Date: Thu, 25 May 2000 21:27:43 +0400 From: Victor Ponomarev <vick@unet.ru> To: Stable <freebsd-stable@FreeBSD.ORG> Subject: Improvement of VLAN Support badly needed... Message-ID: <392D628F.32905FAF@unet.ru>
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Hi All!
Now VLAN support in stable is bad.
Suppose you would like to really route two VLAN using a FreeBSD box as
router.
host---vlan port---trunk port---vlan port---host
|
|
|
router
Usually in that config router port configured as a trunk also,
this mean that it can received large packet.
When host send a packet about 1514 byte switch trunk port add 4 byte and
router trunk port substitute vlan tag to another and send it back to
switch. The latter remove vlan header and send packet to appropriate
vlan ports.
Currently FreeBSD router simply drop large packet on it's interface.
That's very bad...
Second, standard ethernet MTU size is 1500, now we have vlan interface
with MTU 1496, so large packet will be fragmented in BSD router on
large and small packet. It's also bad because it's
a) stupid resource consumed work for a router in that ethernet
environment,
b) small packet have large overhead and at last
c) we should transmit two packet to medium instead one...
The existing solution on these problem for Intel card may be found at
http://www.euitt.upm.es/~pjlobo/
But there's another problem with small ip packet. When BSD router strip
ethernet header for payload < 46 it strip padding bytes also. But when
it reinserted data with another vlan header it don't add padding bytes
and we have runts packets on interface...
Sorry but I'm not a kernel programming expert so I can't change this
things myself :(
Bye,
Vick.
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