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

Stan,

I think you're over-complicating this.  Given a Data Item is a TLV,
then as long as the lengths are consistent on a per-session basis, I'd
be happy letting the modem implementer decide on the length.  As far as
the router is concerned, it really doesn't matter.  Zero-padding fixed
length fields seems a bit unwieldy...

Rick

On Sun, 2017-06-04 at 12:15 -0400, Stan Ratliff wrote:
> Hi, 
> 
> So, what about the notion of allocating a 64-bit quantity for the
> LID? That way, a MAC address would fit, and by definition, all LIDs
> would be the same length. We can specify the characteristics of the
> data in the LID (right-justify, fill character 0x00, etc). Or, we
> could even use the first octet of that 64-bit quantity as a set of
> bit flags to indicate what's in the LID (e.g., is it a MAC address,
> or an integer, or...)
> 
> Regards,
> Stan
> 
> 
> On Fri, Jun 2, 2017 at 3:58 AM, Morgan, Keith <kmorga07@harris.com>
> wrote:
> > Hi,
> > 
> > We have to provide the MAC address in the current protocol so we
> > think it makes sense to use it if Link ID's are accepted.
> > 
> > I think all Link ID's should be the same length in a session, to
> > keep it simple.
> > 
> > Regards
> >  
> > Keith
> > 
> > Keith Morgan
> > Director of Engineering
> > COMMUNICATION SYSTEMS / HARRIS DEFENCE LIMITED
> > Office: +44 (0)1256 383132 / Mobile: +44 (0)7917 012248
> > www.harris.com / Keith.Morgan@Harris.com
> > Jays Close, Viables Estate, Basingstoke, Hampshire, RG22 4BA,
> > United Kingdom
> > 
> > 
> > 
> > 
> > 
> > Registered in England No. 2803090 Harris Defence Limited a UK
> > Subsidiary of Harris Corporation, USA
> > CONFIDENTIALITY NOTICE:  This email and any attachments may contain
> > material that is "Harris Proprietary Information" for the sole use
> > of the intended recipient.  Any review, reliance, distribution,
> > disclosure, or forwarding without expressed permission is strictly
> > prohibited.  If you are not the intended recipient, please contact
> > the sender and delete all copies without reading, printing, or
> > saving in any manner.  Thank You.
> > 
> > 
> > -----Original Message-----
> > From: Rick Taylor [mailto:rick@tropicalstormsoftware.com]
> > Sent: 31 May 2017 15:57
> > To: Morgan, Keith (Non U.S.); manet@ietf.org
> > Subject: Re: [manet] Mail regarding draft-dlep-lid
> > 
> > Hi Keith,
> > 
> > Comments inline...
> > 
> > On Wed, 2017-05-31 at 13:30 +0000, Morgan, Keith wrote:
> > > Hello,
> > >  
> > > I have been reviewing the proposed Link Identifier Extension to
> > DLEP
> > > 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
> > _______________________________________________
> > manet mailing list
> > manet@ietf.org
> > https://www.ietf.org/mailman/listinfo/manet
> > 