17 Oct
2014
17 Oct
'14
12:19 p.m.
Also - just to throw something out there, this architecture is pretty cool:
http://libre-mesh.org/projects/libre-mesh/wiki/Network_Architecture?version…
I think there may be some implications here though for whether or not
clients actually have network addressable hostnames and/or how something
like mdns or an equivalent would work. It's also important to keep in
mind that we may be able to iterate towards more complicated setups, and
that there will likely always be the hot new idea that we want to
incorporate but that we have VERY constrained developer hours and may
need to make some satisficing decisions.
On 10/17/14, 12:06 PM, Max B wrote:
Not that I'm arguing in favor of layer 2 vs layer
3 forwarding
(although we're already pretty deep in certain parts of layer 2
implementations), but why can't we just match the MTU of the open0
interface to the bat0 interface?
On 10/17/14, 11:51 AM, Alexander Papazoglou wrote:
Hello mesh-dev.
I think we may finally have an explanation of the vexing issue of "I
can't
connect to the internet over peoplesopen.net <http://peoplesopen.net>."
Marc and I spent some time staring at wireshark dumps and thinking
about why some clients are unable to consistently connect via the
tunnel last night. I think Marc came up with a disappointing but correct
answer: it is basically an mtu issue (mtu is not being discovered
correctly), BUT there is no good fix because we are tunneling at layer 2.
When a packet arrives at a node from a client with too large an mtu,
what SHOULD happen in a normal forwarding situation (per RFC 1191)
is that the node issue a ICMP "Destination Unreachable" packet with a
"Fragmentation required" code. The client then uses this information to
reset its mtu.
This doesn't happen because we aren't really forwarding (forwarding
happens
at layer 3). Instead, our interfaces (open0 and bat0) are bridged. So
if a frame
coming from open0 doesn't fit into bat0 it most likely gets silently
dropped.
So bridging open0 with bat0 is a disaster. A quick fix might be to
replace
bridging with forwarding (at the IP level). I suspect this is not the
right thing
to do. It might be better to abandon the idea of meshing at layer 2;
there
are numerous advantages to this.
In any case; we should discuss options this Tuesday.
Alex
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