draft-ietf-forces-sctptml-06.txt   draft-ietf-forces-sctptml-07.txt 
Network Working Group J. Hadi Salim Network Working Group J. Hadi Salim
Internet-Draft Mojatatu Networks Internet-Draft Mojatatu Networks
Intended status: Standards Track K. Ogawa Intended status: Standards Track K. Ogawa
Expires: April 2, 2010 NTT Corporation Expires: May 27, 2010 NTT Corporation
September 29, 2009 November 23, 2009
SCTP based TML (Transport Mapping Layer) for ForCES protocol SCTP based TML (Transport Mapping Layer) for ForCES protocol
draft-ietf-forces-sctptml-06 draft-ietf-forces-sctptml-07
Abstract
This document defines the SCTP based TML (Transport Mapping Layer)
for the ForCES protocol. It explains the rationale for choosing the
SCTP (Stream Control Transmission Protocol) and also describes how
this TML addresses all the requirements required by and the ForCES
protocol.
Status of this Memo Status of this Memo
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provisions of BCP 78 and BCP 79. This document may contain material provisions of BCP 78 and BCP 79.
from IETF Documents or IETF Contributions published or made publicly
available before November 10, 2008. The person(s) controlling the
copyright in some of this material may not have granted the IETF
Trust the right to allow modifications of such material outside the
IETF Standards Process. Without obtaining an adequate license from
the person(s) controlling the copyright in such materials, this
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Copyright Notice Copyright Notice
Copyright (c) 2009 IETF Trust and the persons identified as the Copyright (c) 2009 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Abstract include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the BSD License.
This document defines the SCTP based TML (Transport Mapping Layer) This document may contain material from IETF Documents or IETF
for the ForCES protocol. It explains the rationale for choosing the Contributions published or made publicly available before November
SCTP (Stream Control Transmission Protocol) [RFC4960] and also 10, 2008. The person(s) controlling the copyright in some of this
describes how this TML addresses all the requirements described in material may not have granted the IETF Trust the right to allow
[RFC3654] and the ForCES protocol [FE-PROTO] draft. modifications of such material outside the IETF Standards Process.
Without obtaining an adequate license from the person(s) controlling
the copyright in such materials, this document may not be modified
outside the IETF Standards Process, and derivative works of it may
not be created outside the IETF Standards Process, except to format
it for publication as an RFC or to translate it into languages other
than English.
Table of Contents Table of Contents
1. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Protocol Framework Overview . . . . . . . . . . . . . . . . . 4 3. Protocol Framework Overview . . . . . . . . . . . . . . . . . 3
3.1. The PL . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3.1. The PL . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.2. The TML . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.2. The TML . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.2.1. TML and PL Interfaces . . . . . . . . . . . . . . . . 6 3.2.1. TML and PL Interfaces . . . . . . . . . . . . . . . . 5
3.2.2. TML Parameterization . . . . . . . . . . . . . . . . . 7 3.2.2. TML Parameterization . . . . . . . . . . . . . . . . . 6
4. SCTP TML overview . . . . . . . . . . . . . . . . . . . . . . 7 4. SCTP TML overview . . . . . . . . . . . . . . . . . . . . . . 7
4.1. Rationale for using SCTP for TML . . . . . . . . . . . . . 9 4.1. Rationale for using SCTP for TML . . . . . . . . . . . . . 7
4.2. Meeting TML requirements . . . . . . . . . . . . . . . . . 10 4.2. Meeting TML requirements . . . . . . . . . . . . . . . . . 8
4.2.1. SCTP TML Channels . . . . . . . . . . . . . . . . . . 11 4.2.1. SCTP TML Channels . . . . . . . . . . . . . . . . . . 9
4.2.2. Satisfying TML Requirements . . . . . . . . . . . . . 16 4.2.2. Satisfying TML Requirements . . . . . . . . . . . . . 14
5. SCTP TML Channel Work . . . . . . . . . . . . . . . . . . . . 18 5. SCTP TML Channel Work . . . . . . . . . . . . . . . . . . . . 16
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
7. Security Considerations . . . . . . . . . . . . . . . . . . . 18 7. Security Considerations . . . . . . . . . . . . . . . . . . . 17
7.1. IPsec Usage . . . . . . . . . . . . . . . . . . . . . . . 19 7.1. IPsec Usage . . . . . . . . . . . . . . . . . . . . . . . 17
7.1.1. SAD and SPD setup . . . . . . . . . . . . . . . . . . 20 7.1.1. SAD and SPD setup . . . . . . . . . . . . . . . . . . 18
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 20 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 18
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 20 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18
9.1. Normative References . . . . . . . . . . . . . . . . . . . 20 9.1. Normative References . . . . . . . . . . . . . . . . . . . 18
9.2. Informative References . . . . . . . . . . . . . . . . . . 21 9.2. Informative References . . . . . . . . . . . . . . . . . . 19
Appendix A. Suggested SCTP TML Channel Work Implementation . . . 21 Appendix A. Suggested SCTP TML Channel Work Implementation . . . 20
A.1. SCTP TML Channel Initialization . . . . . . . . . . . . . 22 A.1. SCTP TML Channel Initialization . . . . . . . . . . . . . 20
A.2. Channel work scheduling . . . . . . . . . . . . . . . . . 22 A.2. Channel work scheduling . . . . . . . . . . . . . . . . . 20
A.2.1. FE Channel work scheduling . . . . . . . . . . . . . . 22 A.2.1. FE Channel work scheduling . . . . . . . . . . . . . . 21
A.2.2. CE Channel work scheduling . . . . . . . . . . . . . . 23 A.2.2. CE Channel work scheduling . . . . . . . . . . . . . . 21
A.3. SCTP TML Channel Termination . . . . . . . . . . . . . . . 23 A.3. SCTP TML Channel Termination . . . . . . . . . . . . . . . 22
A.4. SCTP TML NE level channel scheduling . . . . . . . . . . . 24 A.4. SCTP TML NE level channel scheduling . . . . . . . . . . . 22
Appendix B. Suggested Service Interface . . . . . . . . . . . . . 24 Appendix B. Suggested Service Interface . . . . . . . . . . . . . 23
B.1. TML Boot-strapping . . . . . . . . . . . . . . . . . . . . 25 B.1. TML Boot-strapping . . . . . . . . . . . . . . . . . . . . 23
B.2. TML Shutdown . . . . . . . . . . . . . . . . . . . . . . . 26 B.2. TML Shutdown . . . . . . . . . . . . . . . . . . . . . . . 25
B.3. TML Sending and Receiving . . . . . . . . . . . . . . . . 27 B.3. TML Sending and Receiving . . . . . . . . . . . . . . . . 26
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 28 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 27
1. Definitions 1. Definitions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119. document are to be interpreted as described in RFC 2119.
The following definitions are taken from [RFC3654]and [RFC3746]: The following definitions are taken from [RFC3654]and [RFC3746]:
Logical Functional Block (LFB) -- A template that represents a fine-
grained, logically separate aspects of FE processing.
ForCES Protocol -- The protocol used at the Fp reference point in the ForCES Protocol -- The protocol used at the Fp reference point in the
ForCES Framework in [RFC3746]. ForCES Framework in [RFC3746].
ForCES Protocol Layer (ForCES PL) -- A layer in ForCES protocol ForCES Protocol Layer (ForCES PL) -- A layer in the ForCES
architecture that defines the ForCES protocol architecture and the architecture that embodies the ForCES protocol and the state transfer
state transfer mechanisms as defined in [FE-PROTO]. mechanisms as defined in [I-D.ietf-forces-protocol].
ForCES Protocol Transport Mapping Layer (ForCES TML) -- A layer in ForCES Protocol Transport Mapping Layer (ForCES TML) -- A layer in
ForCES protocol architecture that specifically addresses the protocol ForCES protocol architecture that specifically addresses the protocol
message transportation issues, such as how the protocol messages are message transportation issues, such as how the protocol messages are
mapped to different transport media (like SCTP, IP, ATM, Ethernet, mapped to different transport media (like SCTP, IP, TCP, UDP, ATM,
etc), and how to achieve and implement reliability, security, etc. Ethernet, etc), and how to achieve and implement reliability,
security, etc.
