value is running, the endpoint
   shall first stop the T2 timer, piggyback an Ack unto the out-bound
   datagram, and then start a T3-send timer.

E) If the T3-send timer expires, the endpoint shall attempt
   re-transmission according to last sequence number
      that the rules described in 5.5.

F) No more than one timer sender of any type should be running on an
   endpoint at any given moment.

G) When a T2-receive timer expires, any bundled data waiting to be
   transmitted should be sent immediately with a piggy-backed Ack to
   acknowledge all un-acked data previously received.

H) Whenever a T3-send timer is to be started, any running timer should
   be stopped and supplanted by the T3-send timer.

I) In bundling mode, if this datagram received from the total size
      receiver of all application messages
   pending to be sent this datagram.

    Sequence Number (or Send): 32 bits

      If DAT flag is less than set, this value represents the bundle size, sequence number of
      the messages should
   be withheld and current data unit following this header. Otherwise, this
      value will be the T4-bundle timer should sequence number of the next data unit that
      will be started.

J) If sent.

    Data Size: 16 bits

      This value represents, in number of octets, the total size of all application messages pending to be sent
   exceeds the bundle size, data
      field that follows this header in the T4-bundle timer should be stopped and current datagram.

    Part: 8 bits

      shall have value '0' (reserved for fragmentation, see Appendix C)

    Of: 8 bits

      shall have value '1' (reserved for fragmentation, see Appendix C)

2.2 Data Field

When the message(s) should be immediately sent.

K) If a T4-bundle timer DAT flag is running and data arrives, set to 1, the T2-receive
   timer should not be started.

L) A T4-bundle timer should never MDTP datagram header will be canceled unless it is being
   supplanted
followed by a T3-send timer.

M) When the first datagram with the Tag which unlocks the initiation
   is received, no T2-receive timer should be started, instead an
   acknowledgment must be sent without delay.

The following example shows data field. An implementation may choose to pad some
'0's at the use end of various timers.

Endpoint A                                         Endpoint Z
{App sends 2 messages}
[Header Flags=DAT|ACK
	Mode=GAR
	Part=0,Of=1
        Seen=1,Send=501,Size=100]-----------> (Start T2-receive timer)
(Start T3-send timer)

[Header Flags=DAT|ACK
	Mode=GAR
	Part=0,Of=1                           {App sends 1 message}
        Seen=1,Send=601,Size=100]-\       /-- (cancel T2-receive timer)
(stop and restart T3-send timer)   \     /    [Header Flags=DAT|ACK
                                    \   /      Mode=GAR
                                     \ /       Part=0,Of=1
                                      \        Seen=601,Send=1,Size=100]
                                     / \       (Start T3-send timer)
                                    /   \
                              <----/     \-->
..
{T3-send timer expires}
[Header Flags=DAT|ACK
	Mode=GAR
	Part=0,Of=1
        Seen=101,Send=601,Size=100]---------> (Cancel T3-send timer)
(Restart T3-send timer)                       (Start T2-receive timer)

                                              ..
                                              {Timer T2 expires}
(Cancel T3-send timer)        <-------------- [Header Flags=ACK
                                               Mode=0
                                               Part=0,Of=0
                                               Seen=701,Send=101]

In this example, the application at Endpoint A sends 2 messages data field so as to
Endpoint Z. Both messages align with certain memory
boundaries. However, the padded '0' octets, if there are 100 octets any, shall
not be counted in length. Before the second
datagram arrives at Endpoint Z, Endpoint Z's application sends Data Size.

The maximal Data Size for a
message to Endpoint A. This causes Endpoint Z to cancel its T2-receive
timer and piggyback single MDTP datagram is the Ack to MTU size of
the first received datagram on underlying transport protocol (e.g., UDP) minus the
out-bound datagram destined to MDTP header
size.

3.  Transmission Initialization

3.1 Endpoint A. After transmitting Association Initialization

Before the
datagram Endpoint Z starts its T3-send timer. When first data transmission can take place from one endpoint
("A") to another endpoint ("Z"), the T3-send timer
at Endpoint A expires, it two endpoints will re-send its earlier datagram. need to
complete an initialization process in order to set up an association
between them.

The
retransmitted datagram is initialization procedure should be made transparent to the same except for now upper
layer protocol, i.e., it acknowledges all
outstanding packets that Endpoint Z has sent. After retransmitting should take place automatically whenever the
upper layer tries to send a datagram Endpoint to an endpoint which has never
been sent to before. The user datagram shall be withheld by MDTP from
transmission till the completion of the initialization.

A restarts its T3-send timer. tag-and-lock mechanism is employed during the initialization in
order to guard against erroneous or stale datagrams (this is
especially true if redundant networks are deployed).

The arrival initialization process consists of the retransmitted datagram causes Endpoint Z following steps (assuming
the upper layer at "A" tries to cancel
its T3-send timer send data to "Z" for the first time):

A) "A" first sends an Initiation (FIR) to "Z", with Seen field set
   to 0 and discard Send field set to Tag_A, and then enters the duplicate datagram, Tag-lock mode
   (see below).

B) "Z" responds immediately with an Initiation Ack (FIR|ACK), with
   Seen set to Tag_A and it now

starts its T2-receive timer. At the expiration of Send set to Tag_Z, and then enters the T2-receive timer
Endpoint Z sends
   Tag-lock mode, too (see below).

Note that no user data should be carried in the Initiation or
Initiation Ack datagram.

At this point "Z" is ready to Endpoint A. Endpoint A send user data to "A". And upon receipt of the
Ack Cancels its T3 timer.

5.2 Gap Acknowledgments

If a datagram becomes missing during a series of transmissions, a
special type
receipt of acknowledgment known as the gap Ack will be sent. The
gap above Initiation Ack tells the sender of from "Z", "A" can also start
sending user data to "Z".

However, the missing first datagram that retransmission with user data transmitted by "A" to "Z"
shall have the Seen value set to Tag_Z, which is needed.

The following example shows obtained from the use of gap
Initiation Ack.

Endpoint A                                       Endpoint Z
{App sends 3 messages}
[Header Flags=DAT|ACK
	Mode=GAR
	Part=0,Of=1
        Seen=146,Send=701,Size=100]--------> (Start T2-receive timer)
(Start T3-send timer)

[Header Flags=DAT|ACK
	Mode=GAR
	Part=0,Of=1
        Seen=146,Send=801,Size=100]-----X (lost)
(Restart T3-send timer)

[Header Flags=DAT|ACK
	Mode=GAR
	Part=0,Of=1
        Seen=146,Send=901,Size=100]--------> (A gap detected in data)
(Restart T3-send timer)
                                             ..
                                             {T2-receive timer expires}
                                     /------ [Header Flags=ACK
                                    /         Mode=0
                                   /          Seen=801,Send=146,
                                  /           Part=1,Of=1
                                 /            data=(long integer)901]
(Prepare retransmit)   <--------/

In this example, when Endpoint Z received And similarly, the third first datagram from
Endpoint A it realizes that a gap exists in the received data.  At the
expiration of T2-receive timer, Endpoint Z sends a gap Ack, in place
of a normal Ack, with user data
transmitted by "Z" to Endpoint A "A" shall have the Seen value set to indicate Tag_A,
which comes from the missing data. Initiation datagram.

In the gap Ack, the Part and Of fields are both set to '1', as opposed
to '0' as in a normal Ack. The Tag-lock mode, each side will silently discard any datagrams
with user data field of from the gap Ack other side until it receives the first
datagram with user data and with a Seen value that matches its own
Tag. Once that datagram is received, that endpoint will leave the
Tag-lock mode and immediately send back a four (4)
octet long integer containing data acknowledgment, and
start using the sequence number of the last octet of
the gap (which numbers to filter out missing and duplicate
datagrams.

If another Initiation from "A" is 901 in received by "Z" after it sent out
the Initiation Ack, "Z" will acknowledge this example).  The Seen field in Initiation by re-sending
the gap Initiation Ack
will contain only when the sequence number Send field of this new Initiation has
the first octet same tag as that of the gap.

Using these two values, Endpoint A should be able original Initiation.  Otherwise, "Z" will
send an Initiation of its own with Send field set to calculate Tag_Z back to "A"
to elicit an Initiation Ack from "A".

In the
position and size of following example, "A" initiates the missing data (which is 801-900 in this
example) association first and thus determine which datagrams will need to be
retransmitted.

Gap Acks cannot be piggy-backed with application data. The following is
another example of using gap Ack:

Endpoint A                                       Endpoint Z
{App sends 3 messages}
[Header Flags=DAT|ACK
	Mode=GAR
	Part=0,Of=1
        Seen=146,Send=701,Size=100]--------> (Start T2-receive timer)
(Start T3-send timer)

[Header Flags=DAT|ACK
	Mode=GAR
	Part=0,Of=1
        Seen=146,Send=801,Size=100]-----X (lost)
(Restart T3-send timer)

[Header Flags=DAT|ACK
	Mode=GAR
	Part=0,Of=1
        Seen=146,Send=901,Size=100]--------> (A gap is detected)
(Restart T3-send timer)
                                             ..
                                             {App then
sends a message}
                                             (Cancel T2-receive timer)
                                     /------ [Header Flags=ACK
                                    /         Mode=0
                                   /          Seen=801,Send=146,
                                  /           Part=1,Of=1
                                 /            data=(network long)901]
(Retransmit missing data) <-----/
[Header Flags=DAT|ACK                      - [Header Flags=DAT|ACK
        Mode=GAR                          /  Mode=GAR
        Part=0,Of=1                      /   Part=0,Of=1
        Seen=146,Send=801,Size=100]-    /    Seen=801,Send=146,Size=100]
(Restart T3-send timer)             \  /     (Start T3-send timer)
                                     \/
                                     /\
                          <---------/  \
                                        \
                                         \-->
                                             ..
                                             {T3-Send timer expires}
                                             (Retransmit datagram with user data to "Z":

   Endpoint A                                          Endpoint Z

   {first app data)
(Cancel T3-send timer)    <--------------- message to Z}
   [Header Flags=DAT|ACK Flags=FIR
             & other options
           Seen=0,Send=Tag_A] ----------------------->
   (Start T2-receive timer)                    Mode=GAR
                                            Part=0,Of=1
                                            Seen=1001,Send=146,Size=100]
                                             (Restart T3-send T1-init timer)
..
{T2-receive timer expires}
   (Enter Tag_A-lock mode)
                                              [Header Flags=ACK
        Part=0,Of=0
        Seen=246,Send=1001]----------------> Flags=FIR|ACK
                                                        & other options
                                   /---------- Seen=Tag_A,Send=Tag_Z]
                                  /           (Enter Tag_Z-lock mode)
   (Cancel T1-init timer)<-------/

   [Header Flags=ACK|DAT
             & other options
           Seen=Tag_Z,Send=1]
           [data field]   -----------\
   (Start T3-send timer)

In this example, Endpoint Z detected              \
                                       \----> (Leave Tag_Z-lock mode)

If T1-init timer expires at "A" after the missing data when it received Initiation sent, the second datagram. However, before same
Initiation datagram with the same Tag_A value will be retransmitted
and the T2-receive timer expired, restarted. This will be repeated Max.Init.Retransmit
times before "A" considers "Z" unreachable and optionally reports the
failure.

3.1.1 Choice of Tag Value

Tag values should be selected from the range of 0x80000000 to
0xffffffff.

3.2 Data Field Format of Initiation Datagrams

If redundant networks exist between two endpoints, the data field of
the Initiation and Initiation Ack datagrams will carry the redundant
network information.

The following shows the data field format carrying N IPv4 redundant
network information:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Number of Networks = N                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Size of address=8       |    Type of Address=AF_INET (2)|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             IP Address of Network 1                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Port # 1              |      Padding = 0              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                                                               /
   \                              ...                              \
   /                                                               /
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Size of address=8       |    Type of Address=AF_INET (2)|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             IP Address of Network N                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Port # N              |      Padding = 0              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Additional implementation-specific data is allowed after the
application at Endpoint Z requested redundant
network information. No user data, however, is allowed to send a message (of 100 octets be
transported in length). This caused Endpoint Z to cancel its T2-receive timer and
send the gap Initiation or Initiation Ack before it sent out datagrams.

3.3 Initialization Collision

If two endpoints attempt to initialize an association with each other
at about the same instance, a collision will occur, i.e., each side
will receive an Initiation datagram containing the
application message. After transmitting from the application message
Endpoint Z started its T3-send timer. When Endpoint Z's T3-send timer
expired other side after it retransmitted
transmitted its own. In such a case, both sides shall acknowledge the previous
Initiation datagram and at the same time
acked all of Endpoint A's outstanding datagrams. Upon the receipt of the retransmission from Endpoint Z, Endpoint A started its own
T2-receive timer. At the expiration of its T2-receive timer Endpoint A
sent an Ack to Endpoint Z and resolved other side in the outstanding datagram at
Endpoint Z.

5.3 Congestion Control

Three different mechanisms should normal procedure as
described above.

3.4 Association Re-initialization

An endpoint shall be used jointly allowed to achieve flow
and congestion control in MDTP.

First, a limit should be set on the number of out-bound messages
queued up at re-initialize an established
association with another endpoint. If the limit is reached, new send requests
from

In such a case, the application should be rejected until endpoint that initiates the number of messages
in re-initialization
(i.e, the queue drops back.

Secondly, MDTP uses initiator) shall use a transmission window to control tag different from the number of
outstanding datagrams, i.e., datagrams that have been sent, but yet to
be acknowledged. The length of one used in
the window is defined previous initialization. And the initiator shall follow the normal
initialization procedure as stated in section 3.1.

Once left the maximal
number Tag-lock mode of outstanding datagrams a sending endpoint can allow. This
length is adjusted dynamically, depending on the current number of
successful transmissions as well association initialization,
an endpoint shall treat any new incoming Initiation from its peer as a
re-initialization event. Upon the number arrival of lost datagrams.

