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IMS Signalling flows for session initiation: Non Hiding

MO#1a / S-S#1a / MT#1a   (page 3 of 3)

- Mobile origination, roaming
- Different network operators performing origination and termination
- Mobile termination, roaming
MO#1a / S-S#1a / MT#1a
1) INVITE (UE1 to UE2) 2) 183 Session Progress 3) PRACK (UE1 to UE2) 4) 200 OK   Prev Next
5) UPDATE (UE1 to UE2) 6) 200 OK 7) 180 Ringing (INVITE) 8) PRACK (UE1 to UE2)     a)
9) 200 OK 10) 200 OK (INVITE) 11) ACK (UE1 to UE2)     p.#1 Top

fig7

7a)  from UE2 to P-CSCF2   (a) (b) (c) (d) (e) (f) Prev Next Up

fig7a

- Before proceeding with session establishment, UE2 waits for two events. First, the resource reservation initiated previously must complete successfully. Second, the resource reservation initiated by the originating endpoint must complete successfully (which is indicated by message UPDATE received by UE2). UE2 may now immediately accept the session or alert the destination subscriber of an incoming session attempt; if the latter it indicates this to the calling party by a 180 Ringing provisional response sent to P-CSCF2.
7b)  from P-CSCF2 to S-CSCF2   (a) (b) (c) (d) (e) (f) Prev Next Up

fig7b

- Record-Route: P-CSCF2 rewrites the Record-Route header field value to remove the port number and the comp=sigcomp parameter from its own entry.
7c)  from S-CSCF2 to I-CSCF2   (a) (b) (c) (d) (e) (f) Prev Next Up

fig7c

7d)  from I-CSCF2 to S-CSCF1   (a) (b) (c) (d) (e) (f) Prev Next Up

fig7d

7e)  from S-CSCF1 to P-CSCF1   (a) (b) (c) (d) (e) (f) Prev Next Up

fig7e

7f)  from P-CSCF1 to UE1   (a) (b) (c) (d) (e) (f) Prev Next Up

fig7f

- Record-Route: P-CSCF1 rewrites the Record-Route header to add the comp=sigcomp parameter to its own SIP URI and its port number negotiated during the security agreement.
MO#1a / S-S#1a / MT#1a
1) INVITE (UE1 to UE2) 2) 183 Session Progress 3) PRACK (UE1 to UE2) 4) 200 OK   Prev Next
5) UPDATE (UE1 to UE2) 6) 200 OK 7) 180 Ringing (INVITE) 8) PRACK (UE1 to UE2)     a)
9) 200 OK 10) 200 OK (INVITE) 11) ACK (UE1 to UE2)     p.#1 Top

fig8

8a)  from UE1 to P-CSCF1   (a) (b) (c) (d) (e) Prev Next Up

fig8a

- Request-URI: takes the value of the Contact header of the received 180 Ringing response.
- Security-Verify: contains the security agreement as represented by the received Security-Server header.
8b)  from P-CSCF1 to S-CSCF1   (a) (b) (c) (d) (e) Prev Next Up

fig8b

- P-CSCF1 removes the Security-Verify header and associated "sec-agree" option-tags prior to forwarding the request. As the Require and Proxy-Require headers are empty, it removes these headers completely.
8c)  from S-CSCF1 to S-CSCF2   (a) (b) (c) (d) (e) Prev Next Up

fig8c

8d)  from S-CSCF2 to P-CSCF2   (a) (b) (c) (d) (e) Prev Next Up

fig8d

8e)  from P-CSCF2 to UE2   (a) (b) (c) (d) (e) Prev Next Up

fig8e

- Via: P-CSCF2 adds the port number negotiated during the security agreement and the comp=sigcomp parameter to its own entry in the Via header.
MO#1a / S-S#1a / MT#1a
1) INVITE (UE1 to UE2) 2) 183 Session Progress 3) PRACK (UE1 to UE2) 4) 200 OK   Prev Next
5) UPDATE (UE1 to UE2) 6) 200 OK 7) 180 Ringing (INVITE) 8) PRACK (UE1 to UE2)     a)
9) 200 OK 10) 200 OK (INVITE) 11) ACK (UE1 to UE2)     p.#1 Top

fig9

9a)  from UE2 to P-CSCF2   (a) (b) (c) (d) (e) Prev Next Up

fig9a

9b)  from P-CSCF2 to S-CSCF2   (a) (b) (c) (d) (e) Prev Next Up

fig9b

9c)  from S-CSCF2 to S-CSCF1   (a) (b) (c) (d) (e) Prev Next Up

fig9c

9d)  from S-CSCF1 to P-CSCF1   (a) (b) (c) (d) (e) Prev Next Up

fig9d

9e)  from P-CSCF1 to UE1   (a) (b) (c) (d) (e) Prev Next Up

fig9e

MO#1a / S-S#1a / MT#1a
1) INVITE (UE1 to UE2) 2) 183 Session Progress 3) PRACK (UE1 to UE2) 4) 200 OK   Prev Next
5) UPDATE (UE1 to UE2) 6) 200 OK 7) 180 Ringing (INVITE) 8) PRACK (UE1 to UE2)     a)
9) 200 OK 10) 200 OK (INVITE) 11) ACK (UE1 to UE2)     p.#1 Top

fig10

10a)  from UE2 to P-CSCF2   (a) (b) (c) (d) (e) (f) Prev Next Up

fig10a

- When the called party answers UE2 sends a 200 OK final response to the INVITE request to P-CSCF2, and starts the media flow(s) for this session.
10b)  from P-CSCF2 to S-CSCF2   (a) (b) (c) (d) (e) (f) Prev Next Up

fig10b

10c)  from S-CSCF2 to I-CSCF2   (a) (b) (c) (d) (e) (f) Prev Next Up

fig10c

10d)  from I-CSCF2 to S-CSCF1   (a) (b) (c) (d) (e) (f) Prev Next Up

fig10d

10e)  from S-CSCF1 to P-CSCF1   (a) (b) (c) (d) (e) (f) Prev Next Up

fig10e

10f)  from P-CSCF1 to UE1   (a) (b) (c) (d) (e) (f) Prev Next Up

fig10f

MO#1a / S-S#1a / MT#1a
1) INVITE (UE1 to UE2) 2) 183 Session Progress 3) PRACK (UE1 to UE2) 4) 200 OK   Prev Next
5) UPDATE (UE1 to UE2) 6) 200 OK 7) 180 Ringing (INVITE) 8) PRACK (UE1 to UE2)     a)
9) 200 OK 10) 200 OK (INVITE) 11) ACK (UE1 to UE2)     p.#1 Top

fig11

11a)  from UE1 to P-CSCF1   (a) (b) (c) (d) (e) Prev Next Up

fig11a

- UE1 starts the media flow for this session, and responds to the 200 (OK) response with an ACK request sent to P-CSCF1.
11b)  from P-CSCF1 to S-CSCF1   (a) (b) (c) (d) (e) Prev Next Up

fig11b

11c)  from S-CSCF1 to S-CSCF2   (a) (b) (c) (d) (e) Prev Next Up

fig11c

11d)  from S-CSCF2 to P-CSCF2   (a) (b) (c) (d) (e) Prev Next Up

fig11d

11e)  from P-CSCF2 to UE2   (a) (b) (c) (d) (e) Prev Next Up

fig11e

  
Last update: September 29, 2005 
  
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