Subject: Two questions

From: "yinshaohua" <[email-masked]>
Date: Mon, 6 Mar 2000 12:56:41 +0800

Hi:
    I have two questions about RFC2543,:
    A. In RFC2543bis, there has " A BYE request from either called or
calling party terminates any pending INVITE, but the INVITE request
transaction must be completed with a final response". is it necessary to
send response to INVITE and BYE simultaneously ? If necessary, we can define
single response that indicate the above case. so it is simpler.

    B. A forking proxy can forward a request to different UAS, then UAS add
Tag to TO header field of backward response in order to distinguish the Call
Leg. So how can we guarantee the Tag added by different UAS single ? In
other words, different UAS may add the same Tag, so we can not distinguish
the response from them.

    have there any rational explanation ? Regards!

Shaohua Yin

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From: Igor Slepchin <[email-masked]>
Date: Mon, 06 Mar 2000 01:11:55 -0500

> single response that indicate the above case. so it is simpler.

It is simpler to have all transactions complete in a consistent manner
than to create special cases by making the behavior dependent on
consecutive transactions. Besides, BYE/CANCEL and a response to INVITE
may cross on the wire so the UAC should still be prepared to send an ACK
should a final response be received.

> So how can we guarantee the Tag added by different UAS single ? In

The draft says that "the tag value MUST be globally unique". You are
free to use any algorithm that ensures such uniqueness. RFC2543 suggests
that you use UUID for tags; a copy of UUID/GUID draft can be found at
http://www.ics.uci.edu/pub/ietf/webdav/uuid-guid/draft-leach-uuids-guids-01.txt.
Note that the draft itself has expired and is no longer maintained in
IETF archives; the same algorithm is described in an appendix to
ISO-11578 (ISO RPC standard), the only tangible difference is the extra
information in the IETF draft on how to generate GUIDs without embedding
hardware ethernet addresses.

---
Igor Slepchin