When the number of outstanding datagrams reaches new Initiation
datagram from the current window
length, peer, the receiving endpoint may still accept send requests from the
application, but will transmit no more datagram until an Ack is
received.

Also, when shall also follow the window length
procedure stated in section 3.1 to respond.

4.  Reliable Transfer of Datagrams

Reliable transfer is reached, the next send request from indicated if the

application will trigger datagram being transferred has
GAR bit set to 1 and the sending endpoint UNR bit set to transmit 0. The receiver of a special
Window Up message. Upon receiving this Window Up message
reliable datagram shall always acknowledgment the receiver
must respond with sender.

Normally, delayed acknowledgment is used, and the acknowledgment can
either be sent separately or piggy-backed on a Window Up Response message, as illustrated by datagram traveling
in the opposite direction.

The following diagram (assume current window length is 3): example illustrates both separate and piggy-backed
acknowledgments with both ends transmitting in reliable mode:

Endpoint A                                      Endpoint Z
{App sends 3 messages}
[Header Flags=DAT|ACK
	Mode=GAR Flags=DAT|ACK|GAR
        Part=0,Of=1
        Seen=146,Send=1001,Size=100]-------->
        Seen=0,Send=1,Size=100]-------------> (Start T2-receive timer)
(Start T3-send timer)

[Header Flags=DAT|ACK
	Mode=GAR Flags=DAT|ACK|GAR
        Part=0,Of=1
        Seen=146,Send=1101,Size=100]-------->
        Seen=0,Send=2,Size=100]----------->
(Restart T3-send timer)

[Header Flags=DAT|ACK
	Mode=GAR Flags=DAT|ACK|GAR
        Part=0,Of=1
        Seen=146,Send=1201,Size=100]-------->
        Seen=0,Send=3,Size=100]----------->
(Restart T3-send timer)
                                              ...
                                              {Timer T2 expires}
                                 /----------- [Header Flags=ACK
                                /              Part=0,Of=0
                               /               Seen=3,Send=1]
                              /
(cancel T3-send timer) <------
...
...
{App sends 1 messages}
{ queue 100 byte message } message}
[Header Flags=WIN|ACK
        Seen=146,Send=1301]-----------------> Flags=DAT|ACK|GAR
        Part=0,Of=1
        Seen=1,Send=4,Size=100]-----------> (Start T2-receive timer)
(Start T3-send timer)
                                              ...
                                              {App sends 1 message}
                                              (cancel T2-receive timer)
                                         /---
                                 /----------- [Header Flags=ACK Flags=DAT|ACK|GAR
                                /       Mode=WNR              Part=0,Of=1
                               /        Part=0,Of=0               Seen=4,Send=1,Size=45]
                              /         Seen=1301,Send=146]
[Header Flags=DAT|ACK      <---------/
	Mode=GAR
	Part=0,Of=1
        Seen=146,Send=1301,Size=100]-------->               (Start T3-send timer)
(cancel T3-send timer) <------
(Start T2-receive timer)

In this example, after the transmission of
..
{Timer T2 Expires}
[Header Flags=ACK
        Part=0,Of=0
        Seen=1,Send=5]------------------> (cancel T3-send timer)

Note that if the first three datagrams,
Endpoint A reached its window length. The next message datagrams previously received from the
application triggered a Window Up message that same sending
endpoint was sent to Endpoint
Z. The Window Up message always contains no data and has transmitted in Unreliable transfer mode (see Appendix E
for details on Unreliable transfer), the receiving endpoint must
reset its WIN flag
set. In response, Endpoint Z cancelled timer T2 and immediately sent
an Ack with Seen counter to the WNR set value of the Send field in the Mode field. current
reliable datagram.

4.1 Timer Management Rules

The arrival of this Ack
from Endpoint Z effectively resolved all the outstanding datagrams at
Endpoint A, thus allowed Endpoint A following rules shall be used to send out manage the next datagram.

The window length timers during
normal Reliable transfer, unless otherwise stated for some special
cases:

A) When a reliable datagram with user data (i.e., with DAT flag set) is initially set to 2, and
   received, the endpoint shall start a T2-receive timer if no other
   timer is then dynamically
adjusted based on running, and upon the performance expiration of the underlying networks.

If T2-receive timer,
   the current window length is equal endpoint shall ack to or greater than 4, every time

when 4 consecutive outstanding datagrams are acknowledged at once by the receiver, sender all the sender's window length will be raised by 1 until un-acked datagrams
   it
reaches 20. has received.

B) When a reliable datagram with user data is sent out, the sending
   endpoint shall start a T3-send timer. If the T3-send timer is
   already running, the endpoint shall first stop the old T3 timer
   and then start a new one. If the length T2-receive timer is less than 4, every time when running, the number
   endpoint shall first stop the T2 timer, piggyback an Ack unto the
   out-bound datagram, and then start a T3-send timer. Upon the
   expiration of
consecutively acknowledged outstanding datagrams is equal to or
greater than the current window length, T3-send timer, the sender's window will be
raised by 1 until it reaches 20.

The sender's window length will be decreased if datagram loss
occurs. If between 1 to 3 consecutive datagrams are lost, endpoint shall follow the window
length will rules
   described in 4.5 for possible re-transmission of the un-acked
   datagrams. Whenever the T3-send timer is started the RTT estimate
   last calculated for that network should be decreased by 1. If between 4 added to 7 datagrams are lost, the window length will be decreased by 2. If 8 or more base
   T3-send timer value (if a RTT value is measured, see section 4.6).

C) When all outstanding datagrams are
lost, acknowledged, the window length will T3-send timer
   shall be decreased by 4. When stopped if one is still running.

The following example shows the window length
reaches use of various timers.

Endpoint A                                         Endpoint Z
{App sends 2 it will not be decreased any further.

Moreover, any messages}
[Header Flags=DAT|ACK|GAR
        Part=0,Of=1
        Seen=1,Send=6,Size=100]-----------> (Start T2-receive timer)
(Start T3-send timer)

[Header Flags=DAT|ACK|GAR
        Part=0,Of=1                           {App sends 1 message}
        Seen=1,Send=7,Size=100]---\      /--- (cancel T2-receive timer)
(Restart T3-send timer)            \    /     [Header Flags=DAT|ACK|GAR
                                    \  /       Part=0,Of=1
                                     \/        Seen=6,Send=2,Size=100]
                                     /\       (Start T3-send timer)
                                    /  \
                              <----/    ---->
...
...
{T3-send timer expires}
(re-transmit 2nd datagram)
[Header Flags=DAT|ACK|GAR
        Part=0,Of=1
        Seen=2,Send=7,Size=100]---------> (Cancel T3-send timer)
(Restart T3-send timer)                       (Start T2-receive timer)

                                              ..
                                              {Timer T2 expires}
(Cancel T3-send timer)        <-------------- [Header Flags=ACK
                                               Part=0,Of=0
                                               Seen=7,Send=3]

4.1.1 Link Rotation

When multiple networks exist between two communicating endpoints,
every time the application transmits a Window Up is datagram, the MDTP
implementation MUST keep track of which network the transmission was
sent to on (if more than one network exists) in the receiving endpoint MDTP protocol variable
'last.sent.intf'. If the
sender's window length will user does not specifically override rotation,
each send should be decreased by 1. Also, if a timeout
forces rotated in a retransmission round robin fashion amongst all
available networks and the sender's window length will protocol variable 'last.sent.intf' should
be decreased
by 1. Moreover if a duplicate Ack is received by updated to indicate which interface was used last.

The MDTP implementation MUST allow a sender, user to override this should
indicate rotation
defeating MDTP's rotation upon each send. The implementation must also
provide a network congestion situation interface to add and remove a link from rotation eligibility.

4.2 Gap Acknowledgment for Missing Datagrams

If reliable datagrams become missing during a series of transmissions,
a special type of acknowledgment known as the number of outstanding
packets allowed should be decreased by 4.

The following table summarizes these rules:
-----------------------------------------------------------------------
  Duplicate Ack received by sender  | Adjust down by 4
-----------------------------------------------------------------------
  Greater than 8 datagrams lost     | Adjust down by 4
-----------------------------------------------------------------------
  Greater than 4 datagrams lost     | Adjust down by 2
-----------------------------------------------------------------------
  Greater than 0 datagrams lost     | Adjust down by 1
-----------------------------------------------------------------------
  Timeout forces retransmission     | Adjust down by 1
-----------------------------------------------------------------------
  Window Up sent                    | Adjust down by 1
-----------------------------------------------------------------------
  4 or more consecutive datagrams   | Adjust up by 1
  acknowledged (window length > 4)  |
-----------------------------------------------------------------------
  1/2 Window length or more acked   | Adjust up by 1
  (window length <=4)               |
-----------------------------------------------------------------------

Finally, the third flow control mechanism is Gap Ack will be sent
back to exchange incoming
queue information between the two communicating endpoints. By using the
In Queue field in the MDTP header, the sender can inform the receiver
the number of pending datagrams which the sender has received, but yet to deliver to its application. re-transmit the missing datagrams.

The following example shows how the
endpoints use In Queue value to accomplish flow control.

Assume that of Gap Ack.

Endpoint A sent                                    Endpoint Z 20 datagrams, and
{App sends 3 messages}
[Header Flags=DAT|ACK|GAR
        Part=0,Of=1
        Seen=3,Send=8,Size=100]-----------> (Start T2-receive timer)
(Start T3-send timer)

[Header Flags=DAT|ACK|GAR
        Part=0,Of=1
        Seen=3,Send=9,Size=100]-----X (lost)
(Restart T3-send timer)

[Header Flags=DAT|ACK|GAR
        Part=0,Of=1
        Seen=3,Send=10,Size=100]-----------> (A gap detected in data)
(Restart T3-send timer)
                                             ..
                                             {T2-receive timer expires}
                                    /------- [Header Flags=ACK
                                   /          Seen=9,Send=3,
                                  /           Part=1,Of=1
                                 /            data=(long integer)10]
(Prepare retransmit)   <--------/

In this example, when Endpoint

Z acked "Z" receives the receipt of all third datagram from "A" it
realizes that a gap exists in the 20 datagrams, only received data.  At the first one expiration of
the 20 datagrams was delivered to the application at Endpoint Z.  In
the last Ack sent by Endpoint Z, the In Queue field would then have
T2-receive timer, "Z" sends a
value of 19, indicating the number Gap Ack, in place of datagrams pending for delivery
to its application. This value would be checked by Endpoint A before
it sent the next datagram to Endpoint Z. If this value was found to be
greater than its current window length, Endpoint A would not send the
next datagram. Instead, Endpoint A would start its T3-send timer and
send a Window Up message normal Ack, to Endpoint Z at
"A" to indicate the expiration of missing datagram.

In the timer.
This would force Endpoint Z Gap Ack, the Part and Of fields are both set to send an '1', as opposed
to '0' as in a normal Ack. The data field of the Gap Ack with an updated In Queue
value. If is a four (4)
octet long integer containing the new In Queue value was still greater than its window
length, Endpoint A would restart its T3-send timer, repeating sequence number of the next datagram
after the Gap (which is 10 in this
procedure until example).  The Seen field in
the In Queue value Gap Ack will contain the sequence number of Endpoint Z dropped below the
current window length datagram of Endpoint A.  Then, the transmission at
Endpoint A would resume.

5.4 Sequence Number Reset

It may become necessary for an endpoint
gap.  Using these two values, "A" should be able to reset calculate the sequence number
while it
the missing datagram numbers (which is sending 9 in this
example) and thus determine which datagrams will need to be
retransmitted.

Note that Gap Acks cannot be piggy-backed with user data; if there is
user data to be sent when a peer. However, gap is detected, the endpoint Gap Ack must inform be sent
out first before the peer about this event by:

1) datagram carrying user data can be sent.

4.3 Flow and Congestion Controls

Several different mechanisms shall be used jointly to achieve
flow and congestion controls in MDTP.

4.3.1 Sending with Window Control

The sending endpoint shall use a Window Up message transmission window to force control the peer to acknowledge all
   received
number of outstanding datagrams, i.e., datagrams which that have not been acknowledged, and

2) sending sent,
but yet to be acknowledged. The length of the next datagram with RES bit set in window is defined as the Flags field.

3) A
maximal number of outstanding datagrams a sending endpoint should always reset it sequence counter before can
allow. This length is adjusted dynamically, depending on the counter reaches 0x7fffffff. current
number of successful transmissions as well as the number of lost
datagrams.

When the counter number of outstanding datagrams reaches this
   value the sending endpoint is required to reset its sequence
   counter.

4) A sending current window
length, the endpoint should never reset shall still accept send requests from its sequence counter upper
layer, but shall transmit no more datagrams until
   after reaching 0x7fff05ff.

Note: This section an Ack is received.

Moreover, when the window length is reached, the next send request
from the upper layer will be obsoleted in a future version of trigger the
draft and be replaced by sending endpoint to transmit a deterministic roll-over algorithm.

The following example illustrates
special Window Up message. Upon receiving this Window Up (WIN|ACK) the sequence number reset procedure
(assume that Endpoint A opts to do
receiver must respond with a reset when Window Up Response (WNR|ACK), as
illustrated by the data sequence
number becomes greater than 0x7fffff000). following example (assuming current window length
is 3):

Endpoint A                                      Endpoint Z
{App sends 2 3 messages}
[Header Flags=DAT|ACK
	Mode=GAR Flags=DAT|GAR|ACK
        Part=0,Of=1
        Seen=46,Send=0x7ffff000,Size=100]---->
        Seen=0,Send=11,Size=100]-----------> (Start T2-receive T2-recv timer)
(Start T3-send timer)
(Reset sequence number)
[Header Flags=WIN|ACK
        Seen=146,Send=0x7ffff100]------------> (cancel T2-receive timer)
                                      /-------

[Header Flags=ACK
                                     /          Mode=WNR
                                    /           Part=0,Of=0
                                   /            Seen=7fffff100,Send=46]
(Cancel Flags=DAT|GAR|ACK
        Part=0,Of=1
        Seen=0,Send=12,Size=100]----------->
(Restart T3-send timer)     <------/

[Header Flags=DAT|ACK|RES
	Mode=GAR Flags=DAT|GAR|ACK
        Part=0,Of=1
        Seen=46,Send=2,Size=100]-------------> (Start T2-receive timer)
        Seen=0,Send=13,Size=100]----------->
(Restart T3-send timer)

                                               ..

