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Network Working Group                                        S. Shalunov
Internet Draft                                                 Internet2
Expiration Date: June 2001                                 B. Teitelbaum
                               Advanced Network & Services and Internet2
                                                            M. Zekauskas
                                             Advanced Network & Services
                                                           December 2000



                  A One-way Delay Measurement Protocol
                     <draft-ietf-ippm-owdp-01.txt>


1. 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.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   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

   This memo provides information for the Internet community.  This memo
   does not specify an Internet standard of any kind.  Distribution of
   this memo is unlimited.


2. Motivation and Goals

   The IETF IP Performance Metrics (IPPM) working group has proposed
   draft standard metrics for one-way packet delay [RFC2679] and loss
   [RFC 2680] across Internet paths.  Although there are now several
   measurement platforms that implement collection of these metrics
   [SURVEYOR], [RIPE], there is not currently a standard that would
   permit initiation of test streams or exchange of packets to collect



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   singleton metrics in an interoperable manner.

   With the increasingly wide availability of affordable global
   positioning system (GPS) and CDMA based time sources, hosts
   increasingly have available to them very accurate time
   sources--either directly or through their proximity to NTP primary
   (stratum 1) time servers.  By standardizing a technique for
   collecting IPPM one-way delay measurements, we hope to create an
   environment where IPPM metrics may be collected across a far broader
   mesh of Internet paths than is currently possible.  One particularly
   compelling vision is of widespread deployment of open OWDP servers
   that would make measurement of one-way delay as commonplace as
   measurement of round-trip time using an ICMP-based tool like ping.

   Additional design goals of OWDP include stealth, security, logical
   separation of control and test functionality, and support for small
   test packets.

   Stealth is achieved by making test packet streams look as much as
   possible like ordinary Internet traffic.  Towards this goal, OWDP's
   test protocol is layered over UDP and allows for a wide range of
   packet sizes and port numbers.  Additionally, OWDP supports an
   encrypted mode that obscures all transmitted data, making detection
   of OWDP test activity by Internet service providers very difficult.

   Security features include optional authentication and/or encryption
   of control and test messages.  These features may be useful to
   prevent unauthorized access to results or man-in-the-middle attackers
   who attempt to provide special treatment to OWDP test streams or who
   attempt to modify sender-generated timestamps to falsify test
   results.

   OWDP actually consists of two inter-related protocols: OWDP-Control
   and OWDP-Test.  OWDP-Control is used to initiate, start, stop and
   retrieve test sessions, while OWDP-Test is the actual one-way delay
   test protocol that exchanges singleton test packets between two
   measurement nodes.

   Several roles are logically separated to allow for broad flexibility
   in use.  Specifically, we define:

     Session-Sender     the sending endpoint of an OWDP-Test session;

     Session-Receiver   the receiving endpoint of an OWDP-Test session;

     Server             an end system that manages one or more OWDP-Test
                        sessions, is capable of configuring per-session
                        state in session endpoints, and is capable of



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                        returning the results of a test session;

     Control-Client     an end system that initiates requests for
                        OWDP-Test sessions, triggers the start of a set
                        of sessions, and may trigger their termination;

     Retrieve-Client    an end system that initiates requests to retrieve
                        the results of completed OWDP-Test sessions;

   One possible scenario of relationships between these roles is shown
   below.

       +----------------+              +------------------+
       | Session-Sender |--OWDP-Test-->| Session-Receiver |
       +----------------+              +------------------+
         ^                                     ^
         |                                     |
         |                                     |
         |                                     |
         |  +----------------+<----------------+
         |  |     Server     |<-------+
         |  +----------------+        |
         |    ^                       |
         |    |                       |
         |  OWDP-Control            OWDP-Control
         |    |                       |
         v    v                       v
       +----------------+     +-----------------+
       | Control-Client |     | Retrieve-Client |
       +----------------+     +-----------------+

   (Unlabeled links in the figure are unspecified by this draft and may
   be proprietary protocols.)

   Different logical roles can be played by the same host.  For example,
   in the figure above, there could actually be only two hosts: one
   playing the roles of Control-Client, Retrieve-Client, and Session-
   Sender, and the other playing the roles of Server and Session-
   Receiver. This is shown below.

