NN10265-111 MCS 5100 3.5 Standard 4.0 January 2006
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Copyright © Nortel Networks Limited 2006
Basic call with firewalls

Figure 54, Basic call flow using the RTP Media Portal (with obscured

endpoints), on page 114 shows the basic call flow for a client-to-client

call using an RTP Media Portal with Address and Port Discovery (APD)

functions enabled to facilitate firewall/NAPT traversal requirements.

Figure 54 Basic call flow using the RTP Media Portal (with obscured endpoints)

SIP
Module
Application
Client A Client B
2. Resource request for B
3. Response with A’
1. Invite (SDP of B)
11. BYE
RTP
Portal
Media
4. Invite (SDP of A’)
5. Answer (SDP of B)
6. Resource request for A
9. First media packet
13. Delete resource A’
15. Resource deleted
Firewall/NAT A
14. Delete resource B’
Firewall/NAT B
8. Answer
10. First media packet
12. BYE
7. Response with B’
Media Path established between A and B
Connect new resource to A’
16. Resource deleted
from A to B’
from B to A’
(SDP of B’)