{App sends 1 a new message}
(queue new message and send Win Up)
[Header Flags=WIN|ACK
        Seen=0,Send=14]--------------------> (cancel T2-receive timer)
(Cancel T3-send T2-recv timer)     <----------------
                                      /----- [Header Flags=DAT|ACK
(Start T2-receive timer)                      Mode=GAR Flags=WNR|ACK
                                     /        Part=0,Of=0
                                    /         Seen=14,Send=0]
[Header Flags=DAT|GAR|ACK <--------/
        Part=0,Of=1
                                              Seen=102,Send=46,Size=100]
        Seen=0,Send=15,Size=100]-----------> (Start T2-recv timer)
(Restart T3-send timer)

In the above example, after transmitting the transmission of the first datagram Endpoint A
determines that three
datagrams, "A" reached its data sequence number needs to be reset before it
transmits the window length. The next datagram. It first sends out message from the
user triggered a Window Up message to
force Endpoint Z that was sent to send back "Z". The Window Up shall
contain no user data. In response, "Z" cancelled timer T2 and
immediately sent a Window Up Response. The arrival of this Window Up
Response to ack effectively resolved all the outstanding received data. Then, it transmits the datagram
it has been withholding, with datagrams at "A",
thus allowed "A" to send out the new sequence number next datagram.

4.3.2 Window Length Adjustment

The window length shall be initially set to 2, and shall then be
dynamically adjusted based on the RES flag
set. Upon detecting the RES flag in the header datagram loss and acknowledgment
conditions of the incoming datagram,
Endpoint Z resets its data sequence counter on Endpoint A.

5.5 Retransmission on Multiple Networks

Whenever a T3-send timer expires, underlying network.

When 4 consecutive outstanding datagrams are acknowledged at once by
the endpoint receiver, the sender's window length will take one of be raised by 1 until it
reaches the
following three actions:

A) protocol parameter 'Max.Outstanding.dg' (which should be a
user configurable parameter).

If the current window length is not reached (see 5.3) and there is
   application data pending, less than 4, every time when the
number of consecutively outstanding datagrams acknowledged in a new datagram will be sent out.

B) If single
Ack is equal to or greater than the current window length, the
sender's window length is reached, a Window Up message will shall be sent out.

C) If raised by 1, until it reaches
'Max.Outstanding.dg'.

In the following circumstances, the sender's window length is not reached, but there is no pending
   application data to send, The datagram with shall be
decreased. However, when the lowest Send value
   that is still outstanding (i.e., window length reaches 2 it shall not been acked) be
decreased any further.

If between 1 to 3 consecutive datagrams are lost, the window length
will be
   retransmitted.

When multiple networks exist decreased by 1. If between two communicating endpoints, 4 to 7 datagrams are lost, the
re-transmission should
window length will be attempted on the network specified
in decreased by 2. If 8 or more datagrams are lost,
the MDTP protocol variable 'last.good.intf'. The value of
'last.good.intf' window length will be decreased by 4.

Moreover, any time a Window Up is always updated to refer sent to the network on which
the last datagram from the peer receiving endpoint arrived.

Moreover, the number of consecutive re-transmissions is also recorded
in a variable 'retran.count' for each network. Every time
sender's window length will be decreased by 1. Also, if a datagram is
received from timeout
forces a network, retransmission the corresponding retran.count is reset sender's window length will be reduced
to '0'.

If half of its currently value.

The following table summarizes these rules:
- -----------------------------------------------------------------------
  Duplicate Ack received by sender  | Adjust down by 4
- -----------------------------------------------------------------------
  Greater than 8 datagrams lost     | Adjust down by 4
- -----------------------------------------------------------------------
  Greater than 4 datagrams lost     | Adjust down by 2
- -----------------------------------------------------------------------
  Greater than 0 datagrams lost     | Adjust down by 1
- -----------------------------------------------------------------------
  Timeout forces retransmission     | Adjust down by 1/2 of the value current
                                    | window.
- -----------------------------------------------------------------------
  Window Up sent                    | Adjust down by 1
- -----------------------------------------------------------------------
  4 or more consecutive datagrams   | Adjust up by 1
  acknowledged (window length > 4)  |
- -----------------------------------------------------------------------
  1/2 Window length or more acked   | Adjust up by 1
  (window length <=4)               |
- -----------------------------------------------------------------------

4.3.3 Flow Control using In-Queue Information

By using the In Queue field in the retran.count of the current network exceeds a half
of MDTP header, the value of sender can inform
the protocol parameter 'Max.Retransmit', receiver the
'last.good.intf' will be changed, so as to force number of pending datagrams which the next
re-transmission sender has
received, but yet to be directed deliver to an alternate network. its application. The total number of consecutive re-transmissions across all following example
shows how the
networks is also recorded. If this endpoints use In Queue value exceeds the limit defined by
'Max.Retransmit', the sending endpoint should consider the peer
endpoint unreachable and stop transmitting data to it, and optionally
report the failure.

5.5.1 Randomization of the T3-send timer at retransmission

When a T3-send timer is started after retransmitting a packet, the
value of the next T3-send timer for this destination should be
extended by a random amount. The amount must be bounded so accomplish Flow control.

Assume that the
application can predict with some reasonable degree of precision when
the destination endpoint is declared unreachable.

For performance considerations, this can be implemented by
pre-calculating a set of random values Endpoint A has sent Endpoint Z 20 datagrams, and then using a different
value to extend the T3-send timer for each re-transmission to the
same destination endpoint.

5.6 Termination of an when
Endpoint

When Z sends an endpoint terminates, it should send a shutdown message
to each Ack on the reception of these 20 datagrams, only
the peer endpoints it first one of them has ever initiated for a
communication. The shutdown message is sent in unreliable transfer
mode and need not been delivered to be acknowledged. When an endpoint receives a
shutdown message from its peer, it will remove the sender from its
record, and optionally report upper layer at
Endpoint Z.

In the Ack sent by Endpoint Z, the termination of that peer.

The following sequence shows an example In Queue field would then have a
value of 19, indicating the termination number of an
endpoint (Endpoint A). datagrams pending for delivery
to its upper layer. This value would be checked by Endpoint A

{App indicates termination}
[Header Flags=FIR
	Mode=SHU
        Seen=146,Send=1301,------------------------> before
it sent the next datagram to Endpoint X

[Header Flags=FIR
	Mode=SHU
        Seen=1496,Send=101,------------------------> Z. If this value was found to be
greater than its current window length, Endpoint Y

[Header Flags=FIR
	Mode=SHU
        Seen=1460,Send=201-------------------------> A would not send the
next datagram. Instead, Endpoint A would start its T3-send timer and
send a Window Up message to Endpoint Z

As shown in this example, at the shutdown message is indicated by having
both FIR flag and SHU mode bit set. Also, notice that no
acknowledgment is sent back by Endpoint X, Y, or X.

5.7 expiration of the timer.
This would force Endpoint Drain

An endpoint may decide Z to "drain" a connection without completely
shutting it down. By draining a connection, both endpoints will remove
any record and pending datagrams associated send another Ack with an updated In
Queue value. If the connection.
Further communications between the two endpoints can be resumed by
going through a re-initialization procedure. new In Queue value was still greater than its
window length, Endpoint A "drain" message is specified with would re-start its T3-send timer, and repeat
this procedure until the UNR bit set in a shutdown
message. No Ack is required for a "drain" message.

The following sequence shows an example. In Queue value of Endpoint A

{App indicates termination}
[Header Flags=FIR|UNR
	Mode=SHU
        Seen=146,Send=1301]------------------------> to Z dropped below
the current window length of Endpoint A.  Then, the transmission at
Endpoint X

5.8 Advisory Acknowledgments.

To increase bandwidth utilization a sending endpoint may (at its option)
request an advisory acknowledgment. A endpoint would typically do this
when 1/2 of its window resume.

4.3.4 T3-send Timer Adjustment with RTT

If the RTT measurement is unacknowledged and upon its last datagram
that will fill its window. Upon reception of available on a advisory Acknowledgment
request specific network, the receiver sender
shall with no delay transmit an acknowledgment of
all received packets canceling any T2-Receive adjust the T3-send timer that may be running. each time when sending datagram using
this network. The sequence would look as follows:

Endpoint A                                      Endpoint Z
{App sends 3 messages}
[Header Flags=DAT|ACK
	Mode=GAR
	Part=0,Of=1
        Seen=1,Send=1,Size=100]-------------> (Start T2-receive timer)
(Start T3-send timer)

[Header Flags=DAT|ACK
	Mode=GAR
	Part=0,Of=1
        Seen=1,Send=101,Size=100]----------->
(Restart T3-send timer)

[Header Flags=DAT|ACK
	Mode=GAR|RE1
	Part=0,Of=1
        Seen=1,Send=201,Size=100]----------->
(Stop calculation and restart T3-send timer)

                                              (cancel T2-receive timer)
                <---------------------------- [Header Flags=ACK
                                              Mode=0
                                              Part=0,Of=0
                                              Seen=301,Send=1]

5.9 adjustment of the timer should
follow the method described in [4]. RTT Measurement

On occasion either end may wish to do a Round Trip Time measurement of
a network.  There shall be tracked
for each network if redundant networks are in use.

MDTP defines two optional methods of measuring Round Trip Time.
Method 1 involves a ping-pong using a special ACK, Method 2 involves a
rider on top of a datagram. If Method 2 is invoked then to obtain RTT measurements, see
sections 4.6 and 4.7.

4.4 Sequence Number Reset

When the Round Trip
Time includes datagram sequence number reaches the T2-Receive timer (this actually may value 0x7fffffff the
next sequence number shall be more useful
then pure RTT time since each set to 1.

4.5 Datagram Re-transmission

Whenever a T3-send timer expires, the endpoint may have shall re-transmit the
un-acked datagram that has the lowest Send value, unless:

A) If the current window length is reached, a different T2-Receive Window Up message will
   be sent out (see 4.3 Congestion Control), or

B) If the current window length is not reached and there is still
   user data pending for transmission, a new datagram with user data
   shall be sent out and T3-send timer value).

Method 1: shall be restarted.

When a endpoint wishes a RTT measurement it shall send T3-send timer is started at a ACK
datagram with RE2 set to 1, GAR set to 1 and DAT set to 0.  The sender
should place in Time Int 1 and Time int 2 re-transmission, the value length of
the current
time of day in seconds/microseconds.

Upon receipt of a datagram with RE2 set to 1, GAR set to 1 next T3-send timer for this destination should be doubled and DAT set
to 0, the recipient
last estimated RTT value for that network should return the datagram be added to the sender over timer.

4.5.1 Re-transmission on Redundant networks

When redundant networks exist between two communicating endpoints, the
re-transmission shall be attempted on the
arriving network with specified in the NOG bit set.
MDTP protocol variable 'last.good.intf'. The sender can then use the
Time Int 1 and Time Int 2 to calculate the current RTT.

Endpoint A                                      Endpoint Z
RTT - Request Now=x.y
[Header Flags=ACK
	Mode=GAR|RE2
	Part=0,Of=1
        Seen=1,Send=301,Size=0
        Time-Int1=x
        Time-Int2=y]------------->
                <---------------------------- [Header Flags=ACK|NOG
                                              Mode=0
                                              Part=0,Of=0
                                              Seen=301,Send=1
                                              Time-Int1=x
                                              Time-Int2=y]

Endpoint A uses
current time subtracted from
X.y (in arriving Datagram) value of 'last.good.intf'
is always updated to
calculate the RTT.

Method 2:

If a endpoint wishes refer to piggyback a RTT test including the T2-Timer at network on which the remote endpoint last datagram
from the sending peer endpoint fills out arrived.

Moreover, the datagram number of consecutive re-transmissions is also recorded
in the
normal way a variable 'retran.count' for reliable communication but also sets the RE2 flag, and
places at each network. Every time a datagram
is received on a network, the end of corresponding 'retran.count' shall be
reset to 0.

If the datagram (outside value in the length 'retran.count' of the data) two
long integers has a trailer.

When current network exceeds
half of the receiving endpoint recognizes value of the RE2 flag, it should extract protocol parameter 'Max.Retransmit', the two integers and place them in internal storage until
'last.good.intf' will be changed, so as to force the next
datagram is scheduled
re-transmission to be returned (i.e. at the expiration directed to an alternate network and
optionally report a failure condition.

The total number of consecutive re-transmissions across all the
T2-Recv timer).
networks in an association is also recorded. If this value exceeds the The T2-Recv timer expires
limit defined by 'Max.Retransmit', the receiving sending endpoint should send shall consider
the acknowledgment as above with peer endpoint unreachable and stop transmitting data to it, and
optionally report the failure.

4.6 RTT Measurement

This defines the addition mechanism for round-trip-time (RTT) measurement in
MDTP.

On occasions either side of an association may need to perform an RTT
measurement of the NOB flag as well.  If network (or one of the receiving endpoints upper layer sends a
datagram causing redundant networks) between
them.

4.6.1 RTT Datagram Header Format

The following shows the header format an endpoint shall use for RTT
measurement:

                   MDTP Header Format - RTT measurement

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  MDTP Protocol Identifier                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Version     |           Flags               |   In Queue    |
   |               |N N W I F R D A M S W R R F G U|               |
   |               |O O I S I T A C U H N E T L A N|               |
   |               |M B N B R M T K L U R 1 C O R R|               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 Acknowledgment Number (Seen)                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                   Sequence Number (Send)                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        Data Size              |    Part       |      Of       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  Transparent Time Int-1                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  Transparent Time Int-2                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Two long integers are used in the T2-Recv timer data field to be canceled then carry the time value.
The RTT datagram
should include the Trailing integers and have the NOB flag set.  In
cases where a intervening Window UP is received identified by setting the receiving RTC or RTM bit to 1.

