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@nokia.com Sasha Ruditsky sasha@tlv.radvision.com Paul Jones paul.jones@ties.itu.int Michael Boaz boaz_michaely@icomverse.com Lincoln Haresign haresign@comverse-in.com Roy Radhika rrroy@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) (http://www.ietf.org/internet-drafts/draft-ietf-sigtran-sctp-07.txt)
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) http://www.ietf.org/internet-drafts/draft-xie-stewart-sigtran-ddp-00.txt
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 failure.
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@nokia.com www.nokia.com