Comparison of SIP Proxy and Redirect Servers Presented

Comparison of SIP Proxy and Redirect Servers Presented By: Greg Osterhout Sr. Mgr, SIP Services Development and Evolution

SIP Reference Architecture I 2004 Ether. Sets SIP Soft Client SIP USB Phone Terminal Endpoints • SIP User Agent for user devices User Proxy SIP User Proxy Network/User Proxy • Registration of SIP endpoints • Provides endpoint mobility • User specific services • Domain resolution SIP Network Nodes SIP SIP Mobil Oil Network User Proxy PSTN SS 7/PRI PSTN Gateway • SIP User Agent for PSTN Trks • SIP services for PSTN terminations

SIP User Proxy • Primarily exist in customer IP networks • Provides endpoint mobility services via SIP registration methods • Provides wide range of user specific services — simple canned service — full user controlled services via CGI or CPL scripts or servlets Network User Proxy • Provides Domain mapping for network endpoints • Could provide SIP services to customers that can’t feasibly manage their own user proxy Proxy Capability Driven By Network

1. INVITE sip: jeff. pulver@pulver. com SIP/2. 0 From: sip: user@nortel. com 2. INVITE sip: pulver@von 1 SIP/2. 0 From: sip: user@nortel. com 3. SIP/2. 0 200 ok From: sip: pulver@von 1 pulver. com nortel. com pulver@von 1 user@nortel. com jeff. pulver Location Server pulver@von 1 4. SIP/2. 0 100 OK From: sip: jeff. pulver@pulver. com 5. ACK sip: jeff. pulver@pulver. com SIP/2. 0 From: sip: user@nortel. com 6. ACK sip: pulver@von 1 SIP/2. 0 From: sip: user@nortel. com Proxy server

SIP Proxy Servers • “Network Servers” that Proxy requests to other server • User Proxies manage sets of SIP users • Provides dynamic association of SIP endpoints • Proxy capabilities: — outgoing calls — address lookup — policy management — firewalls — call path hiding • Proxy servers can be stateful or stateless Proxies Provide SIP User Management

Stateful Proxy Servers • Maintains call context • Replicates User Agent Server/User Agent Client to process requests/responses • Call state and transaction state can be maintained • Forking proxies require state • TCP proxies must be stateful for reliability • Enhanced services require state for execution • Can populate billing information Services Dictate Statefulness of Proxy

Stateless Proxy Servers • • No call context Response is not based on User Agent replication Provides client anonymity Restricted gateway access High processing capacity Allows for easier replication than stateful proxy Can have semi-stateful proxy for ultimate benefits Stateless Proxies Geared for Capacity

pulver. com Location Server Jeff. pulver@von 1 nortel. com user@nortel. com Pulver@von 1 Redirect Server 1. INVITE sip: jeff. pulver@pulver. com From: sip: user@nortel. com 2. SIP/2. 0 320 Moved temporarily Contact: sip: pulver@von 1. pulver. com 4. INVITE sip: pulver@von 1. pulver. com From: user@nortel. com 5. SIP/2. 0 200 OK To: user@nortel. com 3. ACK sip: jeff. pulver@pulverr. com From: sip: user@nortel. com 6. ACK sip: pulver@von 1. pulver. com From: sip: user@nortel. com

SIP Redirect Servers • Accept SIP requests, map the address into new addresses, and return these addresses to the client • Do not initiate requests • Do not accept calls • Lower state overhead required than proxy servers • High processing capacity due to fewer messages to process • Services are client device dependent Service Dependence on Client

• Can be stateful or stateless • High capacity • Flexible, network service • Minimal state overhead implemenations • Reliability achieved through • Service execution pushed to clien replication • Scalability achieved through partitioning • Overload potential if not properly scaled • Hybrid (semi-stateful) model provides maximum benefits Hybrid Proxy Is Best Alternative