Re: Exchanges that matter...
It is actually quite hard in practice to push a FDDI switch into trouble, although theoretically it should be simple, modulo the interesting effects that token-withholding can produce.
Hm. Not sure what you mean. FDDI can certainly be over-utilized, that's not hard. On the other hard, FDDI doesn't fall down and die like Ethernet does when congested.
In practice, the limiting factor will tend to be the per-port bandwidth rather than the aggregate bandwidth. One would have
Bingo.
On Sun, 8 Dec 1996, Joe Rhett wrote:
It is actually quite hard in practice to push a FDDI switch into trouble, although theoretically it should be simple, modulo the interesting effects that token-withholding can produce.
Hm. Not sure what you mean. FDDI can certainly be over-utilized, that's not hard. On the other hard, FDDI doesn't fall down and die like Ethernet does when congested.
In practice, the limiting factor will tend to be the per-port bandwidth rather than the aggregate bandwidth. One would have
At the Atlanta-NAP we offer full duplex FDDI, why not try to get MFS to do it? Cisco now has a full duplex FDDI card, so you can do 200 Mbs into the NAP. Nathan Stratton CEO, NetRail, Inc. Tracking the future today! --------------------------------------------------------------------------- Phone (703)524-4800 NetRail, Inc. Fax (703)534-5033 2007 N. 15 St. Suite 5 Email sales@netrail.net Arlington, Va. 22201 WWW http://www.netrail.net/ --------------------------------------------------------------------------- "Therefore do not worry about tomorrow, for tomorrow will worry about itself. Each day has enough trouble of its own." Matthew 6:34
At the Atlanta-NAP we offer full duplex FDDI, why not try to get MFS to do it? Cisco now has a full duplex FDDI card, so you can do 200 Mbs into the NAP.
Every NAP with a GIGAswitch/FDDI offers full duplex FDDI; the MAEs, Sprint, PAIX, and you. Buy a full-duplex-capable card, install it, and you get full duplex. You, the NAP operator, do nothing; the devices negotiate in and out of full duplex mode themselves. I'm somewhat confused as to why you would say you offer full duplex FDDI in a manner that implies no-one else does. If someone walked up to your GIGAswitch/FDDI (or anyone's) with a full duplex line card, they'd get full duplex unless you took some specific action to prevent it (by, say, putting three stations on a ring), or if you disable it in management (it comes enabled by default).
From Chapter 1 of the Big Book of GIGAswitch/FDDI (June 1993):
"Point-to-point links can operate in a full-duplex mode to increase bandwidth and reduce latency. Using FDDI, simultaneous transmission and reception in a point-to-point connection between two FDDI adapters that support full-duplex communication can provide twice the raw bandwidth of the data link. When a point-to-point link is created with a station that can use full-duplex mode, the communication mode is changed from token ring to full-duplex. No token is passed in full-duplex mode. Configurations can automatically move in and out of full-duplex mode as the opportunity (two stations on a ring, both capable) becomes available, or unavailable. Full-duplex mode can be disabled using MIB objects in version 2.7 of the DEC Vendor MIB." Since you point it out as a specific offering, does that mean you turn it off by default? Do you charge more for it? Stephen
On Sun, 8 Dec 1996, Stephen Stuart wrote:
At the Atlanta-NAP we offer full duplex FDDI, why not try to get MFS to do it? Cisco now has a full duplex FDDI card, so you can do 200 Mbs into the NAP.
Every NAP with a GIGAswitch/FDDI offers full duplex FDDI; the MAEs, Sprint, PAIX, and you. Buy a full-duplex-capable card, install it, and you get full duplex. You, the NAP operator, do nothing; the devices negotiate in and out of full duplex mode themselves.
Ah, if I have a FDDI connection into MAE-East I cant do full duplex unless they enable it, it now is disabled.
