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What should contain by END MARKER ?

+4 votes
1,128 views

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?

posted Apr 24, 2014 by Rajni

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2 Answers

+2 votes

In case of X2 based handover, source eNodeB sends "Handover Request" message to the target eNodeB.
Handover Request message itself may contains "DL Forwarding" IE (optional ie) for a bearer. It indicates that for which of the bearer source want to do forward handover. Till that time, there is no source eNodeB and source SGW interaction, source SGW is not aware about this forwarding.

Once the handover command (RRC Connection reconfiguration) sends to UE, source enodeb forward the data to target eNodeB (downlink data). After successful handover, target eNodeB sends "Path switch request" message to the MME. MME receives the "Path Switch Request" message from the target eNodeB and sends "Modify bearer request" to SGW to change the end of downlink data.
SGW responds with the "Modify bearer response" and sends "End marker" message to source eNodeB and in turn source eNodeB sends "End marker" message to target eNodeB. Only message type "END marker" is sufficient to send to source eNodeB from SGW to release the associated context of data planes.
But if source eNodeB was doing data forwarding towards the target eNodeB then only source eNodeB should send "End marker" to target eNodeB. Otherwise it should not required

answer Apr 25, 2014 by Vimal Kumar Mishra
0 votes

End marker packet contains nothing.
Significance: This packet just means that this is the last packet of this stream in tunnel. And the data packet recieves after end marker can be discarded.
After Handover SGW has to switch the DL path from source eNB to target eNB. The path from SGW to target eNB already established, so end marker is send on to the source eNB and the DL data packet shall be send to the target eNB afterwards.

answer Jun 13, 2014 by Sanjeet Kumar
Similar Questions
+1 vote

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 ?

+2 votes

Hello,

I am working on GTPV2 control plane. I want to implement negative test scenarios for GTPV2-C messages in my project. Can anybody list out the possible negative test case scenarios for GTPV2-C messages.??

+1 vote

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 ?

+2 votes

Could somebody explain about Recovey IE in GTPC message .I know this is restart counter of GW .Then what is the importance of this IE?

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