Table Of Contents

H.323-SIP Interworking

Contents

Restrictions for H.323-SIP Interworking

Information About H.323-SIP Interworking

Additional References

Related Documents

Standards

MIBs

RFCs

Technical Assistance

H.323-SIP Interworking

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The H.323-SIP interworking feature is very important in Voice over IP services since both protocols are widely used in the industry. When one VoIP service provider uses SIP and another provider uses H.323, the two protocols need to interwork to enable the customers to contact each other. H.323 is an older protocol that is gradually supplanted by SIP. The customers who have their VoIP network managed using H.323 may have to transition to SIP in the future. During this transition, both protocols need to interwork on the customers' VoIP network.

Feature History for H.323-SIP Interworking

Release	Modification
Release 3.5.0	This feature was introduced on the Cisco XR 12000 Series Router.
Release 3.6.0	No modification.

Contents

This module contains the following sections:

•Restrictions for H.323-SIP Interworking

•Information About H.323-SIP Interworking

•Additional References

Restrictions for H.323-SIP Interworking

The following features are not supported:

•Call hold on an interworking call.

•Transcoding of interworking calls.

•Renegotiation of the media of interworking calls, either before or after the call is connected.

•Receiving an offer (apart from the initial offer in the case of a SIP-to-H.323 call) from a remote SIP endpoint at any time during the call establishment.

•Media bypass for interworking calls.

•DTMF within the RTP stream of an interworking call.

•H.323 DTMF signaling using any method other than the alphanumeric method of UserInputIndication.

•Interworking of endpoint registrations (not supported by H.323).

•Failover of interworking calls (because H.323 call legs cannot be preserved across a failover).

•Interworking of any SIP method other than INVITE, ACK, CANCEL, BYE, INFO and PRACK.

•End-to-end authentication on an interworking call. For example, an H.323 call branch cannot challenge a SIP call branch and vice versa. The SBC itself can challenge a SIP call branch, but not an H.323 call branch.

•User-configurable mapping of cause codes.

•User-configurable mapping of codec types.

•Interworking of signaling support for Silence Suppression / VAD. It is assumed that the majority of endpoints interoperate correctly without explicitly signaling silence suppression.

•Interworking of Video or Fax calls.

Information About H.323-SIP Interworking

Following the usual process, after the SBC applies the call and number policy tables, a final adjacency and account are chosen. In this feature, the originating and terminating adjacencies are configured for different protocols. For example, the originating adjacency can be configured for SIP, and the terminating adjacency can be configured for H.323.

The SBC supports the following features of SIP-to-H.323 interworking:

•SIP upstream, H.323 fast-start downstream, offer received on the SIP INVITE.

•SIP upstream, H.323 slow-start downstream, offer received on the SIP INVITE. First, H.323 fast-start is tried downstream. The SBC drops back to slow-start procedures when it discovers the downstream endpoint does not support fast-start.

•SIP upstream, H.323 downstream (either fast-start or slow-start), no offer received on the SIP INVITE.

•H.323 fast-start upstream, SIP downstream.

•H.323 slow-start upstream, SIP downstream. SIP downstream is tried with a default SDP offer, containing a single media channel with the following offered codecs in decreasing order of preference: G.729, G.711 U-law, G.711 A-law, G.723.

•Early media.

•DTMF interworking between SIP and H.323 in the signaling plane, using the Alphanumeric method of UserInputIndication.

Additional References

The following sections provide references related to H.323-SIP Interworking.

Related Documents

Related Topic	Document Title
Cisco IOS XR master command reference	Cisco IOS XR Master Commands List
Cisco IOS XR SBC interface configuration commands	Cisco IOS XR Session Border Controller Command Reference
Initial system bootup and configuration information for a router using the Cisco IOS XR Software	Cisco IOS XR Getting Started Guide
Cisco IOS XR command modes	Cisco IOS XR Command Mode Reference

Standards

Standards	Title
No new or modified standards are supported by this feature, and support from existing standards has not been modified by this feature.	—

MIBs

MIBs	MIBs Link
—	To locate and download MIBs using Cisco IOS XR software, use the Cisco MIB Locator found at the following URL and choose a platform under the Cisco Access Products menu: http://cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml

RFCs

RFCs	Title
RFC 2833	RTP Payload for DTMF Digits, Telephony Tones and Telephony Signals
RFC 3261	SIP: Session Initiation Protocol

Technical Assistance

Description	Link
The Cisco Technical Support website contains thousands of pages of searchable technical content, including links to products, technologies, solutions, technical tips, and tools. Registered Cisco.com users can log in from this page to access even more content.	http://www.cisco.com/techsupport