[采日] LifeLOG :: 3GPP TS 24.290 -- IMS Signalling flows

3GPP TS 24.290 -- IMS Signalling flows for Register

Cx-Query, or Diameter UAR: User-Authorization-Request: I-CSCF1 makes a request for information related to the Subscriber registration status by sending the private user identity ("user1_private@home1.net"), public user identity ("user1_public1@home1.net") and visited domain identifier ("Visited Network Number 1") to the HSS.

Cx-Query response, or Diameter UAA: User-Authorization-Answer: The HSS returns S-CSCF required capabilities and I-CSCF1 uses this information to select a suitable S-CSCF.

As the REGISTER request arrived without integrity protection to P-CSCF1, S-CSCF1 shall challenge it. For this, S-CSCF1 requires at least one authentication vector (AV) to be used in the challenge to the user. If a valid AV is not available, then S-CSCF1 requests at least one AV from the HSS.

S-CSCF1 indicates to the HSS that it has been assigned to serve this user.

S-CSCF1 selects an authentication vector for use in the authentication challenge. For detailed description of the authentication vector, see 3GPP TS 33.203.
NOTE: The authentication vector may be of the form as in 3GPP TS 33.203 (if IMS AKA is the selected authentication scheme): AV = RANDn||AUTNn||XRESn||CKn||IKn where:

RAND: random number used to generate the XRES, CK, IK, and part of the AUTN. It is also used to generate the RES at the UE.
AUTN: Authentication token (including MAC and SQN).
XRES: Expected (correct) result from the UE.
CK: Cipher key (optional).
IK: Integrity key.

I-CSCF1 requests information related to the Subscriber registration status by sending the private user identity, public user identity and visited domain name to the HSS. The HSS returns the S-CSCF name which was previously selected in step 1d.

Authentication: Upon receiving an integrity protected REGISTER request carrying the authentication challenge response, S-CSCF1 checks that the expected response (calculated by S-CSCF1 using XRES and other parameter as defined in RFC 3310) matches the received challenge response. If the check is successful then the user has been authenticated and the public user identity is registered in the S-CSCF.

Cx-Put, or Diameter SAR: Server-Assignment-Request: On registering a user, S-CSCF1 informs the HSS that the user has been registered at this instance.

Cx-Put response, or Diameter SAA: Server-Assignment-Answer: Upon being requested by S-CSCF1, the HSS will also include the user profile in the response sent to the S-CSCF.

3GPP TS 24.290 -- IMS Signalling flows for Session Initiation

S-CSCF#1 validates the service profile of this subscriber and evaluates the initial filter criterias. For this example, assume no Application Server involvement.

I-CSCF2 sends a query to the HSS (the public user identity is provided in the Request-URI) to find out the S-CSCF of the called user. The HSS responds with the address of the current S-CSCF for the terminating subscriber.

S-CSCF#2 validates the service profile of this subscriber and evaluates the initial filter criterias.

P-CSCF2 authorizes the resources necessary for this session. The approval of QoS commitment either happens at this stage or after 200 OK of INVITE based on operator local policy.

P-CSCF1 authorizes the resources necessary for this session. The approval of QoS commitment either happens at this stage or after 200 OK of INVITE based on operator local policy.

Reference

http://tech-invite.com/Ti-ims-regflow-1.html

http://tech-invite.com/Ti-ims-sesflow-1.html

http://ofdm.jp/3GPP/Specs/24229-920.pdf