2. Introduction 2. Introduction
The ForCES (Forwarding and Control Element Separation) working group The ForCES (Forwarding and Control Element Separation) working group
in the IETF defines the architecture and protocol for separation of in the IETF defines the architecture and protocol for separation of
Control Elements(CE) and Forwarding Elements(FE) in Network Control Elements(CE) and Forwarding Elements(FE) in Network
Elements(NE) such as routers. [RFC3654] and [RFC3746] respectively Elements(NE) such as routers. [RFC3654] and [RFC3746] respectively
define architectural and protocol requirements for the communication define architectural and protocol requirements for the communication
between CE and FE. The ForCES protocol layer specification between CE and FE. The ForCES protocol layer specification
[FE-PROTO] describes the protocol semantics and workings. The ForCES [I-D.ietf-forces-protocol] describes the protocol semantics and
protocol layer operates on top of an inter-connect hiding layer known workings. The ForCES protocol layer operates on top of an inter-
as the TML. The relationship is illustrated in Figure 1. connect hiding layer known as the TML. The relationship is
illustrated in Figure 1.
This document defines the SCTP based TML for the ForCES protocol This document defines the SCTP based TML for the ForCES protocol
layer. It also addresses all the requirements for the TML including layer. It also addresses all the requirements for the TML including
security, reliability, etc as defined in [FE-PROTO]. security, reliability, etc as defined in [I-D.ietf-forces-protocol].
3. Protocol Framework Overview 3. Protocol Framework Overview
The reader is referred to the Framework document [RFC3746], and in The reader is referred to the Framework document [RFC3746], and in
particular sections 3 and 4, for an architectural overview and particular sections 3 and 4, for an architectural overview and
explanation of where and how the ForCES protocol fits in. explanation of where and how the ForCES protocol fits in.
There is some content overlap between the ForCES protocol draft There is some content overlap between the ForCES protocol
[FE-PROTO] and this section (Section 3) in order to provide basic specification [I-D.ietf-forces-protocol] and this section (Section 3)
context to the reader of this document. in order to provide basic context to the reader of this document.
The ForCES protocol layering constitutes two pieces: the PL and TML The ForCES protocol layering constitutes two pieces: the PL and TML.
layer. This is depicted in Figure 1. This is depicted in Figure 1.
+----------------------------------------------+ +----------------------------------------------+
| CE PL | | CE PL |
+----------------------------------------------+ +----------------------------------------------+
| CE TML | | CE TML |
+----------------------------------------------+ +----------------------------------------------+
^ ^
| |
ForCES PL |messages ForCES PL |messages
| |
skipping to change at page 5, line 28 skipping to change at page 5, line 33
+-----------------------------------------------+ +-----------------------------------------------+
| FE TML | | FE TML |
+-----------------------------------------------+ +-----------------------------------------------+
| FE PL | | FE PL |
+-----------------------------------------------+ +-----------------------------------------------+
Figure 1: Message exchange between CE and FE to establish an NE Figure 1: Message exchange between CE and FE to establish an NE
association association
The PL is in charge of the ForCES protocol. Its semantics and The PL is in charge of the ForCES protocol. Its semantics and
message layout are defined in [FE-PROTO]. The TML is necessary to message layout are defined in [I-D.ietf-forces-protocol]. The TML is
connect two ForCES end-points as shown in Figure 1. necessary to connect two ForCES end-points as shown in Figure 1.
Both the PL and TML are standardized by the IETF. While only one PL Both the PL and TML are standardized by the IETF. While only one PL
is defined, different TMLs are expected to be standardized. The TML is defined, different TMLs are expected to be standardized. The TML
at each of the nodes (CE and FE) is expected to be of the same at each of the nodes (CE and FE) is expected to be of the same
definition in order to inter-operate. definition in order to inter-operate.
When transmitting from a ForCES end-point, the PL delivers its When transmitting from a ForCES end-point, the PL delivers its
messages to the TML. The TML then delivers the PL message to the messages to the TML. The TML then delivers the PL message to the
destination TML(s). destination TML(s).
On reception of a message, the TML delivers the message to its On reception of a message, the TML delivers the message to its
destination PL level (as described in the ForCES header). destination PL (as described in the ForCES header).
3.1. The PL 3.1. The PL
The PL is common to all implementations of ForCES and is standardized The PL is common to all implementations of ForCES and is standardized
by the IETF [FE-PROTO]. The PL level is responsible for associating by the IETF [I-D.ietf-forces-protocol]. The PL is responsible for
an FE or CE to an NE. It is also responsible for tearing down such associating an FE or CE to an NE. It is also responsible for tearing
associations. down such associations.
An FE may use the PL level to asynchronously send packets to the CE. An FE may use the PL to asynchronously send packets to the CE. The
The FE may redirect via the PL (from outside the NE) various control FE may redirect via the PL (from outside the NE) various control
protocol packets (e.g. OSPF, etc) to the CE. Additionally, the FE protocol packets (e.g. OSPF, etc) to the CE. Additionally, the FE
delivers various events that CE has subscribed-to via PL [FE-MODEL]. delivers various events that CE has subscribed-to via PL
[I-D.ietf-forces-model].
The CE and FE may interact synchronously via the PL. The CE issues The CE and FE may interact synchronously via the PL. The CE issues
status requests to the FE and receives responses via the PL. The CE status requests to the FE and receives responses via the PL. The CE
also configures the associated FE's LFBs' components using the PL also configures the associated FE's LFBs' components using the PL
[FE-MODEL]. [I-D.ietf-forces-model].
3.2. The TML 3.2. The TML
The TML level is responsible for transport of the PL level messages. The TML is responsible for transport of the PL messages.
[FE-PROTO] section 5 defines the requirements that need to be met by [I-D.ietf-forces-protocol] section 5 defines the requirements that
a TML specification. The SCTP TML specified in this document meets need to be met by a TML specification. The SCTP TML specified in
all the requirements specified in [FE-PROTO] section 5. this document meets all the requirements specified in
Section 4.2.2 describes how the TML requirements are met. [I-D.ietf-forces-protocol] section 5. Section 4.2.2 describes how
the TML requirements are met.
3.2.1. TML and PL Interfaces 3.2.1. TML and PL Interfaces
There are two interfaces to the PL and TML, both of which are out of There are two interfaces to the PL and TML. The specification of
scope for ForCES. The first one is the interface between the PL and these interfaces is out of scope for this document, but the
TML and the other is the CE Manager (CEM)/FE Manager (FEM)[RFC3746] interfaces are introduced to show how they fit into the architecture
interface to both the PL and TML. Both interfaces are shown in and summarize the function provided at the interfaces. The first
Figure 2. interface is between the PL and TML and the other is the CE Manager
(CEM)/FE Manager (FEM)[RFC3746] interface to both the PL and TML.
Both interfaces are shown in Figure 2.
+----------------------------+ +----------------------------+
| +----------------------+ | | +----------------------+ |
| | | | | | | |
+---------+ | | PL Layer | | +---------+ | | PL | |
| | | +----------------------+ | | | | +----------------------+ |
|FEM/CEM |<---->| ^ | |FEM/CEM |<---->| ^ |
| | | | | | | | | |
+---------+ | |TML API | +---------+ | |TML API |
| | | | | |
| V | | V |
| +----------------------+ | | +----------------------+ |
| | | | | | | |
| | TML Layer | | | | TML | |
| | | | | | | |
| +----------------------+ | | +----------------------+ |
+----------------------------+ +----------------------------+
Figure 2: The TML-PL interface Figure 2: The TML-PL interface
Figure 2 also shows an interface referred to as CEM/FEM[RFC3746] The CEM/FEM[RFC3746] interface is responsible for bootstrapping and
which is responsible for bootstrapping and parameterization of the parameterization of the TML. In its most basic form the CEM/FEM
TML. In its most basic form the CEM/FEM interface takes the form of interface takes the form of a simple static config file which is read
a simple static config file which is read on startup in the pre- on startup in the pre-association phase.
association phase.