I'm somewhat confused as to why you would say you offer full duplex FDDI in a manner that implies no-one else does. If someone walked up to your GIGAswitch/FDDI (or anyone's) with a full duplex line card, they'd get full duplex unless you took some specific action to prevent it (by, say, putting three stations on a ring), or if you disable it in management (it comes enabled by default).
Well, because when I talked to MFS they said they would don't turn on full duplex modem, I got the same thing from PAIX.
From Chapter 1 of the Big Book of GIGAswitch/FDDI (June 1993):
"Point-to-point links can operate in a full-duplex mode to increase bandwidth and reduce latency. Using FDDI, simultaneous transmission and reception in a point-to-point connection between two FDDI adapters that support full-duplex communication can provide twice the raw bandwidth of the data link. When a point-to-point link is created with a station that can use full-duplex mode, the communication mode is changed from token ring to full-duplex. No token is passed in full-duplex mode. Configurations can automatically move in and out of full-duplex mode as the opportunity (two stations on a ring, both capable) becomes available, or unavailable. Full-duplex mode can be disabled using MIB objects in version 2.7 of the DEC Vendor MIB."
Since you point it out as a specific offering, does that mean you turn it off by default? Do you charge more for it?
No, I turn it on, so far all the NAPs I have turned it off. If MFS and PAIX wants to turn it on then great. Nathan Stratton CEO, NetRail, Inc. Tracking the future today! --------------------------------------------------------------------------- Phone (703)524-4800 NetRail, Inc. Fax (703)534-5033 2007 N. 15 St. Suite 5 Email sales@netrail.net Arlington, Va. 22201 WWW http://www.netrail.net/ --------------------------------------------------------------------------- "Therefore do not worry about tomorrow, for tomorrow will worry about itself. Each day has enough trouble of its own." Matthew 6:34
On Sun, 8 Dec 1996, Nathan Stratton wrote: |} > Every NAP with a GIGAswitch/FDDI offers full duplex FDDI; the MAEs, |} > Sprint, PAIX, and you. Buy a full-duplex-capable card, install it, and |} > you get full duplex. You, the NAP operator, do nothing; the devices |} > negotiate in and out of full duplex mode themselves. |} |} Ah, if I have a FDDI connection into MAE-East I cant do full duplex |} unless they enable it, it now is disabled. Perhaps you should talk to them again. Steve Feldman (MFS) has said multiple times that FFDT is enabled on the MFS Gigaswitches. At the last NANOG, he suggested people try out the 'new' feature implemented by Cisco and send him feedback. As Stephen Stuart (PAIX) pointed out you have to disable the feature as it's enabled by default. Perhaps a better theory on the reason certain providers are de-emphasizing their MAE/NAP connections is that they're concerned about people "stealing" bandwidth on their links via 3rd party routing. -jh-
On Sun, 8 Dec 1996, Nathan Stratton wrote:
|} > Every NAP with a GIGAswitch/FDDI offers full duplex FDDI; the MAEs, |} > Sprint, PAIX, and you. Buy a full-duplex-capable card, install it, and |} > you get full duplex. You, the NAP operator, do nothing; the devices |} > negotiate in and out of full duplex mode themselves. |} |} Ah, if I have a FDDI connection into MAE-East I cant do full duplex |} unless they enable it, it now is disabled.
Perhaps you should talk to them again. Steve Feldman (MFS) has said multiple times that FFDT is enabled on the MFS Gigaswitches. At the last NANOG, he suggested people try out the 'new' feature implemented by Cisco and send him feedback. As Stephen Stuart (PAIX) pointed out you have to disable the feature as it's enabled by default.