4.6.2 Measure RTT

AT the request of its upper layer, an endpoint
should respond shall initiate an RTT
measurement by sending an RTT datagram with GAR, ACK, and RTC bits set
to 1 (to a window Up Response (per specific network if redundant networks exist). No
user data shall be carried. The sender shall also place in Time Int-1
and Time Int-2 the window up procedure)
but NOT cancel its T2-Recv timer.

Example 1 - T2-Recv timer expires

Endpoint A                                      Endpoint Z
RTT - Request Now=x.y
[Header Flags=ACK|DAT
	Mode=GAR|RE2
	Part=0,Of=1
        Seen=1,Send=301,Size=100
	{data value of 100 octets}
        Time-Int1=x
        Time-Int2=y]------------->            (started T2-Recv)
		                              {T2-Recv Expires }
                <---------------------------- [Header Flags=ACK|NOG|NOB
                                              Mode=0
                                              Part=0,Of=0
                                              Seen=301,Send=1
                                              Time-Int1=x
                                              Time-Int2=y]
Example 2 - Datagram causes T2-Recv timer cancel

Endpoint A                                      Endpoint Z
RTT - Request Now=x.y
[Header Flags=ACK|DAT
	Mode=GAR|RE2
	Part=0,Of=1
        Seen=1,Send=301,Size=100
	{data the current time of 100 octets}
        Time-Int1=x
        Time-Int2=y]------------->            (started T2-Recv)
		                              {datagram sent by application}
			                      (cancel T2-Recv)
                <---------------------------- [Header Flags=DAT|ACK|NOG
                                              Mode=GAR
                                              Part=0,Of=1,Size=100
                                              Seen=401,Send=1
                                              {data day in seconds and
microseconds.

Upon the reception of 100 octets}
                                              Time-Int1=x
                                              Time-Int2=y]

5.10 Heart Beat Ack

At request by this RTT datagram, the application, recipient shall
immediately return the user may wish a Heart Beat
acknowledgment sent. The Heart Beat should only be allowed datagram to be
enabled if the senders Mod is Gar (reliable delivery) and version is
2. Once enabled when no datagrams are being transmitted, a T5-Heart
Beat timer should be started. When the T5 timer expires a ACK should
be sent using sender (over the next available link, following same network
on which the link rotation
procedure outlined in "4.5 Link Rotation". After sending datagram arrives if redundant networks exist), with the Ack
another T5-Heart Beat timer should be started. If, before
RTM and ACK bits set to 1.

Upon the
expiration reception of T5-Heart Beat, a datagram is transmitted or received, this reply, the T5 timer should be stopped sender shall use the Time Int-1
and Time Int-2 in the appropriate T2-T4 timer should
be started.  The T5 timer has reply datagram to calculate the lowest precedence of all timers.

When sending a Heart Beat Ack, RTT (of the format should be that of a
specific network if redundant networks exist).

Endpoint A                                      Endpoint Z
RTT - Request Now=x.y
[Header Flags=ACK|GAR|RTC
        Part=0,Of=1
        Seen=1,Send=31,Size=0
        Time-Int1=x
        Time-Int2=y] ----------------------->
                                      ------ [Header Flags=ACK|RTM
                                     /        Part=0,Of=0
                                    /         Seen=31,Send=1
                                   /          Time-Int1=x
                                  /           Time-Int2=y]
                                 /
(Endpoint A uses     <-----------
 current time
test. subtracted from
 x.y to calculate RTT)

4.7 Link Heart Beat

This will require defines the receiver to respond mechanism for activating and transmitting of link
heart beats in MDTP.

At request by its upper layer, an endpoint shall enable heart beat on the network. If
the sender does not get
a response on specific peer with which it has an established association in the network
Reliable transfer mode.

The RTT datagram defined in section 4.6.1 shall be used as the heartbeat
arrived on by Heart
Beat.

After having heart beat enabled, the time endpoint shall transmit a next heartbeat is Heart
Beat to be sent, then the
network that specific peer and start a T5-heartBeat timer. The peer
shall immediately respond to the last heartbeat was sent upon should be counted Heart Beat in the same manner as an
RTT as a
transmission failure has described in section "5.5 Retransmission on
Multiple Networks", and should counted against 4.6.  This response shall be stored by the 'retran.count' and
protocol parameter 'Max.Retransmit'.

6.  Unreliable Transfer Mode

The unreliable transfer mode allows two endpoints to send
first endpoint (also can be used to each
other without acknowledging update its RTT measurement).

When the receiving. This can usually achieve
higher data throughput than T5-heartBeat timer expires, the reliable transfer mode. To indicate endpoint shall first check if
the previous heart beat has been responded (on the
unreliable transfer mode same network it was
sent in the sender case of a datagram simply sets redundant network). If not, the UNR
in network that the mode field. The
last Heart Beat was sent upon shall be counted as a transmission
failure, and be handled following sequence illustrates unreliable data
transfer.

Endpoint A                                      Endpoint Z
{App sends 2 messages}
[Header Flags=DAT|ACK
	Mode=UNR
	Part=0,Of=1
        Seen=1,Send=11001,Size=100]-------->

[Header Flags=DAT|ACK
	Mode=UNR
	Part=0,Of=1
        Seen=1,Send=11101,Size=100]-------->

                                             {App sends 1 message}
                                   <------- [Header Flags=DAT|ACK
                                             Mode=UNR
                                             Part=0,Of=1
                                             Seen=11201,Send=1,Size=450]

{App sends 2 more messages}
[Header Flags=DAT|ACK
	Mode=UNR
	Part=0,Of=1
        Seen=451,Send=11201,Size=100]------>

[Header Flags=DAT|ACK
	Mode=UNR
	Part=0,Of=1
        Seen=451,Send=11301,Size=100]------>

Note that no timers are started by either end. Also note that even

though both ends are the rules described in UNR mode, section 4.5.
Then, the ACK flag is still set by endpoint shall send another Heart Beat and re-start the
sender of
T5-heartBeat timer.

In the datagram. This means that case where redundant networks exist, the Seen field sending of Heart beats
shall follow the link rotation rules outlined in section 4.1.1.

If, before the expiration of T5-heartBeat timer, a datagram
header is still valid to indicating the sequence number of the last
octet
transmitted or received by the sender. However, endpoint, the sender makes T5-heartBeat timer shall
be stopped and the appropriate T2-T4 timer shall be started. In other
words, the T5-heartBeat timer has the lowest precedence.

When no claim as datagram to
whether pieces of data send and no other timers are missing. running, the
T5-heartBeat timer shall be start and the above procedure shall
continue.

The upper application can suggested interval for T5-heartBeat timer is 4000 ms.

4.8 Advisory Acknowledgment

This defines the mechanism for sending and handling of the Advisory
Acknowledgments in MDTP.

An endpoint may use this
information to help detecting missing or duplicated pieces. In
unreliable mode, MDTP makes no effort Advisory Acks to re-transmit missing data or increase bandwidth utilization
when transmitting over a reliable association.

An Advisory Ack shall be indicated by setting RE1 flag to screen out duplicated datagrams.

6.1 Ordered reception

In unreliable transfer if 1 in the sender sets
datagram.

The endpoint shall send an Advisory Ack to its peer when it reaches
half of its current window length, and also when it detects that the RE1 bit
next send will reach the receiver
should order full window length.

Upon the datagrams upon arrival. Any datagrams that have not
been read by reception of an Advisory Ack, the receivers application should be ordered so that peer endpoint shall
immediately acknowledge all the datagrams will be it has received in order the datagrams were transmitted
(using the sendStartsAt field). If a datagram arrives after a
new datagram but yet
acked upon, and then cancel the datagram should be discarded. T2-recv timer if one is still
running.

The sequence would
look as follows: following shows an example of using Advisory Ack:

Endpoint A                                      Endpoint Z
{App sends 4 3 messages}
[Header Flags=DAT|ACK
	Mode=UNR|RE1 Flags=DAT|GAR|ACK
        Part=0,Of=1
        Seen=1,Send=11001,Size=100]-------->

[Header Flags=DAT|ACK
	Mode=UNR|RE1
	Part=0,Of=1
        Seen=1,Send=11101,Size=100]\       /-->
                                    \     /
                                     \   /   (User reads/Receives all
        Seen=0,Send=1,Size=100]-------------> (Start T2-recv timer)
(Start T3-send timer)

[Header Flags=DAT|ACK                 \ /     datagrams 11001 & 11201)
	Mode=UNR|RE1                   \ Flags=DAT|GAR|ACK
        Part=0,Of=1                   / \
        Seen=451,Send=11201,Size=100]/   \---> { Datagram is discarded }
        Seen=0,Send=2,Size=100]----------->
(Restart T3-send timer)
{detects window half full, use Advisory Ack}
[Header Flags=DAT|ACK
	Mode=UNR|RE1 Flags=DAT|GAR|ACK|RE1
        Part=0,Of=1
        Seen=1,Send=11301,Size=100]\       /-->
                                    \     /
        Seen=0,Send=3,Size=100]------\
(Stop and restart T3-send timer)      \   /
                                       \----> (cancel T2-receive timer)
                      <---------------------- [Header Flags=DAT|ACK                 \ /
	Mode=UNR|RE1                   \
	Part=0,Of=1                   / \
        Seen=451,Send=11401,Size=100]/   \--->(User reads/Receives all
                                               datagrams in order
                                               11301 & 11401)

7.  Reliable flows

A flow is a ordered reliable sequence Flags=ACK
                                               Part=0,Of=0
                                               Seen=3,Send=1]

4.9 Termination of datagrams that is delivered an Association

When an endpoint terminates, it shall send a Shutdown datagram
(FIR|SHU) to each of the receiver peer endpoints in order without constraint to other flows. There all its existing
associations.  The Shutdown datagram itself is a
set way to initiate (open) a flow sent in unreliable
transfer mode and close a flow. Each flow is
initiated by the sender. Multiple flows may thus needs not to be initiated between two
endpoints at the same time. Once initiated acknowledged.

When a flow peer endpoint receives the Shutdown, it will follow remove the same
retransmission sender
from its record, and link rotation schema's has optionally report the rest of MDTP. However
each flow is independent of any other flow, so if datagram 1 and 2 of
flow 5 arrives, but datagram 1 of flow 4 is lost (having been sent
ahead termination of flow 5's datagrams), flow 5's datagrams are delivered the sender
to the
application without blocking for retransmission upper layer.

The following shows an example of the lost datagram
from flow 4 (datagram 1 termination of flow 4).  All flow related datagrams will
have the NOB bit set. Each flow will also have Endpoint A:

Endpoint A
{App indicates termination}
[Header Flags=FIR|SHU
        Seen=3,Send=14,    ------------------------> to Endpoint X

[Header Flags=FIR|SHU
        Seen=1496,Send=101,------------------------> to Endpoint Y

[Header Flags=FIR|SHU
        Seen=14,Send=2    -------------------------> to Endpoint Z

4.10 Draining of an Association

An endpoint in a separate timer
associated with association may decide to "drain" the association
without completely shutting it that is unique and different from any non-flow
related timers that are running. The Seen and Send fields down. By draining an association, both
endpoints will be
broken down remove any record and interpreted in pending datagrams associated with
the following manner.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Flow Number           |    Datagram number in flow    | (Seen)
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Flow Number           |    Datagram number in flow    | (Send)
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

The Send field will contain association.  Further communications between the two endpoints can
be resumed by going through a re-initialization procedure (see
section 3).

In such a case, a Drain datagram (FIR|SHU|UNR) is sent to the flow number peer
endpoint of this datagram, flow 0
is always reserved the association, and no Ack is NOT used. required.

The datagram number is the
sequential number following sequence shows an example of the datagram. Draining:

Endpoint A
{App indicates draining}
[Header Flags=FIR|SHU|UNR
        Seen=146,Send=1301]------------------------> to Endpoint X

5. Interface with upper level protocols

The Seen field is used upper layer protocols (ULP) shall request for services by passing
primitives to
acknowledge receipt of the indicated datagram MDTP and shall receive notifications from MDTP for the specified
flow.
various events.

The flow number primitives and notifications described in the acknowledgment does NOT need to this section should be the
same
used as the flow number in the Send field. a guideline for implementing MDTP.

A) Init.MDTP primitive

This format is only used primitive allows MDTP to initialize its internal data structures
and allocate necessary resources for flow datagrams.

A flow setting up its operation
environment. Note that once MDTP is initialized, ULP can have bundled data (see section 9) but cannot have
fragmented messages. communicate
directly with any other endpoints without re-invoking this primitive.

Mandatory attributes:

None.

Optional attributes:

The reason fragmented messages are not supported
is two fold, following types of attributes may be passed along with
the primitive:

 o Timer selection and its operation syntax -- to attempt indicate to simplify MDTP
   an alternative timer the flows a little bit. And flows
are thought of has call control related limiting there MDTP should use for its operation.
 o Initial MDTP operation mode;
 o IP port number, if ULP wants it to be specified;

B) Send.Data primitive

This is the main method to send datagrams via MDTP.

Mandatory attributes:

 o data - This is the payload ULP wants to transmit;
 o size - The size to be no
larger than one datagram per message.

If a flow packet number reaches 0xffff, then of the next packet payload in number
should wrap to 1.

Before a flow of octets;
 o to-address - The IP address and port number of the intended
   receiver. In case of redundant networks, to-address can be used it must be initiated, after any one
   of the flow is
complete it should multiple IP addresses of the receiver. The network which the
   datagram will actually be closed. Note it is assumed that before any flows
can sent through will be opened determined by MDTP due
   to the link rotation, unless the current mode prohibits MDTP initiate sequence has taken place link
   rotation; in such case the datagram will be sent through the network
   specified by to-address (see section
4). When 4.5).