Appendix B discusses in more details the service interfaces. Appendix B discusses in more details the service interfaces.
3.2.2. TML Parameterization 3.2.2. TML Parameterization
It is expected that it should be possible to use a configuration It is expected that it should be possible to use a configuration
reference point, such as the FEM or the CEM, to configure the TML. reference point, such as the FEM or the CEM, to configure the TML.
Some of the configured parameters may include: Some of the configured parameters may include:
skipping to change at page 8, line 6 skipping to change at page 8, line 24
controlled, congestion controlled data exchange. Unlike TCP, it does controlled, congestion controlled data exchange. Unlike TCP, it does
not provide byte streaming and instead provides message boundaries. not provide byte streaming and instead provides message boundaries.
Like UDP, it can provide unreliable, unordered data exchange. Unlike Like UDP, it can provide unreliable, unordered data exchange. Unlike
UDP, it does not provide multicast support UDP, it does not provide multicast support
Like DCCP, it can provide unreliable, ordered, congestion controlled, Like DCCP, it can provide unreliable, ordered, congestion controlled,
connection-oriented data exchange. connection-oriented data exchange.
SCTP also provides other services that none of the 3 transport SCTP also provides other services that none of the 3 transport
protocols mentioned above provide. These include: protocols mentioned above provide that we found attractive. These
include:
o Multi-homing o Multi-homing
An SCTP connection can make use of multiple destination IP
addresses to communicate with its peer.
o Runtime IP address binding o Runtime IP address binding
With the SCTP Dynamic Address Reconfiguration ([RFC5061]) feature,
a new IP address can be bound at runtime. This allows for
migration of endpoints without restarting the association
(valuable for high availability).
o A range of reliability shades with congestion control o A range of reliability shades with congestion control
SCTP offers a range of services from full reliability to none, and
from full ordering to none. With SCTP, on a per message basis,
the application can specify a message's time-to-live. When the
expressed time expires, the message can be "skipped".
o Built-in heartbeats o Built-in heartbeats
SCTP has built-in heartbeat mechanism that validate the
reachability of peer addresses.
o Multi-streaming o Multi-streaming
A known problem with TCP is head of line (HOL) blocking. If you
have independent messages, TCP enforces ordering of such messages.
Loss at the head of the messages implies delays of delivery of
subsequent packets. SCTP allows for defining up to 64K
independent streams over the same socket connection, which are
ordered independently.
o Message boundaries with reliability o Message boundaries with reliability
SCTP allows for easier message parsing (just like UDP but with
reliability built in) because it establishes boundaries on a PL
message basis. On a TCP stream, one would have to use techniques
such peeking into the message to figure the boundaries.
o Improved SYN DOS protection o Improved SYN DOS protection
Unlike TCP, which does a 3 way connection setup handshake, SCTP
does a 4 way handshake. This improves against SYN-flood attacks
because listening sockets do not set up state until a connection
is validated.
o Simpler transport events o Simpler transport events
An application (such as the TML) can subscribe to be notified of
both local and remote transport events. Events that can be
subscribed-to include indication of association changes,
addressing changes, remote errors, expiry of timed messages, etc.
These events are off by default and require explicit subscription.
o Simplified replicasting o Simplified replicasting
Although SCTP does not allow for multicasting it allows for a
single message from an application to be sent to multiple peers.
This reduces the messaging that typically crosses different memory
domains within a host (example in a kernel to user space domain of
an operating system).
4.1. Rationale for using SCTP for TML 4.1. Rationale for using SCTP for TML
SCTP has all the features required to provide a robust TML. As a SCTP has all the features required to provide a robust TML. As a
transport that is all-encompassing, it negates the need for having transport that is all-encompassing, it negates the need for having
multiple transport protocols in order to satisfy the TML requirements multiple transport protocols in order to satisfy the TML requirements
([FE-PROTO] section 5). As a result it allows for simpler coding and ([I-D.ietf-forces-protocol] section 5). As a result it allows for
therefore reduces a lot of the interoperability concerns. simpler coding and therefore reduces a lot of the interoperability
concerns.
SCTP is also very mature and widely used making it a good choice for SCTP is also very mature and widely used, making it a good choice for
ubiquitous deployment. ubiquitous deployment.
4.2. Meeting TML requirements 4.2. Meeting TML requirements
PL PL
+----------------------+ +----------------------+
| | | |
+-----------+----------+ +-----------+----------+
| TML API | TML API
TML | TML |
skipping to change at page 10, line 38 skipping to change at page 9, line 41
| | IP | | | | IP | |
| +-------------+ | | +-------------+ |
+----------------------+ +----------------------+
Figure 3: The TML-SCTP interface Figure 3: The TML-SCTP interface
Figure 3 details the interfacing between the PL and SCTP TML and the Figure 3 details the interfacing between the PL and SCTP TML and the
internals of the SCTP TML. The core of the TML interacts on its internals of the SCTP TML. The core of the TML interacts on its
north-bound interface to the PL (utilizing the TML API). On the north-bound interface to the PL (utilizing the TML API). On the
south-bound interface, the TML core interfaces to the SCTP layer south-bound interface, the TML core interfaces to the SCTP layer
utilizing the standard socket interface[SCTP-API] There are three utilizing the standard socket interface[I-D.ietf-tsvwg-sctpsocket].
SCTP socket connections opened between any two PL endpoints (whether There are three SCTP socket connections opened between any two PL
FE or CE). endpoints (whether FE or CE).
4.2.1. SCTP TML Channels 4.2.1. SCTP TML Channels
+--------------------+ +--------------------+
| | | |
| TML core | | TML core |
| | | |
+-+-------+--------+-+ +-+-------+--------+-+
| | | | | |
| Med prio, | | Med prio, |
skipping to change at page 11, line 40 skipping to change at page 10, line 40
| | | |
+---------------------+ +---------------------+
Figure 4: The TML-SCTP channels Figure 4: The TML-SCTP channels
Figure 4 details further the interfacing between the TML core and Figure 4 details further the interfacing between the TML core and
SCTP layers. There are 3 channels used to separate and prioritize SCTP layers. There are 3 channels used to separate and prioritize
the different types of ForCES traffic. Each channel constitutes a the different types of ForCES traffic. Each channel constitutes a
socket interface. It should be noted that all SCTP channels are socket interface. It should be noted that all SCTP channels are
congestion aware (and for that reason that detail is left out of the congestion aware (and for that reason that detail is left out of the
description of the 3 channels). SCTP port 6700, 6701, 6702 are used description of the 3 channels). SCTP port 6704, 6705, 6706 are used
for the higher, medium and lower priority channels respectively. for the higher, medium and lower priority channels respectively.
SCTP Payload Protocol ID (PPID) values of 21, 22, and 23 are used for SCTP Payload Protocol ID (PPID) values of 21, 22, and 23 are used for
the higher, medium and lower priority channels respectively. the higher, medium and lower priority channels respectively.
4.2.1.1. Justifying Choice of 3 Sockets 4.2.1.1. Justifying Choice of 3 Sockets
SCTP allows up to 64K streams to be sent over a single socket SCTP allows up to 64K streams to be sent over a single socket
interface. The authors initially envisioned using a single socket interface. The authors initially envisioned using a single socket
for all three channels (mapping a channel to an SCTP stream). This for all three channels (mapping a channel to an SCTP stream). This
simplifies programming of the TML as well as conserves use of SCTP simplifies programming of the TML as well as conserves use of SCTP
skipping to change at page 12, line 19 skipping to change at page 11, line 19
delivery could block higher priority packets (needing reliable delivery could block higher priority packets (needing reliable
delivery) under congestion situation for an indeterminate period of delivery) under congestion situation for an indeterminate period of
time (depending on how many outstanding lower priority packets are time (depending on how many outstanding lower priority packets are
pending). For this reason, we elected to go with mapping each of the pending). For this reason, we elected to go with mapping each of the
three channels to a different SCTP socket (instead of a different three channels to a different SCTP socket (instead of a different
stream within a single socket). stream within a single socket).
