Please see inline [Tiru]

From: Lorenzo Colitti [mailto:[email protected]]
Sent: Wednesday, October 24, 2012 8:24 AM
To: Tirumaleswar Reddy (tireddy)
Cc: [email protected]
Subject: Re: [mif] FW: New Version Notification for 
draft-reddy-mif-dhcpv6-precedence-ops-02.txt


On Thu, Oct 18, 2012 at 9:32 PM, Tirumaleswar Reddy (tireddy) 
<[email protected]<mailto:[email protected]>> wrote:
This draft proposes new DHCPv6 options to be added by the DHCPv6 relay agent 
when it generates a Relay-Forwarded message to influence the DHCPv6 server's 
response that modify the host's address policy table 
[I-D.ietf-6man-addr-select-opt] based on observed network characteristics. 
These options can also be used to conditionally disable IPv6 temporary 
addresses in a managed network for selective hosts without authentication 
supplicant.

Comments and suggestions are welcome.

A few general points:

1. The draft deals with two DHCPv6 options, with different use cases. Why are 
you combine the options? I believe things would be much clearer if each option 
had its own draft with its own use case.
[Tiru] Sure, we will create two different drafts. After we split the draft into 
two [1] we will post Absolute Precedence Option with relevant use cases in 6man 
[2] Relay-supplied prefix option in DHCP WG.

2. Why is this draft in MIF? The address selection option has nothing to do 
with multiple interfaces, and is already being discussed in 6man. The 
relay-supplied prefix option also has nothing to do with multiple interfaces.
[Tiru] Yes. Only Absolute Precedence Option deals with MIF scenario where 
Mobile Node is assigned prefixes from both Local Access Network and Home 
Network. We had other multi-homing use cases in 01 version which are removed in 
02.

3. The introduction does not provide a problem statement that matches the 
solutions. The introduction says that "DHCPv6 allows relatively static 
information to be configured in hosts, which is somewhat limiting", but then 
states that the problem can be fixed by introducing DHCPv6 options. I don't see 
how this is possible. DHCPv6 options cannot make things more dynamic, since in 
DHCPv6, options are only handed out at request/response time, and DHCPv6 
options cannot change how often requests are made. Since the options being 
proposed as solutions do not solve the problem, the draft needs another problem 
statement.
[Tiru] Agreed the problem statement needs to be fixed in this version.

But we are evaluating other scenarios for the next version  For e.g. In IPv6 
multi-homing, dual stack scenarios - where Relay agent dynamically influences 
the host policy table If IPv6 connectivity is detected to be broken (Section 
10.3.1 of RFC 6724). This can be achieved by Relay Agent sending 
RECONFIGURE-REQUEST 
(http://tools.ietf.org/html/draft-ietf-dhc-triggered-reconfigure-01) to the 
DHCPv6 server providing the updated policy table in Absolute Precedence Option. 
DHCPv6 server will in turn initiate reconfigure message with the client, 
resulting in the client to initiate Renew/Reply or information-request/Reply 
transaction with the server to receive updated Policy Table OR

Do you think we can send the dynamic policy table in RA itself and solve the 
problem (but then it brings in complexity on the host if it is receiving policy 
table from two different sources)

Please let us know your opinion before we proceed on this path .


4. The draft confuses RFC4941 privacy addresses with IA_TA options. Ignoring 
IA_TA options will not disable RFC4941 privacy addresses, because they are only 
used by SLAAC. The references to RFC 4941 should be removed.
[Tiru] Yes, will remove this part.

As regards the address selection option specifically:

1. The option itself is still work in progress in 6man. So the modifications 
should happen in 6man, not here. Otherwise we will have two working groups 
working on the same option which is likely to have bad results.
[Tiru] Agreed

3. I don't understand the use case (Section 3.1). If the DHCPv6 relay is in the 
mobile access gateway, then it's in the mobile operator's network. If it's in 
the mobile operator's network, then how can it "influence the DHCPv6 Server in 
the home network"? In general, the DHCPv6 server in the home network has no way 
of talking to the mobile operator's network.

[Tiru] This use case is specific to Proxy Mobile IPv6 (RFC 5213). Where there 
is tie-up b/w the Local Access Network and Mobile Network. Mobile. MAG in the 
Local Access Network establishes tunnel with LMA in the Home network. MAG can 
act as a DHCP relay agent and can communicate with the DHCP server in the home 
network.


  MN   MAG(DHCP-R) LMA   DHCP-S

   |       |------->|      | 1. Proxy Binding Update *

   |       |<-------|      | 2. Proxy Binding Acknowledgement

   |       |========|      | 3. Tunnel/Route Setup*

   |------>|-------------->| 4. Solicit via DHCP-R

   |<------|<--------------| 5. Advertise via DHCP-R

   |------>|-------------->| 6. Request via DHCP-R

   |<------|<--------------| 7. Reply via DHCP-R

   |       |               |
We will add more details to explain these details in next version.

--Tiru.
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