What is TEID Control in GTPv1-C ?

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Papa Tana

Jul 12, 2020, 9:35:21 AM7/12/20
Hi World,

I am confused regarding TEID in GTPv1-C.

As per my understanding, GTP-C manages the creation, deletion of a GTP-U tunnel.
GTP-C can be managed from a user space program and it's not a tunnel at this stage, but GTP-U is a tunnel, and is set up at kernel level.

When GTP-C sends a request to the peer, he is sending:

- the Local TEID that he has reserved on his side for Data (user plane)
- upon receipt of such a request, the peer is saying it's ok, I will deliver you a Local TEID on my side, so that we can instruct GTP-U to setup a tunnel with these 2 TEID,
- The sequence of the messages are identified by Sequence Number.

At GTP-U level, there is no Sequence Number, but TEID is used.

So I have 2 questions please:
- Is it okay to say that GTP-C is only some GTP message sent through UDP, and the system can follow the sequence by using Sequence Number, thus there is no tunnel at all at this stage.
- GTP-C is using Sequence Number, why is there a TEID Control Plane in addition to TEID Data Plane in GTP-C message?
what is the purpose of this TEID Control plane, because Sequence Number is used to map and follow the subsequent messages and why a TEID Control because GTP-C is not a tunnel? or is it?



Papa Tana

Jul 23, 2020, 3:01:27 AM7/23/20
So, the answer is: they are needed as input parameters for GTP tunnel.

Such GTP tunnel can be established and managed by using:

- Linux GTP.ko
- or Vector Packet Processing

Best Regards,

Papa Tana

Aug 18, 2020, 2:58:41 AM8/18/20
As stated here:
# https://www.juniper.net/documentation/en_US/junos-mobility11.2/topics/concept/gtp-mobility-teid-allocation-overview.html

GTP-C allocates a TEID to identify a set of endpoints for a GTP-C tunnel, as shown in Figure 1. For each bearer, a separate GTP-U tunnel with its own TEID is established.

My understanding of that is: TEID at GTP-C is used only at GTP-C side, and they are just needed to identify the set of endpoints addressed to the GTP-U side.

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