SiGnet X.25 GATEWAY
- Gateway between X.25 and UNIX/Ethernet environment
- Up to 64 two-way Switching (SVC) or Permanent (PVC) Virtual
- Circuits
- Baud rate limited by X.25 network's maximal baud rate
- Pacnet Assembler Disassem-bler (PAD) emulation under X.3, X.28
- and X.29 standards
- TCP/IP over X.25 links
- Line cost optimization
The primary function of the Ei SiGraf's SiGnet X25GW Gateway is to connect
UNIX/Ethernet environment to the X.25 network(s). That provides connections between
UNIX hosts from one Local Area Network to remote hosts which do not need to run UNIX
operating system but have to be attached to the same public X.25 network. Having in
mind that all world wide public X.25 networks are easily reachable, connections to very
long distances are available. Another application of SiGnet X25GW is to link two (or more)
Local Area Networks using X.25 connections as a carrier. Namely, TCP/IP traffic is being
encapsulated into X.25 pacnets and transferred to remote site. The last function is very
applicable in the Wide Area Networks design.
Connection to and from remote hosts located on any X.25 network is supported by PAD
commutation. All proper standards (X.3, X.28 and X.29, known also as triple X) are
confirmed. If we consider the example given at the figure on the next page, PAD emulation
incorporated in iGnet X25GW provides
logins from any host in LAN1, for example, to any host in LAN2 and LAN3, as well as to
the hosts A and B that are connected to X.25 network directly. SiGnet X25GW supports up
to 64 simultaneous PAD links. Actually, the number of possible links depends on
subscription to X.25 network. Here, remote login is performed using the tool very similar
to standard UNIX cu facility.
This feature of SiGnet X25GW enables two remote LANs to be routed over X.25 network. If
such link is established between LAN1 and LAN2 in the example under consideration, any
host on both sides may use standard UNIX networking tools (rlogin, telnet, ftp, etc.) in
order to connect to other hosts, regardless the hosts are in LAN1 or LAN2. Simple
mechanism, mentioned above, of TCP/IP pacnets transfer over X.25 is used. SiGnet
X25GW currently supports up to two X.25/IP links. Behavior of more than two X.25/IP links
is not tested. Since X.25 links are intended to be used in WANs, where the data traffic
between remote sites is not very frequent, mechanism of line cost optimization is
incorporated. Namely, logical connections used by X.25/IP links are active while the traffic
exists. After some time of link inactivity, X.25 logical connection is being broken down.
Connection will be reestablished again when the data transfer is requested. This
mechanism leads to significant X.25 subscription cost decrease. Furthermore, the usage
of available logical channels is optimized too. Of course, SiGnet X25GW supports
simultaneous PAD and X.25/IP sessions.
SiGnet X25GW operates as a mini host. Simple shell, menu driven, for X25GW
configuration and administration is incorporated. This shell could be invoked through the
network or using some asynchronous terminal attached directly to SiGnet X25GW over
RS232.
Features