rf@infopro.UUCP (Randolph Fritz) (11/14/85)
Please write to tell me of file-server & vitrual terminal standards. I know that DEC has them, SUN has them, and Xerox has them. Are there any other such standards? Perhaps ARPA standards? Are any of the standards multi-vendor or are they all proprietary? Also, is there some sort of fault-tolerant inter-LAN gateway? Something that would allow interconnection of two LANs & keep one going even if the other is completely dead? (I'm aware that this should go in net.lan, but we don't get that group.) -- Randolph Fritz wu1!rf
ron@brl-sem.ARPA (Ron Natalie <ron>) (11/15/85)
> Please write to tell me of file-server & vitrual terminal standards. I > know that DEC has them, SUN has them, and Xerox has them. DEC uses DECNET, it's pretty well documented but no one outside of DEC bothers. SUN uses two different protocols. The older one ND, is really the file server protocol. It runs on top of a protocol called IP (I'll get into this later). People outside of SUN know how this works. NFS is a virtual filesystem to allow multiple systems to share the same disks on a file by file basis. This is a protocol over TCP/IP, but SUN is very tight lipped about telling anybody how this works. Xerox protcols are based on their Ethernet protocol XNS. > Are there any > other such standards? Perhaps ARPA standards? Are any of the standards > multi-vendor or are they all proprietary? The ARPA standards provide for several levels. The lowest, the internet protocol (IP) handles getting raw datagrams accross multiple dissimilar networks. Over this, the transmission control protocol (TCP) is used to provide a reliable virtual circuit. Finally, there are many application protocols including virtual terminals (which is called TELNET). > > Also, is there some sort of fault-tolerant inter-LAN gateway? Something > that would allow interconnection of two LANs & keep one going even if the > other is completely dead? (I'm aware that this should go in net.lan, but > we don't get that group.) The key to IP's popularity is that it will send packets transparently across networks. This is accomplished by a device called an Internet Gateway. It can either be a stand-alone system or incorporated into a regular host (There are more 4.2 systems functioning as gateways than all the other types of gateways combined). I work with the protcols as they apply to these gateways. -Ron
guy@sun.uucp (Guy Harris) (11/17/85)
> 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