Optional attributes:

 o mode-flags - This indicates a new MDTP initiate sequence occurs, any endpoint being
re-initialized will cause a closing of all outstanding flows during
that re-initialization. Before opening a flow operation mode, taking effect
   immediately including the opening end should
verify current datagram send;

 o context - optional information that will be carried in the version number of
   Send.Failure notification to the receiving MDTP endpoint is at
least 3. If ULP if the version number is less than 3 then transportation of
   this datagram fails.

C) Receive.Data primitive

This primitive shall return the MDTP endpoint
must NOT attempt to open a flow.

7.1 Initiating a flow.

A flow is initiated by sending a Flow Initiate/Close Message. In all
flow first datagram in the NOB bit MDTP in-queue to
ULP, if there is set. For the Flow Initiate Message one available. It may, depending on the
UNR mode bit set specific
implementation, also return other informations such as well. The Acknowledgment number (Seen) and the
Sequence Number (Send) sender's
address, whether there are more datagrams available for retrieval,
etc. The behavior is set to 0 unless undefined if no datagram is available when this
primitive is invoked.

Mandatory attributes:

 o buffer - the first message in
which case memory location indicated by the TAG unlock value is set in ULP to store the Send (see section 4.1).

Until
   received datagram and other information.

Optional attributes:

   None.

D) Data.Arrive notification

MDTP shall invoke this notification on the ULP when a flow datagram is open
successfully received and ready for retrieval.

E) Send.Failure notification

If a receiver of a non-opened flow datagram will silently discard the datagram. Upon sending a flow
initiation a T3-Send timer will can not be started delivered MDTP shall invoke this notification
on flow 0. The timer will
follow the same rules for retransmission and timing as outlined in
section 5. ULP.

The following illustration demonstrates the opening of flow 5:

Endpoint A                                      Endpoint Z
{App Initiates flow 5}
[Header Flags=NOB
	Mode=UNR
	Part=0,Of=1
        Seen=00000000,Send=0x0000 0000,Size=0,
	flow=0x0005 dg=0000	]------>
(Start T3-send timer f=5)
(Cancel T3-send timer f=5) <----------------- [Header Flags=NOB|ACK
                                               Mode=UNR
                                               Part=0,Of=1
                                               Seen=0x00000005,Send=0x00000000,
                                               Size=0, flow=0000 dg=0000]

In the above example note that for flow 0, unlike all others, no T2-Recv
timer is ever started. Each flow open/close must may be independently
acknowledged. Note also that in the reply acknowledgment the ACK bit is
set. If unlikely event that Endpoint-Z wished to piggy back the open of
flow 5 optionally passed with a flow open of its own the sequence would look as follows:

Endpoint A                                      Endpoint Z
{App Initiates flow 5}
[Header Flags=NOB
	Mode=UNR
	Part=0,Of=1
        Seen=0,Send=0,
	Size=0,
	flow=5, dg=0 ]------>
(Start T3-send timer f-5)                       {App Initiates flow 8}
(Cancel T3-send timer f-5)   <----------------- [Header Flags=NOB|ACK
                                                 Mode=UNR
                                                 Part=0,Of=1
                                                 Seen=5,
                                                 Send=0,
                                                 Size=0,flow=0008 dg=0000]
	                                         (Start T3-send timer - f8)
[Header Flags=NOB|ACK
   Mode=0
   Part=0,Of=1
   Seen=8,Send=0,Size=0,
   flow=0, dg=0]-------------------------------->(Cancel T3-send timer notification:

 o data - f8)

Note that at the initiate of a flow, the timer started is considered
the first timer for the flow, but it is sent over flow 0. Note also
that location ULP can find the un-delivered datagram.
 o context - optional information associated with this datagram (see
   13.2).

F) Link.Status.Change notification

When a piggyback open link is not allowed if the TAG sequences have not
been exchanged.

7.2 Flow acknowledgments

Normal dataflow's follow the normal marked down (e.g., when MDTP transmission formats (see
section 5) Acknowledgments detects a link failure),
or marked up (e.g., when possible are piggy-backed MDTP detects a link recovery), MDTP shall
invoke this notification on
datagrams.  Each flow maintains its own send timer. When no piggyback
of data and acknowledgments is possible, more than one flow can be be
acknowledged at the same time by using the Flow Extend Acknowledgment
format. ULP.

The Send field (now considered following shall be passed with the number of extended
acknowledgments) will contain notification:

 o link-address - This indicates the number IP address of acknowledgments in the
array.

During data transfer if the when affected link;
 o new-status - This indicates the datagram number reaches 0xffff new status of the next packet should be labeled 1. Pkt 0 link;

G) Communication.Up notification

This notification is never used for datagram
transfer.

One T2-Recv timer is maintained for all flows. If more than one flow
is being timed and when MDTP becomes ready to send or receive
datagrams, or when a datagram is lost communication to an endpoint is restored.

The following shall be transmitted then one of passed with the
flows will be acknowledged notification:

 o status - This indicates what type of event that has occurred;
 o endpoint-id - The IP address and port number to identify the T2-Recv timer will be left running
until expiration, which will then cause
   endpoint;

H) Communication.Lost notification

When MDTP loses communication to an endpoint completely or detects
that the endpoint has performed a shut-down operation, it shall invoke
this notification on the Flow Extended
Acknowledgment to be sent, acknowledging all remaining flows. ULP.

The following examples illustrate examples shall be passed with the notification:

 o status - This indicates what type of flow acknowledgments. For
this example we assume event that Endpoint A has 3 flows open 5,7 and
9. Endpoint Z has 4 flows open 0x11, 8 4 occurred;
 o endpoint-id - The IP address and 1.

Example 1: Endpoint A sends to Endpoint Z T2-Recv timer expires

Endpoint A                                      Endpoint Z
{ App sends first datagram on flow 5}
[Header Flags=NOB|DAT
	Mode=REL
	Part=0,Of=1
        Seen=0x0000 0000,Send=0x0005 0001,Size=20]------>(Start T2-Recv)
(Start T3-send timer-f5)
                                            { T2-Recv Timer Expires }
(Cancel T3-send timer)     <--------------- [Header Flags=NOB|ACK
                                             Mode=REL
                                             Part=0,Of=1
                                             Seen=0x00050001,Send=0x00000000,
                                             Size=0]
	                                     (Start T3-send timer)

Example 1: Endpoint A sends to Endpoint Z T2-Recv timer expires

Endpoint A                                      Endpoint Z
{ App sends first datagram on flow 5}
[Header Flags=NOB|DAT
	Mode=REL
	Part=0,Of=1
        Seen=0x0000 0000,Send=0x0005 0001,Size=20]------>(Start T2-Recv)
(Start T3-send timer-f5)
                                            { T2-Recv Timer Expires }
(Cancel T3-send timer)     <--------------- [Header Flags=NOB|ACK
                                             Mode=REL
                                             Part=0,Of=1
                                             Seen=0x00050001,Send=0x00000000,
                                             Size=0]
                                      (Start T3-send timer)

Example 2: Endpoint A sends multiple messages port number to Endpoint Z identify the
   endpoint;
 o packets-enqueue - The number and
           T2-Recv timer expires

Endpoint A                                      Endpoint Z
{ App sends 1 datagram on flow 5}
[Header Flags=NOB|DAT
	Mode=REL
	Part=0,Of=1
        Seen=0x0000 0000,Send=0x0005 0002,Size=20]------>(Start T2-Recv)
(Start T3-send timer-f5)
{ App sends 1 datagram on flow 9}
[Header Flags=NOB|DAT
	Mode=REL
	Part=0,Of=1
        Seen=0x0000 0000,Send=0x0009 0004,Size=20]------>
(Start T3-send timer-f9)
{ App sends 1 datagram on flow 5}
[Header Flags=NOB|DAT
	Mode=REL
	Part=0,Of=1
        Seen=0x0000 0000,Send=0x0005 0003,Size=20]------>
{ App sends 1 datagram on flow 7}
[Header Flags=NOB|DAT
	Mode=REL
	Part=0,Of=1
        Seen=0x0000 0000,Send=0x0007 0011,Size=20]------>

                                              { T2-Recv Timer Expires }
(Cancel T3-send timer-f5)     <-------------- [Header Flags=NOB|ACK
(Cancel T3-send timer-f9)                      Mode=REL
(Cancel T3-send timer-f7)                      Part=0,Of=1
                                               Seen=0x00050003,
	                                       Send=0x00000002,
                                               Size=0,
	                                       ex[0]=0x00090004,
	                                       ex[1]=0x00070011
                                               ]

Example 3: Endpoint A sends a message to Endpoint Z, Endpoint Z
           piggy-backs a ack.

{ App sends 1 datagram on flow 5}
[Header Flags=NOB|DAT
	Mode=REL
	Part=0,Of=1
        Seen=0x0000 0000,Send=0x0005 0004,Size=20]------>(Start T2-Recv)
(Start T3-send timer-f5)                      { App sends 1 message flow 0x11}
                                              ( cancel T2-Recv Timer )
(Cancel T3-send timer-f5)  <----------------- [Header Flags=NOB|DAT|ACK
(Start T2-Recv timer)                          Mode=REL
                                               Part=0,Of=1
                                               Seen=0x0005 0004,
                                               Send=0x0011 0008,
                                               Size=10]
	                                       (Start T3-send timer-f0x11)
{ T2-Recv Timer Expires }
[Header Flags=NOB|ACK
	Mode=REL
	Part=0,Of=1
        Seen=0x0000 0000,Send=0x0011 0008,Size=0]------>(Cancel T3-send-f0x11)

Example 4: Endpoint A sends location of un-sent datagrams
   still holding by MDTP;
 o last-acked - the sequence number last acked by that peer endpoint;
 o last-sent - the sequence number last sent to that peer endpoint;

I) Change.Link.Rotation primitive

When the upper layer wants to inform MDTP to make a multiple message specific network
eligible or ineligible for in link rotation, the upper layer will send
this primitive to Endpoint Z, Endpoint Z
           piggy-backs MDTP.

Mandatory attributes:

 o  action - This indicates if the network is to be made eligible or
             ineligible for link rotation.
 o  network-id - This is the IP address and port of the network to be
    added or removed from link rotation consideration.

J) Open.Stream primitive

This shall be used by the upper layer to open a ack new stream.

Mandatory attributes:

 o endpoint-id - The IP address and sends port number to identify the
   peer endpoint to which the stream is to be opened. An association
   must have existed at the time of stream open.

Returned attributes:

 o The stream number that is opened.

K) Close.Stream primitive

This shall be used by the upper layer to request to close a Extended flow Ack.

{ App sends 1 datagram on flow 5}
[Header Flags=NOB|DAT
	Mode=REL
	Part=0,Of=1
        Seen=0x0000 0000,Send=0x0005 0005,Size=20]------>(Start T2-Recv)
(Start T3-send timer-f5)
{ App sends 1 datagram stream.

Mandatory attributes:

 o endpoint-id - The IP address and port number to identify the
   peer endpoint to which the stream is to be closed.

 o stream number - The stream number to identify the stream to be
   closed (this should be the number returned by the Stream.Open
   primitive on flow 9}
[Header Flags=NOB|DAT
	Mode=REL
	Part=0,Of=1
        Seen=0x0000 0000,Send=0x0009 0004,Size=20]------>
(Start T3-send timer-f9)
                                           { App sends 1 message flow 0x4}
(Cancel T3-send timer-f5)  <-------------- [Header Flags=NOB|DAT|ACK
(Start T2-Recv timer)                       Mode=REL
                                            Part=0,Of=1
                                            Seen=0x00050005,Send=0x00040004,
                                            Size=10]
	                                    (Start T3-send timer-f0x4)
                                            { T2-Recv this stream).

6. Suggested MDTP Protocol Parameter Values

The following are suggested timer values for MDTP:

T1-init Timer Expires }
	                                    (Start T3-send timer)
(Cancel    -  160 ms
T2-receive Timer -   20 ms
T3-send timer)     <-------------- [Header Flags=NOB|ACK
                                            Mode=REL
                                            Part=0,Of=1
                                            Seen=0x00090004,Send=0x00000000,
                                            Size=0]
{ T2-Recv Timer Expires }
[Header Flags=NOB|ACK
	Mode=REL
	Part=0,Of=1
        Seen=0x0000 0000,Send=0x0004 0004,Size=0]------>(Cancel T3-send-f0x4)

Retransmissions and resends    -  160 ms + Last calculated RTT for that network.

The following protocol parameters are handled per section recommended:

Max.Outstanding.dg      - 20 messages
Max.Retransmit          - 10 attempts
Max.Init.Retransmit     - 8  attempts
Min.Mcast.Time.To.Reset - 5 but using the
flow formats (i.e. the NOB bit set) as described above. seconds
Num.Of.Mcast.Reset.Msg  - 5 messages

7. Acknowledgments

The rules for
retransmission, windowing, flow control authors wish to thank Brian Wyld, A. Sankar, Henry Houh, Gary
Lehecka, Ken Morneault, Lyndon Ong, and declaration of endpoint
death are applied has defined others for their very valuable
comments.

8.  Author's Addresses

Randall R. Stewart                          Tel: +1-847-632-7438
Cellular Infrastructure Group               EMail: stewrtrs@cig.mot.com
Motorola, Inc.
1475 W. Shure Drive, #2C-6
Arlington Heights, IL 60004
USA

Qiaobing Xie                                Tel: +1-847-632-3028
Cellular Infrastructure Group               EMail: xieqb@cig.mot.com
Motorola, Inc.
1501 W. Shure Drive, #2309
Arlington Heights, IL 60004
USA

Tom Bova                                    Tel: +1-703-484-3331
Cisco Systems Inc.                          EMail: tbova@cisco.com
13615 Dulles Technology Drive
Herndon, VA  20171

Suheel Hussain                              Tel: +1-919-472-2312
Cisco Systems Inc.                          EMail:ssh@cisco.com
7025 Kit Creek Road
Research Triangle Park, NC  27709

Ted Krivoruchka                             Tel: +1-703-484-3331
Cisco Systems Inc.                          EMail: tedk@cisco.com
13615 Dulles Technology Drive
Herndon, VA  20171

Renee Revis                                 Tel: +1-703-472-5681
Cisco Systems Inc.                          EMail: drrevis@cisco.com
7025 Kit Creek Road
Research Triangle Park, NC  27709

9. References

[1] Postel, J. (ed.), "Internet Protocol - DARPA Internet Program
Protocol Specification", RFC 791, USC/Information Sciences Institute,
September 1981.

