Re: two GbE interfaces and maximum bandwidth achievable

From: Antoine EMERIT (gnagnagna_at_incredebilous.blackhole)
Date: 08/12/05 

Date: 12 Aug 2005 17:32:13 GMT

"jimjim" <netuser@blueyonder.co.uk> écrivait
news:RtOKe.87020$G8.43162@text.news.blueyonder.co.uk:

> Hello all,
>
> I have been posed the following question: "A PC motherboard has two
> GbE interfaces, and is acting as a bridge. The theoretical maximum
> bandwidth achievable across the bridge is 2Gbps. In practice only
> about one half of this is achieved. Why might this be?"
>
> First of all, I cant really understand if the term bridge means layer
> 2 switching or its just a misuse of the term and means in reality
> layer 3 routing. Can you give me some pointers regarding the reasons
> why only half the theoritical bw can be achieved?

BRIGING or ROUTING with two "inline" GB interfaces give you 1GB in each
direction, not 2GB.

TRUNKING with two "paralelle" GB interfaces give you 2GB in both
direction. You must use the same trunking protocol between the two
components (pc<->switch with Cisco trunking, or linuxbox<->linuxbox with
linux trunking).
 
> (in case bridge means in reality layer 3 routing, inefficient
> scheduling on a perhaps loaded systems may slow down the routing
> process).

In any case, harware architecture (bus efficiency) and cpu load may
reduce the bandwidth.

On Linux, there is a fast path network option (at compile time if I
remember).

Regards

Relevant Pages

  • Re: Bridging network interfaces on Windows 2000 Prof.
    ... routing its not what i've asked, since i need bridging. ... I need to bridge two interfaces together, in orden to make them work ... Routing won't do the trick, because the two interfaces will be under the ...
    (microsoft.public.win2000.networking)
  • Re: Routing Problem
    ... Subject: Routing Problem ... each with a different subnet. ... it should use the second default gateway. ... > routers configured on multiple interfaces connected to two or more ...
    (freebsd-questions)
  • Re: distributed bridging [script]
    ... >> I'm trying to create a configuration that would bridge interfaces on ... Each host would have at least two interfaces, ... here's a completely untested script. ...
    (freebsd-net)
  • Re: bridge with access on both interfaces
    ... >>'inside' and 'outside' IPs separately on each bridge interface, ... Some tcpdumps on both in and outside interfaces suggest an ARP ... > If you want to use IP while bridging, ... and net4801 is that the 3 ethernet controllers now share one interrupt. ...
    (freebsd-net)
  • Re: redundancy on multi-homed hosts for outgoing mail
    ... automatically retries out the other with the other source address? ... I don't believe that's a sendmail issue - but a routing table issue within ... I don't think this is a routing issue. ... The two interfaces have ...
    (comp.mail.sendmail)