Address Resolution

The first step in routing the SIP request is to compute the mapping between the URI and a specific user at a specific host/address.

This is a very general process and the source of much of SIP’s power.

providing support for mobility and portability
Can utilize:
- DNS SRV lookup
- ENUM
- Location Server lookup

We will look at this in detail (see DNS and ENUM later in the lecture notes), but for now will assume a simple DNS lookup based on the URI.

Transcript

[slide125] So address resolution, why do we need that? We want mobility and portability. So I ought to be able to take my SIP user agent go home and it's still me, I should still be reachable by it. Well, we can think about using DNS and do a service lookup. So, if I change, I need a dynamic DNS entry, I put a DNS entry. We can think about using ENUM, we'll come back to that later, or we could do something, hey we have a location server that the registrar updates my location, and now when calls come in, my proxy knows, hey, look in the location server, these are the locations where his UAs currently are. And we'll take a look at this one first, we'll come back to the others later.