[SIPForum-discussion] Is there a explanation about the route rules in 3261?

[肖锐]

Hi, all 
Is there a book or any technical article to explanation the ALL route rules in SIP(rfc3261), 
for example: 
what's the difference between Request-URI and To ? 
And the route , record-route, via ? 
UAC, UAS, proxy behavior?
it's really trouble me. 
And I want a explanation in-depth, not that I can know it from 3261 easily.Thanks!
  Regards! 

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