       +-----------------+                  +------------------+
       | Control-Client  |<--OWDP-Control-->| Server           |
       | Retrieve-Client |                  |                  |
       | Session-Sender  |---OWDP-Test----->| Session-Receiver |
       +-----------------+                  +------------------+

   Finally, because many Internet paths include segments that transport
   IP over ATM, delay and loss measurements can include the effects of



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   ATM segmentation and reassembly (SAR).  Consequently, OWDP has been
   designed to allow for small test packets that would fit inside the
   payload of a single ATM cell (this is only achieved in
   unauthenticated and encrypted modes).


3. Protocol Overview

   OWDP consists of two inter-related protocols: OWDP-Control and OWDP-
   Test.  The former is layered over TCP and is used to initiate and
   control measurement sessions and to fetch their results.  The latter
   protocol is layered over UDP and is used to send singleton
   measurement packets along the Internet path under test.

   The initiator of the measurement session establishes a TCP connection
   to a well-known port on the target point and this connection remains
   open for the duration of the OWDP-Test sessions.  IANA will be
   requested to allocate a well-known port number for OWDP-Control
   sessions.  An OWDP server SHOULD listen to this well-known port.

   OWDP-Control messages are transmitted only before OWDP-Test sessions
   are actually started and after they complete (with the possible
   exception of an early Stop-Session message).

   The OWDP-Control and OWDP-Test protocols support three modes of
   operation: unauthenticated, authenticated, and encrypted.  The
   authenticated or encrypted modes require endpoints to possess a
   shared secret.


4. OWDP-Control


4.1. Connection Setup

   Before either a Control-Client or a Retrieve-Client can issue
   commands of a Server, it must establish a connection to the server.

   First, a client opens a TCP connection to the server on a well-known
   port.  The server responds with a server greeting:











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         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
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                                                               |
        .                      Unused (15 octets)                       .
        .                                                               .
        .                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                               |              Modes            |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                                                               |
        .                                                               .
        .                     Challenge (16 octets)                     .
        .                                                               .
        |                                                               |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The following mode values are meaningful: 1 for unauthenticated, 2
   for authenticated, 4 for encrypted.  The value of the Modes field
   sent by the server is the bit-wise OR of the mode values that it is
   willing to support during this session.

   If the Modes octet is zero, the server doesn't wish to communicate
   with the client and MAY close the connection immediately.  The client
   SHOULD close the connection if it gets a greeting with Modes equal to
   zero.

   Otherwise, the client MUST respond with the following 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
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |           Mode                |              Unused           |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                              KID                              |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                                                               |
        .                                                               .
        .                       Token (32 octets)                       .
        .                                                               .
        |                                                               |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                                                               |
        .                                                               .
        .                     Client-IV (16 octets)                     .
        .                                                               .
        |                                                               |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+




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   Here Mode is the mode that the client chooses to use during this
   OWDP-Control session.  It will also be used for all OWDP-Test
   sessions started under control of this OWDP-Control session.

   In unauthenticated mode, KID, Token, and Client-IV are unused.

   Otherwise, KID (key ID) is a 4-octet indicator of which shared secret
   the client wishes to use to authenticate or encrypt and Token is the
   concatenation of a 16-octet challenge and a 16-octet Session-key,
   encrypted using the AES (Advanced Encryption Standard) [AES] in
   Cipher Block Chaining (CBC). Encryption MUST be performed using an
   Initialization Vector (IV) of zero and a key value that is the shared
   secret associated with KID.

   Session-key and Client-IV are generated randomly by the client.

   The server MUST respond with the following 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
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                                                               |
        .                      Unused (15 octets)                       .
        .                                                               .
        .                                               +-+-+-+-+-+-+-+-+
        |                                               |   Yes/No      |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                                                               |
        .                                                               .
        .                     Server-IV (16 octets)                     .
        .                                                               .
        |                                                               |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   A zero value in the "Yes/No" field means that the server accepts the
   authentication and is willing to conduct further transactions.  Any
   non-zero value means that the server does not accept the
   authentication provided by the client or, for some other reason, is
   not willing to conduct further transactions in this OWDP-Control
   session.  If a "No" response is sent, the server MAY close the
   connection after this message.  The client SHOULD close the
   connection if it gets message that says "No" at this stage.

   The previous transactions constitute connection setup.







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4.2. OWDP-Control Commands

   In authenticated or encrypted mode (which are identical as far as
   OWDP-Control is concerned, and only differ in OWDP-Test) all further
   communications are encrypted with the Session-key, using CBC mode.
   The client encrypts its stream using Client-IV.  The server encrypts
   its stream using Server-IV.

