🚀 go-pugleaf

Two solutions are currently used for providing CONS over Ethernets and
other LANS. One is orthodox (OIS wise) and the other one is popular.

The orthodox line is to stack the X.25 PLP (ie. iso 8208) over IEEE 802
LLC-2, and use NSAP addressing, considering that the Ethernet address
is somehow a SNPA. It is quite a piece of code, not so easy to
optimize. Five years ago, we experimented with the CNET in France a
lighter version of it (using LLC-1), but although the performances were
good, it failed to reach a general agreement in the community. A full
implementation of that has been done at Edinburgh University. It is
used in JANET, and can in principle be ordered from your favorite manufacturer.

The popular line is to stack a small convergence protocol over TCP-IP,
e.g. in order to provide packet delimitation within a byte stream. Here
again, one can use NSAP addressing, and consider the TCP-IP <host
address + port> as a 48 bits SNPA. This is implemented in ISODE, and
also in the EAN X.400 service, as well as by CISCO. Problem here is the
lack of an agreed convergence protocol (RFC?).

In both cases, a fully working solution need to use a CONS "ARP"  for
converting between NSAP and SNPAs. It is called a Connection Oriented
ES/IS protocol in the lingo, and is not completely formalized within
ISO (DP stage, as far as I remember). A secundary problem is that it is
tailored for passing X.25 addresses, which are 15 digits, and that you
need an agreement for the representation of 48 bits over 15 digits.

Christian Huitema

PS.
A full implementation of X.25 over LLC-2 has been done at Edinburgh
University. It is used in JANET, and can in principle be ordered from
your favorite manufacturer.