Subject: [netlmm] Some comments on

From: "Soininen Jonne (NSN FI/Espoo)" <[email-masked]>
Date: Tue, 12 Feb 2008 23:33:34 +0200

Hi,

I was reading the ipv4 support document and some questions and suggestions
came up in my mind. I did just a quick scan on the document. So, it is
possible that I have missed something.

1) Section 3:
 "If the mobile node connects to the Proxy Mobile IPv6 domain, through
   multiple interfaces and simultaneously through different access
   networks, each of the connected interfaces will obtain an address
   from a unique IPv4 home network prefix.  In such configuration, there
   will be multiple Binding Cache entries on the local mobility anchor
   for that mobile node and with one entry for each connected interface,
   as specified in Section 5.4 [ID-PMIP6]."

Question: Why does the IPv4 prefix have to be unique? Should we rather talk
about subnets in the IPv4 case?

2) Section 3:
"Unlike as specified in [ID-DSMIP6], the mobile node is not
   required to have an IPv6 home address for obtaining IPv4 home address
   mobility" 
Edit: Remove the word "as".

3) Section 3.1 (Paragraph 1): "A mobile node on attaching to an access link
connected to a mobile
   access gateway, and if the network allows the mobile node for IPv4
   home address mobility service, the mobile node using any of the IPv4
   address configuration procedures, such as DHCP [RFC-2131], IPCP or
   IKEv2 that are supported on that access link, will be able to obtain
   required information for its IPv4 home address configuration."
Edit proposal: Maybe rephrase the text (doesn't read well). In addition, it
might be better to say that MN can use any available address allocation
mechanism provided by the access network - DHCP or link layer specific
mechanism. IPCP most probably is not used much.

4) Section 3.1 (paragraph 1):
 " The
   required information includes the IPv4 home address, the IPv4 home
   network prefix and IPv4 home network prefix length."
Question: Aren't the address and the subnet mask enough? What about any
other needed configuration (DNS, etc).

5) Section 3.1 (Paragraph 1): "Any available
   IPv4 address configuration mechanisms can be used such as static
   configuration method specific to the access link or dynamic
   configuration from DHCP."
Question: Isn't this a bit of repetition from earlier?

6) Section 3.2.2 (Bullet 2): " If the mobile access gateway learns the
mobile node's IPv4 home
      network prefix or the IPv4 home address either from its policy
      store or from the DHCP messages exchanged between the mobile node
      and the DHCP server, the mobile access gateway can specify the
      same in the IPv4 Home Address option for requesting the local
      mobility anchor to allocate that address or to allocate an address
      from the specified home network prefix.  If the specified value is
      0.0.0.0, then the local mobility anchor will consider this as a
      request for dynamic address allocation."
Edit: Consider rephrasing of the wording. This is a bit hard to understand.

7) Section 3.2.2:
" The mobile access gateway when sending the Proxy Binding Update
      request to the local mobility anchor for requesting IPv4 home
      address mobility support MUST construct the message as specified
      below.

               IPv6 header (src=Proxy-CoA, dst=LMAA)
                    Mobility header
                        -BU /*P & A flags are set*/
                       Mobility Options
                          - Timestamp Option (optional)
                          - Mobile Node Identifier option
                          - Access Technology Type option (Mandatory)
                          - Mobile Node Interface Identifier option
                            (Optional)

                          - IPv4 Home Address option (Mandatory)"
Edit: Maybe this could be described just by describing a delta to the base
spec. If the header structure or the optionality/mandatory fields change in
the base spec, this has to be changed as well.

8) Section 3.2.2:
" *  When a mobile access gateway is a DHCP server, it MUST send a
         proxy binding update right after receiving a DHCP discovery
         message from a mobile node.  By sending the proxy binding
         update, it will learn the assigned IPv4 home address from the
         local mobility anchor."
Question: Why does the MAG have to send the proxy binding update after the
DHCP discovery message? Why cannot it send the request when the MN is
identified to be on the link even before the DHCP discovery if that
information is available?

Cheers,

Jonne.
-- 
Jonne Soininen
Nokia Siemens Networks

Tel: +358 40 527 46 34
E-mail: [email-masked]

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---

From: "Soininen Jonne (NSN FI/Espoo)" <[email-masked]>
Date: Tue, 12 Feb 2008 23:40:18 +0200

Hi,

To be perfectly clear: The comments were on
draft-ietf-netlmm-pmip6-ipv4-support-02.txt... Sorry.

Cheers,

Jonne.

-- 
Jonne Soininen
Nokia Siemens Networks

Tel: +358 40 527 46 34

---

From: Sri Gundavelli <[email-masked]>
Date: Tue, 12 Feb 2008 17:01:22 -0800 (PST)

Hi Jonne,

> about subnets in the IPv4 case?

Terminology, IPv4 prefix is IPv4 subnet. We should be more specific.

> Edit: Remove the word "as".

Ok

> mechanism. IPCP most probably is not used much.

Ok

> other needed configuration (DNS, etc).

Again terminology. Prefix length or subnet mask. W.r.t DNS and other
config, its upto what is enabled in DHCP.

> information is available?

Agreed. Good point. We will fix it.

---

From: Vijay Devarapalli <[email-masked]>
Date: Tue, 19 Feb 2008 13:37:05 -0800

> Agreed. Good point. We will fix it.

Perhaps the trigger for the MAG to send a proxy BU (irrespective
of whether the MAG is a DHCP relay or a DHCP server) should be
link layer establishment between the mobile node and the MAG.
This is what we assume in the PMIPv6 base document. So why should
it be different for the IPv4 support document? A DHCP discover
message can also be the trigger.

Vijay

---

From: Sri Gundavelli <[email-masked]>
Date: Tue, 19 Feb 2008 15:16:07 -0800 (PST)

Hi Vijay,

> message can also be the trigger.

This touches the earlier issue of how the MAG decides if to
ask for an IPv4 mobility, IPv6 mobility or both. What options
to specify in the PBU. Sure, the trigger is L2 ATTACH, that is
fine, but should we depend on DHCP query or other address config
event to ask for the IPv4 address. The one question that remains
is and is related to the prev question, how the MAG determines
this.

Sri