Re: [rtcweb] STUN for keep-alive

"Muthu Arul Mozhi Perumal (mperumal)" <mperumal@cisco.com> Wed, 14 September 2011 11:22 UTC

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Date: Wed, 14 Sep 2011 16:53:52 +0530
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From: "Muthu Arul Mozhi Perumal (mperumal)" <mperumal@cisco.com>
To: "Christer Holmberg" <christer.holmberg@ericsson.com>, <rtcweb@ietf.org>
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Subject: Re: [rtcweb] STUN for keep-alive
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|Well, it depends on the amount of outgoing media traffic, 
|but in cases where you only receive media you would still 
|need to send keep-alives.

If you are not sending anything the NAT binding in that direction will
likely timeout. On the other hand, if you are operating in a controlled
environment ICE already allows you to set the STUN keepalive duration to
the longest duration possible in your environment, so it is already
flexible.

However, it mandates STUN keepalives to be used when an agent is a full
ICE implementation and is communicating with a peer that supports ICE
(lite/full). Are you saying it should allow a different UDP keepalive
method because it can possible have a lesser performance impact?

Muthu

|-----Original Message-----
|From: Christer Holmberg [mailto:christer.holmberg@ericsson.com]
|Sent: Wednesday, September 14, 2011 3:59 PM
|To: Muthu Arul Mozhi Perumal (mperumal); rtcweb@ietf.org
|Subject: RE: [rtcweb] STUN for keep-alive
|
|
|Hi,
|
|>|Because, eventhough the keep-alives messages aren't authenticated,
and
|>|do not trigger responses, a gateway would still have to
|>|process them, and since a gateway typically would serve a large
number of browser
|>|clients, that could have quite big performance impact (the number of
|>|STUN keep-alives sent per session of course depend on how much other
|>|media traffic there is, but still).
|>
|>STUN keepalives are required by ICE only in the absence of
|>media traffic.
|
|Yes. That's what I meant with the:
|
|	"(the number of STUN keep-alives sent per session of course
depend on how much other media
|traffic there is, but still)"
|
|...statement :)
|
|>Here are the snip from RFC 5245:
|>
|><snip>
|>10.  Keepalives
|>
|>If there has been no packet sent on the candidate pair ICE is
|>using for a media component for Tr seconds (where packets
|>include those defined for the component (RTP or RTCP) and
|>previous keepalives), an agent MUST generate a keepalive on
|>that pair.  Tr SHOULD be configurable and SHOULD have a
|>default of 15 seconds.  Tr MUST NOT be configured to less
|>than 15 seconds.
|></snip>
|>
|><snip>
|>20.2.3.  Keepalives
|>
|>STUN keepalives (in the form of STUN Binding Indications) are
|>sent in the middle of a media session.  However, they are
|>sent only in the absence of actual media traffic. In
|>deployments that are not utilizing Voice Activity Detection
|>(VAD), the keepalives are never used and there is no increase
|>in bandwidth usage.  When VAD is being used, keepalives will
|>be sent during silence periods.  This involves a single
|>packet every 15-20 seconds, far less than the packet every
|>20-30 ms that is sent when there is voice.  Therefore,
|>keepalives don't have any real impact on capacity planning.
|></snip>
|>
|>Do you think there is still a problem?
|
|Well, it depends on the amount of outgoing media traffic, but in cases
where you only receive media
|you would still need to send keep-alives.
|
|Regards,
|
|Christer