NAT Optimized SIP Media Path Without SDP

The NAT Optimized SIP Media Path Without SDP feature provides the ability to optimize the media path taken by a SIP VoIP session when NAT is used. NAT forces the VoIP traffic to take at least one extra hop in the network, which usually results in several additional hops being added to the path between two IP hosts.

The Message Digest 5 (MD5) algorithm is supported.

Information About the NAT Optimized SIP Media Path Without SDP Feature

Benefits of NAT Optimized SIP Media Path Without SDP

  • The media path can be shortened, decreasing voice delay.

  • More control of voice policy is possible because the media path is closer to the customer domain and not deep within the service provider cloud.

  • Processes all packets sent through the NAT-enabled router, even those without the Session Description Protocol (SDP).

NAT Optimized SIP Media Path Without SDP Feature Design

Cisco IOS NAT will add the relevant translation information per SIP session within the SIP protocol messages. The SIP Application Layer Gateway support within Cisco IOS NAT will extract this translation information from the SIP packets and create NAT table entries.

The “piggybacking” of NAT translation information within the SIP call flows, the design of how users interact with the application when they talk to it, will allow the media path of a SIP VoIP session between two calling parties to take the optimized routing path between each other.

How to Configure NAT Optimized SIP Media Path Without SDP

Configuring a NAT Optimized SIP Media Path Without SDP Messages Including MD5 Authentication

Perform this task to configure messages with a NAT optimized SIP Media path including MD5 authentication.

SUMMARY STEPS

  1. enable
  2. configure terminal
  3. ip nat piggyback-support sip-alg all-messages router router-id [md5 -authentication md5-authentication-key ]

DETAILED STEPS

  Command or Action Purpose
Step 1

enable

Example:


Router> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

configure terminal

Example:


Router# configure terminal

Enters global configuration mode.

Step 3

ip nat piggyback-support sip-alg all-messages router router-id [md5 -authentication md5-authentication-key ]

Example:


Router(config)# ip nat piggyback-support sip-alg all-messages router 100 md5-authentication md5-key

Enables messages with a NAT optimized SIP Media path including MD5 authentication.

Configuring a NAT Optimized SIP Media Path Without SDP Messages

Perform this task to configure SDP messages with a NAT optimized SIP Media path without MD5 authentication.

SUMMARY STEPS

  1. enable
  2. configure terminal
  3. ip nat piggyback-support sip-alg all-messages router router-id

DETAILED STEPS

  Command or Action Purpose
Step 1

enable

Example:


Router> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

configure terminal

Example:


Router# configure terminal

Enters global configuration mode.

Step 3

ip nat piggyback-support sip-alg all-messages router router-id

Example:


Router(config)# ip nat piggyback-support sip-alg all-messages router 100

Enables messages with a NAT optimized SIP Media path without MD5 authentication.

Configuration Examples for NAT Optimized SIP Media Path Without SDP

Configuring a NAT Optimized SIP Media Path Without SDP Including MD5 Authentication Example

The following example shows how to configure a NAT optimized SIP media path without SDP including MD5 authentication: 


ip nat piggyback-support sip-alg all-messages router 100 md5-authentication md5-key

Configuring a NAT Optimized SIP Media Path Without SDP or MD5 Authentication Example

The following example shows how to configure a NAT optimized SIP media path without SDP or MD5 authentication: 


ip nat piggyback-support sip-alg all-messages router 100

Additional References

Related Documents

Related Topic

Document Title

Cisco IOS commands

Cisco IOS Master Commands List, All Releases

NAT commands: complete command syntax, command mode command history, defaults, usage guidelines, and examples

Cisco IOS IP Addressing Services Command Reference

Application-level gateways

Using Application Level Gateways with NAT module

IP access list sequence numbering

IP Access List Sequence Numbering document

NAT-on-a-Stick technology note

Network Address Translation on a Stick technology note

NAT maintenance

Monitoring and Maintaining NAT module

RADIUS attributes overview

RADIUS Attributes Overview and RADIUS IETF Attributes module

Using HSRP and stateful NAT for high availability

Configuring NAT for High Availability module

Using NAT with MPLS VPNs

Integrating NAT with MPLS VPNs module

Standards and RFCs

Standard/RFC

Title

RFC 1597

Internet Assigned Numbers Authority

RFC 1631

The IP Network Address Translation (NAT)

RFC 1918

Address Allocation for Private Internets

RFC 2663

IP Network Address Translation (NAT) Terminology and Considerations

RFC 3022

Traditional IP Network Address Translation (Traditional NAT)

Technical Assistance

Description

Link

The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.

http://www.cisco.com/cisco/web/support/index.html

Feature Information for NAT Optimized SIP Media Path Without SDP

The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
Table 1. Feature Information for NAT Optimized SIP Media Path Without SDP

Feature Name

Releases

Feature Information

NAT Optimized SIP Media Path Without SDP

12.4(2)T

The NAT Optimized SIP Media Path Without SDP feature provides the ability to optimize the media path taken by a SIP VoIP session when NAT is used. NAT forces the VoIP traffic to take at least one extra hop in the network, which usually results in several additional hops being added to the path between two IP hosts.