   The following commands are available for the client: Request-Session,
   Start-Sessions, Stop-Session, Retrieve-Session.  The command Stop-
   Session is available to both client and server.

   After Start-Sessions is sent/received by the client/server, and
   before it both sends and receives Stop-Session (order unspecified),
   it is said to be conducting active measurements.

   While conducting active measurements, the only command available is
   Stop-Session.

   These commands are described in detail below.


4.3. Creating Test Sessions

   Individual one-way delay measurement sessions are established using a
   simple request/response protocol. An OWDP client MAY issue zero or
   more Request-Session messages to an OWDP server, which MUST respond
   to each with an Accept-Session message.  An Accept-Session message
   MAY refuse a request.

   The format of Request-Session message is as follows:




















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         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
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |      1        |IPVN-S | IPVN-R| Conf-Sender   | Conf-Receiver |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                        Sender Address                         |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |              Sender Address (cont.) or Unused                 |
        |                                                               |
        |                                                               |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                        Receiver Address                       |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |              Receiver Address (cont.) or Unused               |
        |                                                               |
        |                                                               |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |          Sender Port          |         Receiver Port         |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                                                               |
        |                        SID (16 octets)                        |
        |                                                               |
        |                                                               |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |     TTL       |     Flags     |            PHB ID             |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                          Inv-Lambda                           |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                            Packets                            |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                         Padding Length                        |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                           Start Time                          |
        |                                                               |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |        Sender Precision       |       Receiver Precision      |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                                                               |
        |                           Zero Padding                        |
        |                                                               |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Here the first octet (1) indicates that this is Request-Session
   command.

   IPVN-S and IPVN-R are IP version numbers for Sender and Receiver.  In
   the case of IP version number being 4, twelve unused octets follow
   the four-octet address.



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   Conf-Sender and Conf-Receiver can be 0 or 1.  If 1, the server is
   being asked to configure the corresponding agent (sender or
   receiver).  In this case, the corresponding Port value SHOULD be
   disregarded by the server.  At least one of Conf-Sender and Conf-
   Receiver MUST be 1.

   The Sender Address and Receiver Address fields contain respectively
   the sender and receiver addresses of the end points of the Internet
   path over which an OWDP test session is requested.

   SID is the session identifier.  It can be used in later sessions as
   an argument for Retrieve-Session command.  It is meaningful only if
   Conf-Receiver is 1.

   The field Inv-Lambda is an unsigned integer and is the scaled
   reciprocal of rate (in microseconds) at which the Poisson test stream
   is to be generated.  This allows the average Poisson sampling
   interval for the requested test session to be set to between 1
   microsecond and over an hour.

   The value Packets is the number of active measurement packets to be
   sent during this OWDP-Test session (note that both server and client
   can abort the session early).

   Padding length is the number of octets to be appended to normal OWDP-
   Test packet (see more on padding in discussion of OWDP-Test).

   Start Time is the time when the session is to be started (but not
   before Start-Sessions command is issued).

   Sender Precision and Receiver Precision are signed integers in the
   range +32 to -32 indicating the precision of the corresponding
   clocks, in seconds to the nearest power of two, as described in
   RFC 958.  Sender Precision is meaningful only if Conf-Sender is not
   set.  Receiver Precision is meaningful only if Conf-Receiver is not
   set.

   To each Request-Session message, an OWDP server MUST respond with an
   Accept-Session message:












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         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
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |    Accept     |  Unused       |            Port               |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
        |                                                               |
        |                        SID (16 octets)                        |
        |                                                               |
        |                                                               |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |        Sender Precision       |       Receiver Precision      |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                                                               |
        |                                                               |
        |                          Zero Padding                         |
        |                                                               |
        |                                                               |
        |                                                               |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Zero in the Accept field means that the server is willing to conduct
   the session.  Any non-zero value indicates rejection of the request.

   If the server rejects a Request-Session command, it SHOULD not close
   the TCP connection.  The client MAY close it if it gets negative
   response to Request-Session.

   The meaning of Port depend on the values of Conf-Sender and Conf-
   Receiver in the query that solicited the response.  If both were set,
   Port field is unused.  If only Conf-Sender was set, Port is the port
   to expect OWDP-Test packets from.  If only Conf-Receiver was set,
   Port is the port to send OWDP-Test packets to.

   If only Conf-Sender was set, SID is unused.  Otherwise, SID is a
   unique server-generated session identifier.  It can be used later as
   handle to retrieve the results of a session.

