Subject: [Mip4] RFC 3024 vs RFC 3344 FA Registration Request IP TTL Checking

From: Acee Lindem <[email-masked]>
Date: Tue, 12 Jun 2007 12:42:35 -0400

In RFC 3344 Section 3.6.1.1 (and the bis draft), it says one the TTL  
MUST be 1 if the destination address is "All Mobility Agents".

    IP Time to Live:

       -  The IP TTL field MUST be set to 1 if the IP destination  
address
          is set to the "All Mobility Agents" multicast address as
          described above.  Otherwise a suitable value should be chosen
          in accordance with standard IP practice [38].

In RFC 3024, it says unequivocally that the IP TTL must be 255.

4.1.1. Sending Registration Requests to the Foreign Agent

    In addition to the considerations in [1], a mobile node sets the 'T'
    bit in its Registration Request to petition a reverse tunnel.

    The mobile node MUST set the TTL field of the IP header to 255.   
This
    is meant to limit the reverse tunnel hijacking attack (Section 6).

    The mobile node MAY optionally include an Encapsulating Delivery
    Style Extension.

How should an implementation handle this discrepancy? Shouldn't these  
drafts agree?

Thanks,
Acee 

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---

From: "Kent Leung \(kleung\)" <[email-masked]>
Date: Tue, 12 Jun 2007 10:58:48 -0700

Hi Acee.
 
There were discussions during RFC 3024 which dictated the use of IP TTL
set to 255.  The issue is covered in that RFC.  
 
For interoperability, I believe that FA must check if IP TTL is set to
255 when registration request has T bit set for reverse tunnel.  Else,
follow specification in RFC 3344 for non-reverse tunnel case.
 
Kent

________________________________

From: Acee Lindem [mailto:[email-masked]] 
Sent: Tuesday, June 12, 2007 9:43 AM
To: [email-masked]
Subject: [Mip4] RFC 3024 vs RFC 3344 FA Registration Request IP TTL
Checking

   IP Time to Live:

      -  The IP TTL field MUST be set to 1 if the IP destination address
         is set to the "All Mobility Agents" multicast address as
         described above.  Otherwise a suitable value should be chosen
         in accordance with standard IP practice [38].

   The mobile node MUST set the TTL field of the IP header to 255.  This
   is meant to limit the reverse tunnel hijacking attack (Section 6).

Thanks,
Acee