root@ttsi.UUCP (Super user) (07/19/89)
Hello Netlanders, Is RPC available over X.25? The documents I have indicate that it is based on TCP/IP and relies on this as the transport mechanism. Does anyone have experience with RPC over X25? Thanks -Alex
guy@auspex.auspex.com (Guy Harris) (07/20/89)
>Is RPC available over X.25? The documents I have indicate that it is >based on TCP/IP and relies on this as the transport mechanism. The Sun RPC implementation is set up to allow RPC to run over different transports (even on "TCP/IP", it runs over two transports - TCP and UDP). You might want to look at the "clnt_{tcp,udp}.c" and "svc_{tcp,udp}.c" files to get a feel for how transport implementations are done (the documentation may cover this as well), and see what would be involved in doing an implementation across whatever X.25 interface you have. Some particular RPC features (e.g., broadcast RPC) may, of course, depend on features of specific transports (e.g., broadcasts). The biggest problem appears to be to be the portmapper; at present, it seems to "know" that it's running in a TCP/UDP/IP environment, so you'd have to figure out how to handle registration of program/version pairs for X.25. It also appears that the RPC code would like to have transport-level addresses be composed of a host address and something like a TCP/UDP port number - e.g., it would want to find the portmapper for a given host given only the host's "address", or name, and then construct the address for some service on that host based on the host's "address" and the data it gets back from the portmapper.
jms@tardis.Tymnet.COM (Joe Smith) (07/22/89)
In article <2260@auspex.auspex.com> guy@auspex.auspex.com (Guy Harris) writes:
<<Is RPC available over X.25? The documents I have indicate that it is
<<based on TCP/IP and relies on this as the transport mechanism.
<
<The biggest problem appears to be to be the portmapper; at present, it
<seems to "know" that it's running in a TCP/UDP/IP environment, so you'd
<have to figure out how to handle registration of program/version pairs
<for X.25. It also appears that the RPC code would like to have
<transport-level addresses be composed of a host address and something
<like a TCP/UDP port number - e.g., it would want to find the portmapper
<for a given host given only the host's "address", or name, and then
<construct the address for some service on that host based on the host's
<"address" and the data it gets back from the portmapper.
Portmapper is not a problem. All you have to do is run TCP/IP over the X.25
link. The only X.25 programming needed is to build a virtual circuit from
one machine to the other at system startup and then use ifconfig to start
the IP protocols. Once you do that, the internet connection between two
machines looks the same to programs. RPC does not care whether the systems
are connected via an ethernet cable or via an X.25 cable.
You can do an NFS mount over an IP link that uses a 56Kb X.25 line, but the
throughput is not great. We use the rcp program instead; it keeps the users
fully aware of the fact that they are copying data to a distant machine, so
they understand the reason for the slowness.
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