4.2.1.2. Higher Priority, Reliable channel 4.2.1.2. Higher Priority, Reliable channel
The higher priority (HP) channel uses a standard SCTP reliable socket The higher priority (HP) channel uses a standard SCTP reliable socket
on port 6700. SCTP PPID 21 is used for all messages on the HP on port 6704. SCTP PPID 21 is used for all messages on the HP
channel. The HP channel is used for CE solicited messages and their channel. The HP channel is used for CE solicited messages and their
responses: responses:
1. ForCES configuration messages flowing from CE to FE and responses 1. ForCES configuration messages flowing from CE to FE and responses
from the FE to CE. from the FE to CE.
2. ForCES query messages flowing from CE to FE and responses from 2. ForCES query messages flowing from CE to FE and responses from
the FE to the CE. the FE to the CE.
PL priorities 4-7 MUST be used for all PL messages using this PL priorities 4-7 MUST be used for all PL messages using this
skipping to change at page 12, line 47 skipping to change at page 11, line 47
o Association Teardown (default priority: 7) o Association Teardown (default priority: 7)
o Config (default priority: 4) o Config (default priority: 4)
o Config Response (default priority: 4) o Config Response (default priority: 4)
o Query (default priority: 4) o Query (default priority: 4)
o Query Response (default priority: 4) o Query Response (default priority: 4)
If PL priorities outside of the specified range (4-7) priority, PPID
or PL message types other than the above are received on the HP
channel, then the PL message MUST be dropped.
Although an implementation may choose different values from the Although an implementation may choose different values from the
defined range (4-7), it is strongly recommended that default defined range (4-7), it is RECOMMENDED that default priorities be
priorities be used. A response to a ForCES message MUST contain the used. A response to a ForCES message MUST contain the same priority
same priority as the request. Example, a config sent by the CE with as the request. Example, a config sent by the CE with priority 5
priority 5 MUST have a config-response from the FE with priority 5. MUST have a config-response from the FE with priority 5.
4.2.1.3. Medium Priority, Semi-Reliable channel 4.2.1.3. Medium Priority, Semi-Reliable channel
The medium priority (MP) channel uses SCTP-PR on port 6701. SCTP The medium priority (MP) channel uses SCTP-PR on port 6705. SCTP
PPID 22 MUST be used for all messages on the MP channel. Time limits PPID 22 MUST be used for all messages on the MP channel. Time limits
on how long a message is valid are set on each outgoing message. on how long a message is valid are set on each outgoing message.
This channel is used for events from the FE to the CE that are This channel is used for events from the FE to the CE that are
obsoleted over time. Events that are accumulative in nature and are obsoleted over time. Events that are accumulative in nature and are
recoverable by the CE (by issuing a query to the FE) can tolerate recoverable by the CE (by issuing a query to the FE) can tolerate
lost events and therefore should use this channel. For example, a lost events and therefore should use this channel. For example, a
generated event which carries the value of a counter that is generated event which carries the value of a counter that is
monotonically incrementing fits to use this channel. monotonically incrementing fits to use this channel.
PL priority 3 MUST be used for PL messages on this channel. The PL priority 3 MUST be used for PL messages on this channel. The
following PL messages MUST use the MP channel for transport: following PL messages MUST use the MP channel for transport:
o Event Notification (default priority: 3) o Event Notification (default priority: 3)
If PL priority outside of the specified priority, PPID or PL message
type other than the above are received on the MP channel, then the PL
message MUST be dropped.
4.2.1.4. Lower Priority, Unreliable channel 4.2.1.4. Lower Priority, Unreliable channel
The lower priority (LP) channel uses SCTP port 6702. SCTP PPID 23 is The lower priority (LP) channel uses SCTP port 6706. SCTP PPID 23 is
used for all messages on the LP channel. The LP channel also MUST used for all messages on the LP channel. The LP channel also MUST
use SCTP-PR with lower timeout values than the MP channel. The use SCTP-PR with lower timeout values than the MP channel. The
reason an unreliable channel is used for redirect messages is to reason an unreliable channel is used for redirect messages is to
allow the control protocol at both the CE and its peer-endpoint to allow the control protocol at both the CE and its peer-endpoint to
take charge of how the end-to-end semantics of the said control take charge of how the end-to-end semantics of the said control
protocol's operations. For example: protocol's operations. For example:
1. Some control protocols are reliable in nature, therefore making 1. Some control protocols are reliable in nature, therefore making
this channel reliable introduces an extra layer of reliability this channel reliable introduces an extra layer of reliability
which could be harmful. So any end-to-end retransmits will which could be harmful. So any end-to-end retransmits will
happen from remote. happen from remote.
2. Some control protocols may desire to have obsolescence of 2. Some control protocols may desire to have obsolescence of
messages over retransmissions; making this channel reliable messages over retransmissions; making this channel reliable
contradicts that desire. contradicts that desire.
Given ForCES PL level heartbeats are traffic sensitive, sending them Given ForCES PL heartbeats are traffic sensitive, sending them over
over the LP channel also makes sense. If the other end is not the LP channel also makes sense. If the other end is not processing
processing other channels it will eventually get heartbeats; and if other channels it will eventually get heartbeats; and if it is busy
it is busy processing other channels heartbeats will be obsoleted processing other channels heartbeats will be obsoleted locally over
locally over time (and it does not matter if they did not make it). time (and it does not matter if they did not make it).
PL priorities 1-2 MUST be used for PL messages on this channel. PL PL priorities 1-2 MUST be used for PL messages on this channel. PL
messages that MUST use the MP channel for transport are: messages that MUST use the MP channel for transport are:
o Packet Redirect (default priority: 2) o Packet Redirect (default priority: 2)
o Heartbeats (default priority: 1) o Heartbeats (default priority: 1)
If PL priorities outside of the specified priority range, PPID or PL
message types other than the above are received on the LP channel,
then the PL message MUST be dropped.
4.2.1.5. Scheduling of The 3 Channels 4.2.1.5. Scheduling of The 3 Channels
Strict priority work-conserving scheduling is used to process both on Strict priority work-conserving scheduling is used to process both on
sending and receiving (of the PL messages) by the TML Core as shown sending and receiving (of the PL messages) by the TML Core as shown
in Figure 5. in Figure 5.
This means that the HP messages are always processed first until This means that the HP messages are always processed first until
there are no more left. The LP channel is processed only if a there are no more left. The LP channel is processed only if channels
channel that is higher priority than itself has no more messages left that are a higher priority than itself has no more messages left to
to process. This means that under congestion situation, a higher process. This means that under congestion situation, a higher
priority channel with sufficient messages that occupy the available priority channel with sufficient messages that occupy the available
bandwidth would starve lower priority channel(s). bandwidth would starve lower priority channel(s).
The design intent of the SCTP TML is to tie prioritization as The design intent of the SCTP TML is to tie processing prioritization
described in Section 4.2.1.1 and transport congestion control to as described in Section 4.2.1.1 and transport congestion control to
provide implicit node congestion control. This is further detailed provide implicit node congestion control. This is further detailed
in Appendix A.2. in Appendix A.2.
SCTP channel +----------+ SCTP channel +----------+
Work available | DONE +---<--<--+ Work available | DONE +---<--<--+
| +---+------+ | | +---+------+ |
Y ^ Y ^
| +-->--+ +-->---+ | | +-->--+ +-->---+ |
+-->-->-+ | | | | | +-->-->-+ | | | | |
| | | | | | ^ | | | | | | ^
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is expected these parameters will be extracted via the FEM/CEM is expected these parameters will be extracted via the FEM/CEM
interface for each PL ID. interface for each PL ID.
