Subject: Re: 3c985B ?
To: Justin T. Gibbs <>
From: David Maxwell <>
List: current-users
Date: 12/08/1999 16:33:36
On Wed, Dec 08, 1999 at 10:52:25AM -0700, Justin T. Gibbs wrote:
> >On Wed, Dec 08, 1999 at 10:52:54AM -0500, Thor Lancelot Simon wrote:
> >> 
> >> Do we actually support GigE-sized frames yet?
> >
> >Gig-E frames aren't bigger.
> Gig-E allows for "jumbo-frames" which most vendors allow to be up to
> 9000 bytes in length.  If you don't use jumbo-frames, at least across
> networks that support an MTU of that size, your Gig-E performance is
> completely CPU bound with todays processors.

Ok. There was a development I didn't know about. Vendors were proposing this,
and it was a proprietary extension:

>  Alteon also features Jumbo frames, a proprietary technology that permits the
>       NIC to create huge packets of data. This is highly beneficial to throughput,
>       since the NIC need only generate one-fifth the transmit and receive
>       interrupts to get the job done. However, these jumbo frames can be used only
>       in a back-to-back environment, or in an environment where Alteon's
>       switches are deployed.
>To overcome some of the bottlenecks caused by the host, a few vendors have
>supported a proprietary solution known as ?jumbo frames? to provide a
>better data payload-to-packet overhead ratio. A jumbo frame has a non-Ethernet
>standard maximum transmission unit (MTU), exceeding 1518 bytes. For example, one
>jumbo frame size supported is that of 9 Kbytes. Although they provide some
>performance benefits, the major drawback of jumbo frames is that the frame format
>itself is proprietary. Any switch or NIC that supports jumbo frames cannot
>                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>interoperate directly with other standards-based Ethernet switches and NICs on
> the network. 

Other vendors are starting to accept this: (Nov 2)

>Jumbo Frames takes step forward
>November 2, 1998 9:00 AM ET
>In a quest to accelerate data delivery over enterprise networks, a
>variety of hardware and software makers are supporting Alteon
>Networks Inc.'s Jumbo Frames Ethernet technology.

David Maxwell,| --> Mastery of UNIX, like
mastery of language, offers real freedom. The price of freedom is always dear,
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