[2] Postel, J., "User Datagram Protocol", RFC 768, USC/Information Sciences
Institute, August 1980.

[3] Postel, J. (ed.), "Transmission Control Protocol", RFC 793, USC/
Information Sciences Institute, September 1981.

[4] Jacobson V., "Congestion Avoidance and Control", Proceedings of
SIGCOMM '88, pp 314-329, August, 1988.

[5] Seth, T., etc. "Performance Requirements for Signaling in section 5.

Note that messages to the different flows are handed up ordered
correctly within the flow but not delayed with respect to any other
flows transmission or retransmission.

7.3 Flow session closing

The application may signal Internet
Telephony", Internet-Draft <draft-seth-sigtran-req-00.txt>, May, 1999.

Appendix A: Stream-based Reliable and Ordered Delivery

This defines a closing of reliable and ordered stream mechanism for MDTP. It is
optional for implementation.

A stream in MDTP is defined as a flow. If this occurs the
implementation will inform its peer sequence of the closing so that resources
used to track and maintain the flow can user datagrams that needs
to be reused/freed. The following reliably delivered with sequence is used to release preservation of its own. In
other words, the delivery of a flow stream shall not be delayed because of
the losses or re-transmissions occurred in this example we see other streams within the closing
of flow 5. Note it
same MDTP association. This capability is up to the sender to assure that all outstanding a critical requirement of
some telephony call signaling protocols [5].

Stream datagrams are acknowledged before closing a flow:

Endpoint A                                      Endpoint Z
{App Initiates flow 5}
[Header Flags=NOB|RES
	Mode=UNR
	Part=0,Of=1
        Seen=0,Send=0,Size=0,
	flow=5, dg=0 ]------>
(Start T3-send timer f-5)
(Cancel T3-send timer f-5) <----------------- [Header Flags=NOB|ACK|RES
                                               Mode=UNR
                                               Part=0,Of=1
                                               Seen=5,Send=0,
                                               Size=0,
                                               flow=0, dg=0]

Datagrams received identified by a endpoint directed setting FLO bit to a closed flow should 1.

A.1 Stream Initiation

First, an MDTP association between the two endpoints must be
silently discarded.

8. Mixed Mode Data Transmission

An endpoint initiated
before any stream operation.

A stream shall be initiated (opened) by the sender before datagrams
can switch between reliable be sent in the stream, and unreliable transfer modes
at any time during after the data transfer. stream is complete it shall
be terminated (closed) by the user. Also, both sides of the
association shall be able to initiate or terminate streams
independently.

The following sequence illustrates such sender initiates a transfer mode change, in
which both endpoints starts with stream by sending a Stream Initiation
(NOB|UNR), using the unreliable transfer mode, and
then Endpoint following header format:

                          Stream Initiation

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 MDTP Protocol Identifier                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Version     |              Flags            |   In Queue    |
   |               |N N W I F R D A M S W R R F G U|               |
   |               |O O I S I T A switches to reliable transfer mode.

Endpoint C U H N E T L A                                  Endpoint Z
                                            {App send 1 message}
                        <------------------ [Header Flags=DAT|ACK
                                             Mode=UNR
                                             Part=0,Of=1
                                             Seen=11201,Send=1,Size=450]
..
{App send 1 message}
[Header Flags=DAT|ACK
	Mode=UNR
	Part=0,Of=1
        Seen=451,Send=11201,Size=100]------>

..
{App send 1 message}
[Header Flags=DAT|ACK
	Mode=GAR
	Part=0,Of=1
        Seen=451,Send=11301,Size=100]------> (Start T2-receive timer)
(Start T3-send timer)
                                             {App sends 1 message}
                                             (Cancel T2-receive timer)
                                    /------- [Header Flags=DAT|ACK
                                   /         Mode=UNR
                                  /          Part=0,Of=1
                                 /           Seen=11401,Send=1,Size=450]
(Cancel T3-send timer)  <-------/

..
{App sends N|               |
   |               |M B N B R M T K L U R 1 message}
[Header Flags=DAT|ACK
	Mode=GAR
	Part=0,Of=1
        Seen=451,Send=11401,Size=100]------> (Start T2-receive timer)
(Start T3-send timer)

                                             ..
                                             {Timer T2 Expires}
(Cancel T3-send timer)  <------------------- [Header Flags=ACK
                                              Mode=0
                                              Part=0,Of=0
                                              Seen=11501,Send=146] C O R R|               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         Seen = 0x0 (or Tag)                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           Send = 0x0                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        Data Size              |    Part       |      Of       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        New Stream Number      |              0x0              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Note that in the second datagram sent by Endpoint A the mode is
switched to reliable transfer mode (with GAR bit set). This causes
Endpoint A to start its T3-send timer. When Endpoint Z receives the
datagram and realizes the mode change, it starts its T2-receive timer.
At this point, Endpoint Z also must update its Seen value to 11301.
This will allow Endpoint Z to align its Seen counter
to Stream Initiation, the Seen value of this first reliable datagram from Endpoint
A. This prevents Endpoint Z from requesting retransmission of data
that Endpoint A may not have.

9.  Bundled Messages

In order to increase network utilization, MDTP allows an endpoint to
bundle small application messages into one single datagram for
transmission. This bundled mode can be applied to both reliable and
unreliable datagrams.

An endpoint indicates Send shall be set to its peer that it is currently in bundled

mode by setting 0,
and the BUN bit number of the new stream being initiated shall be indicated
in the mode field.

9.1 Format first two octets of Bundled Datagram

The ISB bit in the flag field data field.

However, if this is the first datagram sent out after receiving the
Initiation Ack from the peer (see section 3.1), the Seen field of
above Stream Initiation shall be set to indicate the current datagram is
bundled, i.e., it contains multiple messages. The format Tag value carried in the
Initiation Ack.

Upon the reception of the Stream Initiation, the peer shall respond
immediately with a bundled
datagram is defined as follow: Stream Initiation Ack (NOB|UNR|ACK), using the
following header format:

                        Stream Initiation Ack

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 MDTP Protocol Identifier 1                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 MDTP Protocol Identifier 2                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 Acknowledgment Number (Seen)                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Sequence Number (Send)                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        Data Size              |    Part       |      Of       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   Version     |              Flags            |     Mode      |   Version     | Num On   In Queue    |
   |               |N N W I F R D A|B A M S W R R B F G U|               |
   |               |O O I S I E A C|R H N E E U A N|               |               |
   |G B N B R S T K|O A C U R 1 2 H N R R|               |               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Number Of Messages        |   Size of first message B1    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                     B1 octets of data                         |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Size of second message B2  |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
   |                     B2 octets of data                         |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   \                                                               \
   /                                                               /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Size of last message BL    |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
   |                     BL octets of data                         |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Data Size in a bundled datagram indicates the actually size of the
data field of the datagram, including both the bundling overhead and
the actually application data. Since no fragmentation is allowed in a
bundled datagram, the E T L A N|               |
   |               |M B N B R M T K L U R 1 C O R R|               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Seen = Stream Number                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           Send = 0x0                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        Data Size              |    Part field will always be '0' and the       |      Of field
always be '1'.       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

The first two octets of the data field is a 16 bit integer indicating following example shows the number opening of messages bundled in the datagram. This is followed
immediately stream 5 by a list of bundled messages. Each bundled message starts
with "A":

Endpoint A                                      Endpoint Z
{App Initiates stream 5}
[Header Flags=FLO|UNR
        Part=0,Of=1
        Seen=0,Send=0,Size=0,
        Stream=5 ]--------------------------->
(Start T3-send timer)
(Cancel T3-send timer) <--------------------- [Header Flags=FLO|UNR|ACK
                                               Mode=UNR
                                               Part=0,Of=1
                                               Seen=5,Send=0]

A.2 Stream Termination

For an integer of two octets indicating the size of the data in the
message, followed by the data itself.

All integers in the datagram should existing stream, either side shall be transmitted in the network byte
order.

9.2 Bundled Transfer

Two protocol parameters, namely the Min.Bundle and Max.Bundle, are
used allowed to control the assembly of bundled datagrams. If terminate the current size
of
stream by sending a bundled datagram is smaller than Min.Bundle, the endpoint will
withhold the datagram from transmission and start T4-bundle timer. If
new out-bound data becomes available for transmission, the endpoint
will attempt Stream Termination (FLO|UNR|SHU) to bundle the new data with the current withheld datagram
by using the following rules:

A) If the size of the new data is greater than or equal to
   Min.Bundle, other side.

Besides flag RES, The Stream Termination shall use the current withheld same header
format as that used in Stream Initiation datagram will be transmitted and
   T4-bundle timer will be canceled. Then, the new data will (see A.2)

A Stream Termination Ack (FLO|UNR|SHU|ACK) shall be
   transmitted sent by the peer
endpoint in a separate datagram.

B) If response.

The following example shows the size termination of the new data stream 5 by "A":

Endpoint A                                      Endpoint Z
{App terminates stream 5}
[Header Flags=FLO|UNR|SHU
        Part=0,Of=1
        Seen=0,Send=0,Size=0,
        Stream=5 ]--------------------->
(Start T3-send timer s-5)
(Cancel T3-send timer s-5) <------------ [Header Flags=FLO|UNR|SHU|ACK
                                          Part=0,Of=1
                                          Seen=5,Send=0]

Datagrams associated to a terminated stream received by either side
should be silently discarded. It is less than Min.Bundle, but the
   combined size of up to the current datagram and side which terminates
the new data is greater
   than or equal stream to Max.Bundle, assure that all outstanding user datagrams in the current datagram will be sent and stream
are acknowledged before the new termination.

A.3 Stream Datagram Transfer

A.3.1 Header Format in Stream Datagrams with User Data

The MDTP header in a stream datagram with user data will be withheld as the new current datagram.

C) If the size of shall have the new
following format:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  MDTP Protocol Identifier                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Version     |              Flags            |   In Queue    |
   |               |N N W I F R D A M S W R R F G U|               |
   |               |O O I S I T A C U H N E T L A N|               |
   |               |M B N B R M T K L U R 1 C O R R|               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Seen                              |
   |         Stream Number         |    Sequence Number            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Send                              |
   |         Stream Number         |    Sequence Number            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        Data Size              |    Part       |      Of       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   \                                                               \
   /                             data is less than Min.Bundle, and the
   combined size of the current datagram                              /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

The stream number and sequence number in the new data is less than
   Max.Bundle, the new data will Send field shall be bundled into used
by the sender to identify the current
   datagram stream datagram. And, the
stream number and sequence number in the bundled datagram will Seen field shall be immediately transmitted.

D) If used
by the size sender to acknowledgment of the new data is less than Min.Bundle, stream datagrams it has received.

Stream number 0 and the
   combined size sequence number 0 are reserved for special
purposes and are not valid stream number or sequence number.

A.3.2 Transmission of Stream Datagrams

The rules of using the current datagram Seen Sequence Number and Send Sequence Number
are similar to those defined for normal MDTP non-stream datagram
transmissions (see section 4), except that for stream transfer the new data is less than
   Min.Bundle, the new data will be bundled into the current
   datagram. And the T4-bundle timer will be restarted.

E) If T4-bundle
sequence numbers shall roll-over to 1 after 0xFFFF.

Moreover, each stream maintains its individual T3-send timer, but only
one global T2-receive timer expires, the current is maintained for all existing streams.

Acknowledgment to a stream datagram will shall either be sent
   immediately.

F) If the size of separately
or be piggy-backed with a stream datagram (not necessarily belonging
to the new data is greater than same stream) traveling in the Max.Bundle, opposite direction. For a
separate Stream Ack, the
   current datagram Send field will be sent. Then, the new set to 0000:0000.

The following shows an example of transmitting a stream datagram
(FLO|REL|DAT) and a separate Stream Ack (FLO|REL|ACK):

Endpoint A                                      Endpoint Z
{App sends first data will be fragmented
   for transmission (see 9). on stream 5}
[Header Flags=FLO|REL|DAT
        Part=0,Of=1
        Seen=0-0,Send=5-1,Size=20]----\
(Start T3-send timer-s5)               \--->(Start T2-recv)
                                            ...
                                            {T2-recv Timer Expires}
(Cancel T3-send timer-s5)   <--------------- [Header Flags=FLO|REL|ACK
                                             Part=0,Of=1
                                             Seen=5-1,Send=0-0,Size=0]

The following is an example shows the use of bundled data transfer, assuming
Max.Bundle=4096 and Min.Bundle=1700:

Endpoint A                                      Endpoint Z

{App sends 1 messages of 100 octets}
(withhold and Start T4-Bundle timer)

.. a piggy-backed Stream Ack.

{App sends 1 messages of 100 octets}
(bundling into current datagram)

.. new data on stream 5}
[Header Flags=FLO|REL|DAT
        Part=0,Of=1
        Seen=0-0,Send=5-4,Size=20]--------->(Start T2-recv)
(Start T3-send timer-s5)                    ...
                                            {App sends 1 messages of 100 octets}
(bundling into current datagram)

..
{T4-bundle timer expires} data on stream 11}
                                            (cancel T2-recv Timer)
                                     /----- [Header Flags=DAT|ACK
	Mode=GAR|BUN Flags=FLO|REL|DAT|ACK
                                    /        Part=0,Of=1
        Seen=146,Send=1001,Size=308]-------->
                                   /         Seen=5-4,Send=11-8,Size=10]
                                  /         (Start T2-receive T3-send timer-s11)
(Cancel T3-send timer-s5)  <-----/
(Start T2-recv timer)
(T3-send timer starts)
                                              ..
                                              {Timer T2
...
{T2-recv Timer Expires}
(cancel T3-send)            <----------------
[Header Flags=ACK
                                               Mode=0
                                               Part=0,Of=0
                                               Seen=1309,Send=146]

Notice Flags=FLO|REL|ACK
        Part=0,Of=1
        Seen=11-8,Send=0-0,Size=0]--------->(Cancel T3-send-s11)

Note that when piggy-back a Stream Ack with an out-bound stream
datagram when more than one streams have un-acked datagrams, the
endpoint shall choose one stream and piggy-back a Stream Ack on one of
the datagrams, and shall leave the T2-recv timer running.

