From cd78b2f395982fc7e2ed2dbfd52595c57b69f3b9 Mon Sep 17 00:00:00 2001 From: chris Date: Wed, 26 Apr 2000 22:30:21 +0000 Subject: [PATCH] Small fixup --- share/man/man4/vlan.4 | 36 ++++++++++++++++++++---------------- 1 file changed, 20 insertions(+), 16 deletions(-) diff --git a/share/man/man4/vlan.4 b/share/man/man4/vlan.4 index be3be312c56..a83aa9c9bae 100644 --- a/share/man/man4/vlan.4 +++ b/share/man/man4/vlan.4 @@ -1,4 +1,4 @@ -.\" $OpenBSD: vlan.4,v 1.1 2000/04/26 19:00:57 chris Exp $ +.\" $OpenBSD: vlan.4,v 1.2 2000/04/26 22:30:21 chris Exp $ .\" .Dd 09 January 2000 .Dt VLAN 4 @@ -24,11 +24,12 @@ bits for the priority field (not used in this implementation), 1 bit for the canonical field (always 0), and 12 bits for the vlan identifier. Following the vlan header is the actual ether type for the packet and length information. .Pp -The 802.1Q header specifies the virtual LAN -and thus allows an ethernet switch or other 802.1Q compliant -network devices to be aware of which device the packet was intended for. -This driver allows OpenBSD to group packets logically with separate -interfaces. +The 802.1Q header specifies the virtual LAN number, +and thus allows an ethernet switch (or other 802.1Q compliant +network devices) to be aware of which LAN the packet is part of, and +in the case of a switch, which port(s) the packet can go to. +This driver allows OpenBSD to separate packets logically with separate +virtual ethernet network interfaces. .El .Pp The network interfaces are named @@ -74,23 +75,26 @@ The 802.1Q specification allows for operation over FDDI and Token Ring as well as Ethernet. This driver only supports such operation with ethernet devices. .Pp -Some ethernet chips (notably the Intel 82558/82559) automatically +Some ethernet chips (notably the Intel 82558 and 82559) automatically discard frames that are larger then 1500 bytes. All ethernet -chips sporting this feature should allow for it to be turned off. -Optimally, upon loading, the chip's OpenBSD driver would do this. -A temporary kludge is to set the MTU for each machine behind each VLAN to -1496 or less. Refer to the hardware manual for your ethernet chip to determine +chips sporting this sort of feature should allow for it to be turned off. +Optimally, upon loading, the chip's driver would do this (The +.Xr fxp 4 +driver currently does for the Intel 82558/82559 chips.) +Refer to the hardware manual for your ethernet chip to determine if it has this feature, and if so, for information on how to turn it off. -A symptom of this problem is that small packets (ICMP) -but packets which are >MTU size are dropped, thus causing -bulk TCP transfers to hang. +A symptom of this problem is that small frames pass through the VLAN +(such as a frame carrying an ICMP packet), but frames which are at MTU size +are dropped. When these frames are dropped, the TCP session will hang. +A temporary kludge is to set the MTU for each machine behind each VLAN to +1496 or less. .Pp Some ethernet chips support 802.1Q tagging/untagging in hardware, but -do not have the appropriate hooks in their driver to pass the packet +do not have the appropriate hooks in their driver to pass the frame directly to if_vlan. The PCI device driver if_ti is able to do this, use it as a reference. .Pp -This driver could be extended to support the Cisco ISL VLAN protocol, +This driver could be the basis for support of the Cisco ISL VLAN protocol, detailed at http://www.cisco.com/warp/public/741/4.html. Unfortunately, public reimplementation of this protocol is currently prevented by patent (at least in the USA). -- 2.20.1