1. The IP address(es) or a resolvable DNS/hostname(s) of the CE/FE. 1. The IP address(es) or a resolvable DNS/hostname(s) of the CE/FE.
2. Whether to use IPsec or not. If IPsec is used, how to 2. Whether to use IPsec or not. If IPsec is used, how to
parameterize the different required ciphers, keys etc as parameterize the different required ciphers, keys etc as
described in Section 7.1 described in Section 7.1
3. The HP SCTP port, as discussed in Section 4.2.1.2. The default 3. The HP SCTP port, as discussed in Section 4.2.1.2. The default
HP port value is 6700 (Section 6). HP port value is 6704 (Section 6).
4. The MP SCTP port, as discussed in Section 4.2.1.3. The default 4. The MP SCTP port, as discussed in Section 4.2.1.3. The default
MP port value is 6701 (Section 6). MP port value is 6705 (Section 6).
5. The LP SCTP port, as discussed in Section 4.2.1.4. The default 5. The LP SCTP port, as discussed in Section 4.2.1.4. The default
LP port value is 6702 (Section 6). LP port value is 6706 (Section 6).
4.2.2. Satisfying TML Requirements 4.2.2. Satisfying TML Requirements
[FE-PROTO] section 5 lists requirements that a TML needs to meet. [I-D.ietf-forces-protocol] section 5 lists requirements that a TML
This section describes how the SCTP TML satisfies those requirements. needs to meet. This section describes how the SCTP TML satisfies
those requirements.
4.2.2.1. Satisfying Reliability Requirement 4.2.2.1. Satisfying Reliability Requirement
As mentioned earlier, a shade of reliability ranges is possible in As mentioned earlier, a shade of reliability ranges is possible in
SCTP. Therefore this requirement is met. SCTP. Therefore this requirement is met.
4.2.2.2. Satisfying Congestion Control Requirement 4.2.2.2. Satisfying Congestion Control Requirement
Congestion control is built into SCTP. Therefore, this requirement Congestion control is built into SCTP. Therefore, this requirement
is met. is met.
4.2.2.3. Satisfying Timeliness and Prioritization Requirement 4.2.2.3. Satisfying Timeliness and Prioritization Requirement
By using 3 sockets in conjunction with the partial-reliability By using 3 sockets in conjunction with the partial-reliability
feature, both timeliness and prioritization can be achieved. feature, both timeliness and prioritization requirements are
addressed.
4.2.2.4. Satisfying Addressing Requirement 4.2.2.4. Satisfying Addressing Requirement
There are no extra headers required for SCTP to fulfil this There are no extra headers required for SCTP to fulfil this
requirement. SCTP can be told to replicast packets to multiple requirement. SCTP can be told to replicast packets to multiple
destinations. The TML implementation will need to translate PL level destinations. The TML implementation will need to translate PL
addresses, to a variety of unicast IP addresses in order to emulate addresses, to a variety of unicast IP addresses in order to emulate
multicast and broadcast PL addresses. multicast and broadcast PL addresses.
4.2.2.5. Satisfying HA Requirement 4.2.2.5. Satisfying High Availability Requirement
Transport link resiliency is one of SCTP's strongest point. Failure Transport link resiliency is one of SCTP's strongest point. Failure
detection and recovery is built in, as mentioned earlier. detection and recovery is built in, as mentioned earlier.
o The SCTP multi-homing feature is used to provide path diversity. o The SCTP multi-homing feature is used to provide path diversity.
Should one of the peer IP addresses become unreachable, the Should one of the peer IP addresses become unreachable, the
other(s) are used without needing lower layer convergence other(s) are used without needing lower layer convergence
(routing, for example) or even the TML becoming aware. (routing, for example) or even the TML becoming aware.
o SCTP heartbeats and data transmission thresholds are used on a per o SCTP heartbeats and data transmission thresholds are used on a per
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planned migration of activity from one FE/CE to another. In such planned migration of activity from one FE/CE to another. In such
a case, part of the provisioning recipe at the CE for replacing an a case, part of the provisioning recipe at the CE for replacing an
FE involves migrating activity of one FE to another. FE involves migrating activity of one FE to another.
4.2.2.6. Satisfying Node Overload Prevention Requirement 4.2.2.6. Satisfying Node Overload Prevention Requirement
The architecture of this TML defines three separate channels, one per The architecture of this TML defines three separate channels, one per
socket, to be used within any FE-CE setup. The scheduling design for socket, to be used within any FE-CE setup. The scheduling design for
processing the TML channels (Section 4.2.1.5) is strict priority. A processing the TML channels (Section 4.2.1.5) is strict priority. A
fundamental desire of the strict prioritization is to ensure that fundamental desire of the strict prioritization is to ensure that
more important work always gets node resources such as CPU and more important processing work always gets node resources over lesser
bandwidth over lesser important work. important work.
When a ForCES node CPU is overwhelmed because the incoming packet When a ForCES node CPU is overwhelmed because the incoming packet
rate is higher than it can keep up with, the channel queues grow and rate is higher than it can keep up with, the channel queues grow and
transport congestion subsequently follows. By virtue of using SCTP, transport congestion subsequently follows. By virtue of using SCTP,
the congestion is propagated back to the source of the incoming the congestion is propagated back to the source of the incoming
packets and eventually alleviated. packets and eventually alleviated.
The HP channel work gets prioritized at the expense of the MP which The HP channel work gets prioritized at the expense of the MP which
gets prioritized over LP channels. The preferential scheduling only gets prioritized over LP channels. The preferential scheduling only
kicks in when there is node overload regardless of whether there is kicks in when there is node overload regardless of whether there is
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scenario where an overwhelming amount redirected packets (from scenario where an overwhelming amount redirected packets (from
outside the NE) coming into the NE may overload the FE while it has outside the NE) coming into the NE may overload the FE while it has
outstanding config work from the CE. In such a case, the FE, while outstanding config work from the CE. In such a case, the FE, while
it is busy processing config requests from the CE essentially ignores it is busy processing config requests from the CE essentially ignores
processing the redirect packets on the LP channel. If enough processing the redirect packets on the LP channel. If enough
redirect packets accumulate, they are dropped either because the LP redirect packets accumulate, they are dropped either because the LP
channel threshold is exceeded or because they are obsoleted. If on channel threshold is exceeded or because they are obsoleted. If on
the other hand, the FE has successfully processed the higher priority the other hand, the FE has successfully processed the higher priority
channels and their related work, then it can proceed and process the channels and their related work, then it can proceed and process the
LP channel. So as demonstrated in this case, the TML ties transport LP channel. So as demonstrated in this case, the TML ties transport
and node overload implicitly together. congestion and node overload implicitly together.
4.2.2.7. Satisfying Encapsulation Requirement 4.2.2.7. Satisfying Encapsulation Requirement
The SCTP TML sets SCTP PPIDs to identify channels used as described The SCTP TML sets SCTP PPIDs to identify channels used as described
in Section 4.2.1.1. in Section 4.2.1.1.
5. SCTP TML Channel Work 5. SCTP TML Channel Work
There are two levels of TML channel work within an NE when a ForCES There are two levels of TML channel work within an NE when a ForCES
node (CE or FE) is connected to multiple other ForCES nodes: node (CE or FE) is connected to multiple other ForCES nodes:
1. NE-level I/O work where a ForCES node (CE or FE) needs to choose 1. NE-level I/O work where a ForCES node (CE or FE) needs to choose
which of the peer nodes to process. which of the peer nodes to process.
2. Node-level I/O work where a ForCES node, handles the three SCTP 2. Node-level I/O work where a ForCES node, handles the three SCTP
TML channels separately for each single ForCES endpoint. TML channels separately for each single ForCES endpoint.
NE-level scheduling definition is left up to the implementation and NE-level scheduling definition is left up to the implementation and
is considered out of scope for this document. Appendix A.4 discuss is considered out of scope for this document. Appendix A.4 discuss
briefly some constraints that an implementor needs to worry about. briefly some constraints that an implementer needs to worry about.
