That matches my view, Satoru. Still both edges require states hence the 
associated node has to have an
interface to the control plane. But I agree that in total fewer states are 
required because egress
does not need a host state for decap/re-write and removing the SRv6 header at 
egress is standard behavior. 


-----Original Message-----
From: Satoru Matsushima [] 
Sent: Mittwoch, 7. März 2018 12:23
To: Marco Liebsch
Cc: dmm
Subject: Re: [DMM] Fwd: I-D Action: draft-ietf-dmm-srv6-mobile-uplane-01.txt


> 2018/03/07 18:41、Marco Liebsch <>のメール:
> 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?

2x unidirectional tunnels to form bidirectional paths require 4 states in total 
at both the ingress and egress.
In SR case it requires just 2 states at the ingresses for both directions.


> marco
> -----Original Message-----
> From: dmm [] 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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