[SIPForum-discussion] Difference between stateless and stateful proxy in SIP protocol

Tue Sep 28 19:27:16 UTC 2010

Most UAC's will not be able to traverse 100 proxy's.  The standard is to set Max-forwards to 70 in the initial REQUEST:

8.1.1.6 Max-Forwards

   The Max-Forwards header field serves to limit the number of hops a

   request can transit on the way to its destination.  It consists of an

   integer that is decremented by one at each hop.  If the Max-Forwards

   value reaches 0 before the request reaches its destination, it will

   be rejected with a 483(Too Many Hops) error response.

   A UAC MUST insert a Max-Forwards header field into each request it

   originates with a value that SHOULD be 70.  This number was chosen to

   be sufficiently large to guarantee that a request would not be

   dropped in any SIP network when there were no loops, but not so large

   as to consume proxy resources when a loop does occur.  Lower values

   should be used with caution and only in networks where topologies are

   known by the UA.

Corey Thornburg

VoIP Architect

-----Original Message-----
From: discussion-bounces at sipforum.org [mailto:discussion-bounces at sipforum.org] On Behalf Of Kevin P. Fleming
Sent: Tuesday, September 28, 2010 1:03 PM
To: discussion at sipforum.org
Subject: Re: [SIPForum-discussion] Difference between stateless and stateful proxy in SIP protocol

On 09/27/2010 11:06 PM, Ruben Roque wrote:

> 1) I want to know an example of a stateless proxy and a stateful proxy.

> Is B2BUA a stateless or stateful proxy?

Neither. Proxies are not UAs, by definition, so a B2BUA cannot be a proxy.

> 2) If a INVITE request is to be sent from user A to user B, but there

> are 100 stateless proxies in path -- will the request be successfully

> delivered to user B?

There isn't enough information in this question to be able to answer

it... but assuming that all the proxies are configured properly, and

that the network elements between them are working correctly, sure,

there's no reason to think the request wouldn't be successfully delivered.

--

Kevin P. Fleming

Digium, Inc. | Director of Software Technologies

445 Jan Davis Drive NW - Huntsville, AL 35806 - USA

skype: kpfleming | jabber: kfleming at digium.com

Check us out at www.digium.com & www.asterisk.org

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