North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: Strange public traceroutes return private RFC1918 addresses
> From: "Terry Baranski" <[email protected]> > Date: Tue, 3 Feb 2004 16:42:55 -0600 > Sender: [email protected] > > > Leo Bicknell wrote: > > > Since most POS is 4470, adding a jumbo frame GigE edge makes > > this application work much more efficiently, even if it doesn't > > enable jumbo (9k) frames end to end. The interesting thing > > here is it means there absolutely is a PMTU issue, a 9K edge > > with a 4470 core. > > This brings up the question of what other MTUs are common on the > Internet, as well as which ones are simply defaults (i.e., could easily > be increased) and which ones are the result of device/protocol > limitations. > > And why 4470 for POS? Did everyone borrow a vendor's FDDI-like default > or is there a technical reason? PPP seems able to use 64k packets (as > can the frame-based version of GFP, incidentally, POS's likely > replacement). 4470 was, as you surmised, to allow a full sized FDDI packet to be packed into a single POS packet. At the time FDDI was using larger packets than anything else. Now the recommendation for research and education networks (Abilene, ESnet, NASA, and many Asian and European R&Es) is 9000 and, within that community, is almost universally adopted when the hardware will support it. -- R. Kevin Oberman, Network Engineer Energy Sciences Network (ESnet) Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab) E-mail: [email protected] Phone: +1 510 486-8634
|