ISO-TP0 bridge between TCP and X.25 (RFC1086)
Original Publication Date: 1988-Dec-01
Included in the Prior Art Database: 2000-Sep-12
Internet Society Requests For Comment (RFCs)
J.P. Onions: AUTHOR [+2]
This memo specifies a protocol that is used to bridge ISO TP0 packets between X.25 and TCP networks. This technique is useful when interconnecting a DDN IP internet to an X.25 subnetwork. This is not a "magic bullet" solution to the DDN/ISO interoperability problem. Rather, if one is running higher-layer ISO protocols in both networks (namely ISO TP0), then a TP0 bridge can be used to achieve connectivity.
Network Working Group J. Onions
Request for Comments: 1086 Nottingham
ISO-TP0 bridge between TCP and X.25
Status of this Memo
This memo proposes a standard for the Internet community. Hosts on
the Internet that choose to implement ISO TP0 transport connectivity
between TCP and X.25 based hosts are expected to experiment with this
proposal. TCP port 146 is reserved for this proposal. Distribution
of this memo is unlimited and comments are highly encouraged.
This memo specifies a protocol that is used to bridge ISO TP0 packets
between X.25 and TCP networks. This technique is useful when
interconnecting a DDN IP internet to an X.25 subnetwork. This is not
a "magic bullet" solution to the DDN/ISO interoperability problem.
Rather, if one is running higher-layer ISO protocols in both networks
(namely ISO TP0), then a TP0 bridge can be used to achieve
The protocol itself is fairly simple as the method of operation for
running TP0 over the TCP and X.25 protocols have previously been
defined. A bridge offering ISO-TP0 gateway services simply applies
both methods as appropriate. The protocol works by TP0/TCP hosts
"registering" an X.25 subaddress (and corresponding TCP port/IP
address) with the bridge. TP0/X.25 hosts use the standard method for
establishing, maintaining, and releasing connections. When a
connection is established, the bridge establishes the corresponding
TCP connection and simply shuffles TP0 packets between the two. When
a TP0/TCP host initiates a connection, it establishes a TCP
connection to the bridge using port number 146 and communicates the
desired X.25 address. The bridge establishes a connection to the
native X.25 host and simply shuffles TP0 packets between the two.
1. Introduction and Motivation
The migratory protocol described in [RFC1006] makes possible the
transmission of TP0 packets between hosts on TCP/IP internets. With
the addition of a small protocol converter, a TCP/IP host can be made
to appear in the X.25 addressing space and be able to accept and make
connections using the TP0 protocol.
This procedure is particularly useful in the following cases:
1. A host on an IP based internet can communicate with hosts on
X.25 based networks providing the hosts are running ISO protocols.
This also assumes a friendly gateway willing to run the actual TP0
bridge and make available to the IP host part of its X.25 address
2. A site having sparse connections to an X.25 network and using
a TCP/IP based local area network for local communications. In
this case all hosts on the LAN can ha...