Subject: [DMM] I-D Action: draft-ietf-dmm-srv6-mobile-uplane-05.txt

From: [email-masked]
Date: Mon, 08 Jul 2019 05:16:07 -0700

A New Internet-Draft is available from the on-line Internet-Drafts directories.
This draft is a work item of the Distributed Mobility Management WG of the IETF.

        Title           : Segment Routing IPv6 for Mobile User Plane
        Authors         : Satoru Matsushima
                          Clarence Filsfils
                          Miya Kohno
                          Pablo Camarillo
                          Daniel Voyer
                          Charles E. Perkins
	Filename        : draft-ietf-dmm-srv6-mobile-uplane-05.txt
	Pages           : 28
	Date            : 2019-07-08

Abstract:
   This document shows the applicability of SRv6 (Segment Routing IPv6)
   to the user-plane of mobile networks.  The network programming nature
   of SRv6 accomplish mobile user-plane functions in a simple manner.
   The statelessness of SRv6 and its ability to control both service
   layer path and underlying transport can be beneficial to the mobile
   user-plane, providing flexibility, end-to-end network slicing and SLA
   control for various applications.  This document describes the SRv6
   mobile user plane behavior and defines the SID functions for that.

The IETF datatracker status page for this draft is:
https://datatracker.ietf.org/doc/draft-ietf-dmm-srv6-mobile-uplane/

There are also htmlized versions available at:
https://tools.ietf.org/html/draft-ietf-dmm-srv6-mobile-uplane-05
https://datatracker.ietf.org/doc/html/draft-ietf-dmm-srv6-mobile-uplane-05

A diff from the previous version is available at:
https://www.ietf.org/rfcdiff?url2=draft-ietf-dmm-srv6-mobile-uplane-05

Please note that it may take a couple of minutes from the time of submission
until the htmlized version and diff are available at tools.ietf.org.

Internet-Drafts are also available by anonymous FTP at:
ftp://ftp.ietf.org/internet-drafts/

---

From: "Kentaro Ebisawa" <[email-masked]>
Date: Mon, 08 Jul 2019 13:36:35 +0000

Hi,

Thank you for updating the draft. Nice to see T.M.Tmap was renamed to 
T.M.GTP4.D corresponding to End.M.GTP4.E. :)

Some feedback about the updated description.

 > 6.6. T.M.GTP4.D
 > ...
 > The prefix of B’ SHOULD be an End.M.GTP4.E SID with its format
 > instantiated at an SR gateway with the IPv4 SA of the receiving
 > packet.

"The B’" is IPv6 SA so I think this should correspond to S' in 
End.M.GTP4.E rather than to SID.
So it might be more clear to depict the packet format (diagram) again 
and mention B' has the following format with the IPv4 SA of the 
receiving packet.

0                                                         127
+----------------------+--------+--------------------------+
| Source UPF Prefix    |IPv4 SA | any bit pattern(ignored) |
+----------------------+--------+--------------------------+
        128-a-b             a                 b

--
Kentaro Ebisawa <[email-masked]>

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Sent: 2019/07/08 21:16:07
Subject: [DMM] I-D Action: draft-ietf-dmm-srv6-mobile-uplane-05.txt

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---

From: Satoru Matsushima <[email-masked]>
Date: Mon, 8 Jul 2019 23:50:26 +0900

Thanks Kentaro for you prompt review prior to my announce. :-)

> Thank you for updating the draft. Nice to see T.M.Tmap was renamed to T.M.GTP4.D corresponding to End.M.GTP4.E. :)

It helps to improve consistency of the draft, thanks.

> "The B’" is IPv6 SA so I think this should correspond to S' in End.M.GTP4.E rather than to SID.

Actually no, because it is assumed that the prefix of B’ could be a SID for End.GTP4.E instantiated in SRGW. But you’re correct the B’ doesn’t need to be filled with arg.mob.session.

Cheers,
--satoru

> So it might be more clear to depict the packet format (diagram) again and mention B' has the following format with the IPv4 SA of the receiving packet.
> 
> 0                                                         127

---

From: Kentaro Ebisawa <[email-masked]>
Date: Tue, 9 Jul 2019 13:02:17 +0900

> Actually no, because it is assumed that the prefix of B’ could be a SID
for End.GTP4.E instantiated in SRGW. But you’re correct the B’ doesn’t need
to be filled with arg.mob.session.

So the assumption here is that both T.M.GTP4.D and End.M.GTP4.E are
instantiated on the same SRGW.
If that's what you intend,  considering B' doesn't need arg.mob.session, it
might be more natural to say like below, since the source IPv6 of the
packet translated by T.M.GTP4.D corresponds to S' mentioned in 6.5.
End.M.GTP4.E.
(And since GTP-U is uni-directional, T.M.GTP4.D and End.M.GTP4.E might not
be instantiated on the same SRGW. e.g. for scaling purpose)

If End.M.GTP4.E is also instantiated on the SR gateway, the Source UPF
Prefix of B' SHOULD be SRGW-IPv6-LOC-FUNC of End.M.GTP4.E SID
instantiated on the SR gateway.

Just my two cents.

On Mon, Jul 8, 2019 at 11:50 PM Satoru Matsushima <
[email-masked]> wrote:

> Actually no, because it is assumed that the prefix of B’ could be a SID
> for End.GTP4.E instantiated in SRGW. But you’re correct the B’ doesn’t need
> to be filled with arg.mob.session.
>
> Cheers,
> --satoru
>
> So it might be more clear to depict the packet format (diagram) again and
> mention B' has the following format with the IPv4 SA of the receiving
> packet.
>
> 0                                                         127