Cisco Cisco Customer Voice Portal 8.0(1)
SIP, H.323 Comparison
The following table provides a partial comparison of SIP and H.323.
Table 2: Comparison of SIP and H.323
H.323
SIP
Clients are intelligent
Clients (User Agents) are intelligent
Gatekeepers provide network intelligence and services
Servers (Proxy, Redirect, Registrar) provide network
intelligence and services
intelligence and services
Follows the Telephony/Q.SIG model
Follows the Internet/WWW model
Uses TCP for signaling (UDP optional in v3)
Uses UDP or TCP for signaling
Uses RTP for media
Uses RTP for media
Is a full-featured multimedia protocol
Is a full-featured multimedia protocol
Is binary-based (ASN.1 encoding)
Is text-based (ASCII)
Utilizes ITU / ISDN protocols - H.225, H.245, H.450. All
portions fall under H.323
portions fall under H.323
Utilizes IETF/IP protocols - SDP, HTTP/1.1, SMTP, MIME,
and so forth
and so forth
Interoperability is done with iNOW or IMTC
Only defines signaling, not all elements
H.323 and Unified CVP
For users of previous versions of CVP, where SIP was not an alternative, upgrading while
keeping their call flows unchanged (at least initially) is a useful option. Indeed, a Unified CVP
solution is capable of running as a hybrid, that is, some call flows using H.323 and some using
SIP. The software should all be upgraded first; then flows should be cut over in groups, perhaps
by DNIS or by application (see the discussion in Installation and Upgrade Guide for Cisco
Unified Customer Voice Portal). A single call can be controlled by either SIP or H.323, but not
both. However, a single Unified CVP component can carry some calls in each category.
keeping their call flows unchanged (at least initially) is a useful option. Indeed, a Unified CVP
solution is capable of running as a hybrid, that is, some call flows using H.323 and some using
SIP. The software should all be upgraded first; then flows should be cut over in groups, perhaps
by DNIS or by application (see the discussion in Installation and Upgrade Guide for Cisco
Unified Customer Voice Portal). A single call can be controlled by either SIP or H.323, but not
both. However, a single Unified CVP component can carry some calls in each category.
Note that certain call control capabilities which are available in H.323 are not yet available in
SIP. Customers who require these particular capabilities will wish to remain with H.323. In
addition, most customers who are staying with H.323 are advised to move to Comprehensive
call flow if they currently use Queue and Transfer, but there are some cases where these customers
will not be able to do so. These situations are discussed below.
SIP. Customers who require these particular capabilities will wish to remain with H.323. In
addition, most customers who are staying with H.323 are advised to move to Comprehensive
call flow if they currently use Queue and Transfer, but there are some cases where these customers
will not be able to do so. These situations are discussed below.
SIP Restrictions
SIP cannot perform all operations that H.323 can perform, because the endpoints, the Unified
CVP implementation, or the protocol itself does not yet support those operations. Customers
who require such call control capabilities must use H.323.
CVP implementation, or the protocol itself does not yet support those operations. Customers
who require such call control capabilities must use H.323.
Planning Guide for Cisco Unified Customer Voice Portal 4.0(1)
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Chapter 2: - Choosing a Call Control Protocol
SIP, H.323 Comparison