Subject: [Manet-dt] Minor MANET Generic Message Format Comments

From: Brian Adamson <[email-masked]>
Date: Thu, 23 Mar 2006 15:04:35 -0500

We discussed some of these at the working group meeting.

1)  For <msg-header-info>, it seems the order of the fields should be:

<originator-address>
<msg-seq-number>
<ttl>
<hop-count>

since the presence of <originator-address>/<msg-seq-number> are 
commonly determined by bit0 of <msg-semantics>  _and_ the presence of 
<ttl>/<hop-count> are commonly determined by bit1 of <msg_semantics>

This makes for more logical message building ...

(BUT, I understand a "backwards compatibility with OLSRv1" issue here 
may need to take precedence over this nit-pick?)

Also here, with regards to <ttl> and <hop-count> as discussed, <ttl> 
might be better renamed <hop-limit> ... Also if <hop-count> is an 
accumulated count of hops traversed, would it be possible to then 
leave <hop-limit> fixed (don't decrement) and stop forwarding when 
incremented <hop-count> > <hop-limit> ...

Or ... should we leave the use of these fields open in message format 
document as perhaps suggested.

2) Similarly, for <tlv>, it seems the field order should be:

<type>
<tlv-semantics>
<index-start>
<index-stop>
<length>
<value>

The reason for this is that in constructing a TLV, particularly a 
multi-value TLV it would seem that the choice as to whether (noindex) 
is set could be made ahead of setting TLV values and that <length> 
could be updated as multiple tlv's are added ...

And also, this seems more logical since <length> does _not_ include 
the <index-start> and <index-stop> content, but is the length of the 
<value> field that follows ...

3) In the <addr-block>, it also seems cleaner to have <num-tails> 
precede <head>, and hey, why not call it <num-addrs> since that is 
what it is?  So the new suggested format would be:

<address-block> = <num-addrs>
                   <head-length>
                   <head>
                   <tail>+

Brian
__________________________________
Brian Adamson
<mailto:[email-masked]>

-- 
Brian
__________________________________
Brian Adamson
<mailto:[email-masked]>

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---

From: "Dearlove, Christopher (UK)" <[email-masked]>
Date: Tue, 28 Mar 2006 09:54:04 +0100

With regard to these points

1 - I think I'd rather keep OLSRv1 compatibility.
2 - On balance is probably a good idea, but I'm open to either way.
However if we are going
     to change I'd like to make the decision as soon as possible (code
depends on it).
3 - I beat Brian to this one (both parts) - see bugtracker (where I also
had other ideas I
    think we won't do). But generally my comments are  as 2, i.e. can
live with decision
    either way as long as quickly. Note that <tail>+ should probably be
<tail>* as we
    have no tails if <head-length> is maximal. (It's even possible in
this case for the
    number of addresses to be >1, provided they have different netmask
lengths.)

Thomas, Justin?

  _____ 

From: Brian Adamson [mailto:[email-masked]]
Sent: 23 March 2006 20:05
To: Thomas Heide Clausen; Dearlove, Christopher (UK); Joe Macker;
[email-masked]
Cc: [email-masked]; [email-masked]
Subject: Minor MANET Generic Message Format Comments

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<originator-address>
<msg-seq-number>
<ttl>
<hop-count>

since the presence of <originator-address>/<msg-seq-number> are commonly
determined by bit0 of <msg-semantics>  _and_ the presence of
<ttl>/<hop-count> are commonly determined by bit1 of <msg_semantics>

Also here, with regards to <ttl> and <hop-count> as discussed, <ttl>
might be better renamed <hop-limit> ... Also if <hop-count> is an
accumulated count of hops traversed, would it be possible to then leave
<hop-limit> fixed (don't decrement) and stop forwarding when incremented
<hop-count> > <hop-limit> ...

<type>
<tlv-semantics>
<index-start>
<index-stop>
<length>
<value>

The reason for this is that in constructing a TLV, particularly a
multi-value TLV it would seem that the choice as to whether (noindex) is
set could be made ahead of setting TLV values and that <length> could be
updated as multiple tlv's are added ...

And also, this seems more logical since <length> does _not_ include the
<index-start> and <index-stop> content, but is the length of the <value>
field that follows ...

3) In the <addr-block>, it also seems cleaner to have <num-tails>
precede <head>, and hey, why not call it <num-addrs> since that is what
it is?  So the new suggested format would be:

Brian

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