Comparison of SIP Proxy and Redirect Servers

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

2. PSTN SIP Reference Architecture I2004 EtherSets User Proxy SIP Soft Client • Terminal Endpoints • SIP User Agent for • user devices SIP User Proxy SIP USB Phone • Network/User Proxy • Registration of SIP endpoints • Provides endpoint mobility • User specific services • Domain resolution SIP Network Nodes SIP SIP SIP Mobil Oil Network User Proxy • PSTN Gateway • SIP User Agent for PSTN Trks • SIP services for PSTN terminations SS7/PRI

3. 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

4. Sip Proxy Mode pulver.com nortel.com jeff.pulver pulver@von1 user@nortel.com pulver@von1 Proxy server 1. INVITE sip:jeff.pulver@pulver.com SIP/2.0 From: sip:user@nortel.com 2. INVITE sip:pulver@von1 SIP/2.0 From: sip:user@nortel.com 3. SIP/2.0 200 ok From: sip:pulver@von1 Location Server 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@von1 SIP/2.0 From: sip:user@nortel.com

5. 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

6. 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

7. 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

8. Sip Redirect Mode pulver.com nortel.com pulver@von1 Jeff.pulver user@nortel.com Pulver@von1 RedirectServer Location Server 1. INVITE sip:jeff.pulver@pulver.com From: sip:user@nortel.com 4. INVITE sip:pulver@von1.pulver.com From: user@nortel.com 5. SIP/2.0 200 OK To: user@nortel.com 2. SIP/2.0 320 Moved temporarily Contact: sip:pulver@von1.pulver.com 6. ACK sip:pulver@von1.pulver.com From: sip:user@nortel.com 3. ACK sip:jeff.pulver@pulverr.com From: sip:user@nortel.com

9. 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

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