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Andrew Wood wrote:
Is there ay reason why I couldnt / shouldnt use DUM as a base for a proxy server. Im unclear as to the difference between repro and DUM, I know repro is for proxies and DUM for user agents but from an implementation perspective what is the difference. I prefer the look of DUM
RFC 3261 defines some extremely important differences between proxies and user agents. Repro implements the rules for proxies. DUM implements the rules for user agents.
You can build a "back-to-back user agent" (aka B2BUA) using DUM, and you can make it do some of the things that people use proxies for -- at least, kind of. But B2BUAs have a variety of shortcomings that make them inappropriate for general use.
For example, when a new service is defined, it can usually be implemented by adding appropriate behaviors in the end-points, without touching the proxies in the middle. (Most of the rules about what proxies must do and what they must not do are aimed at ensuring that they don't get in the way of new services). On the other hand, if there are B2BUAs between the endpoints, then they all need to be upgraded to support the new service as well.
This is one of several problems introduced by B2BUAs; others include breaking the security model of the SIP network, and inherently poorer scaling characteristics due to the need to keep more state in the network.
To reiterate: it is actually impossible to build a proxy with DUM. The best you can build is a B2BUA, and you probably don't want to do that.
/a