Hello all,
I have a query on the IMS.
What options does the various PGW/GGSN vendors offer when load balancing the traffic to an array of P-CSCFs?
GSMA/3GPP have not standardized anything in particular.
Any vendors have provided anything extra than the traditional round-robin model?
Does anyone have dynamic distribution based on the current weight (active IPSec tunnels in a P-CSCF)?
In Huawei PGW, we have option of assigning Primary Secondary.
Second option they go with weight option between active / active P-CSCFs.
Like 80-20 which is configurable as per capacity.
Note: This is for /// EPG(PGW).
Did you check S CSCF which has the routing?
The Serving Call Session Control Function (S-CSCF) is the main node in the IP Multimedia Subsystem (IMS) signaling plane.
The S-CSCF, which acts as both a SIP server and registrar, is assigned to serve end users for the duration of their connection to the IMS network.
The assignment of users to an S- CSCF is performed by the Interrogating CSCF (I-CSCF) during the user SIP agent registration.
The I-CSCF assigns the S-CSCF based on the capabilities required in the user profile.
You have the option of setting P-CSCF discovery either in the PCO of the PGW, or on the SIM.
If you set it on the SIM you can use DNS-SRV based load balancing, however most commonly it’s the static list in the PCO.
Usually traffic from PGW towards PCSCF(SBG) is achived via carefully allocating UE IPs from UE IP Pools during default bearer creation, which are configured in PCRF and the routing is based on those IPs in PGW towards PCSCF.This has become easier now due to IPv6 availability and no longer operators using IPv4 for handset unless for some specific apns like sos .IMS core usually has no control over subscriber distribution towards PCSCF since it is totally in the control of PS core.But If you see any uneven distribution in PCSCF due to miss allignment in Pscore you can configure PCSCF restoration procedure for some faliure sip cause codes like 504 and 404,Which will normalise the registered PCSCF subscribers to some extenent since this procedure triggers a fresh registration not a re-registration.Re-registraion only try the PCSCF address which you already have in the handset.