Call Flow methods

[Syed]

Dear All,

Could someone help me understand, why do I need H323 fast start, SIP early offer & SIP early media, when calls can be established with H323 slow start, SIP delay offer? How does it make difference to calls? In what scenario do these benefit?

1. H323 slow start
2. H323 fast start (Call setup message contain OLC)
3. SIP early offer (Invite message with SDP)
4. SIP delay offer
5. SIP early media (183 session progress with SDP)

Thanks in advance

[Deepak Mehta · Accepted solution]

To explain it in simple terms,most service provider's prefer early offer .

The reason is when you invoke an early offer you are providing the power of negotiating the capabilities to the other side.They can choose among the list of attributes/parameters  shared in initial invite .Also it is almost always used by IP PSTN service providers because that allows one-way media to be established to the calling device on receipt of the SDP Offer in the initial INVITE

Whereas with delayed offer the call agent (CUCM,CUBE) dictate what capabilities (codec,payload type) and it doesn't give much flexibility to the providers.

For more you can refer to below portion of SRND doc.

http://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cucm/srnd/collab10/collab10/trunks.html

Thanks

[Syed]

Thank you, Deepak. Appreciate your quick response.

I shall go through the document and come back to you for any doubts.

[Syed]

I have gone the SRND document and it is very informative.

Thank you!

[Syed]

Hi Deepak,

I have gone through the SRND document and it is very informative to me.

Appreciate your help,Thank you!