[Robustneness] Telecon minutes March 20, 2000

Maureen Stillman Maureen.Stillman at NOKIA.COM
Tue Mar 21 16:19:31 EST 2000

Minutes of H.323 Robustness Teleconference - March 20, 2000
Prepared by Maureen Stillman, Nokia

Next Teleconference:  Tentatively set for April 6, 2000 9AM EST USA

Action items from this teleconference:

        1.      Post meeting minutes to mailing list
        2.      Jorg Ott will provide failure scenarios for gatekeepers for
the Robustness Framework document.
        3.      Terry Anderson will provide H.225 and H.245 state machines
for us to review.
        4.      Terry Anderson will provide failure scenarios involving a GK
which exchanges information with a clearinghouse
        5.      Ask Randy Stewart, Qiaobing Xie of Motorola and Chip Sharp
of Cisco to join us for the next teleconference to discuss SCTP and DDP and
answer questions (see below for details).

Attending the 3/20/2000 teleconference:

Maureen Stillman maureen.stillman at nokia.com
Sasha Ruditsky sasha at tlv.radvision.com
Paul Jones paul.jones at ties.itu.int
Michael Boaz boaz_michaely at icomverse.com
Lincoln Haresign haresign at comverse-in.com
Roy Radhika rrroy at att.com

Summary of Teleconference:

SDL for the robustness procedure:

We discussed the SDL for the robustness procedure produced by Sasha Ruditsky
of Radvision (attached).   This SDL is for the Geneva SG-16 document from
the February 2000 meeting, document TD87 from WP2. Since there was not
adequate time for the participants to read the SDL document, we decided to
put it on the agenda for the next teleconference.  Sasha gave an overview
and summary of the SDL.

SCTP (Simple Control Transmission Protocol)

>From the IETF internet-draft abstract:

"SCTP is designed to transport PSTN signaling messages over IP networks, but
is capable of broader applications.  SCTP is a reliable datagram transfer
protocol operating on top of an unreliable routed packet network such as IP.
It offers the following services to its users:

  -- acknowledged error-free non-duplicated transfer of user data,
  -- data segmentation to conform to discovered path MTU size,
  -- sequenced delivery of user messages within multiple streams,
     with an option for order-of-arrival delivery of individual
     user messages,
  -- optional multiplexing of user messages into SCTP datagrams, and
  -- network-level fault tolerance through supporting of multi-homing
     at either or both ends of an association.

The design of SCTP includes appropriate congestion avoidance behavior
and resistance to flooding and masquerade attacks."

It can take several minutes to discover that a TCP connection has failed.
Using SCTP however, you can find this out in 63 seconds or less.  The group
decided to examine SCTP in closer detail and evaluate its use for robustness
purposes for the call signaling and call control channels.  We wanted an
expert to discuss this with at our next telecon, so we decided to ask Chip
Sharp to join us.  Chip referred us also to Randy Stewart and Quiobing Xie
of Motorola.

DDP (Distributed Data protocol)

>From the IETF internet-draft abstract:

"Data Distribution Protocol (DDP) provides a fault tolerant data transfer
mechanism over IP networks. DDP uses a name-based addressing model which
isolates a logical communication endpoint from its IP address(es), thus
effectively eliminating the binding between the communication endpoint and
its physical IP address(es) which normally constitutes a single point of

In addition, DDP defines each logical communication destination as a named
group, providing full transparent support for server-pooling and load
sharing. It also allows dynamic system scalability - members of a server
pool can be added or removed at any time without interrupting the service.

DDP is designed to take full advantage of the network level redundancy
provided by the Simple Transmission Control Protocol (SCTP). But it can also
use other transport protocol like TCP."

The group will review the DDP protocol and discuss it at the next
teleconference.  This Internet draft was released on March 6.  The group
will explore its application to H.323.

-- maureen

Maureen Stillman
Member of Scientific Staff             Voice: (607)273-0724 x62
Nokia IP Telephony                      Fax: (607)275-3610
127 W. State Street                     Mobile: (607)227-2933
Ithaca, NY 14850
e-mail: maureen.stillman at nokia.com

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