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- Path: sparky!uunet!charon.amdahl.com!amdahl!rtech!decwrl!olivea!sgigate!sgi!rhyolite!vjs
- From: vjs@rhyolite.wpd.sgi.com (Vernon Schryver)
- Newsgroups: comp.sys.sgi
- Subject: Re: DMA transfers between machines
- Message-ID: <vcaeso0@rhyolite.wpd.sgi.com>
- Date: 26 Jan 93 19:12:57 GMT
- References: <35223@adm.brl.mil>
- Organization: Silicon Graphics, Inc. Mountain View, CA
- Lines: 44
-
- In article <35223@adm.brl.mil>, beyer@bflsgu.fl.bs.dlr.de (Ralf Beyer DLR) writes:
- > ...
- > In fact, both machines are single user and not connected to
- > any net. They are, however, connected via Ethernet controllers
- > on both machines and the Ethernet cable. On the LSI-11 side
- > we are controlling the Ethernet controller directly by
- > accessing its registers and buffer and using its instruction
- > set. We are looking now for an opportunity to do the same on
- > the SGI machine. The 4D35 has controllers ec0 and ENP-10 (one
- > of each). They need not be configured for TCP/IP or other
- > protocols, they are available only for the low level protocol
- > connection to the LSI-11.
- >
- > Is there a handbook available for the ec0 and ENP-10
- > controllers with information on registers, buffers and the
- > instruction set ?
-
-
- There simpler and more portable ways to solve this problem.
- The following two solutions are serveral years old in Silicon
- Graphics systems:
-
- 1. The solution most people pick at first, which I DO NOT recommend, is
- to write user code to send and receive raw ethernet packets.
-
- See `man raw` and `man 7 snoop`.
-
- 2. A much better solution is to "spoof UDP". This consists of taking
- whatever packets you were going to send from the other LSI11,
- and inserting a 28-byte nearly constant block of IP and UDP headers
- between the 14-byte ethernet header and the payload.
-
- The IP and UDP headers are trivial, and only 2 16-bit fields change
- from packet to packet. If you are willing to give up the
- UDP checksum, only 1 16-bit field needs to change from one UDP/IP
- packet to the next, and it is simply a packet sequence number.
-
- (1) is slightly easier to implement on the LSI-11, but (2) is
- much simpler on the IRIS. By using a standard protocol like UDP/IP,
- uour code will work on other brands of machines. You can test
- in many more environments, including internets involving routers.
-
-
- Vernon Schryver, vjs@sgi.com
-