mesh portal discovery

[Michail Bletsas]

John Watlington <wad at laptop.org> wrote on 01/09/2008 11:34:29 AM:

> 
> Right now we have a problem with mesh portal discovery.
> 
> The DHCP procedure currently being used only discovers
> the nearest mesh portal when it is first run (DHCP_DISCOVER),
> not when it tries to renew (DHCP_REQUEST).   Furthermore,
> as the address previously assigned indicates which mesh portal
> was selected, it seems like we should always be discovering, not
> renewing...
This is the expected behavior since the special anycast address is only 
used during discovery.


> 
> There are larger issues which will probably need a day of discussion
> later surrounding IPv6 deployment, such as cooperation between RADVD
> and mesh portal discovery...   (Please defer discussion on this right 
> now)
> 
The largest issue is how wrong, ugly and painful is to use DHCP on a mesh 
network.
Because of RADV, IPv6 doesn't have that issue. The original mesh portal 
discovery method was
proprietory but also extremely lightweight and did what it was supposed to 
do with minimal code.

Using DHCP is the absolutely ugliest hack that I have even encounter 
because you can't legally have more than one server per layer-2 network to 
begin with, it makes the address configuration inconsistent (different 
method for a school server and different for a non-school server mesh) and 
to add insult to the injury, it forces the use of a DHCP server process, 
utilizing several megabytes of RAM in every laptop to just distribute name 
server and GW ip addresses, having effectively broken Internet sharing via 
the mesh for several months now.

I am not even mentioning the uneccesary broadcasts forced by the fact that 
you have to have pretty short leases given the dynamic character of the 
network.

We put a lot of effort to put the anycast address support in the mesh, to 
specifically address the need of selecting the optimal path to a specific 
service in the path discovery process itself. We ended up with the DHCP 
monstrocity just so that we don't use anything new in what is in effect a 
new way of doing local area networking.

M.