A.3.3 Extended Stream Ack

Upon the expiration of T2-recv timer, if there are more than one
stream datagrams received but yet acked upon by the endpoint, an
Extended Stream Ack shall be used.

The following defines the header format of the Extended Stream Ack
that acknowledges N stream datagrams received:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  MDTP Protocol Identifier                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Version     |              Flags            |   In Queue    |
   |               |N N W I F R D A M S W R R F G U|               |
   |               |O O I S I T A C U H N E T L A N|               |
   |               |M B N B R M T K L U R 1 C O R R|               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Seen                              |
   |         Stream Number #0      |    Sequence Number #0         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  Number of Extra Acks = N-1                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        Data Size in the datagram sent by Endpoint A is not
300 but 308. This is due to the fact              |    Part       |      Of       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Stream Number #1      |    Sequence Number #1         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   \                                                               /
   /                                                               \
   \                                                               /
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Stream Number #N-1    |    Sequence Number #N-1       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Note that this size reflects the
size of an Extended Stream Ack is identified by setting the data Seen
field of the datagram including the bundling overhead.

When the bundled datagram arrives at the receiving endpoint, each
message is unbundled and delivered separately to the upper level
application.

10. Fragmented Messages

When the size of an out-bound message exceeds the value defined in the
protocol parameter Max.Bundle, the endpoint will fragment the message
into smaller pieces number of sizes equal to or smaller than Max.Bundle and
send each piece out extra acks carried in a separate datagram.

The Part and Of fields are used to disassemble and reassemble the
fragmented message. its data field, as shown
above. Also, Extended Stream Acks shall not be piggy-backed.

The following example shows the transmission using of a fragmented message
(assuming Max.Bundle=4096, Min.Bundle=1700): an Extended Stream Ack
(NOB|REL|ACK) by "Z":

Endpoint A                                      Endpoint Z
{App sends 1 messages 8544 octets long} data on stream 5}
[Header Flags=DAT|ACK
	Mode=GAR|BUN
	Part=0,Of=3
        Seen=146,Send=1001,Size=4072]-------> Flags=FLO|REL|DAT
        Part=0,Of=1
        Seen=0-0,Send=5-2,Size=20]----------> (Start T2-receive timer) T2-recv)
(Start T3-send timer-s5)
{App sends data on stream 9}
[Header Flags=DAT|ACK
	Mode=GAR|BUN
	Part=1,Of=3
        Seen=146,Send=5073,Size=4072]-------> Flags=FLO|REL|DAT
        Part=0,Of=1
        Seen=0-0,Send=9-4,Size=20]---------->
(Start T3-send timer-s9)
{App sends more data on stream 5}
[Header Flags=DAT|ACK
	Mode=GAR|BUN
	Part=2,Of=3
        Seen=146,Send=9145,Size=400]--------> Flags=FLO|REL|DAT
        Part=0,Of=1
        Seen=0-0,Send=5-3,Size=20]---------->
(Restart T3-send timer-s5)
{App sends data on stream 7}
[Header Flags=FLO|REL|DAT
        Part=0,Of=1
        Seen=0-0,Send=7-11,Size=20]--------->
(Start T3-send timer)
                                              ..
                                              {Timer T2 timer-s7)
                                              ...
                                              {T2-recv Timer Expires}
                                 /-----------
(Cancel T3-send timer-s5)     <-------------- [Header Flags=ACK
                                /              Mode=0
                               /               Part=0,Of=0
(cancel timer T3) <-----------/                Seen=9545,Send=146]

Notice that Endpoint A is using the reliable transfer mode to send the
fragmented message. In this mode, Endpoint Z will hold Flags=FLO|REL|ACK
(Cancel T3-send timer-s7)                      Part=0,Of=1
(Cancel T3-send timer-s9)                      Seen=5-3,NumExtAck=2,
                                               Size=0,
                                               ext[0]=9-4,
                                               ext[1]=7-11]

A.4 Other Issues with Stream Transfer

- -- Congestion control, including the fragments rules for timer management and request retransmission if a fragment is found missing, i.e., a gap
is found in window
management, shall apply to Stream Transfer the received data (see 5). same way as it does to
non-Stream based transfer, as defined in section 4.3.

- -- When an association is re-initialized (see section 3.4), all the parts of the
fragmented message are received, the endpoint existing
stream within that association will re-assemble the
message be automatically terminated.

- -- The receiver shall silently discard any datagrams associated
with a stream which has not been initiated or has already been
terminated.

- -- The same re-transmission and dispatch it to the upper level application.

It is also allowed link rotation rules as defined in MDTP
section 4 shall apply to send fragmented message using unreliable
transfer mode. However, Stream Transfer.

- -- Bundled Message (see Appendix B) may be allowed in unreliable mode, each fragment datagram
will Stream Transfer,
but fragmentation (see Appendix C) shall not be dispatch to allowed.

Appendix B: Bundled Message Transfer

This defines the application upon its arrival, and no
retransmission will be requested even if a fragment mechanism for bundled datagram transport in MDTP. It
is found missing. optional for implementation.

Bundling is prohibited if sometimes desired by the current datagram contains user when transferring small
datagrams, as a fragment way of
a fragmented message.

11. Non-protocol Datagrams

The improving network utilization.

In bundled transfer, MDTP protocol allows an endpoint to send bundle small
application messages into one single datagram for transmission. This
bundled mode can be applied to both reliable and receive non-protocol
datagrams such as the traditional UDP datagrams. Non-protocol unreliable datagrams are detected by the absence of the MDTP protocol
identifiers at the beginning of the datagram. A non-protocol
transmission received by
(see Appendix E for Unreliable Delivery).

Note that an MDTP endpoint is termed as a "raw"
datagram. When shall never send bundled messages to a raw datagram arrives, the receiving peer if
that peer endpoint will set
itself into raw mode and start sending back NOB bit to its peer 1 during their association
initialization (see section 3).

B.1 Format of Bundled Datagram

The ISB bit in raw mode
as well.

Once an endpoint the flag field is in raw mode with a peer, only a change of
operational mode by set to indicate the application or a reception current datagram
is bundled, i.e., it contains multiple messages. The format of a MDTP
bundled datagram
will bring the endpoint out is defined as follows:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  MDTP Protocol Identifier                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Version     |              Flags            |   In Queue    |
   |               |N N W I F R D A M S W R R F G U|               |
   |               |O O I S I T A C U H N E T L A N|               |
   |               |M B N B R M T K L U R 1 C O R R|               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 Acknowledgment Number (Seen)                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Sequence Number (Send)                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        Data Size              |    Part       |      Of       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Total Number Of Messages=N   |   Message #1 Size = B1        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                     B1 octets of data                         |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Message #2 Size = B2        |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
   |                     B2 octets of data                         |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   \                                                               \
   /                                                               /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Message #N Size = BN        |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
   |                     BN octets of raw mode. In the latter case, the

endpoint will use the default MDTP operational mode predefined by the
application for MDTP transmissions. When an endpoint changes from raw
mode into MDTP mode, the normal MDTP initiation messages must be
exchanged between the two endpoints, as described data                         |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Data_Size in 4.

12. Broadcast and Multicast

Broadcast and multicast are supported by MDTP when a bundled datagram indicates the underlying
transport layer supports them. Both types actually size of transmissions are carried
out in unreliable transfer mode.

For broadcast datagrams, the BRO bit will be set to '1' and the UNR
bit will be set to '0' in the mode field. For multicast datagrams,
both the BRO bit and the UNR bit will be set to '1'.

For multicast datagrams, the value in the Send
data field will indicate
the number of multicast datagrams transmitted by the sender. This
information makes it possible for the receiver of the multicast to
detect duplicated multicast datagrams and also to detect lost
multicast datagrams. A multicast datagram transmission MUST use
the alternate multicast header filling in datagram, including both the multicast transmit
to address as well as its lowest network address in the multicast
from address.

Bundling bundling overhead and fragmentation are not allowed in either multicast or
broadcast datagrams.

12.1 Multicast/Broadcast initialization.

No initiation is needed for an endpoint to transmit multicast or
broadcast datagrams. However, caution should be taken when
transmitting non-protocol datagrams (i.e., datagrams with
the actually user data. Since no MDTP
protocol header) in multicast or broadcast transmission. This fragmentation is
because the non-protocol datagrams may inadvertently force all the
receiving endpoints of the multicast or broadcast transmission into
raw mode (see 10).

12.2 Transmission of Broadcast Datagrams.

When sending allowed in a broadcast bundled
datagram, the endpoint Part field will not take effort
to prevent duplicate transmissions (this is likely to occur
especially when multiple networks exist). The application at always be '0' and the
receiving end must Of field always be prepared to handle duplicate
broadcast messages.
'1'.

The following first two octets of the data field is an example a 16 bit integer indicating
the number of broadcast datagram transmission:

Endpoint A                                               Endpoint Z
{application sends 2 messages }
[Header Flags=DAT
	Mode=BRO
	Part=0,Of=1
        Seen=0,Send=0,Size=200]--------------> (Datagram may appear
                                                more than once.)
[Header Flags=DAT
	Mode=BRO
	Part=0,Of=1
        Seen=0,Send=0,Size=100]-------------->

Notice that no timers are used on either end, and Seen and Send values bundled in the datagrams are always '0'.

12.3 Transmission current datagram. This is
followed immediately by a list of Multicast Datagrams.

Unlike bundled messages. Each bundled
message starts with an integer of two octets indicating the broadcast transmission, when multicast datagrams are
transmitted size of
the receiving endpoints data in the message, followed by the data itself.

All integers in the datagram should take effort be transmitted in the network byte
order.

B.2 Bundled Datagram Transfer

The T4-bundling timer and two protocol parameters, namely the
Min.Bundle and Max.Bundle, are used to prevent
duplicate copies control the bundling of datagrams from being distributed to their
applications.

This is possible because user
datagrams.

The endpoint will withhold the datagram from transmission and start
T4-bundle timer, if the combined size of multicast all user datagrams is
usually addressed to a special multicast network address. The receiving
endpoints can thus use this multicast address currently
pending for transmission in combination with the
sender's address to detect duplicate transmissions of a multicast
datagram.

The following example illustrates multicast transmissions between two
endpoints.

Endpoint A                                               Endpoint Z
{app multicasts a message}
[Header Flags=DAT
	Mode=BRO|UNR
	Part=0,Of=1
        Seen=0,Send=5,Size=250]--------------> (may receive more out-bound buffer is smaller than one copy)
..

{app multicasts
'Min.Bundle'.

Each time a message}
[Header Flags=DAT
	Mode=BRO|UNR
	Part=0,Of=1
        Seen=0,Send=6,Size=500]--------------> (may receive more
                                                than one copy)

Notice new out-bound user data becomes available for
transmission, the values endpoint will attempt to bundle the new data with
the current withheld datagram by using the following rules:

A) If the size of the Send field in new data is greater than or equal to
   'Min.Bundle', the multicast datagrams (which
are 5 current withheld datagram will be transmitted and 6, respectively). They represent
   T4-bundle timer will be canceled. Then, the sequence numbers new data will be
   transmitted in a separate datagram.

B) If the size of the
multicast datagrams Endpoint A has sent out. Endpoint Z should use new data is less than 'Min.Bundle', but the

Send value found in
   combined size of the incoming multicast datagrams to detect any
missing current datagram and the new data is greater
   than or duplicate datagrams.

Duplicate datagrams equal to 'Max.Bundle', the current datagram will be discarded sent and no effort
   the new data will be made to
retransmit lost multicast datagrams.

For example, each endpoint can track withheld as the last 32 datagrams received by
using a sliding window new current datagram.

C) If the size of 32 bits. Each time a the new datagram with a
sequence number higher data is less than 'Min.Bundle', and the
   combined size of the current window head datagram and the new data is received, greater
   than 'Min.Bundle', but less than 'Max.Bundle', the
window can new data will be moved up. If a datagram received has a sequence number
below
   bundled into the current window head, then a check of datagram and the last 32 received
datagrams' sequence numbers can determine whether bundled datagram will be
   immediately transmitted. and T4-bundle timer will be canceled.

D) If the size of the new datagram data is a
duplicate. If less than 'Min.Bundle', and the sequence number
   combined size of the new current datagram and the new data is below less than
   Min.Bundle, the new data will be bundled into the current window tail then
   datagram. And the T4-bundle timer will be restarted.

E) If T4-bundle timer expires, the current datagram will be sent
   immediately.

F) When a T2-receive timer expires, any bundled data waiting to be
   transmitted should be considered sent immediately with a duplicate
and discarded.

12.4 Reset of the Multicast Datagram Sequence Number piggy-backed Ack to
   acknowledge all un-acked data previously received.

G) If the Seen field in a multicast datagram T4-bundle timer is set to '1', running and data arrives, the T2-receive
   timer should not be started.

H) A T4-bundle timer should never be canceled unless it is an
indication that the sender has reset its multicast being
   supplanted by a T3-send timer.

When a bundled datagram sequence
number. The arrives at the receiving endpoint, upon detecting this reset indicator in
the incoming multicast datagram, should start a procedure to adopt the
new sequence number for error detection. However, caution
should be taken to prevent false resets due each
message is unbundled and delivered separately to duplicated datagrams
with reset indicator propagating through multiple networks.

To guarantee that all receivers of the multicast group adopt upper layer.