   SIDs SHOULD be constructed by concatenation of 4-octet IPv4 IP number
   belonging to the generating machine, 8-octet timestamp, and 4-octet
   random value.

   Sender Precision and Receiver Precision have the same meaning as in
   Request-Session command.  Sender Precision is meaningful only if
   Conf-Sender is set.  Receiver Precision is meaningful only if Conf-
   Receiver is set.






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4.4. Starting Test Sessions

   Having requested one or more test sessions and received affirmative
   Accept-Session responses, an OWDP client may start the execution of
   the requested test sessions by sending a Start-Sessions message to
   the server.

   The format of this message is 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
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |      2        |                                               |
        +-+-+-+-+-+-+-+-+                                               |
        |                             Unused                            |
        |                                                               |
        |                                                               |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                                                               |
        |                    Zero Padding (16 octets)                   |
        |                                                               |
        |                                                               |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The server MUST respond with an Control-Ack message (which SHOULD be
   sent as quickly as possible). Control-Ack messages have the 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
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |     Accept    |                                               |
        +-+-+-+-+-+-+-+-+                                               |
        |                             Unused                            |
        |                                                               |
        |                                                               |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                                                               |
        |                    Zero Padding (16 octets)                   |
        |                                                               |
        |                                                               |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   If Accept has any non-zero value, the Start-Sessions request was
   rejected; zero means that the command was accepted.  The server MAY
   and the client SHOULD close the connection in the case of a negative
   response.




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   The server SHOULD start all OWDP-Test streams immediately after it
   sends the response or immediately after their specified start times,
   whichever is later.  (Note that a client can effect an immediate
   start by specifying in Request-Session a Start Time in the past.)  If
   the client represents a Sender, the client SHOULD start its OWDP-Test
   streams immediately after it sees the Control-Ack response from the
   Server.


4.5. Stop-Sessions

   The Stop-Sessions message may be issued by either the Control-Client
   or the Server.  The format of this command is 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
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |      3        |    Accept     |                               |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
        |                             Unused                            |
        |                                                               |
        |                                                               |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                                                               |
        |                    Zero Padding (16 octets)                   |
        |                                                               |
        |                                                               |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Normally, the client SHOULD send this command after the OWDP-Test
   streams have completed.  However, either client or server MAY send it
   prematurely.

   Non-zero value of Accept indicates a failure of some sort.  Zero
   values indicates normal (but possibly premature) completion.  If
   Accept had non-zero value (from either party), or if it was not
   transmitted at all (for whatever reason, including TCP connection
   used for OWDP-Control breaking), results of all OWDP-Test sessions
   spawned by this OWDP-Control session SHOULD be considered invalid,
   even if Retrieve-Session with SID from this session works during a
   different OWDP-Control session.

   The party that receives this command MUST stop its OWDP-Test streams
   and respond with a Stop-Sessions message.  Any non-zero value in
   Accept field means something went wrong.  A zero value means OWDP-
   Test streams have been successfully stopped.





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4.6. Retrieve-Session

   The format of this client command is 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
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |      4        |                                               |
        +-+-+-+-+-+-+-+-+                                               |
        |                             Unused                            |
        |                                                               |
        |                                                               |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                                                               |
        |                              SID                              |
        |                                                               |
        |                                                               |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                                                               |
        |                    Zero Padding (16 octets)                   |
        |                                                               |
        |                                                               |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The server MUST respond with a Control-Ack message. Again, any non-
   zero value in the Accept field means rejection of command.  Zero
   means that data will follow.

   If Yes/No was 0, the server then MUST send the OWDP-Test session data
   in question, followed by 16 octets of zero padding.

   The transmission starts with 4 octets that contain the number of
   records that will follow, each record representing one received
   packet.  This is followed by 2 octets of Sender Precision, 2 octets
   of Receiver precision, and 8 octets of zero padding.

   Each packet is represented with 20 octets, and includes 4 octets of
   sequence number, 8 octets of send timestamp, and 8 octets of receive
   timestamp.

   The last (possibly full, possibly incomplete) block (16 octets) of
   data is padded with zeros.  A zero padding consisting of 16 octets is
   then appended.








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5. OWDP-Test

   This section describes OWDP-Test protocol.  It runs over UDP using
   sender and receiver IP and port numbers negotiated during Session-
   Prepare exchange.

   As OWDP-Control, OWDP-Test has three modes: unauthenticated,
   authenticated, and encrypted.  All OWDP-Test sessions spawned by an
   OWDP-Control session inherit its mode.

