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

2. SIP Reference Architecture
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
SS7/PRI
PSTN Gateway
SIP User Agent for PSTN Trks
SIP services for PSTN terminations

3. Proxy Capability Driven By Network
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
1. INVITE SIP/2.0
From:
2. INVITE SIP/2.0
From:
3. SIP/ ok
From:
pulver.com
Proxy server
nortel.com
Location Server
jeff.pulver
4. SIP/ OK
From:
5. ACK SIP/2.0
From:
6. ACK SIP/2.0
From:

5. Proxies Provide SIP User Management
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
Redirect Server
Location Server
nortel.com
Jeff.pulver
1. INVITE
From:
4. INVITE
From:
2. SIP/ Moved temporarily
Contact:
5. SIP/ OK
To:
6. ACK
From:
3. ACK
From:

9. Service Dependence on Client
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. Hybrid Proxy Is Best Alternative
Proxy Server
Redirect Server
Can be stateful or stateless
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