> -----Original Message----- > From: James Carlson [mailto:[EMAIL PROTECTED] > Sent: Monday, February 20, 2006 12:18 PM > To: Veera Tubati (vtubati) > Cc: Pekka Savola; [EMAIL PROTECTED]; [email protected]; [email protected] > Subject: RE: [Pppext] Re: Last Call: 'Accommodating an MTU/MRU greater > than1492 in PPPoE' to Informational RFC > > Veera Tubati (vtubati) writes: > > That can be done but then that means for PPPoE sessions to go beyond > > 1492 BRAS always have to incur this cost of verification; > > "Cost?" > > We're talking about a single MTU-sized packet transmitted and one > received on an Ethernet link.
Correct, but it could be in the order of 20k or more sessions trying to come up at once after the outage of a BRAS box. For the broken clients asking for 1500, it is more overhead to timeout and retry something else. Whatever can be avoided reasonably is a bonus. > > Why is that a cost worth optimizing -- especially at the risk of > losing correctness? > > > as BRAS may > > not be able to turn off that verification selectively either as it > > wouldn't be certain which clients really are asking for 1500 MRU (due to > > underlying network really supporting it) or which are asking 1500 MRU > > due to their config/implementation being broken. Seems fixing these > > broken clients would be a much overhead for Service provider. > > Right, I think that may well be one of the concerns: existing old > implementations that use an incorrect MTU would end up causing the > peer to probe and time out. > > I think it'd still be possible to do something reasonable here without > the extra flag, but it's probably not worth the effort. > > However, that doesn't mean that turning off the check for new > implementations with this new feature is a good idea. I think it's a > hazard and I see no benefit. May be there would be cases where ISP is sure that their underlying network and clients support 1500 MRU indeed... Veera > > -- > James Carlson, KISS Network <[EMAIL PROTECTED]> > Sun Microsystems / 1 Network Drive 71.232W Vox +1 781 442 2084 > MS UBUR02-212 / Burlington MA 01803-2757 42.496N Fax +1 781 442 1677 _______________________________________________ Ietf mailing list [email protected] https://www1.ietf.org/mailman/listinfo/ietf
