Point to Point Ethernet

Cayle Spandon cayle.spandon at gmail.com
Thu Jul 9 09:29:56 CDT 2009


I frequently run into scenarios where two devices (two routers, or a
router and a host) need a point-to-point connection to each other with
a capacity of (much) more than 10 Gbps.

For cost reasons, Ethernet is often used.

Since more than 10 Gbps is needed, we end up with multiple parallel
10GE point-to-point connections.

Because the devices often don't support LAG or have limitations on the
number of links in a LAG, we often cannot use LAG at all or cannot put
all 10GE links in a single LAG group.

So, we end up with multiple parallel layer-3 point-to-point
connections where each connections is either an Ethernet or a LAG
group.

Furthermore, in order to conserve IP addresses, there is a desire to
make these interfaces unnumbered.

The involved devices have a numbered loopback interface whose address
is used as the "donor" for the unnumbered Ethernet / LAG interfaces.
Most router vendors already support unnumbered point-to-point
Ethernet, see for example:

http://www.juniper.net/techpubs/en_US/junos9.5/information-products/topic-collections/config-guide-network-interfaces/interfaces-configuring-an-unnumbered-interface.html#id-10432956

However, there are some interoperability issues / open questions
related to point-to-point unnumbered Ethernet, see for example:

http://forums.juniper.net/jnet/board/message?board.id=JUNOS&message.id=130

http://forums.juniper.net/jnet/board/message?board.id=switch&thread.id=835

I would be very interested in some standards (i.e. an IETF BCP) to
describe the best current practices for these applications of
Ethernet.

I am not particularly interested in re-inventing a new flavor of
Ethernet for this application. All that is needed, in my opinion, is
some clarifications or best practices on how to use the existing
standards to create point-to-point unnumbered Ethernet connections.

PS -- I am also aware of some esoteric BRAS applications of Ethernet
where one side is numbered and the other side is unnumbered.




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