Re: Another UUNET Explanation
I've noticed that several of the larger networks use frame-relay. Why? Our experience with frame-relay with the local telco has had mixed results. What technical advantages does a frame-relay network have over an IP routed network? Thanks! Joe
layer 2 vs. layer 3 tis like comparing a motorcyle to an automobile--both get you places but in fairly different ways rob
I've noticed that several of the larger networks use frame-relay.
Why? Our experience with frame-relay with the local telco has had mixed results.
What technical advantages does a frame-relay network have over an IP routed network?
Thanks!
Joe
At 05:00 PM 07/01/97 -0700, Robert Bowman wrote:
layer 2 vs. layer 3
tis like comparing a motorcyle to an automobile--both get you places but in fairly different ways
I shouldn't be contributing to this thread, but what the hell. Its not really Layer 2 vs. Layer 3, its how to integrate the two layers and make it work. Mike O'Dell is fond of saying, "Pure Layer 3 routed networks are dead," and I can understand his point, although I don't necessarily agree with it. I do understand, and I think its important for everyone else to understand the point here. Yes, they both get you there, but the pertinent summary to be drawn from this comparison is that 'you' are the IP packet, and you really don't care what the mode of transport is (e.g. frame-relay, leased point-to-point lines, ATM). Each provide a pipe. Some have more intrinsic flexibility than others (e.g. virtual circuits) and therefore represent a significant reason to employ a specific technology over another, given pricing, and geographic availability. Again, IP packets don't really care if it's a motorcycle, an airplane, or an automobile (unless its a Harley :-). It should also be noted that some technologies, such as frame-relay are used only in *topologically significant* places, ie. customer aggregation, for precisely these reasons. In some networks, frame-relay is used for customer aggregation, fast-ethernet is used in the PoP, and ATM is used in the wide-area (just an example). - paul
Agreed.. the distinction between the two layers is becoming somewhat more and more vague by the day, especially with companies like Ipsilon and with Cisco's integration of eclipse switching and/or the RSM into the Catalyst.. how the two layers interact is really the only importance to the IP packet. rob
At 05:00 PM 07/01/97 -0700, Robert Bowman wrote:
layer 2 vs. layer 3
tis like comparing a motorcyle to an automobile--both get you places but in fairly different ways
I shouldn't be contributing to this thread, but what the hell.
Its not really Layer 2 vs. Layer 3, its how to integrate the two layers and make it work. Mike O'Dell is fond of saying, "Pure Layer 3 routed networks are dead," and I can understand his point, although I don't necessarily agree with it. I do understand, and I think its important for everyone else to understand the point here.
Yes, they both get you there, but the pertinent summary to be drawn from this comparison is that 'you' are the IP packet, and you really don't care what the mode of transport is (e.g. frame-relay, leased point-to-point lines, ATM). Each provide a pipe. Some have more intrinsic flexibility than others (e.g. virtual circuits) and therefore represent a significant reason to employ a specific technology over another, given pricing, and geographic availability.
Again, IP packets don't really care if it's a motorcycle, an airplane, or an automobile (unless its a Harley :-).
It should also be noted that some technologies, such as frame-relay are used only in *topologically significant* places, ie. customer aggregation, for precisely these reasons. In some networks, frame-relay is used for customer aggregation, fast-ethernet is used in the PoP, and ATM is used in the wide-area (just an example).
- paul
At 05:00 PM 07/01/97 -0700, Robert Bowman wrote:
layer 2 vs. layer 3
Kind of a weird one in a way given that FR has internally its own Layer 2 as well as [stripped down] Layer 3 ... not unlike the [very short] time when ARAPANET was routed over X.25 many moons ago. Lots of overhead by this funny layer 2 (error correction, flow control the work). On the other head, if it works ..... One thing I am curious about .... does anyone actually uses SVC with FR for use as an underlying network for IP transport? If so, I am curious as to the pros/cons especially with respect to connection establishment / tear down overhead. Regards, John Leong
This is not exactly true. Frame Relay -- if designed properly, and with good frame switches -- can be - IMHO - 10's of times better. Frame Relay allows yout he ability to psuedo-directly connection various pop's together, and gives that clean appearance of a 'no-hop' back bone. Why route when you can switch? On Tue, 1 Jul 1997, Robert Bowman wrote:
layer 2 vs. layer 3
tis like comparing a motorcyle to an automobile--both get you places but in fairly different ways
rob
I've noticed that several of the larger networks use frame-relay.
Why? Our experience with frame-relay with the local telco has had mixed results.
What technical advantages does a frame-relay network have over an IP routed network?
Thanks!
Joe
On the inverse, routers--if designed properly, can be 10 times better because of lower overhead, cost effectiveness, etc. I don't think this is going to be a debate that one will win in this forum. There are many router only based backbones, such as ours, Digex, etc. Then there are the many on the fr/router side.. just as "effective" one might say.. rob
This is not exactly true. Frame Relay -- if designed properly, and with good frame switches -- can be - IMHO - 10's of times better.
Frame Relay allows yout he ability to psuedo-directly connection various pop's together, and gives that clean appearance of a 'no-hop' back bone. Why route when you can switch?
On Tue, 1 Jul 1997, Robert Bowman wrote:
layer 2 vs. layer 3
tis like comparing a motorcyle to an automobile--both get you places but in fairly different ways
rob
I've noticed that several of the larger networks use frame-relay.
Why? Our experience with frame-relay with the local telco has had mixed results.
What technical advantages does a frame-relay network have over an IP routed network?
Thanks!