This document provides suggestions on SCTP channel work This document provides suggestions on SCTP channel work
implementation in Appendix A. implementation in Appendix A.
The FE SHOULD do channel connections to the CE in the order of The FE SHOULD do channel connections to the CE in the order of
incrementing priorities i.e. LP socket first, followed by MP and incrementing priorities i.e. LP socket first, followed by MP and
ending with HP socket connection. The CE, however, MUST NOT assume ending with HP socket connection. The CE, however, MUST NOT assume
that there is ordering of socket connections from any FE. that there is ordering of socket connections from any FE.
6. IANA Considerations 6. IANA Considerations
This document makes request of IANA to reserve SCTP ports 6700, 6701, Following the policies outlined in "Guidelines for Writing an IANA
and 6702. This document also requests for SCTP PPID 21, 22, and 23. Considerations Section in RFCs" [RFC5226], the following name spaces
are defined in ForCES SCTP TML.
o SCTP port 6704 for the HP channel, 6705 for the MP channel, and
6706 for the LP channel.
o SCTP Payload Protocol ID (PPID) 21 for the HP channel, 22 for the
MP channel, and 23 for the LP channel.
XXX [Note to IANA]: Port allocations(SCTP 6700-6702) were made in
August 2009. We have been asked by IESG to change these as
prescribed above.
7. Security Considerations 7. Security Considerations
The SCTP TML provides the following security services to the PL The SCTP TML provides the following security services to the PL:
level:
o A mechanism to authenticate ForCES CEs and FEs at transport level o A mechanism to authenticate ForCES CEs and FEs at transport level
in order to prevent the participation of unauthorized CEs and in order to prevent the participation of unauthorized CEs and
unauthorized FEs in the control and data path processing of a unauthorized FEs in the control and data path processing of a
ForCES NE. ForCES NE.
o A mechanism to ensure message authentication of PL data and o A mechanism to ensure message authentication of PL data and
headers transferred from the CE to FE (and vice-versa) in order to headers transferred from the CE to FE (and vice-versa) in order to
prevent the injection of incorrect data into PL messages. prevent the injection of incorrect data into PL messages.
o A mechanism to ensure the confidentiality of PL data and headers o A mechanism to ensure the confidentiality of PL data and headers
transferred from the CE to FE (and vice-versa), in order to transferred from the CE to FE (and vice-versa), in order to
prevent disclosure of PL level information transported via the prevent disclosure of PL information transported via the TML.
TML.
Security choices provided by the TML are made by the operator and Security choices provided by the TML are made by the operator and
take effect during the pre-association phase of the ForCES protocol. take effect during the pre-association phase of the ForCES protocol.
An operator may choose to use all, some or none of the security An operator may choose to use all, some or none of the security
services provided by the TML in a CE-FE connection. services provided by the TML in a CE-FE connection.
When operating under a secured environment, or for other operational When operating under a secured environment, or for other operational
concerns (in some cases performance issues) the operator may turn off concerns (in some cases performance issues) the operator may turn off
all the security functions between CE and FE. all the security functions between CE and FE.
skipping to change at page 19, line 31 skipping to change at page 18, line 42
security mechanisms. security mechanisms.
IPsec is an IP level security scheme transparent to the higher-layer IPsec is an IP level security scheme transparent to the higher-layer
applications and therefore can provide security for any transport applications and therefore can provide security for any transport
layer protocol. This gives IPsec the advantage that it can be used layer protocol. This gives IPsec the advantage that it can be used
to secure everything between the CE and FE without expecting the TML to secure everything between the CE and FE without expecting the TML
implementation to be aware of the details. implementation to be aware of the details.
The IPsec architecture is designed to provide message integrity and The IPsec architecture is designed to provide message integrity and
message confidentiality outlined in the TML security requirements message confidentiality outlined in the TML security requirements
([FE-PROTO]). Mutual authentication and key exchange protocol are [I-D.ietf-forces-protocol]. Mutual authentication and key exchange
provided by Internet Key Exchange (IKE)[RFC4109]. protocol are provided by Internet Key Exchange (IKE)[RFC2409].
7.1. IPsec Usage 7.1. IPsec Usage
A ForCES FE or CE MUST support the following: A ForCES FE or CE MUST support the following:
o Internet Key Exchange (IKE)[RFC4109] with certificates for o Internet Key Exchange (IKE)[RFC2409] with certificates for
endpoint authentication. endpoint authentication.
o Transport Mode Encapsulating Security Payload (ESP)[RFC4303]. o Transport Mode Encapsulating Security Payload (ESP)[RFC4303].
o HMAC-SHA1-96 [RFC2404] for message integrity protection o HMAC-SHA1-96 [RFC2404] for message integrity protection
o AES-CBC with 128-bit keys [RFC3602] for message confidentiality. o AES-CBC with 128-bit keys [RFC3602] for message confidentiality.
o Replay protection[RFC4301]. o Replay protection[RFC4301].
skipping to change at page 20, line 23 skipping to change at page 19, line 35
use the 3 SCTP TML port numbers as SPD selectors. But as noted above use the 3 SCTP TML port numbers as SPD selectors. But as noted above
this choice will require increased number of SPD entries. this choice will require increased number of SPD entries.
In scenarios where multiple IP addresses are used within a single In scenarios where multiple IP addresses are used within a single
association, and there is desire to configure different policies on a association, and there is desire to configure different policies on a
per IP address, then it is recommended to follow [RFC3554] per IP address, then it is recommended to follow [RFC3554]
8. Acknowledgements 8. Acknowledgements
The authors would like to thank Joel Halpern, Michael Tuxen, Randy The authors would like to thank Joel Halpern, Michael Tuxen, Randy
Stewart, Evangelos Haleplidis and Chuanhuang Li for engaging us in Stewart, Evangelos Haleplidis, Chuanhuang Li, Lars Eggert, Avshalom
discussions that have made this draft better. Houri, Adrian Farrel, Juergen Quittek, Magnus Westerlund, and Pasi
Eronen for engaging us in discussions that have made this document
better.
Ross Callon was an excellent manager who persevered in providing us
guidance and Joel Halpern was an excellent document shepherd without
whom this document would have taken longer to publish.
9. References 9. References
9.1. Normative References 9.1. Normative References
[I-D.ietf-forces-protocol]
Dong, L., Doria, A., Gopal, R., HAAS, R., Salim, J.,
Khosravi, H., and W. Wang, "ForCES Protocol
Specification", draft-ietf-forces-protocol-22 (work in
progress), March 2009.
[RFC2404] Madson, C. and R. Glenn, "The Use of HMAC-SHA-1-96 within [RFC2404] Madson, C. and R. Glenn, "The Use of HMAC-SHA-1-96 within
ESP and AH", RFC 2404, November 1998. ESP and AH", RFC 2404, November 1998.
[RFC2409] Harkins, D. and D. Carrel, "The Internet Key Exchange
(IKE)", RFC 2409, November 1998.
[RFC3554] Bellovin, S., Ioannidis, J., Keromytis, A., and R. [RFC3554] Bellovin, S., Ioannidis, J., Keromytis, A., and R.
Stewart, "On the Use of Stream Control Transmission Stewart, "On the Use of Stream Control Transmission
Protocol (SCTP) with IPsec", RFC 3554, July 2003. Protocol (SCTP) with IPsec", RFC 3554, July 2003.
[RFC3602] Frankel, S., Glenn, R., and S. Kelly, "The AES-CBC Cipher [RFC3602] Frankel, S., Glenn, R., and S. Kelly, "The AES-CBC Cipher
Algorithm and Its Use with IPsec", RFC 3602, Algorithm and Its Use with IPsec", RFC 3602,
September 2003. September 2003.
[RFC4109] Hoffman, P., "Algorithms for Internet Key Exchange version
1 (IKEv1)", RFC 4109, May 2005.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the [RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, December 2005. Internet Protocol", RFC 4301, December 2005.
[RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)", [RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)",
RFC 4303, December 2005. RFC 4303, December 2005.
[RFC4960] Stewart, R., "Stream Control Transmission Protocol", [RFC4960] Stewart, R., "Stream Control Transmission Protocol",
RFC 4960, September 2007. RFC 4960, September 2007.
[RFC5061] Stewart, R., Xie, Q., Tuexen, M., Maruyama, S., and M. [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
Kozuka, "Stream Control Transmission Protocol (SCTP) IANA Considerations Section in RFCs", BCP 26, RFC 5226,
Dynamic Address Reconfiguration", RFC 5061, May 2008.
September 2007.
9.2. Informative References 9.2. Informative References
[FE-MODEL] [I-D.ietf-forces-model]
Halpern, J. and J. Hadi Salim, "ForCES Forwarding Element Halpern, J. and J. Salim, "ForCES Forwarding Element
Model", October 2008. Model", draft-ietf-forces-model-16 (work in progress),
October 2008.
[FE-PROTO] [I-D.ietf-tsvwg-sctpsocket]
Doria (Ed.), A., Haas (Ed.), R., Hadi Salim (Ed.), J., Stewart, R., Poon, K., Tuexen, M., Yasevich, V., and P.
Khosravi (Ed.), H., M. Wang (Ed.), W., Dong, L., and R. Lei, "Sockets API Extensions for Stream Control
Gopal, "ForCES Protocol Specification", November 2008. Transmission Protocol (SCTP)",
draft-ietf-tsvwg-sctpsocket-19 (work in progress),
February 2009.
[RFC3654] Khosravi, H. and T. Anderson, "Requirements for Separation [RFC3654] Khosravi, H. and T. Anderson, "Requirements for Separation
of IP Control and Forwarding", RFC 3654, November 2003. of IP Control and Forwarding", RFC 3654, November 2003.
[RFC3746] Yang, L., Dantu, R., Anderson, T., and R. Gopal, [RFC3746] Yang, L., Dantu, R., Anderson, T., and R. Gopal,
"Forwarding and Control Element Separation (ForCES) "Forwarding and Control Element Separation (ForCES)
Framework", RFC 3746, April 2004. Framework", RFC 3746, April 2004.
[RFC3768] Hinden, R., "Virtual Router Redundancy Protocol (VRRP)", [RFC3768] Hinden, R., "Virtual Router Redundancy Protocol (VRRP)",
RFC 3768, April 2004. RFC 3768, April 2004.
[SCTP-API]
Stewart, R., Poon, K., Tuexen, M., Yasevich, V., and P.
Lei, "Sockets API Extensions for Stream Control
Transmission Protocol (SCTP)", Feb. 2009.
Appendix A. Suggested SCTP TML Channel Work Implementation Appendix A. Suggested SCTP TML Channel Work Implementation
As mentioned in Section 5, there are two levels of TML channel work As mentioned in Section 5, there are two levels of TML channel work
within an NE when a ForCES node (CE or FE) is connected to multiple within an NE when a ForCES node (CE or FE) is connected to multiple
other ForCES nodes: other ForCES nodes:
1. NE-level I/O work where a ForCES node (CE or FE) needs to choose 1. NE-level I/O work where a ForCES node (CE or FE) needs to choose
which of the peer nodes to process. which of the peer nodes to process.
2. Node-level I/O work where a ForCES node, handles the three SCTP 2. Node-level I/O work where a ForCES node, handles the three SCTP
TML channels separately for each single ForCES endpoint. TML channels separately for each single ForCES endpoint.
NE-level scheduling definition is left up to the implementation and NE-level scheduling definition is left up to the implementation and
is considered out of scope for this document. Appendix A.4 discuss is considered out of scope for this document. Appendix A.4 discusses
briefly some constraints that an implementor needs to worry about. briefly some constraints that an implementer needs to worry about.
This document and in particular Appendix A.1, Appendix A.2 and This document and in particular Appendix A.1, Appendix A.2 and
Appendix A.3 discuss details of node-level I/O work. Appendix A.3 discuss details of node-level I/O work.
A.1. SCTP TML Channel Initialization A.1. SCTP TML Channel Initialization
As discussed in Section 5, it is recommended that the FE SHOULD do As discussed in Section 5, it is recommended that the FE SHOULD do
socket connections to the CE in the order of incrementing priorities socket connections to the CE in the order of incrementing priorities
i.e. LP socket first, followed by MP and ending with HP socket i.e. LP socket first, followed by MP and ending with HP socket
connection. The CE, however, MUST NOT assume that there is ordering connection. The CE, however, MUST NOT assume that there is ordering
of socket connections from any FE. Appendix B.1 has more details on of socket connections from any FE. Appendix B.1 has more details on
the expected initialization of SCTP channel work. the expected initialization of SCTP channel work.
A.2. Channel work scheduling A.2. Channel work scheduling
This section provides high level details of the scheduling view of This section provides high level details of the scheduling view of
the SCTP TML core (Section 4.2.1). A practical scheduler the SCTP TML core (Section 4.2.1). A practical scheduler
implementation takes care of many little details (such as timers, implementation takes care of many little details (such as timers,
work quanta, etc) not described in this document. The implementor is work quanta, etc) not described in this document. It is left to the
left to take care of those details. implementer to take care of those details.
The CE(s) and FE(s) are coupled together in the principles of the The CE(s) and FE(s) are coupled together in the principles of the
scheduling scheme described here to tie together node overload with scheduling scheme described here to tie together node overload with
transport congestion. The design intent is to provide the highest transport congestion. The design intent is to provide the highest
possible robust work throughput for the NE under any network or possible robust work throughput for the NE under any network or
processing congestion. processing congestion.
A.2.1. FE Channel work scheduling A.2.1. FE Channel work scheduling
The FE scheduling, in priority order, needs to I/O process: The FE scheduling, in priority order, needs to I/O process:
skipping to change at page 24, line 41 skipping to change at page 24, line 12
processing level. For the sake of illustration consider again two processing level. For the sake of illustration consider again two
FEs connected to a CE. Consider FE1 as having a large number of HP FEs connected to a CE. Consider FE1 as having a large number of HP
and MP messages and FE2 having a large number of MP and LP messages. and MP messages and FE2 having a large number of MP and LP messages.
The scheduling scheme needs to ensure that while FE1 always gets its The scheduling scheme needs to ensure that while FE1 always gets its
messages processed, at some point we allow FE2 messages to be messages processed, at some point we allow FE2 messages to be
processed. A promotion and preemption based scheduling could be used processed. A promotion and preemption based scheduling could be used
by the CE to resolve this issue. by the CE to resolve this issue.
Appendix B. Suggested Service Interface Appendix B. Suggested Service Interface
This section provides high level service interface between FEM/CEM This section outlines high level service interface between FEM/CEM
and TML, the PL and TML, and between local and remote TMLs. The and TML, the PL and TML, and between local and remote TMLs. The
intent of this interface discussion is to provide general guidelines. intent of this interface discussion is to provide general guidelines.
The implementer is expected to worry about details and even follow a The implementer is expected to care of details and even follow a
different approach if needed. different approach if needed.
The theory of operation for the PL-TML service is as follows: The theory of operation for the PL-TML service is as follows:
1. The PL starts up and bootstraps the TML. The end result of a 1. The PL starts up and bootstraps the TML. The end result of a
successful TML bootstrap is that the CE TML and the FE TML successful TML bootstrap is that the CE TML and the FE TML
connect to each other at the transport level. connect to each other at the transport level.
2. Sending and reception of the PL level messages commences after a 2. Transmission and reception of the PL messages commences after a
successful TML bootstrap. The PL uses send and receive PL-TML successful TML bootstrap. The PL uses send and receive PL-TML
interfaces to communicate to its peers. The TML is agnostic to interfaces to communicate to its peers. The TML is agnostic to
the nature of the messages being sent or received. The first the nature of the messages being sent or received. The first
message exchanges that happen are to establish ForCES message exchanges that happen are to establish ForCES
association. Subsequent messages maybe either unsolicited events association. Subsequent messages maybe either unsolicited events
from the FE PL, control message redirects from/to the CE to/from from the FE PL, control message redirects from/to the CE to/from
FE, and configuration from the CE to the FE and their responses FE, and configuration from the CE to the FE and their responses
flowing from the FE to the CE. flowing from the FE to the CE.
