Subject: Comments on draft-koodli-ipv6-in-mobile-networks-02.txt

From: Behcet Sarikaya <[email-masked]>
Date: Mon, 19 Apr 2010 12:14:24 -0700 (PDT)

Hi Rajeev,
  My comments on 
Section 3.2 NAT Placement in the mobile networks

This section nicely narrates the story of GI-DS-Lite as the centralized NAT versus DS-Lite as the distributed DS-Lite. It reads nicely but I found in it too much emphasis on billing and accounting aspects while it lacks emphasis on other aspects (more meaty? aspects at least as much as I am interested).

For example, one very important feature of DS-Lite is to have an IPv6-only network thus savings on IPv4 addresses. This is not mentioned.
Next, why currently mobile operators do not have much interest on DS-Lite is not mentioned.

On the centralized NAT or GI-DS-Lite, firstly, the identification of GI-DS-Lite as the centralized NAT approach is very useful because it was not clear reading the GI-DS-Lite draft. 

However, one important aspect of GI-DS-Lite is that it no longer requires an IPv6-only network and therefore no IPv4 address savings which is not mentioned in the draft.

Regards,

Behcet

---

From: Sri Gundavelli <[email-masked]>
Date: Mon, 19 Apr 2010 19:54:40 -0700

Hi Behcet,

Some of your comments below are not much related this draft under
discussion, they are more specific to GI-DS-lite draft. I'd like to respond
to your comments and also suggest you open up a separate discussion thread
on that draft. Couple of clarification points.

> However, one important aspect of GI-DS-Lite is that it no longer requires an
> IPv6-only network and therefore no IPv4 address savings which is not mentioned
> in the draft.

GI-DS-lite is a variant of DS-lite and it does not require either the access
network or the operator core network to have IPv4 enabled. It can certainly
be applied in operator networks, with IPv6 enabled in the EPC core and in
the operator core (between the gateway and the CGN). However, it can also be
enabled with IPv4 running in one or both of these network segments. The IP
address saving in this context is not from configuring IPv4 on the core
network elements, but the focus is on the end points, that's where the cause
for IPv4 exhaust is.

The key point of the GI-DS-lite is to leverage the existing tunneling
infrastructure in mobile architectures and allow the end points to be
configured with IPv4 overlapping addresses, and by carrying the context
identifiers in the encapsulation headers of the tunneled packets. These
context identifiers provide the needed end-point identity for the network
elements to make the forwarding decisions. This approach has number of
benefits as listed in that document, including the ability to migrate the
operator network to IPv6, still allowing access to IPv4 services and solving
the IPv4 address exhaust issue.

> Next, why currently mobile operators do not have much interest on DS-Lite is

No, Mobile Operators and broadly the 3GPP community does have interest for
applying a variant of DS-lite based approach to mobile architectures. If you
have missed any parts of the discussions in San Francisco, or in Shanghai
related to IPv6 migration, you may want to review the summary/recommendation
slides from that workshop.

Regards
Sri

On 4/19/10 12:14 PM, "Behcet Sarikaya" <[email-masked]> wrote:

> This section nicely narrates the story of GI-DS-Lite as the centralized
> NAT versus DS-Lite as the distributed DS-Lite. It reads nicely but I found in
> it too much emphasis on billing and accounting aspects while it lacks emphasis
> on other aspects (more meaty? aspects at least as much as I am interested).
> 
> For example, one very important feature of DS-Lite is to have an IPv6-only
> network thus savings on IPv4 addresses. This is not mentioned.
> On the centralized NAT or GI-DS-Lite, firstly, the identification of
> GI-DS-Lite as the centralized NAT approach is very useful because it was not
> clear reading the GI-DS-Lite draft.
> 
> However, one important aspect of GI-DS-Lite is that it no longer requires an
> IPv6-only network and therefore no IPv4 address savings which is not mentioned
> in the draft.
> 
> Regards,
> 
> Behcet
> 
> 
> 
>

---

From: Rajeev Koodli <[email-masked]>
Date: Mon, 19 Apr 2010 22:01:08 -0700

Hi Behcet,

> on other aspects (more meaty? aspects at least as much as I am interested).

DS-Lite is not presented as a distributed NAT solution in the document.

Many mobile providers do care for subscriber management. For them, it is
important to be able to do harmonized billing and accounting. With respect
to NAT itself, which introduces binding state between addresses, it is
important to be able to harmonize NAT state with subscriber billing and
accounting.

> Next, why currently mobile operators do not have much interest on DS-Lite is

Clarification: this ID is *not* about evaluating pros and cons of each of
the available transition mechanism. It is about considerations that arise
when deploying IPv6 in mobile networks.

To your point about DS-lite itself, it is perfectly fine in residential
broadband networks. For mobile networks, having a tunnel termination at the
UE (host) is considered undesirable. The 3GPP TR on IPv6 transition looks at
some of the variants FYI, and that document may be a good place for your
questions. 

> IPv6-only network and therefore no IPv4 address savings which is not mentioned

I did not follow this. Care to elaborate?

Regards,

-Rajeev

---

From: Behcet Sarikaya <[email-masked]>
Date: Sat, 24 Apr 2010 07:09:37 -0700 (PDT)

Hi Rajeev,

> This section nicely narrates 
> the story of GI-DS-Lite as the centralized
> NAT versus DS-Lite as the 
> distributed DS-Lite. It reads nicely but I found in
> it too much emphasis 
> on billing and accounting aspects while it lacks emphasis
> on other 
> aspects (more meaty? aspects at least as much as I am 
> interested).

> DS-Lite is not presented as a distributed NAT solution in 

I thought it should be.

>Many mobile providers do care for subscriber management. 
important to be able to do harmonized billing and accounting. 
> With respect
to NAT itself, which introduces binding state between addresses, 
> it is
important to be able to harmonize NAT state with subscriber billing 
> and
accounting.

This is OK as I said before. But it is one kind of consideration when deploying IPv6 in mobile networks. I was asking about some other considerations you have just ignored.

> Next, why currently mobile operators 
> do not have much interest on DS-Lite is
> not 
> mentioned.

>Clarification: this ID is *not* about evaluating pros and cons 
the available transition mechanism. It is about considerations 
> that arise

Please see my point above. You mean savings in IPv4 address usage is not a consideration?

>To your point about 
> DS-lite itself, it is perfectly fine in residential
broadband networks. For 
> mobile networks, having a tunnel termination at the
UE (host) is considered 
> undesirable.

Eaxctly. I am asking these types of considerations to be stated in the distributed NAT text.

> The 3GPP TR on IPv6 transition looks at
some of the variants 
> FYI, and that document may be a good place for your
questions. 

Thanks, I know this document.

> IPv6-only network and therefore no IPv4 address savings 

I did not follow this. Care 
> to elaborate?

GI DS Lite unlike DS Lite is not based on IPv6 only network premise, that is an important consideration when deploying IPv6 in mobile network. I was simplying asking these things to be stated in the centralized NAT discussion.
Also the fact that centralized NAT makes MN to MN communication to take longer paths.

Regards,

Behcet