   OWDP-Control client, OWDP-Control server, OWDP-Test sender, and OWDP-
   Test receiver can potentially all be different machines.  (In a
   typical case we expect that there will be only two machines.)


5.1. Sender Behavior

   The sender sends the receiver a stream of packets with Poisson
   distribution of times between packets.  The format of the body of a
   UDP packet in the stream depends on the mode being used.

   For unauthenticated mode:

         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
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                        Sequence Number                        |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                          Timestamp                            |
        |                                                               |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                                                               |
        .                                                               .
        .                   Packet padding (0-65515 octets)             .
        .                                                               .
        |                                                               |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   For authenticated mode:












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         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
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                        Sequence Number                        |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                                                               |
        |                         Zero Padding                          |
        |                                                               |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                          Timestamp                            |
        |                                                               |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                                                               |
        .                                                               .
        .                   Packet padding (0-65503 octets)             .
        .                                                               .
        |                                                               |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   For encrypted mode:

         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
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                        Sequence Number                        |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                          Timestamp                            |
        |                                                               |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                         Zero Padding                          |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                                                               |
        .                                                               .
        .                   Packet padding (0-65511 octets)             .
        .                                                               .
        |                                                               |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The format of timestamp is the same as that of NTP v3 protocol
   [RFC958]. Quoting from RFC 958:

      NTP timestamps are represented as a 64-bit fixed-point number, in
      seconds relative to 0000 UT on 1 January 1900.  The integer part
      is in the first 32 bits and the fraction part in the last 32 bits,
      as shown in the following diagram.






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       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         Integer Part                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         Fraction Part                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      This format allows convenient multiple-precision arithmetic and
      conversion to Time Protocol representation (seconds), but does
      complicate the conversion to ICMP Timestamp message representation
      (milliseconds).  The low-order fraction bit increments at about
      0.2-nanosecond intervals, so a free-running one-millisecond clock
      will be in error only a small fraction of one part per million, or
      less than a second per year.

   Sequence numbers start with 0.

   The minimum data segment length is therefore 12 octets in
   unauthenticated mode, 24 octets in authenticated mode, and 16 octets
   in encrypted mode.

   In authenticated and encrypted mode, the first block (16 octets) of
   each packet is encrypted using AES ECB mode.

   In unauthenticated mode, no encryption is applied.

   The time elapsed between packets is pseudo-random, with exponential
   distribution (resulting in a Poisson stream of packets).  As
   suggested in RFC 2330, the ith sampling interval Ei may be computed
   using inverse transform:

        Ei = -ln(Ui) * Inv-Lambda

   where Ui is uniformly distributed between 0 and 1 and lambda is the
   desired mean time between packets.

   Pseudo-random stream of bits is obtained using AES with SID as the
   key, running in counter mode (first encrypted block is 0, second
   encrypted block is 1 in network octet order, etc.)  Each block of 64
   bits is used to obtain one pseudo-random number uniformly distributed
   between 0 and 1.  If the bits are Bj (j=1..64, numbered left to
   right), the resulting value is
        U = B1*2^{-1} + B2*2^{-2} + ... B64*2^{-64}

   The parameter lambda is has the value requested in the Request-
   Session message of the OWDP-Control negotiation that spawned the
   session.



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   The logarithm and division in the formula above MUST be computed
   using IEEE 754 standard floating point arithmetic. [HELP WANTED!:
   Someone with a stronger background in numerical analysis to specify
   how to compute the sampling intervals precisely and portably!]

   Finally, Packet Padding SHOULD be pseudo-random (generated
   independently of any other pseudo-random numbers mentioned in this
   document).  However, implementations MUST provide a configuration
   parameter, an option, or a different means of making Packet Padding
   consist of all zeros.


5.2. Receiver Behavior

   Receiver knows when the sender will send packets.  The following
   parameter is defined: loss threshold.  It SHOULD be 10 minutes and
   MAY be more, but not more than 60 minutes.

   As packets are received,

   +  Timestamp the received packet.

   +  In authenticated or encrypted mode, decrypt first block (16
      octets) of packet body.

   +  Store the packet sequence number, send times, and receive times
      for the results to be transferred.

   +  Packets not received within the loss threshold are considered
      lost.  They are recorded with their seqno, presumed send time, and
      receive time consisting of a string of zero bits.


   Packets that have send time in the future MUST be recorded normally,
   without changing their send timestamp, unless they have to be
   discarded.

