IM Threat to Net?

[BigBlueBall News]

NetworkWorldFusion

January 14, 2002

The Internet engineering community has run into a significant technical hurdle in the development of an industry standard to support instant messages with multimedia attachments, such as audio or video clips.

If leading instant messaging service providers such as AOL and Microsoft offer multimedia instant messaging services to their millions of users, Internet communications could ground to a halt. Service providers now support only text-based instant messages.

The Internet Engineering Task Force (IETF), which identified the multimedia instant messaging problem, is soliciting potential fixes from its participants and plans to debate these fixes at its meeting in March.

IETF leaders say protocols being developed to support text-based instant messaging won�Œt handle multimedia instant messaging attachments. They say a new communications protocol is needed to transport those files. This new protocol must provide congestion-control mechanisms to prevent instant messaging users from overwhelming the Internet�Œs backbone with MP3 music files, photos or voice clips.

"There would be a potential for an AOL usage [of multimedia instant messaging] to either swamp out the rest of the Internet or to require major engineering to stop what we call a congestion collapse, where you cannot send new traffic into the network," says Allison Mankin, co-chair of the IETF�Œs transport area. "This is a big enough problem to need urgent attention."

Demand for multimedia instant messaging is expected to be strong. Text-based instant messaging is popular on the Internet and private, corporate intranets. With multimedia instant messaging, users could send attachments along with chat sessions.

"Our researchers would love to have voice chat integrated with instant messaging, mainly to kill the international long-distance calls," says Ross McKenzie, director of IS at Johns Hopkins University. "Our dean has a research center in Nepal. I know that if I offered that service, he�Œd be on it tomorrow."

Johns Hopkins began offering regular instant messaging services to 4,000 faculty and staff members in August. Today, instant messaging is the most popular application on the university�Œs Web portal, with more than 1,500 users racking up 60,000 minutes of instant messaging messages per month.

"If we offered [instant messaging] attachments, our faculty would be exchanging chapters out of books. But what they�Œd really like is voice," McKenzie says. "Our researchers want ad hoc, integrated voice and chat. They want it in Katmandu, at home, at Starbucks or wherever."

Today�Œs instant messaging services use what�Œs called a paging mode, where the signaling information that initiates the chat session is carried along with the text of the chat session using a single protocol.

After four years of effort, the IETF is finalizing a protocol dubbed SIMPLE (SIP for Instant Messaging and Presence Leveraging Extensions) that will let the paging mode work across different instant messaging service providers�Œ offerings. Once deployed, SIMPLE will let AOL users exchange text-based instant messages with users of rival instant messaging services from Microsoft, Yahoo and others. Both AOL and Microsoft have vowed to support SIMPLE.

SIMPLE uses Session Initiation Protocol (SIP) to initiate an instant message and to transport it on a hop-by-hop basis across the Internet. While SIMPLE can handle short, text-based messages of up to 1,000 characters, IETF participants have discovered that it cannot carry attachments to instant messaging sessions. This is because of an inherent problem in SIP, which runs on TCP or User Datagram Protocol (UDP). While TCP features built-in congestion controls, UDP does not.

So UDP should not be used for sending large files. And SIP can�Œt be adjusted to eliminate the possibility that large files would be sent over UDP. That scenario would be catastrophic, Mankin says. "Imagine the after-school surge, with millions of teenagers online and sending MP3s to each other," she says. "We�Œre talking about volumes of traffic that may be half of the backbone."

Mankin says even if AOL were to offer multimedia instant messaging attachments only to its own users, that could still cause congestion problems across the Internet if this issue isn�Œt resolved.

"We can�Œt tell AOL what to do, but they use all the major backbone providers," she says. "If UDP could be used by their [multimedia instant messaging] service, that would be a serious problem."

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