We use 5 PVCs for the IP video and one for Internet. Not as uncommon as you think. Frank -----Original Message----- From: Michael Sokolov [mailto:msokolov@ivan.Harhan.ORG] Sent: Saturday, January 23, 2010 12:53 PM To: nanog@nanog.org Subject: Re: Using /31 for router links Mark Smith <nanog@85d5b20a518b8f6864949bd940457dc124746ddc.nosense.org> wrote:
What about NAT, ATM cell tax, unnecessary addressing fields in PTP protocols (including your beloved HDLC), SSAP, DSAP fields not being big enough in 802.2 necessitating SNAP, IPX directly over 802.3, AAL1 through AAL4, PPPoE "dumbell" MTUs and MSS hacks? Some of those are far worse sins in my opinion.
<snip> As for ATM... The part that totally baffles me about the use of ATM on xDSL lines is that I have never, ever, ever seen an xDSL line carrying more than one ATM VC. OK, there may be someone out there who has set up a configuration like that just for fun, but 99.999% of all ATM'd xDSL lines out there carry a single PVC at 0*35 or 0*38. So what then is the point of running ATM?!?! All the hyped benefits of ATM (a little cell can squeeze in the middle of a big packet without waiting for it to finish, yadda yadda yadda) are contingent upon having more than one VPI/VCI going across the interface! If every single non-idle cell going across that ATM interface is 0*35 or 0*38, the interface will never carry anything other a direct succession of cells making up an AAL5 packet, strictly in sequence and without interruption. So what's the point of ATM then? Why chop that packet up into cells only to transmit those cells in direct sequence one after another? Why not simply send that same packet in plain HDLC over the same copper pairs/fiber? OK, the backhaul network upstream of the DSLAM may be ATM and that one does have many VCs, so ATM *might* be of use there, but even in that case why not do FRF.8 in the DSLAM and keep the ATM strictly on the backhaul, sending HDLC down the copper pairs? <off the soapbox for the moment> MS