Subject: RE: [IPTEL] Call admission control

From: "james.yang" <[email-masked]>
Date: Thu, 15 Jun 2000 17:02:45 -0700

Hi, 

Call admission control is a traditional concept derived from PSTN, ISDN, SONET and ATM networks. Because there is no global resource management on IP network, any effort on call-based resource allocation or traffic engineering in network layer (IP) is opposite to the fundament of Internet. Existing technologies for providing QoS guaranteed call on Internet is session layer control such as RSVP, RTP and MPLS. But they assume that the network has unlimited resource. If you desire to make traffic engineering on resource-limited Internet and refuse some new calls while the traffic is in congestion somewhere, you need a global resource management server, which surveys the traffic on routers and links, as well as free process capacity in routers and residual bandwidth on links. All access points act as the agent of the server and execute admission control functions. Is it possible? No. The only solution for this issue is hierarchical dynamic statistical routing optimization protocol. It intends to update routing tables dynamically in order to reserve enough free resource on routers and links for further use. It can be used with any resource reservation protocol. I have taken a very careful study on it and propose a framework for it, but I don't know whether it has been realized and implemented by now. 

James

-----Original Message-----
From:	Billy Biggs [SMTP:[email-masked]]
Sent:	Wednesday, June 14, 2000 1:50 PM
To:	Larry Cox
Cc:	[email-masked]
Subject:	Re: [IPTEL] Call admission control

Larry Cox ([email-masked]):

> >Does any of you have some references for specific call admission control
> >techniques that might have been considered for traffic engineering in the
> >IP for avoiding congestion in networks carrying telephony flows?
> >Thanks in advance,
> 
> As you are probably already aware, the problem is both very serious and
> rather difficult to resolve. In a public Internet environment, even with
> significant free bandwidth, packet voice is frequently completely
> incomprehensible. Packet jitter can turn voice into nearly completely
> random noise.

  Larry,

  Not that this is the right forum or even the right thread, I'm very
curious about your statements on the unreliability of packet voice over
the public Internet.  I've now had several trans-atlantic telephone calls
over the public Internet, and often use packet voice for shorter range
(100ms avg lag, 20 hops) Internet calls.  64kbps u-law, RTP encapsulated
in each direction.

  I have never experienced the audio to be 'incomprehensible'.  Even with
no traffic shaping or control, and even when talking to people on cable
modems with reasonable amounts of traffic, it's still much better than
most cellphones.

  Do you have any references to papers or web pages which indicate that
strong admission control or traffic management is useful beyond very
extreme networks or specifc cases of heavy bandwidth applications?

  In general, TCP seems back off quite happily.

-- 
Billy Biggs                         [email-masked]
http://www.div8.net/billy       [email-masked]

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