Subject: RE: [SIP] Congestion control

From: "Michel A. Maddux" <[email-masked]>
Date: Sat, 7 Jul 2001 10:54:09 -0600

RE: [SIP] Congestion control
  -----Original Message-----
  From: [email-masked]
[mailto:[email-masked]]On Behalf Of Wai Wu
  Sent: Friday, June 22, 2001 11:16 AM
  To: 'Hidefumi Nakamura'; [email-masked]
  Subject: RE: [SIP] Congestion control

  "but what should "proxy A"
  do if it receives other INVITE messages for proxyB, say, from UAc, within
  the period indicated in "retry-after" field?
  Should proxy-A send "503" to UAc or transfer the INVITE message
  to proxy-B even if proxy-A already has the information that proxy-B
  is in congestion?"

  Wai writes:

   >> In my implementation, proxy A still forwards the INVITE message to
proxy-B for UAc. This is so since the UA the UAc is trying  to contact might
very well be different from that of UAa. Take the example of proxy-B
forwards the request to two different PSTN gateway, one for local calls and
the other for international calls. The international all gateway might be
down but not the local call gateway.

  =====

  I concur.  Proxy A should send the INVITE anyway, as the congestion or
cause of the 503 retry condition is most likely a transient condition.
There is no way to predict in advance whether the congestion has cleared
prior to the INVITE; to assume this knowledge and allow proxy A to send a
503 is an error. thanks. /m.