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LTE: GTP end marker

+1 vote
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LTE -end marker during s1 / x2 Handover...Modify bearer request indication flags information.

23401-a50 ( Figure 5.5.1.1.2-1: X2-based handover without Serving GW relocation )

Point No 5:-
In order to assist the reordering function in the target eNodeB, the Serving GW shall send one or more "end marker" packets on the old path immediately after switching the path as defined in TS 36.300 [5], clause 10.1.2.2.

23401-a50 ( Figure 5.5.1.2.2-1: S1-based handover )

Point No 17:-
If the Serving GW does not change, the Serving GW shall send one or more "end marker" packets on the old path immediately after switching the path in order to assist the reordering function in the target eNodeB.

36300-a50 ( 10.1.2.2 Path Switch )

After the downlink path is switched at the Serving GW downlink packets on the forwarding path and on the new direct path may arrive interchanged at the target eNB. The target eNodeB should first deliver all forwarded packets to the UE before delivering any of the packets received on the new direct path. The method employed in the target eNB to enforce the correct delivery order of packets is outside the scope of the standard.

In order to assist the reordering function in the target eNB, the Serving GW shall send one or more "end marker" packets on the old path immediately after switching the path for each E-RAB of the UE. The "end marker" packet shall not contain user data. The "end marker" is indicated in the GTP header. After completing the sending of the tagged packets the GW shall not send any further user data packets via the old path.

Upon receiving the "end marker" packets, the source eNB shall, if forwarding is activated for that bearer, forward the packet toward the target eNB.

On detection of an "end marker" the target eNB shall discard the end marker packet and initiate any necessary processing to maintain in sequence delivery of user data forwarded over X2 interface and user data received from the serving GW over S1 as a result of the path switch.

On detection of the "end marker", the target eNB may also initiate the release of the data forwarding resource. However, the release of the data forwarding resource is implementation dependent and could also be based on other mechanisms (e.g. timer-based mechanism).

EPC may change the uplink end-point of the tunnels with Path Switch procedure. However, the EPC should keep the old GTP tunnel end-point(s) sufficiently long time in order to minimise the probability of packet losses and avoid unintentional release of respective E-RAB(s).

Question :-

Entities :-

UE, SeNB, TeNB. SMME/TMME(If there), SGW, PGW...
Here if TMME is not there ,only SMME and SGW(as target & souce) will assist the SeNB and TeNB.

end marker is sent in GTP-User plane header.....when sending stream of data continuosly and doing handover....

In wireshark all these data is shown as GTP ...how can we point the exact gtp message which includes the end marker between the source and destination.

Is it SGW which sends the end marker to Target eNodeB in case of S1 handover and Source eNodeB ( SGW -> Source eNodeB -> Target eNodeB ) which sends the end marker to Target eNodeB in case of X2 handover ?

posted Mar 22, 2017 by Yeshwanth

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Similar Questions
+4 votes

In X2-AP Handover scenario, SGW will send "END MARKER" to source E-NodeB saying that any data from S-GW to source E-NodeB will be silently discarded.

So, what the END MARKER should contain?

According to TS 29.281 GTPv1-U "END MARKER" is having only one IE, Private Extension (OPTIONAL). So,

How this to be triggered from SGW and what all information should be sent to source E-NodeB?

+3 votes
+1 vote

I have seen GTP control messages and found that F-TEID consists of an IP address and 32 bit long Tunnel Id. For example: Create Session Response message contains control plane F-TEID and user plane F-TEIDs. I have a question here, why not only TEIDs are included in Create Session Response message when IP address would be common ? or Does it mean control and user plane both F-TEIDs may have different IP address ?

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