3. The PL does a shutdown of the TML after terminating ForCES 3. The PL does a shutdown of the TML after terminating ForCES
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to initialize itself. to initialize itself.
The TML on the FE proceeds to connect the 3 channels to the CE. The The TML on the FE proceeds to connect the 3 channels to the CE. The
socket interface is used for each of the channels. The TML continues socket interface is used for each of the channels. The TML continues
to re-try the connections to the CE until all 3 channels are to re-try the connections to the CE until all 3 channels are
connected. It is advisable that the number of connection retry connected. It is advisable that the number of connection retry
attempts and the time between each retry is also configurable via the attempts and the time between each retry is also configurable via the
FEM. On failure to connect one or more channels, and after the FEM. On failure to connect one or more channels, and after the
configured number of retry thresholds is exceeded, the TML will configured number of retry thresholds is exceeded, the TML will
return an appropriate failure indicator to the PL. On success (as return an appropriate failure indicator to the PL. On success (as
shown in Figure 6), a success indication is presented to the TML. shown in Figure 6), a success indication is presented to the PL.
FE PL FE TML FEM CEM CE TML CE PL FE PL FE TML FEM CEM CE TML CE PL
| | | | | | | | | | | |
| | | | | Bootup | | | | | | Bootup |
| | | | |<-------------------| | | | | |<-------------------|
| Bootup | | | | | | Bootup | | | | |
|----------->| | |get CEM info| | |----------->| | |get CEM info| |
| |get FEM info | |<-----------| | | |get FEM info | |<-----------| |
| |------------>| ~ ~ | | |------------>| ~ ~ |
| ~ ~ |----------->| | | ~ ~ |----------->| |
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| Bootup | | | | Bootup | | |
| succeeded | | | | succeeded | | |
|<-----------| | | |<-----------| | |
| | | | | | | |
Figure 6: SCTP TML Bootstrapping Figure 6: SCTP TML Bootstrapping
On the CE things are slightly different. After initializing from the On the CE things are slightly different. After initializing from the
CEM, the TML on the CE side proceeds to initialize the 3 channels to CEM, the TML on the CE side proceeds to initialize the 3 channels to
listen to remote connections from the FEs. The success or failure listen to remote connections from the FEs. The success or failure
indication is passed on to the CE PL level (in the same manner as was indication is passed on to the CE PL (in the same manner as was done
done in the FE). in the FE).
Post boot-up, the CE TML waits for connections from the FEs. Upon a Post boot-up, the CE TML waits for connections from the FEs. Upon a
successful connection by an FE, the CE TML level keeps track of the successful connection by an FE, the CE TML level keeps track of the
transport level details of the FE. Note, at this stage only transport level details of the FE. Note, at this stage only
transport level connection has been established; ForCES level transport level connection has been established; ForCES level
association follows using send/receive PL-TML interfaces (refer to association follows using send/receive PL-TML interfaces (refer to
Appendix B.3 and Figure 8). Appendix B.3 and Figure 8).
B.2. TML Shutdown B.2. TML Shutdown
Figure 7 shows an example of an FE shutting down the TML. It is Figure 7 shows an example of an FE shutting down the TML. It is
assumed at this point that the ForCES Association Teardown has been assumed at this point that the ForCES Association Teardown has been
issued by the CE. issued by the CE. It should also be noted that different
implementations may have different procedures for cleaning up state
etc.
When the FE PL issues a shutdown to its TML for a specific PL ID, the When the FE PL issues a shutdown to its TML for a specific PL ID, the
TML releases all the channel connections to the CE. This is achieved TML releases all the channel connections to the CE. This is achieved
by closing the sockets used to communicate to the CE. by closing the sockets used to communicate to the CE. This results
in the stack sending a SCTP shutdown which is received on the CE.
FE PL FE TML CE TML CE PL FE PL FE TML CE TML CE PL
| | | | | | | |
| Shutdown | | | | Shutdown | | |
|----------->| | | |----------->| | |
| |-disconnect 3 chans. | | | |-disconnect 3 chans. | |
| |-SCTP level shutdown | |
| |------------------------>| | | |------------------------>| |
| | | | | | | |
| | |TML detects shutdown|
| | |-FE TML info cleanup| | | |-FE TML info cleanup|
| | |-optionally tell PL | | | |-optionally tell PL |
| | |------------------->| | | |------------------->|
| |- clean up any state of | |
| | channels disconnected | |
| | | | | | | |
| |- clean up any state of | |
| |-channels disconnected | |
| |<------------------------| | | |<------------------------| |
| |-SCTP shutdown ACK | |
| | | |
| Shutdown | | | | Shutdown | | |
| succeeded | | | | succeeded | | |
|<-----------| | | |<-----------| | |
| | | | | | | |
Figure 7: FE Shutting down Figure 7: FE Shutting down
On the CE side, a TML level disconnection would result in possible On the CE side, a TML disconnection would result in possible cleanup
cleanup of the FE state. Optionally, depending on the of the FE state. Optionally, depending on the implementation, there
implementation, there may be need to inform the PL about the TML may be need to inform the PL about the TML disconnection. The CE
disconnection. stack level SCTP sends an acknowledgement to the FE TML in response
to the earlier SCTP shutdown.
B.3. TML Sending and Receiving B.3. TML Sending and Receiving
The TML is agnostic to the nature of the PL message it delivers to The TML should be agnostic to the content of the PL messages, or
the remote TML (which subsequently delivers the message to its PL). their operations. The PL should provide enough information to the
Figure 8 shows an example of a message exchange originated at the FE TML for it to assign an appropriate priority and loss behavior to the
and sent to the CE (such as a ForCES association message) which message. Figure 8 shows an example of a message exchange originated
illustrates all the necessary service interfaces for sending and at the FE and sent to the CE (such as a ForCES association message)
receiving. which illustrates all the necessary service interfaces for sending
and receiving.
When the FE PL sends a message to the TML, the TML is expected to When the FE PL sends a message to the TML, the TML is expected to
pick one of HP/MP/LP channels and send out the ForCES message. pick one of HP/MP/LP channels and send out the ForCES message.
FE PL FE TML CE TML CE PL FE PL FE TML CE TML CE PL
| | | | | | | |
|PL send | | | |PL send | | |
|----------->| | | |----------->| | |
| | | | | | | |
| |-Format msg. | | | | | |
| |-pick channel | | | |-pick channel | |
| |-TML Send | | | |-TML Send | |
| |------------->| | | |------------->| |
| | | |
| | |-TML Receive on chan. | | | |-TML Receive on chan. |
| | |-decapsulate |
| | |- mux to PL/PL recv | | | |- mux to PL/PL recv |
| | |--------------------->| | | |--------------------->|
| | | ~ | | | ~
| | | ~ PL Process | | | ~ PL Process
| | | ~ | | | ~
| | | PL send | | | | PL send |
| | |<---------------------| | | |<---------------------|
| | |-Format msg. for send |
| | |-pick chan to send on | | | |-pick chan to send on |
| | |-TML send | | | |-TML send |
| |<-------------| | | |<-------------| |
| |-TML Receive | | | |-TML Receive | |
| |-decapsulate | |
| |-mux to PL | | | |-mux to PL | |
| PL Recv | | | | PL Recv | | |
|<---------- | | | |<---------- | | |
| | | | | | | |
Figure 8: Send and Recv Flow Figure 8: Send and Recv Flow
When the CE TML receives the ForCES message on the channel it was When the CE TML receives the ForCES message on the channel it was
sent on, it demultiplexes the message to the CE PL. sent on, it demultiplexes the message to the CE PL.
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