130 |
SIP: Understanding the Session Initiation Protocol |
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Figure 5.4 Session negotiation with SIP.
5.6.3604 Does Not Exist Anywhere
This response is similar to the 404 Not Found response but indicates that the user in the Request-URI cannot be found anywhere. This response should only be sent by a server that has access to all information about the user.
5.6.4606 Not Acceptable
This response can be used to implement some session negotiation capability in SIP. This response indicates that some aspect of the desired session is not acceptable to the UAS, and as a result, the session cannot be established. The response may contain a Warning header field with a numerical code describing exactly what was not acceptable. The request can be retried with different media session information. An example of simple negotiation with SIP is shown in Figure 5.4. If more complicated negotiation capability is required, another protocol should be used.
5.7Questions
Q5.1 If a UA reboots in the middle of a SIP session and looses all state information, what response is it likely to send to a re-INVITE or BYE from the other UA?
Q5.2 In terms of the behavior of the UAC originator of the request, explain the difference between a 4xx and 5xx response.
Q5.3 Which response would likely be generated to this request?
SIP Response Messages |
131 |
REGISTER sip:registrar.munich.de SIP/2.0
Via: SIP/2.0/UDP 200.201.202.203:5060;branch=z9hG4bKsdus19 Max-Forwards: 70
To: Werner Heisenberg <sip:werner.heisenberg@munich.de> From: Werner Heisenberg <sip:werner.heisenberg@munich.de> ;tag=3431
Call-ID: 7ds376fd4291 CSeq: 1 REGISTER
Contact: <sip:werner.heisenberg@200.201.202.203>;expires=1 Content-Length: 0
Q5.4 Give two differences between a 100 response and a 180 response.
Q5.5 What action should be taken by a UAC that receives a 412 response?
Q5.6 How is a 3xx response different from a REFER?
Q5.7 Generate a SIP call flow with two UAs and a proxy where a 408 response is sent.
References
[1]Rosenberg, J., H. Schulzrinne, G. Camarillo, A. Johnston, J. Peterson, R. Sparks, M. Handley, and E. Schooler, “SIP: Session Initiation Protocol,” RFC 3261, 2002.
[2]Camarillo, G., et al., “Integrated Services Digital Network (ISDN) User Part (ISUP) to Session Initiation Protocol (SIP) Mapping,” RFC 3398, 2002.
[3]Roach, A., “SIP Specific Events,” RFC 3265, 2002.
[4]Niemi, A., “An Extension to Session Initiation Protocol (SIP) Events for Conditional Event Notification,” draft-ietf-sipcore-subnot-etags-09 (work in progress), April 2009.
[5]Niemi, A., “Session Initiation Protocol (SIP) Extension for Event State Publication,” RFC 3903, October 2004.
[6]Schulzrinne, H., and J. Polk, “Communications Resource Priority for the Session Initiation Protocol (SIP),” RFC 4412, February 2006.
[7]Donovan, S., and J. Rosenberg, “Session Timers in the Session Initiation Protocol (SIP),” RFC 4028, April 2005.
[8]Peterson, J., and C. Jennings, “Enhancements for Authenticated Identity Management in the Session Initiation Protocol (SIP),” RFC 4474, August 2006.
[9]Sparks, R., “The SIP Referred-By Mechanism,” RFC 3892, September 2004.
[10]Jennings, C., and R. Mahy, “Managing Client Initiated Connections in the Session Initiation Protocol (SIP),” draft-ietf-sip-outbound-20 (work in progress), June 2009.
[11]Rosenberg, J., “Rejecting Anonymous Requests in the Session Initiation Protocol (SIP),” RFC 5079, December 2007.
[12]Sparks, R., et al., “Addressing an Amplification Vulnerability in Session Initiation Protocol (SIP) Forking Proxies,” RFC 5393, December 2008.
132 |
SIP: Understanding the Session Initiation Protocol |
[13]Rosenberg, J., G. Camarillo, and D. Willis, “A Framework for Consent-Based Communications in the Session Initiation Protocol (SIP),” RFC 5360, October 2008.
[14]Anttalainen, T., Introduction to Telecommunications Network Engineering, Norwood, MA: Artech House, 1999.
[15]Arkko, J., et al., “Security Mechanism Agreement for the Session Initiation Protocol (SIP),” RFC 3329, January 2003.
[16]Rosenberg, J., and H. Schulzrinne, “Session Initiation Protocol (SIP): Locating SIP Servers,” RFC 3263, 2002.
[17]Camarillo, G., W. Marshall, and J. Rosenberg, “Integration of Resource Management and Session Initiation Protocol (SIP),” RFC 3312, October 2002.