   If any of the following is true, packet MUST be discarded:

   +  Send timestamp is more than loss threshold in the past or in the
      future.

   +  Send timestamp differs by more than loss threshold from the time
      when the packet should have been sent according to its seqno.

   +  In authenticated or encrypted mode, any of the bits of zero
      padding inside the first 16 octets of packet body is non-zero.




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6. Security Considerations

   The goal of authenticated mode to let one password-protect service
   provided by a particular OWDP-Control server.  One can imagine a
   variety of circumstances where this could be useful.  Authenticated
   mode is designed to prohibit theft of service.

   Additional design objective of authenticated mode was to make it
   impossible for an attacker who cannot read traffic between OWDP-Test
   sender and receiver to tamper with test results in a fashion that
   affects the measurements, but not other traffic.

   The goal of encrypted mode is quite different: To make it hard for a
   party in the middle of the network to make results look "better" than
   they should be.  This is especially true if one of client and server
   doesn't coincide with neither sender nor receiver.

   Encryption of OWDP-Control using AES CBC mode with blocks of zeros
   after each message aims to achieve two goals: (i) to provide secrecy
   of exchange; (ii) to provide authentication of each message.

   OWDP-Test sessions directed at an unsuspecting party could be used
   for denial of service (DoS) attacks.  In unauthenticated mode servers
   should limits receivers to hosts they control or to the OWDP-Control
   client.

   OWDP-Test sessions could be used as covert channels of information.
   Environments that are worried about covert channels should take this
   into consideration.

   Notice that AES in counter mode is used for pseudo-random number
   generation, so implementation of AES MUST be included even in a
   server that only supports unauthenticated mode.


7. References

   [AES]     Advanced Encryption Standard (AES),
        http://csrc.nist.gov/encryption/aes/

   [RFC958]D. Mills, "Network Time Protocol (NTP)", RFC 958, September
        1985.

   [RFC2026]S. Bradner, "The Internet Standards Process -- Revision 3",
        RFC 2026, October 1996.

   [RFC2119]S. Bradner, "Key words for use in RFCs to Indicate
        Requirement Levels", RFC 2119, March 1997.



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   [RFC2330]     V. Paxon, G. Almes, J. Mahdavi, M. Mathis, "Framework
        for IP Performance Metrics" RFC 2330, May 1998.

   [RFC2679]G. Almes, S. Kalidindi, and M. Zekauskas, "A One-way Delay
        Metric for IPPM", RFC 2679, September 1999.

   [RFC2680]G. Almes, S. Kalidindi, and M. Zekauskas, "A One-way Packet
        Loss Metric for IPPM", RFC 2680, September 1999.

   [RFC2836]S. Brim, B. Carpenter, F. Le Faucheur, "Per Hop Behavior
        Identification Codes", RFC 2836, May 2000.

   [RIPE]     Ripe Test-Traffic Home page, http://www.ripe.net/test-
        traffic/.

   [RIPE-NLUUG]H. Uijterwaal and O. Kolkman, "Internet Delay
        Measurements Using Test-Traffic", Spring 1998 Dutch Unix User
        Group Meeting, http://www.ripe.net/ripencc/mem-
        services/ttm/Talks/9805_nluug.ps.gz.  (NOTE: it's actually
        postscript, not gzip'd postscript.)

   [SURVEYOR]     Surveyor Home Page, http://www.advanced.org/surveyor/.

   [SURVEYOR-INET]S. Kalidindi and M. Zekauskas, "Surveyor: An
        Infrastructure for Network Performance Measurements",
        Proceedings of INET'99, June 1999.
        http://www.isoc.org/inet99/proceedings/4h/4h_2.htm


8. Authors' Addresses

   Stanislav Shalunov
   Internet2 / UCAID
   200 Business Park Drive
   Armonk, NY  10504
   USA

   Phone: +1 914 765 1182
   EMail: shalunov@internet2.edu












Shalunov et al.                                                [Page 19]

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   Benjamin Teitelbaum
   Advanced Network & Services
   200 Business Park Drive
   Armonk, NY 10504
   USA

   Phone: +1 914 765 1118
   EMail: ben@advanced.org

   Matthew J. Zekauskas
   Advanced Network & Services, Inc.
   200 Business Park Drive
   Armonk, NY  10504
   USA

   Phone: +1 914 765 1112
   EMail: matt@advanced.org


   Expiration date: June 2001































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