Subject: [Sip] comments on draft-ietf-sip-hop-limit-diagnostics-03

From: Jonathan Rosenberg <[email-masked]>
Date: Fri, 07 Jul 2006 02:04:32 -0400

major issues:

Well, no change here in these. I think we need more discussion on them:

1. I still think this mechanism is applicable outside of max-forwards 
violations. The current text limits it to 483.

2. I agree with Cullen that we do need to specify a size limit for the 
response. Having thought about it more, I'm worried that the sipfrag 
body can't be more than 200 bytes! Consider a request that loops a lot. 
At some point, the via header itself will grow sufficiently to cause the 
mesage to switch from udp to tcp. That happens at the point at which the 
udp request exceeds 1300 bytes. For a response to that request to be 
also sent over UDP with no fragmentation, the response cannot be larger 
than the request by more than 200 bytes.

Now, you might argue that proxies often strip Via's, and that a small 
max-forwards might never get the request to pop over to tcp. However if 
you are looking for a safe value, its 200  bytes.

Thsi might motivate us to look at something different to return the data 
to the client, rather than in that response. Another option is content 
indirection.

minor issues:

> The SIP protocol imposes a limit on the number of hops a request can
>    transit on the way to its destination.  The number of hops remaining
>    for the request is carried in the Max-Forwards header, and is

header field

>    request has traversed a series of proxies, the response follows the
>    Vias back to the requester - in the case of a typical 483 response it
>    can be difficult to determine even what server the response came

same comment as on -02. Difficult implies that its possible, just hard. 
Its NOT possible.

>     A Warning header with a warn-code of 399 that identifies the
>          system returning the error.

header field

>  If including all Via and Route headers is still too large, the
>    implementation SHOULD remove the oldest Vias (those nearest the
>    message originator) until the size is acceptable; the only exception
>    to this rule is when . 

when....?

Thanks,
Jonathan R.
-- 
Jonathan D. Rosenberg, Ph.D.                   600 Lanidex Plaza
Cisco Fellow                                   Parsippany, NJ 07054-2711
Cisco Systems
[email-masked]                              FAX:   (973) 952-5050
http://www.jdrosen.net                         PHONE: (973) 952-5000
http://www.cisco.com

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