No subject
Thu Jun 19 13:37:34 UTC 2008
because I am using protocol on very limited bandwidth link, also is =
better to have shorter messages anyway. But that is only my opinion.
Robert
-----Original Message-----
From: =
babel-users-bounces+robert.lukan=3Dltfe.org at lists.alioth.debian.org on =
behalf of Juliusz Chroboczek
Sent: Mon 7/7/2008 9:12 PM
To: babel-users at lists.alioth.debian.org
Subject: [Babel-users] Loose ends with Babel
=20
There are a few things that keep nagging me about the current protocol
spec and implementation, and that I may decide to fix at some point.
This is more of a note to self then a public discussion, but don't
hesitate to chime in if you have any comments.
1. The IHU definition is broken
Babel identifies routers with router ids, and interfaces with
link-local addresses.
Link quality is a property of a pair of interfaces, not a pair of
routers. The IHU message should be carrying an interface id (a
link-local address) rather than a router-id. This is the fundamental
reason for the previous issue reported by Robert (the one with
multiple link-local addresses).
(I'm not so sure about HELLO messages; keeping the router id in them
might be a good idea, in order to simplify debugging.)
Fixing that will require an incompatible protocol revision. It's
definitely a good idea.
2. The handling of idle interfaces is idiosyncratic
Idle interfaces (see -i in the manual page) are handled in an
idiosyncratic manner, by a bunch of ifs sprinkled throughout the code.
It'd be nice to clean up this mess.
3. The handling of down interfaces is idiosyncratic
The handling of down interfaces (interfaces that are currently down,
or, if -l was specified, that report no link sense) are handled
idiosyncratically, by a bunch of ifs throughout the code. I'm not
sure this can be fixed, cross-layer indications are notoriously tricky
to do in a modular way.
4. The protocol is bloated
The protocol currently uses fixed-length 24-byte messages, large
enough to contain an IPv6 address. This means its sweet and simple,
but makes some messages somewhat larger than they could be.
Switching to variable-length messages (smaller for IPv4 than for IPv6)
will reduce the size of update messages by 2/3 for pure IPv4 networks,
and by 1/3 on mixed-stack networks. I've done a pretty good job of
reducing unnecessary update traffic, so I'm not sure that it's really
worth the trouble.
This, again, will require an incompatible change, and I'm not sure
it's a good idea.
Juliusz
_______________________________________________
Babel-users mailing list
Babel-users at lists.alioth.debian.org
http://lists.alioth.debian.org/mailman/listinfo/babel-users
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<P><FONT SIZE=3D2>From my point of view, it would be nice to have =
shorter massages, because I am using protocol on very limited bandwidth =
link, also is better to have shorter messages anyway. But that is =
only my opinion.<BR>
<BR>
Robert<BR>
<BR>
-----Original Message-----<BR>
From: =
babel-users-bounces+robert.lukan=3Dltfe.org at lists.alioth.debian.org on =
behalf of Juliusz Chroboczek<BR>
Sent: Mon 7/7/2008 9:12 PM<BR>
To: babel-users at lists.alioth.debian.org<BR>
Subject: [Babel-users] Loose ends with Babel<BR>
<BR>
There are a few things that keep nagging me about the current =
protocol<BR>
spec and implementation, and that I may decide to fix at some point.<BR>
This is more of a note to self then a public discussion, but don't<BR>
hesitate to chime in if you have any comments.<BR>
<BR>
<BR>
1. The IHU definition is broken<BR>
<BR>
Babel identifies routers with router ids, and interfaces with<BR>
link-local addresses.<BR>
<BR>
Link quality is a property of a pair of interfaces, not a pair of<BR>
routers. The IHU message should be carrying an interface id (a<BR>
link-local address) rather than a router-id. This is the =
fundamental<BR>
reason for the previous issue reported by Robert (the one with<BR>
multiple link-local addresses).<BR>
<BR>
(I'm not so sure about HELLO messages; keeping the router id in them<BR>
might be a good idea, in order to simplify debugging.)<BR>
<BR>
Fixing that will require an incompatible protocol revision. =
It's<BR>
definitely a good idea.<BR>
<BR>
<BR>
2. The handling of idle interfaces is idiosyncratic<BR>
<BR>
Idle interfaces (see -i in the manual page) are handled in an<BR>
idiosyncratic manner, by a bunch of ifs sprinkled throughout the =
code.<BR>
It'd be nice to clean up this mess.<BR>
<BR>
<BR>
3. The handling of down interfaces is idiosyncratic<BR>
<BR>
The handling of down interfaces (interfaces that are currently down,<BR>
or, if -l was specified, that report no link sense) are handled<BR>
idiosyncratically, by a bunch of ifs throughout the code. I'm =
not<BR>
sure this can be fixed, cross-layer indications are notoriously =
tricky<BR>
to do in a modular way.<BR>
<BR>
<BR>
4. The protocol is bloated<BR>
<BR>
The protocol currently uses fixed-length 24-byte messages, large<BR>
enough to contain an IPv6 address. This means its sweet and =
simple,<BR>
but makes some messages somewhat larger than they could be.<BR>
<BR>
Switching to variable-length messages (smaller for IPv4 than for =
IPv6)<BR>
will reduce the size of update messages by 2/3 for pure IPv4 =
networks,<BR>
and by 1/3 on mixed-stack networks. I've done a pretty good job =
of<BR>
reducing unnecessary update traffic, so I'm not sure that it's =
really<BR>
worth the trouble.<BR>
<BR>
This, again, will require an incompatible change, and I'm not sure<BR>
it's a good idea.<BR>
<BR>
<BR>
&=
nbsp; &n=
bsp; &nb=
sp; Juliusz<BR>
<BR>
_______________________________________________<BR>
Babel-users mailing list<BR>
Babel-users at lists.alioth.debian.org<BR>
<A =
HREF=3D"http://lists.alioth.debian.org/mailman/listinfo/babel-users">http=
://lists.alioth.debian.org/mailman/listinfo/babel-users</A><BR>
<BR>
<BR>
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