Your understanding is correct: in the traditional mode there is no pushed SRH
•       Less MTU overhead than GTP in traditional mode.
•       In enhanced mode with underlay TE with SLA bandwidth with stateless 
service chaining we use the SRH.

Any solution other than SRv6 requires an independent layer for underlay TE(1) 
and service chaining(2)
•       Do you contemplate combining ILA with RSVP for 1 and NSH for 2 causing 
explosion of state in the underlay??
•       What is the overhead in ILA when supporting IPv4 or Ethernet PDU 
sessions? It must be greater, right?


On 06/03/2018, 17:23, "dmm on behalf of Satoru Matsushima" 
< on behalf of> wrote:

    Hello Tom,
    >> A Big progress is that the draft supports interworking with GTP over 
IPv6 in
    >> addition to GTP over IPv4.
    >> And we have made change SRv6 function to IPv6 encapsulation with SRH 
    >> of SRH insertion by default.
    > Hi Satoru,
    > If there are no intermediate hops od SIDs being set when encapsulating
    > would a SR header still be needed or could this just be simple IP in
    > IP encpasulation?  If is no SR header then it's possible that ILA
    > might then be used to completely eliminate the encapsulation overhead.
    I think you’re right. You would find that case in the draft as ‘Traditional 
Mode’ which is equivalent with traditional GTP-U case. You seem you say ILA is 
also equivalent with that mode. In addition, this draft introduces ‘Enhance 
Mode’ to cover more advanced cases.
    IMO SR is designed not to maintain path states except at an ingress node. 
So the packet need to preserve original DA in the header that keep the egress 
node in stateless. It would be great if ILA is designed in the similar concept 
as well.
    If it’s not, it looks a kind of tradeoff, between reducing the overhead and 
keeping the statelessness. It’s not apple-to-apple comparison. To decide to 
choose which one need to be prioritized would depend on each deployment case in 
operators IMO.
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