difference between video calls through SIP and H323

[baselzind]

what is the difference between making video calls through SIP and H323? what form of addresses the two use? 

[Acevirgil de Ocampo]

Calls through SIP protocol are handled by a SIP Server/Registrar/Proxy server for call control, signaling and messages.To enable SIP calls, the endpoints will need to register to a SIP server to give the endpoints a SIP address in the form of URI/email address (1234@example.com). They can be reached by dialing the full SIP URI or just dialing extension (1234) without the domain as long as they are registered locally in the same SIP server. 

For H323 protocol, calls will be handled by a Gatekeeper (optional) for call control and signaling like H.225 Registration, Admission, and Status (RAS) messages. If endpoints are registered on a Gatekeeper, they will be provided with H323 ID and E.164 alias. Endpoints can be reached by either dialing their H323 ID (1234@example.com) or E.164 alias (1234). For H323 endpoints as standalone without gatekeeper, they can be reached by dialing their IP addresses.

The main difference between SIP and H323 is how the call setup was being handled by the call control between the endpoints and terminals. Once call setup is established, media will flow directly between endpoints.

If you need to do inter-working of calls between SIP and H323, you need a VCS.

Here are some Cisco Validated Designs for references:

http://www.cisco.com/c/dam/en/us/td/docs/solutions/CVD/Aug2013/CVD-SIPVideoUsingVCSDesignGuide-AUG13.pdf

http://www.cisco.com/c/dam/en/us/td/docs/solutions/CVD/Aug2013/CVD-H323VideoInterworkingUsingVCSDesignGuide-AUG13.pdf

And if you want a deep dive explanation regarding the difference between SIP and H323:

https://www.packetizer.com/ipmc/h323_vs_sip/

regards,

Acevirgil

[Dennis Mink]

If you have the choice, do not use H323 for video, as its addressing is less scalable than that of sip that can use URI's.

traditionally H323 inter organisations is used point 2 point using public IP addressing.

can you share the context of your question, thanks

[Paul Jones]

H.323 can use a variety of address forms, including phone numbers (e.g., E.164), URIs, and email addresses.  SIP uses URIs.  Of course, a URI can be a phone number, a "SIP" URI, email address, etc.  So, technically either protocol can address any entity.

In practice, most H.323 devices -- especially gateways -- use only phone numbers, because

1. PSTN interconnection was the main focus early on,
2. URIs were not supported in the first version of H.323, and
3. the "h323:" URI scheme was not defined until 2000.

H.323 URIs are supported in some devices, but not universally supported.  It's more common to see support in video softphones.  It's possible to call most Cisco employees using h323:user@cisco.com, for example.

SIP implementations frequently use either sip: or tel: URIs in practice, though often the addressing is a phone number like sip:12345.  However, there wider adoption for sip:user@domain forms of addressing in SIP in the industry.  Likewise, it is also possible to call most Cisco employees using sip:user@cisco.com addressing.

[nickfasi75260]

Hello, the difference is that they are used for other purposes. H.323 is telephony based while SIP is internet-based. More information can be found here.

[Wayne DeNardi]

They could be identical.  A H.323 ID could look the same as a SIP URI, eg endpoint@domain.com. 

Are you able to provide some more detail on what your requirements are, or what you are trying to do, and we can tailor answers to help better than with a very open and generic question?