Hi Kchitiz, The server adds the received parameter to the top Via entry.
RFC 3261 section 18.2.1: "When the server transport receives a request over any transport, it MUST examine the value of the "sent-by" parameter in the top Via header field value. If the host portion of the "sent-by" parameter contains a domain name, or if it contains an IP address that differs from the packet source address, the server MUST add a "received" parameter to that Via header field value. This parameter MUST contain the source address from which the packet was received. This is to assist the server transport layer in sending the response, since it must be sent to the source IP address from which the request came." ----- From: Kchitiz Saxena [mailto:kchitiz.sax...@gmail.com] Sent: Friday, September 19, 2014 1:20 PM To: Brett Tate Cc: Sip-implementors@lists.cs.columbia.edu Subject: Re: [Sip-implementors] UAS behaviour for sending responses Hi Brett There is no received parameter in the request. Below is the Via header I can see in the pcap taken at UAS - Via:SIP/2.0/UDP XX.YYY.ZZZZ.net;branch=z9hG4bKBW.-tsom1l-91.230.17.136V5060-0-107949759-1337557677-1411112656253- When UAS resolves XX.YYY.ZZZZ, it receives IP address B at top, the source IP address (A) of the INVITE request is also present but that is after IP address B. On Fri, Sep 19, 2014 at 7:34 PM, Brett Tate <br...@broadsoft.com> wrote: Hi Kchitiz, Concerning your question, you skipped the first part of section 18.2.2 bullet 3 (assuming UDP). If first part of bullet 3 is successful, the UAS does not need to resolve the sent-by FQDN. o Otherwise (for unreliable unicast transports), if the top Via has a "received" parameter, the response MUST be sent to the address in the "received" parameter, using the port indicated in the "sent-by" value, or using port 5060 if none is specified explicitly. If this fails, for example, elicits an ICMP "port unreachable" response, the procedures of Section 5 of [4] SHOULD be used to determine where to send the response. _______________________________________________ Sip-implementors mailing list Sip-implementors@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
