Comparison of SIP Proxy and Redirect Servers

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Comparison of SIP Proxy and Redirect Servers

• Presented By Greg Osterhout
• Sr. Mgr, SIP Services Development and Evolution

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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
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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
  cant feasibly manage their own user proxy

Proxy Capability Driven By Network
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Sip Proxy Mode
1. INVITE sipjeff.pulver_at_pulver.com SIP/2.0
From sipuser_at_nortel.com
2. INVITE sippulver_at_von1 SIP/2.0 From
sipuser_at_nortel.com
3. SIP/2.0 200 ok From sippulver_at_von1
Location Server
4. SIP/2.0 100 OK From sipjeff.pulver_at_pulver
.com
5. ACK sipjeff.pulver_at_pulver.com SIP/2.0
From sipuser_at_nortel.com
6. ACK sippulver_at_von1 SIP/2.0 From
sipuser_at_nortel.com
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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
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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
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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
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Sip Redirect Mode
Location Server
1. INVITE sipjeff.pulver_at_pulver.com From
sipuser_at_nortel.com
4. INVITE sippulver_at_von1.pulver.com From
user_at_nortel.com
5. SIP/2.0 200 OK To user_at_nortel.com
2. SIP/2.0 320 Moved temporarily Contact
sippulver_at_von1.pulver.com
6. ACK sippulver_at_von1.pulver.com From
sipuser_at_nortel.com
3. ACK sipjeff.pulver_at_pulverr.com From
sipuser_at_nortel.com
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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
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Redirect Server
Proxy 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