North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: Ethernet NAPs (was Re: Miami ...)
At 09:57 23/08/01, John Kristoff wrote: >Furthermore... Larger frames would be nice if all hosts supported them, >but the problem is that the that most end hosts cannot and probably will >not ever support so called jumbo frames. WindowsNT/Windows2000 [1] and a lot of UNIX servers/hosts do support 9K frames today. Most GigE PCI NIC cards support them. Most of the commodity GigE ASICs support the 9K MTU. You are correct that not all hosts/servers support them today. In any event, any size of jumbo Ethernet frame will only work over an all-switched layer-2 network. My guess is that the trend over time will be for more and more hosts to support the ~9K MTU. YMMV. >What does having 9K ethernet frame support at a NAP get us? Some folks run their end-to-end network with a 9K MTU. So having it at the NAP means they avoid potential fragmentation in their network. Certainly my employer would prefer a WAN network provider that supported the 9K MTU because it would improve NFS performance among our several sites as compared with a smaller end-to-end MTU. >Perhaps the one good approach to jumbo frames is to make use of the >networking layer and ensure hosts are doing Path MTU discovery to avoid >fragmentation. Path MTU Discovery is curiously controversial in some circles. My own experience is that PMTUD works well today (not necessarily true 5 years ago). So I agree that ensuring Path MTU Discovery is deployed is generally clever. Past experience is that many vocal folks will disagree with this view. Ran [email protected] [1] Someone at Microsoft has told me that use of ~9K frames is how Microsoft got their high WinNT network throughput for the SuperComputing conference demo a few years back. I'm also told the POS links used in that demo had also been configured for a ~9K MTU and worked fine.
|