Can GTP-TEID be same for multiple Bearer?

Question

GTP tunnel id is a 32-bit long value over one IP address combination. Suppose there are two nodes A and B which has IP addresses X and Y respectively. Is it possible when first GTP tunnel id range gets exhausted then both the nodes starts using different IP address combination and again GTP tunnel id range can be re-used ? If it is impossible then what could be the reason ?

Answer 1

Can you specifiy which GTP-TEID you mean here ? GTP-C TEID or GTP-U TEID ?

If you asked for GTP-U TEID, then there has to be a one to one mapping between a GTP-U TEID and the EPS bearer at different end points like eNodeB, S-GW and PDN-GW, across their supported interfaces on the data flow path.

If it is a GTP-C TEID, then it is interpreted differently across different interfaces
1. On S11, there has to be only one pair of GTP-C TEID (one on MME and the other on S-GW) for one UE. This must be shared for all the control messages' related operations related to this UE.
2. On S5/S8, the GTP-C TEID has to be unique per PDN connection. And this has to be shared among all the EPS bearers which use this PDN connection. (However the spec doesn't mention anything about the UE here).

Some more interfaces like S3, S10, S16 which are dependent on LTE, See spec 29.274 section 4.1

Answer 2

It has to be unique across all bearers for that end point pair(eNB-SGW pair OR SGW-PGW pair). It is the TEID that uniquely identifies the bearers.

Comments

Could you please explain that do I have a chance to keep the same TEID between eNB-SGW and SGW-PGW pairs or should I change the TEIDs according to the end points.

Answer 3

In LTE, each bearer will be identified by TEID, so it should not be same multiple bearer.

Comments

Hi, could you please suggest the spec where i can get the clarification for the same(1 UE is having 2 bearers and what would be the teid of eNB for first and second bearer)

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Spec is 3GPP 29.281 but pinpointing the specific location is difficult.