Subject: [manet] DLEP address semantics and in-the-wild examples

From: "Sipos, Brian J." <[email-masked]>
Date: Mon, 25 Oct 2021 15:04:50 +0000

All,

I am in the process of investigating and implementing a DLEP router
component and trying to figure out which sets of data items are available
for which contexts (peer session vs. destinations) and how they must/may be
interpreted.

Specifically, it's not fully clear to me what the IPvX and MAC Address data
items [1] are allowed or required to represent for a peer (modem) or a
destination (other router). My assumption is that the IPvX are addresses on
which the router sends/receives traffic for forwarding on past the
DLEP-informed link and the IPvX Attached Subnets are those to-be-forwarded
nets, but the MAC Address is really an opaque identifier for the far-side
destination and may or may not be an address actually associated with or
seen by any of the routers.

In the Link Identifier extension [2] it's more explicitly stated that the
MAC Address is supposed to be an address on the far-side router, but I don't
see that same kind of language in the original DLEP document [1]. And since
there is no signaling of the router MAC Address within the Session
Initialization, I assume that it is implied that the MAC Address of the peer
(router) used to establish the TCP connection is used for this purpose. For
multi-interface routers there may be no relation between the MAC Address and
it's routed-traffic IPvX addresses (if the router is talking DLEP on a
different interface than the routed traffic), but if the MAC Address is
supposed to be just an opaque identifier then this doesn't really matter.

I've been able to dig into the OONF [3] implementation of DLEP to see how it
works, but this is just one implementation and not an authority of the
correct or possible semantics.

Thanks for any clarification,

Brian S.

[1] https://www.rfc-editor.org/rfc/rfc8175.html

[2] https://www.rfc-editor.org/rfc/rfc8703.html

[3] https://github.com/OLSR/OONF