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From: guy@sun.uucp (Guy Harris)
Newsgroups: net.dcom
Subject: Re: I have some questions about distributed computing standards . . .
Message-ID: <3001@sun.uucp>
Date: Sat, 16-Nov-85 16:10:35 EST
Article-I.D.: sun.3001
Posted: Sat Nov 16 16:10:35 1985
Date-Received: Tue, 19-Nov-85 03:43:55 EST
References: <776@infopro.UUCP> <524@brl-sem.ARPA>
Organization: Sun Microsystems, Inc.
Lines: 55

> SUN uses two different protocols.  The older one ND, is really the file
> server protocol.

No, it isn't.  ND - which stands for "network disk" - is a *disk* server
protocol.  The protocol requests do not involve files; you can read and
write specific blocks from an ND disk partition.  Multiple machines can
share an ND partition only if none of them write to it.

> NFS ...  is a protocol over TCP/IP, but SUN is very tight lipped
> about telling anybody how this works.

Go buy a set of the Sun UNIX 2.0 manuals and read:

	External Data Representation Protocol Specification
	Remote Procedure Call Protocol Specification
	Network File System Protocol Specification

I know of at least one organization which has independently implemented an
NFS server, running in user mode; presumably, they just worked from the
protocol specs - I don't know of any help *we* gave them.  The code that
implements XDR (eXternal Data Representation) and RPC has been posted to
"mod.sources".  Be a little more specific about what you mean by
"tight-lipped".  We don't tell you how to put NFS into your operating
system, but then again we don't necessarily know what your operating system
looks like inside (no, it doesn't have to be a version of UNIX).

BTW, it is a protocol over UDP/IP, not TCP/IP.  (For those of you not
familiar with the DARPA protocol family, UDP is a "datagram" protocol which
runs on top of IP; it doesn't provide a reliable virtual circuit.
Applications using UDP either have to live with lost, duplicated, or
out-of-sequence packets - which some can - or have to provide their own
mechanisms for detecting and recovering from errors.  Ron discussed IP in
his article.)

> Xerox protcols are based on their Ethernet protocol XNS.

XNS isn't just an Ethernet protocol family (it's not a single protocol; it
has an Internetwork Datagram Protocol which probably fills roughly the same
role as IP, and has transport protocols on top of it like Sequenced Packet
Protocol and Packet Exchange Protocol); they have also discussed running it
over X.25 connections and leased lines (see "Managing Transient Internetwork
Links in the Xerox Internet", ACM Transactions on Office Information
Systems, Vol. 2, No. 3, July 1984, pp. 213-225).

> Finally, there are many application protocols including virtual
> terminals (which is called TELNET).

Which is one of the two virtual-terminal protocols supplied with 4.2BSD
systems, including Sun's.  The other is more UNIX-specific and is used by a
command called "rlogin".  DEC's Ultrix is also 4.2BSD-based and also has
TELNET and "rlogin"; both have been put into other UNIX versions, such as
System V or Research Version 8.  I believe DECNET has its own virtual
terminal protocol(s), as does Xerox's XNS protocol suite.

	Guy Harris