*cough* *cough* Hate to jump into the middle of this wonderful debate, but has anyone here been able to push more than 60-70mbs through the fddi interfaces in the NetEdges anyhow? We've upgraded to an oc3c line to MAE-West, and discoverd that lo and behold, you don't get that much more out of the link than you did with a DS3 because the fddi cards top off not much farther up. Full duplex is a nice thought, and would win us another 5-10mbs, but since we are far and away a content provider (traffic ratio outbound to inbound is close to 10:1 at MAE-West), what we're concerned about is being able to deliver the content people are asking for. Opening up the back channel from shared to full FDDI is a, well, "nice" feature, but isn't nearly as attractive as getting better FDDI cards for the NetEdges. On the flip side, we've had the same NE's on our prem from MFS for about 2 years now; does MFS have any plan to cycle them out for the newer, faster models that are being released? Is it likely that we would see performance improvements by having a newer box/card combo at both ends of our link? Just some ideas to toss out before the crowd... Thanks for any feedback!
-jh-
Matt Petach Network Engineer, InterNex (working from home)
*cough* *cough* Hate to jump into the middle of this wonderful debate, but has anyone here been able to push more than 60-70mbs through the fddi interfaces in the NetEdges anyhow? We've upgraded to an oc3c line to MAE-West, and discoverd that lo and behold, you don't get that much more out of the link than you did with a DS3 because the fddi cards top off not much farther up. Full duplex is a nice thought, and would win us another 5-10mbs, but since we are far and away a content provider (traffic ratio outbound to inbound is close to 10:1 at MAE-West), what we're concerned about is being able to deliver the content people are asking for. Opening up the back channel from shared to full FDDI is a, well, "nice" feature, but isn't nearly as attractive as getting better FDDI cards for the NetEdges.
Well, order two FDDI ports at MAE-West, each into a router which has two T3s back to your data center. Each two T3s should be able to do 90mbits/sec of hdlc or ppp framing back to you, and route back and forth from the FDDI. Or order an OC3 'WAN' link, but plug it into an AIP card in a 75xx and pull 3 T3s back to your main site. Can a Cisco AIP speak ATM to the wan port of a Gigaswitch?
Matt Petach Network Engineer, InterNex (working from home)
Avi
I'm somewhat confused as to why you would say you offer full duplex FDDI in a manner that implies no-one else does. If someone walked up to your GIGAswitch/FDDI (or anyone's) with a full duplex line card, they'd get full duplex unless you took some specific action to prevent it (by, say, putting three stations on a ring), or if you disable it in management (it comes enabled by default).
Well, because when I talked to MFS they said they would don't turn on full duplex modem, I got the same thing from PAIX.
Full-duplex mode is enabled on all ports on the PAIX GIGAswitch/FDDI; we never disabled it.
No, I turn it on, so far all the NAPs I have turned it off. If MFS and PAIX wants to turn it on then great.
Like I said above, PAIX never turned it off. If you'd like to follow up privately to work out the source of your error, you know where to find me. Stephen
On Dec 8, 1996, Nathan Stratton wrote:
At the Atlanta-NAP we offer full duplex FDDI, why not try to get MFS to do it? Cisco now has a full duplex FDDI card, so you can do 200 Mbs into the NAP.
No, you can do 100Mbps _into_ the peering point, but you can also pull 100Mbps out of it at the same time. But I agree, it would be nice if MFS enabled full duplex FDDI on their gigaswitches. Unfortunately, I think only 75xx series routers can use the full duplex FDDI card, so people will have to upgrade routers. I could be wrong about this, though. However, this does not address the problem of the peering point itself getting overloaded (as has happened at MAE-east). MFS seems to have moved all of the big traffic connections to the first gigaswitch, which has actually made things much better. But this is only a temporary solution at best. Alec -- +------------------------------------+--------------------------------------+ |Alec Peterson - chuckie@panix.com | Panix Public Access Internet and UNIX| |Network Administrator/Architect | New York City, NY | +------------------------------------+--------------------------------------+
participants (7)
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Avi Freedman -
chuckie＠panix.com -
Joe Rhett -
Jonathan Heiliger -
Matthew Petach -
Nathan Stratton -
Stephen Stuart