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Annotation of 43BSDReno/share/man/man4/man4.vax/ec.4, revision 1.1

1.1     ! root        1: .\" Copyright (c) 1983 The Regents of the University of California.
        !             2: .\" All rights reserved.
        !             3: .\"
        !             4: .\" Redistribution and use in source and binary forms are permitted provided
        !             5: .\" that: (1) source distributions retain this entire copyright notice and
        !             6: .\" comment, and (2) distributions including binaries display the following
        !             7: .\" acknowledgement:  ``This product includes software developed by the
        !             8: .\" University of California, Berkeley and its contributors'' in the
        !             9: .\" documentation or other materials provided with the distribution and in
        !            10: .\" all advertising materials mentioning features or use of this software.
        !            11: .\" Neither the name of the University nor the names of its contributors may
        !            12: .\" be used to endorse or promote products derived from this software without
        !            13: .\" specific prior written permission.
        !            14: .\" THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
        !            15: .\" WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
        !            16: .\" MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
        !            17: .\"
        !            18: .\"    @(#)ec.4        6.6 (Berkeley) 6/23/90
        !            19: .\"
        !            20: .TH EC 4 "June 23, 1990"
        !            21: .UC 5
        !            22: .SH NAME
        !            23: ec \- 3Com 10 Mb/s Ethernet interface
        !            24: .SH SYNOPSIS
        !            25: .B "device ec0 at uba0 csr 161000 vector ecrint eccollide ecxint flags 0"
        !            26: .SH DESCRIPTION
        !            27: The
        !            28: .I ec
        !            29: interface provides access to a 10 Mb/s Ethernet network through
        !            30: a 3com controller.
        !            31: .PP
        !            32: The hardware has 32 kilobytes of dual-ported memory on the UNIBUS. 
        !            33: This memory
        !            34: is used for internal buffering by the board, and the interface code reads
        !            35: the buffer contents directly through the UNIBUS.
        !            36: The address of this memory is given in the \fIflags\fP field
        !            37: in the configuration file.
        !            38: The first interface normally has its memory at Unibus address 0.
        !            39: .PP
        !            40: Each of the host's network addresses
        !            41: is specified at boot time with an SIOCSIFADDR
        !            42: ioctl.  The
        !            43: .I ec
        !            44: interface employs the address resolution protocol described in
        !            45: .IR arp (4)
        !            46: to dynamically map between Internet and Ethernet addresses on the local
        !            47: network.
        !            48: .PP
        !            49: The interface normally tries to use a ``trailer'' encapsulation
        !            50: to minimize copying data on input and output.
        !            51: The use of trailers is negotiated with ARP.
        !            52: This negotiation may be disabled, on a per-interface basis,
        !            53: by setting the IFF_NOTRAILERS
        !            54: flag with an SIOCSIFFLAGS ioctl.
        !            55: .PP
        !            56: The interface software implements an exponential backoff algorithm
        !            57: when notified of a collision on the cable.  This algorithm utilizes
        !            58: a 16-bit mask and the VAX-11's interval timer in calculating a series
        !            59: of random backoff values.  The algorithm is as follows:
        !            60: .TP 5
        !            61: 1.
        !            62: Initialize the mask to be all 1's.
        !            63: .TP 5
        !            64: 2.
        !            65: If the mask is zero, 16 retries have been made and we give
        !            66: up.
        !            67: .TP 5
        !            68: 3.
        !            69: Shift the mask left one bit and formulate a backoff by
        !            70: masking the interval timer with the smaller of the complement of this mask
        !            71: and a 5-bit mask, resulting in a pseudo-random number between 0 and 31.
        !            72: This produces the number of slot times to delay,
        !            73: where a slot is 51 microseconds.
        !            74: .TP 5
        !            75: 4.
        !            76: Use the value calculated in step 3 to delay before retransmitting
        !            77: the packet.
        !            78: The delay is done in a software busy loop.
        !            79: .SH DIAGNOSTICS
        !            80: .BR "ec%d: send error" .
        !            81: After 16 retransmissions using the
        !            82: exponential backoff algorithm described above, the packet
        !            83: was dropped.
        !            84: .PP
        !            85: .BR "ec%d: input error (offset=%d)" .
        !            86: The hardware indicated an error
        !            87: in reading a packet off the cable or an illegally sized packet.
        !            88: The buffer offset value is printed for debugging purposes.
        !            89: .PP
        !            90: .BR "ec%d: can't handle af%d" .
        !            91: The interface was handed
        !            92: a message with addresses formatted in an unsuitable address
        !            93: family; the packet was dropped.
        !            94: .SH SEE ALSO
        !            95: netintro(4), inet(4), arp(4)
        !            96: .SH BUGS
        !            97: The hardware is not capable of talking to itself.  The software
        !            98: implements local sending and broadcast by sending such packets to the
        !            99: loop interface.  This is a kludge.
        !           100: .PP
        !           101: Backoff delays are done in a software busy loop.  This can degrade the
        !           102: system if the network experiences frequent collisions.

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