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<TITLE>RE: [Babel-users] FW: Loose ends with Babel</TITLE>
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<P><FONT SIZE=2>First of all, length of message is not so important after all. IMHO its better that you focus on other features of protocol.<BR>
<BR>
Its true, I am using babel with serial link(ppp), and that is weird. In our project I would have to use RF modems(with central frequency around few ten MHz) with serial connectors, so speed will be 19200 or 38400 (simplex!). Thats the reason why I need a little as possible overhead and fast convergence (redundancy), unfortunately is that in contradiction.<BR>
For beginning my plan task/plan is to create 3 nodes in loop, on main node will run also ospf which will be connected to cisco router. Right now I am writing some scripts so system will be "plug and play". So udev and shell script will take care of all new connections, it will create ppp,... I will also use ahcpd for autoconfiguration, I haven't test it yet.<BR>
<BR>
Few months ago, I tried to use AODVUU, on ethernet and wireless was working good, but on serial had some weird problems, so I have to change routing protocol.<BR>
<BR>
I also testing OLSR. I will also make some tests, which protocol is better for wireless concerning bandwidth, time of convergence and stability! :)<BR>
<BR>
If you have any other question, just ask me, I would be glad to tell what I am doing. <BR>
<BR>
<BR>
Robert<BR>
<BR>
-----Original Message-----<BR>
From: Juliusz Chroboczek [<A HREF="mailto:Juliusz.Chroboczek@pps.jussieu.fr">mailto:Juliusz.Chroboczek@pps.jussieu.fr</A>]<BR>
Sent: Tue 7/8/2008 5:39 PM<BR>
To: Robert Lukan<BR>
Cc: babel-users@lists.alioth.debian.org<BR>
Subject: Re: [Babel-users] FW: Loose ends with Babel<BR>
<BR>
<BR>
> From my point of view, it would be nice to have shorter massages,<BR>
> because I am using protocol on very limited bandwidth link,<BR>
<BR>
Speaking about that, Robert, perhaps you could tell us more about your<BR>
setup? You appear to be doing unusual stuff (I have trouble imagining<BR>
why you'd prefer PPP over serial to an Ethernet link).<BR>
<BR>
> also is better to have shorter messages anyway.<BR>
<BR>
I'll expand about that a little.<BR>
<BR>
In Babel, I distinguish between messages and packets. A message is<BR>
always 24 bytes long, and can carry one route, IPv4 or IPv6.<BR>
<BR>
A packet consists of an 8-byte header followed with an arbitrary<BR>
number of messages followed by an optional cryptographic signature<BR>
(not implemented at the current time).<BR>
<BR>
Now 24 bytes for an IPv4 route is overkill; it could fit in 8 bytes.<BR>
If you're compressing your PPP link, you don't care -- the extra data<BR>
are mostly zeroes, and will compress beautifully. What's more, Babel<BR>
sends reachability data at very large intervals (there are other<BR>
mechanisms that ensure that the routing is mostly up-to-date usually,<BR>
and that even when it isn't, the network keeps working, although not<BR>
optimally).<BR>
<BR>
The alternative would be to encode the Babel protocol as<BR>
``type-length-value'' triples. This would make it more complex, more<BR>
difficult to parse, but would save quite a bit of space for IPv4<BR>
routes. I'm not sure if it's worth my while; we'll only know when we<BR>
deploy larger Babel networks.<BR>
<BR>
Regards,<BR>
<BR>
Juliusz<BR>
<BR>
</FONT>
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