Re: [rtcweb] STUN for keep-alive

Christer Holmberg <christer.holmberg@ericsson.com> Wed, 14 September 2011 11:28 UTC

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From: Christer Holmberg <christer.holmberg@ericsson.com>
To: "Muthu Arul Mozhi Perumal (mperumal)" <mperumal@cisco.com>, "rtcweb@ietf.org" <rtcweb@ietf.org>
Date: Wed, 14 Sep 2011 13:30:44 +0200
Thread-Topic: [rtcweb] STUN for keep-alive
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Subject: Re: [rtcweb] STUN for keep-alive
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Hi, 

>>|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.

Sure, but there is still a max time between the keep-alives.

>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?

Yes.

Also, it's not only about how often the STUN keep-alives would be sent, and the perfomance impact that would have. Using e.g. RTP, the media handler would not have to be prepared to receive the STUN keep-alives in the first place, it could simply just relay whatever comes on the media plane.

Regards,

Christer




> |-----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
>