Subject: [manet] Mail regarding draft-dlep-lid

From: "Morgan, Keith" <[email-masked]>
Date: Wed, 31 May 2017 13:30:35 +0000

Hello,

I have been reviewing the proposed Link Identifier Extension to DLEP and have the following comments:

The focus of the proposal appears to be to enable Routers to identify where they cannot reach Destinations via the MAC address provided in the Destination Up message. This would be the case with our Modem.

Our current implementation does use "sleight-of-hand" and will report both the MAC address and IP address in the Destination Up message, however the Destination is only reachable via its IP address.

The concept proposed appears sound; my immediate suggestion would be to recommend a length of 6 bytes for the identifier, this would allow the Modem to use the MAC address of the destination which should ensure uniqueness while allowing the router to determine how to address packets to the Destination based on the use of the Link Identifier Data Item.

Regards

Keith

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From: Rick Taylor <[email-masked]>
Date: Wed, 31 May 2017 14:56:59 +0000

Hi Keith,

Comments inline...

> and have the following comments:

Thanks for the quick review!

>  
> The focus of the proposal appears to be to enable Routers to identify
> where they cannot reach Destinations via the MAC address provided in
> the Destination Up message. This would be the case with our Modem.
>  
> Our current implementation does use “sleight-of-hand” and will report
> both the MAC address and IP address in the Destination Up message,
> however the Destination is only reachable via its IP address.

This is one of the use-cases I was trying to fix, so I'm glad it helps.

>  
> The concept proposed appears sound; my immediate suggestion would be
> to recommend a length of 6 bytes for the identifier, this would allow
> the Modem to use the MAC address of the destination which should
> ensure uniqueness while allowing the router to determine how to
> address packets to the Destination based on the use of the Link
> Identifier Data Item.

4 is only RECOMMENDED.  As a variable length field, Link Id's can be
any length, so if you want to use 6, that's fine.  I only picked 4 as I
imagined people had integer values and felt I had to recommend
something to point people away from using SHA1 hashes or something huge
(although they still can).

It's interesting that your Link Ids actually are MACs, but by using
Link Ids not MAC Address Data Items you are being explicit that the
MACs can't be used in frames.  I hadn't thought of this use-case, but
I'm glad it works for you!

One thing that is probably missing is a requirement that all Link Ids
should be the same length during a session.  Do people think this is a
valid restriction?

Cheers,

Rick