The following are the new
sequence number, suggested protocol parameter values for bundled
datagram transfer:

T4-bundle Timer  -   40 ms
Min.Bundle       - 1000 octets
Max.Bundle       - 1432 octets

Appendix C: Fragmented Message Transfer

This defines the reset indicator should be repeated within mechanism for fragmented datagram transport in
MDTP. It is optional for implementation.

When the
first N multicast datagrams sent out after size of an out-bound user message exceeds the reset. N is predefined
by value defined
in the protocol parameter Num.Of.Mcast.Reset.Msg.

At Max.Bundle, the receiving endpoint, when endpoint shall fragment the reset indicator
message into smaller pieces of size equal to or smaller than
'Max.Bundle' and send each piece out in a separate datagram.

The "Part" and "Of" fields are used to disassemble and reassemble the
fragmented message. The combination of the maximal 'Of' value, which
is detected 255, and the
new sequence number maximal Data Size (see section 2.2) will be adopted. determined
the maximal size of a single user message that the MDTP can send or
receive in fragmented message transfer mode.

However, if two reset events are
detected within an endoint shall never send fragmented datagrams to a predefined time interval (Min.Mcast.Time.To.Reset), peer if
that peer set the second reset indicator will be ignored. NOM bit to 1 during their association
initialization.

The following is an example shows the transmission of a fragmented message
(assuming Num.Of.Mcast.Reset.Msg = 4): Max.Bundle=1432, Min.Bundle=1000):

Endpoint A                                      Endpoint Z

[Header Flags=DAT
	Mode=BRO|UNR
	Part=0,Of=1
        Seen=0,Send=17859,Size=300]---------->
`<
{reset
{App sends message sequence number indicated}

[Header Flags=DAT
	Mode=BRO|UNR
	Part=0,Of=1
        Seen=1,Send=1,Size=250]--------------> (record new sequence
                                                number, datagram may
                                                appear more than once) size=3300 octets}
[Header Flags=DAT
	Mode=BRO|UNR
	Part=0,Of=1
        Seen=1,Send=2,Size=250]--------------> (may appear more than
                                                once) Flags=DAT|ACK|GAR
        Part=0,Of=3
        Seen=3,Send=16,Size=1432]-------> (Start T2-receive timer)
[Header Flags=DAT
	Mode=BRO|UNR
	Part=0,Of=1
        Seen=1,Send=3,Size=500]--------------> (may appear more than
                                                once) Flags=DAT|ACK|GAR
        Part=1,Of=3
        Seen=3,Send=17,Size=1432]------->
[Header Flags=DAT
	Mode=BRO|UNR
	Part=0,Of=1
        Seen=1,Send=4,Size=500]--------------> (may appear more than
                                                once) Flags=DAT|ACK|GAR
        Part=2,Of=3
        Seen=3,Send=18,Size=436]-------->
(Start T3-send timer)
                                              ..
                                              {Timer T2 Expires}
                                 /----------- [Header Flags=DAT
	Mode=BRO|UNR
	Part=0,Of=1
        Seen=0,Send=5,Size=100]--------------> (may appear more than
                                                once)

In Flags=ACK
                                /              Mode=0
                               /               Part=0,Of=0
(cancel timer T3) <-----------/                Seen=18,Send=4]

Notice that "A" is using the above example Endpoint Z would detect reliable transfer mode to send the reset indicator in
fragmented message, therefore "Z" will hold the second multicast datagram fragments and adopt request
retransmission if a fragment is found missing, i.e., if a gap is found
in the received data (see ). When all the parts of the fragmented
message are received, the receiving endpoint will re-assemble the new sequence number which
is 1. Then,
message and dispatch it would ignore the reset indicator in to the subsequent three
(3) datagrams since they arrived within a very short time interval.

13. Interface with upper level protocols

The upper level protocols (ULP) shall request for services by passing
primitives to MDTP and shall receive notifications from MDTP for
various events.

The primitives and notifications described layer.

It is also allowed in this MDTP to send fragmented message using Unreliable
Transfer mode (see section should 4.5). However, in unreliable mode, each
fragment will be

used as a guideline for implementing MDTP.

13.1 Init.MDTP primitive

This primitive allows MDTP dispatch to initialize the application upon its internal data structures arrival, and allocate necessary resources for setting up its operation
environment. Note that once MDTP no
retransmission will be requested even if a fragment is initialized, ULP can communicate
directly with any other endpoints without re-invoking this primitive.

Mandatory attributes:

None.

Optional attributes:

The following types found missing.

Bundling is prohibited if the current datagram contains a fragment of attributes may be passed along with
a fragmented message.

Appendix D: Multicast Datagram Transfer

This defines the primitive:

 o Timer selection mechanism for unreliable transportation of multicast
datagrams in MDTP. It is optional for implementation.

D.1 Multicast Datagram Header Format

Multicast datagrams are identified by setting MUL, UNR, and its operation syntax -- DAT bits
to indicate 1.

Two new fields are added to MDTP
   an alternative timer the standard MDTP should use for its operation.
 o Initial MDTP operation mode;
 o IP port number, if ULP wants it to be specified;

13.2 Send.Data primitive

This is the main method datagram header to send datagrams via MDTP.

Mandatory attributes:

 o data
support multicast:

Multicast To Transmit address - This is the payload ULP wants to transmit;
 o size - The size of the payload multicast address, in number of octets;
 o to-address -
network byte order, that the sender transmitted the data to. The IP
receiver can use this information for internal tracking purposes.

Multicast From - This is the network address and port number of (or the intended
   receiver. In case IP Address of
Network 1 as described in 3.2, if redundant networks, to-address can be any one
   of the multiple IP addresses networks exist) of the receiver. The
sender, in network which the
   datagram will actually be sent through will be determined by byte order.

                 MDTP due
   to the link rotation, unless the current mode prohibits Header Format - Multicast Format

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  MDTP link
   rotation; Protocol Identifier                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Version     |              Flags            |   In Queue    |
   |               |N N W I F R D A M S W R R F G U|               |
   |               |O O I S I T A C U H N E T L A N|               |
   |               |M B N B R M T K L U R 1 C O R R|               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 Acknowledgment Number (Seen)                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Sequence Number (Send)                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        Data Size              |    Part       |      Of       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  Multicast To Transmit address                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             Multicast From - senders base address             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   \                                                               \
   /                             data                              /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

For multicast datagrams, the value in such case the datagram will be sent through Send field shall indicate
the network
   specified sequence number of multicast datagrams transmitted by to-address (see section 4.5).

Optional attributes:

 o mode-flags - This indicates a new MDTP operation mode, taking effect
   immediately including the current datagram send;

 o context - optional
sender. This information that will be carried in helps the
   Send.Failure notification receiver of the multicast to detect
duplicated multicast datagrams and also to detect lost multicast
datagrams from the ULP if same sender. The Seen field shall normally be
set to 0, unless in some special cases stated below.

Bundling and fragmentation are not allowed in either multicast or
broadcast datagrams.

No initiation shall be needed for an endpoint to transmit to a
multicast address.

D.2 Transmission of Multicast Datagrams

The following example illustrates multicast transmissions between two
endpoints.

Endpoint A                                               Endpoint Z
{App multicasts a message}
[Header Flags=MUL|UNR|DAT
        Part=0,Of=1
        Seen=0,Send=5,Size=250]--------------> (no Ack necessary)

...
{App multicasts a message}
[Header Flags=MUL|UNR|DAT
        Part=0,Of=1
        Seen=0,Send=6,Size=500]--------------> (no Ack necessary)

Notice that the transportation values of
   this datagram fails.

13.3 Receive.Data primitive

This primitive shall return the first datagram Send field in the MDTP in-queue to
ULP, if there is one available. It may, depending on multicast datagrams
(which are 5 and 6, respectively). They represent the specific
implementation, also return other informations such as sequence numbers
of the sender's

address, whether there are more multicast datagrams available for retrieval,
etc. The behavior is undefined if no datagram is available when "A" has sent out. Endpoint Z should use
this
primitive is invoked.

Mandatory attributes:

 o buffer - the memory location indicated by the ULP value to detect missing or duplicate datagrams.

Duplicate datagrams will be discarded and no effort will be made to store
retransmit lost multicast datagrams.

D.3 Reset of the
   received datagram and other information.

Optional attributes:

   None.

13.4 Data.Arrive notification

MDTP shall invoke this notification on Multicast Datagram Sequence Number

If the ULP when Seen field of a datagram is
successfully received and ready for retrieval.

13.5 Send.Failure notification

If a multicast datagram can not be delivered MDTP shall invoke equals to '1', this notification
on
indicates that the ULP. sender has reset its multicast datagram sequence
number. The following may receiving endpoint, upon detecting this reset indicator in
the incoming multicast datagram, should start a procedure to adopt the
new sequence number for error detection. However, caution
should be optionally passed taken to prevent false resets due to duplicated datagrams
with reset indicator propagating through multiple networks.

To guarantee that all receivers of the notification:

 o data - multicast group adopt the location ULP can find new
sequence number, the un-delivered datagram.
 o context - optional information associated with this datagram (see
   13.2).

13.5 Link.Status.Change notification

When a link reset indicator should be repeated within the
first N multicast datagrams sent out after the reset. N is marked down (e.g., when MDTP detects a link failure),
or marked up (r.g., predefined
by the protocol parameter 'Num.Of.Mcast.Reset.Msg'.

At the receiving endpoint, when MDTP detects a link recovery), MDTP shall
invoke this notification on the ULP.

The following shall reset indicator is detected the
new sequence number will be passed with adopted. However, if two reset events are
detected within a predefined time interval (Min.Mcast.Time.To.Reset),
the notification:

 o link-address second reset indicator will be ignored.

The suggested values for these two protocol parameters are:
   Min.Mcast.Time.To.Reset - 5 seconds
   Num.Of.Mcast.Reset.Msg  - 5 messages

Appendix E: Unreliable Delivery

This indicates defines the IP address of support for sending Unreliable datagrams in MDTP.  It
is optional for implementation.

The unreliable transfer mode allows two endpoints to send to each
other without acknowledging the affected link;
 o new-status - receiving. This indicates can usually achieve
higher data throughput than the new status of reliable transfer mode. To indicate
the link;

13.6 Communication.Lost notification

When MDTP loses communication to an endpoint completely or detects
that unreliable transfer mode the endpoint has performed sender of a shut-down operation, it shall invoke
this notification on datagram with user data
simply sets the ULP. UNR flag to 1. The following sequence illustrates
unreliable data transfer.

Endpoint A                                      Endpoint Z
{App sends 2 messages}
[Header Flags=UNR|DAT|ACK
        Part=0,Of=1
        Seen=0,Send=4,Size=100]-------->
[Header Flags=UNR|DAT|ACK
        Part=0,Of=1
        Seen=0,Send=5,Size=100]-------->

                                             {App sends 1 message}
                                   <------- [Header Flags=UNR|DAT|ACK
                                             Part=0,Of=1
                                             Seen=5,Send=1,Size=450]
...
{App sends 2 more messages}
[Header Flags=UNR|DAT|ACK
        Part=0,Of=1
        Seen=1,Send=6,Size=100]------>

[Header Flags=UNR|DAT|ACK
        Part=0,Of=1
        Seen=451,Send=7,Size=100]------>

Note that no timers shall be passed with started by either end, and that even
though both ends are in Unreliable transfer mode, the notification:

 o status - This indicates what type ACK flag is
still set by the sender of event the datagram. This means that has occurred;
 o endpoint-id - The IP address and port number the Seen
field in the datagram header is still valid to identify indicating the
   endpoint;
 o packets-enqueue - The sequence
number and location of un-sent datagrams
   still holding the last datagram received by MDTP;
 o last-acked - the sequence number last acked sender.  The upper layer
can use this information to help detecting missing or duplicated
datagrams. However, MDTP shall make no effort to detect or retransmit
missing data or to screen out duplicated datagrams.

E.1 Ordered Unreliable Delivery

In unreliable transfer, the sender should be allowed to request
ordered delivery by that peer endpoint;
 o last-sent - setting the RE1 flag to 1.

When Ordered Unreliable Delivery is indicated, the receiver shall
order the newly arrived datagram with any datagrams it has received
but yet passed to its upper layer.

If it receives a datagram which is older than the sequence number last sent datagram it has
passed to the upper layer, that peer endpoint;

14. Suggested timer and MTU values.

The following are suggested timer values for MDTP:

T1-init Timer    -  160 ms
T2-receive Timer -   20 ms
T3-send Timer    -  160 ms
T4-bundle Timer  -   40 ms
T5-Heart Beat    - 4000 ms

The following protocol parameters are recommended:

Min.Bundle              - 1000 octets
Max.Bundle              - 1432 octets
Max.Retransmit          - 10 attempts
Max.Init.Retransmit     - 8  attempts
Min.Mcast.Time.To.Reset - 5 seconds
Num.Of.Mcast.Reset.Msg  - 5 messages

15. Acknowledgments

The authors wish to thank Brian Wyld, Sankar A, Henry Houh, Gary
Lehecka, Ken Morneault, Lyndon Ong, and others for their very valuable
comments.

16.  Author's Addresses

Randall R. Stewart                          Tel: +1-847-632-7438
Cellular Infrastructure Group               EMail: stewrtrs@cig.mot.com
Motorola, Inc.
1475 W. Shure Drive, #2C-6
Arlington Heights, IL 60004
USA

Qiaobing Xie                                Tel: +1-847-632-3028
Cellular Infrastructure Group               EMail: xieqb@cig.mot.com
Motorola, Inc.
1501 W. Shure Drive, #2309
Arlington Heights, IL 60004
USA

17. References

[1] Postel, J. (ed.), "Internet Protocol - DARPA Internet Program
Protocol Specification", RFC 791, USC/Information Sciences Institute,
September 1981.

[2] Postel, J., "User Datagram Protocol", RFC 768, USC/Information Sciences
Institute, August 1980.

[3] Postel, J. (ed.), "Transmission Control Protocol", RFC 793, USC/
Information Sciences Institute, September 1981. datagram shall be silently discarded.

      This Internet Draft expires in 6 months from April 1999.