[Simple] Queries on Working with MSRP Relays(RFC 4976)

[raveen sharma <raveen.sharma at gmail.com>]

Hello,

I have some queries regarding implemtation of MSRP Clients using
relays, I am referring to rfc4976 currently

1. As referred in RFC 4976, Section 3.1, MSRP Client shall
authenticate with the configured/discovered list of relays.
I want to know if this authentication is per MSRP session that maps to
individual m-line in SIP/SDP.

Lets take a case scenario, wherein I want to transfer 3 files to the
same remote user. A SIP session will be initiated with 3 m-lines.
My network is configured with 2 relays, R1, R2. How authentication will be done?

Approach I - MSRP Client will send AUTH request to set of relays R1,
R2 for each session. 6 (3*2) AUTH requests will be sent.
Approach II - MSRP Client will send AUTH requests to each relay only
once for the SIP session. 2 AUTH requests will be sent.

2. Reference RFC 4976, Section 5.1,page 12:
 Should same authentication vector as required for MD5 (username and
password) be used for authentication with MSRP Relays as in SIP
signaling or It’s a different username and password. ?? Does this auth
vector is same for all relays or its unique for each relay.

3. As per schema Section  7, " algorithm           = "algorithm=" (
"MD5" / token ) "
Is only MD5 based algo targeted to implement or other algos like
MD5v1-AKA can be targeted in future. Typically MD5v1-AKA is suggested
in IMS based network where the private/public Id of ISIM and SQN is
taken as an input parameter for calculating the response and user
manually does not give any username and password for authenticated.

4. RFC 4976 does not give authentication procedure refreshing like the
client should send AUTH request before expiry of the timer as received
in 200 ok of AUTH request. Kindly let us know which specification
should be referred in the case scenario. Is there any specific guide
line to handle the MSRP sessions for the case scenario if failure
response received in AUTH refreshing?


Regards,
Raveen Sharma