Nakul Malik wrote: > passport at heart an ATM switch????????/ > > Passport is FR. > > -Nakul > > > > ""annlee"" wrote in message > news:[EMAIL PROTECTED] > >>John Neiberger wrote: >> >> >>>I'm just now digging deeper into current VPN technologies since I'm >>>researching Qwest's PRN service. I'm awaiting a definitive answer from > > them > >>>but it appears that their PRN service is 2764-based, which apparently > > means > >>>it does not use MPLS like 2547-based VPNs. I'm curious about the >>>implications of choosing one model over the other. >>> >>>I thought the market trend was toward MPLS-based VPNs but 2764 seems to >>>argue against that. What are the implications of choosing one model over >> >>the >> >>>other? Are there any major drawbacks to either one that the other >>>addresses? >>> >>>I'm also a little concerned about vendor choices. Nortel seems to be >> >>pushing >> >>>2764, while Cisco and possibly Juniper are pushing 2547 and MPLS. Is > > that > >>>correct? If so, is that really that important to the customer? >>> >>>Forgive me if these questions seem pretty vague. I'm still learning > > about > >>>the technologies involved and I'm not very familiar with the specifics > > and > >>>the terminology. >>> >>>I'll put in a plug here for Howard's book _Building Service Provider >>>Networks_. Among a number of things it discusses some of these VPN >>>technologies and has been very helpful the last couple of days during my >>>research. >>> >>>John >> >>Also worth looking at is the hardware component: what will run on >>the hardware you've already got (if anything)? IF you already >>have most or all of the hardware pieces to implement Cisco's >>version, then Cisco's probably makes sense. IF you already have >>the requisite Nortel gear (Passports?), you're probably only >>looking at upgrading to a new PCR (software version). >> >>And there's the training and management aspect -- which suite do >>you know better? Where is the rest of your network going--will >>money spent learning Passport command line be transferable to >>other devices, offering a savings there? My guess is no, but it >>could be possible. Finally, what's the underlying architecture -- >>Passport at its heart is an ATM switch, and Nortel's VPNs using >>virtual routers still looks an awful lot like IP over ATM, with >>all the overhead in play there. If it's Passport they're pitching >>at you, have a good look at the layer 2 technology on switch >>egress. What I saw was: >> >> [data+(local IP hdr)+(carrier IP hdr)+layer2 formatting] >> >>as it went through the cloud. Potentially, that's a lot of >>overhead. If that's not a problem, fine. >> >>Annlee The Passport 6000/7000/15000/2000 are all at heart ATM switches. The Passport 8600 series is a renamed Accelar (Bay Networks) switch. They were going to rename it Optera 8600 during the spring of 2002, but then decided to forego that--I never heard why.
The Passport 6-20K series are optimized for ATM. They run everything through the backplane, even if it departs the switch on a different circuit of the same Function Processor (blade)--for instance, traffic comes in on port 3 of an 8p DS1 and goes out port 6 of the same DS1 FP. It comes in, passes through to the backplane, and then back into the FP and egresses. Passage out of the FP and through the backplane (which is a bus on the 6/7K and a fabric on the 15/20K) requires segmentation into what are called Passport cells, of 64K (IIRC), sized to hold an internal header and an ATM cell. SAR for this is done on the FP, I forget the name of the processors that do it (QBIC, maybe), but there's an ingress path on the FP all the way through to the backplane and then an egress path from the backplane to the egress port. Each path runs through one of the processors. Reassembly is performed on egress, if needed, which it isn't for ATM. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=73063&t=73048 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
