[Sip-implementors] UE behavior on receiving a 504 ambiguous as per 3gpp

[RC S]

Hi,

I am trying to determine an IMS UE behavior on receiving a 504 response to
a re-REGISTER request. I have read the 3gpp TS 24.229 and it is ambiguous
as to what the UE should do.

*On receiving a 504 for the REGISTER, does the UE send the initial REGISTER
back to the same PCSCF or to a different PCSCF?*

Here excerpts from the 3gpp TS 24.229version c20.

*--------Section 5.1.1.2. Initial Registration --------*

"On receiving a 408 (Request Timeout) response or 500 (Server Internal
Error) response or 504 (Server Time-Out) or 600 (Busy Everywhere) response
for an initial registration, the UE may attempt to perform initial
registration again."


*--------Section 5.1.1.4 User initiated reregistration and
authentication-------*

"On receiving a 408 (Request Timeout) response or 500 (Server Internal
Error) response or 504 (Server Time-Out) response for a reregistration, the
UE shall perform the procedures for initial registration as described in
subclause 5.1.1.2."


*-------- Section 5.1.2.A Abnormal Case - non REGISTER methods ------- *
"If the UE has discovered multiple P-CSCF addresses and has information
that the P-CSCF was unable to forward the request resulting in sending back
the 504 (Server Time-out) response, when starting the initial registration
it is appropriate for the UE to select a P-CSCF address different from the
one used for the registration binding on which the 504 (Server Time-out)
response was received."

Thanks
RC

[ankur bansal]

Hi

There are few more lines regarding this in 3gpp spec 24.229 :

1)After a first unsuccessful initial registration attempt, if the
Retry-After header field
was not present and the initial registration was not performed as a
consequence of
a failed re-registration, the UE shall not wait more than 5 min before
attempting
a new registration
So some timing less than 5 mins if no retry header (lets say 30 sec) can
be selected as per mutual understanding between UE and network

2) After a maximum of 2 consecutive unsuccessful initial registration
attempts,
the UE shall implement the mechanism defined in sub-clause 4.5 of
RFC5626
for new registration attempts. (base-time 120s, max-time 7,200s)


Register Retry Algo as per RFC 5626:
W = min{ max-time, [base-time * (2 ^ consecutive-failures)]}

base-time = 120 seconds
max-time = 7,200 seconds

For initial Register :504 comes :
Ist Retry to Same PCSCF--->(30sec) --->2nd Retry on Same PCSCF
UE can retry on subsequent P-CSCF and then start again from
Ist PCSCF once list over following retry logic as per RFC 5626.
Like there are 3 PCSCFs then retry can be forever as per RFC
5626
P1 -->P2 -->P3 --->P1 -->P2-->P3.............
UE can put logic to put cap on retry max duration(say 2 hours) otherwise
device can be having performance ,heating issues.

Thanks & Regards
Ankur Bansal

Post by RC S
Hi,
I am trying to determine an IMS UE behavior on receiving a 504 response to
a re-REGISTER request. I have read the 3gpp TS 24.229 and it is ambiguous
as to what the UE should do.
*On receiving a 504 for the REGISTER, does the UE send the initial REGISTER
back to the same PCSCF or to a different PCSCF?*
Here excerpts from the 3gpp TS 24.229version c20.
*--------Section 5.1.1.2. Initial Registration --------*
"On receiving a 408 (Request Timeout) response or 500 (Server Internal
Error) response or 504 (Server Time-Out) or 600 (Busy Everywhere) response
for an initial registration, the UE may attempt to perform initial
registration again."
*--------Section 5.1.1.4 User initiated reregistration and
authentication-------*
"On receiving a 408 (Request Timeout) response or 500 (Server Internal
Error) response or 504 (Server Time-Out) response for a reregistration, the
UE shall perform the procedures for initial registration as described in
subclause 5.1.1.2."
*-------- Section 5.1.2.A Abnormal Case - non REGISTER methods ------- *
"If the UE has discovered multiple P-CSCF addresses and has information
that the P-CSCF was unable to forward the request resulting in sending back
the 504 (Server Time-out) response, when starting the initial registration
it is appropriate for the UE to select a P-CSCF address different from the
one used for the registration binding on which the 504 (Server Time-out)
response was received."
Thanks
RC
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