Satoru,

since I read this at different places, let me ask one clarifying question about 
the stateless motivation: 

I see that for SRv6 you may not need a state at the egress (at least not for 
traffic forwarding) but for
Uplink/Downlink (UL/DL) you need a state at both edges of the communication 
since the DL egress
serves as uplink ingress, correct?

marco


-----Original Message-----
From: dmm [mailto:dmm-boun...@ietf.org] On Behalf Of Satoru Matsushima
Sent: Dienstag, 6. März 2018 17:23
To: Tom Herbert
Cc: dmm
Subject: Re: [DMM] Fwd: I-D Action: draft-ietf-dmm-srv6-mobile-uplane-01.txt

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 
>> instead 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.

Cheers,
--satoru
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