Re: [reSIProcate-users] Using DUM as a proxy server

[Andrew Wood <ajwood@xxxxxxx>]

Thanks Adam.


On 11 Oct 2008, at 16:48, Adam Roach wrote:
> >
>
> 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
>
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