Ser, the sip express router, is a very fast and flexible server for sip (the session initiation protocol). it can act as a sip registrar, proxy or redirect server. ser can be configured to serve specialized purposes such as load balancing or sip front-end to application servers. together with the rtpproxy it can act as media relay or session border controller.

ser features complete support of rfc 3261 functionality, a variety of database backends, management features, load-balancing), nat traversal, telephony features (lcr, speeddial), multidomain hosting, enum, presence, and more.