Presence and IntComm WG

[Ben Teitelbaum <>]

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• From: Henning Schulzrinne <>
• To:
• Cc: Doug Pearson <>, Ben Teitelbaum <>, ,
• Subject: Re: [wg-pic] Tolly's Skype critique
• Date: Fri, 30 Sep 2005 19:41:11 -0400
• Organization: Columbia University
• Xref: desk176.internet2.edu mail.inbox:81269

http://www1.cs.columbia.edu/~salman/skype/index.html

Carl S. Ford wrote:
> Henning, can probably give some thoughts here.
>
>>
>> The Tolly article says "dearth of information available to us, we
>> learned most of what we know by studying Skype 'in the wild'"... but
>> it doesn't share much about those details.
>>
>> Doug Pearson
>>
>>>> In this article, Tolly studied Skype peer-to-peer traffic to evaluate
>>>> the impact on network bandwidth. He quoted the Skype Web site on what
>>>> peer-to-peer means: "A true [peer-to-peer] system, in our opinion, is
>>>> one where all nodes in a network join together dynamically to
>>>> participate in traffic routing-, processing- and bandwidth-intensive
>>>> tasks that would otherwise be handled by central servers." Interesting
>>>> view. Tolly suggests that this means your Skype-enabled workstation
>>>> may be functioning as a traffic relay for otherwise-centralized call
>>>> processing, conferencing, voice mail, etc.
>>>
>>>
>>> That seems like a fair definition of "true peer-to-peer" to me. One
>>> of the big reasons that universities may see a lot of Skype traffic is
>>> the use of public IP addresses. Skype needs a share of its users to
>>> be non-NATted to serve as media relays for hosts behind
>>> tricky-to-traverse NATs.
>>>
>>> -- ben
>>>
>>> --
>>> Ben Teitelbaum http://people.internet2.edu/~ben/
>>
>>
>>
>>
>
>
>



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-- 
Ben Teitelbaum   http://people.internet2.edu/~ben/