Joe
On Tue, 1 Jul 1997, Robert Bowman wrote:
On the inverse, routers--if designed properly, can be 10 times better because of lower overhead, cost effectiveness, etc. I don't think this is going to be a debate that one will win in this forum. There are many router only based backbones, such as ours, Digex, etc. Then there are the many on the fr/router side.. just as "effective" one might say..
There is nothing inherently good or bad about switches either. The problem comes in, as Sean stated far more eloquently than I can, when layer 2 and layer 3 each have their own intelligence and do not work together. This is probably the single most problematic part of the layer 2 + layer 3 designs I've seen implemented. While this has in large part caused by the lack of correct tools to build such a beast, when you are trying to tie a necktie with two hands and your left and right hands don't coordinate, you sometime end up hanging yourself instead. -dorian
On Tue, 1 Jul 1997, Alex Rubenstein wrote:
This is not exactly true. Frame Relay -- if designed properly, and with good frame switches -- can be - IMHO - 10's of times better.
How? Does good frame relay switches accelerate photons or something?
Frame Relay allows yout he ability to psuedo-directly connection various pop's together, and gives that clean appearance of a 'no-hop' back bone. Why route when you can switch?
Yes, both frame relay and ATM give the "appearance" of a 'no-hop' backbone. Just because traceroute doesn't show the switch hop in the middle doesn't mean that they aren't there. So what is inherently better about that, unless you are into marketing vapours? I can see the argument that with current generation of rather deficient routers, switches have smaller per-hop latency, but even this is pretty silly since that difference is a noise lost in the cross continental/cross oceanic propagation delay. This should be a moot point any way with the impending introduction of real routers in to the networks. -dorian
well, where to begin. UUNet obviously *does* have a routed IP network...that's sort of what being an NSP is about. they own their own frame relay infrastructure (big cascade switches, for instance) over which they have complete control. they are acting as a frame relay *provider* rather than a frame relay *customer* as you are. as for precise technical reasons about why certain decisions were made by UUNet, i defer to one of their engineers. On Tue, 1 Jul 1997, Joe McGuckin wrote:
I've noticed that several of the larger networks use frame-relay.
Why? Our experience with frame-relay with the local telco has had mixed results.
What technical advantages does a frame-relay network have over an IP routed network?
Thanks!
Joe
On Tue, 1 Jul 1997, Joe McGuckin wrote:
I've noticed that several of the larger networks use frame-relay.
Why? Our experience with frame-relay with the local telco has had mixed results.
If you mean local or public frame relay clouds, most of us don't run our network on them. NetRail and several other providers run FR over the local loops to our customers using Cascade hardware. As far as backbone links they are clear channel DS3 into a frame switch.
What technical advantages does a frame-relay network have over an IP routed network?
Much lower overhead, but ATM is starting to take over frame relay in the backbone. This is because of several reasons, one of them is the need for higher speed backbones. Frame relay right now does not scale above DS3, this is starting to be way to small for backbone links. One other big reason is that the cost of OC3 and higher links are dropping in cost. We upgraded some of our backbone links to OC3 because the cost of OC3 was much less then several DS3s in a lot of areas. If you can get a OC3 for about 1 - 2 x the cost of a DS3 you don't worry as much about the cell tax. Nathan Stratton President, NetRail,Inc. ------------------------------------------------------------------------ Phone (888)NetRail NetRail, Inc. Fax (404)522-1939 230 Peachtree Suite 500 WWW http://www.netrail.net/ Atlanta, GA 30303 ------------------------------------------------------------------------ "No king is saved by the size of his army; no warrior escapes by his great strength. - Psalm 33:16
Frame-Relay, ATM, IP, X.25, DECnet, LAT, are all methods of encapsulation of information into discrete units and their subsequent delivery. Some are part of the PSTN, and some are not. Each protocol has its set of restrictions/features. None are "bad" per se (not even X.25, Joel ;) Make sure not to confuse the protocol with the medium it uses. For instance, frame-relay DS3s will outperform ATM DS1s for data and voice routing :)* Many people who "hate" frame-relay really despise the predominant practice of overselling non Committed-Information-Rate circuits into an overloaded central hub location. Frame-Relay "routing" is L2, and IP routing is L3, so I won't really go into comparing them any more than, say, discussing the technical advantages of TCP vs. IP. They are two different things with similar form yet different functions. Ehud * There are some purists who would claim that the additional overhead of switching frame-relay packets would increase latency over that inherent in an ATM switched network. They would say that my example above (which is just an example, so reading too much into it is an exercise in being a pedant) is flawed because the frame-DS3 is more latent than the ATM-DS1. Nonetheless I claim the inherent latency of both networks to be less than that noticeable by human ears. Nya. Nee. Nya. Nee. PooPoo.
I've noticed that several of the larger networks use frame-relay.
Why? Our experience with frame-relay with the local telco has had mixed results.
What technical advantages does a frame-relay network have over an IP routed network?
Thanks!
Joe
What technical advantages does a frame-relay network have over an IP routed network?
2 seperate layers so it should be seperate. Shouldn't it? I.E. you can move IP on top of it or a plethora of transport mechanisms..ATM, DDS, etc. Regards, -- Martin Hannigan (hannigan@firefly.net) Voice: 617.528.1099 Firefly Network, Inc. - Network Operations Network Engineer www.firefly.net Semper Cabalis
What technical advantages does a frame-relay network have over an IP routed network?
As long as one's source and destination is identified by IP address, one would need an infrastructure that understand those addresses. There had been some debate whether ATM will remove the need for IP. My view is that it may be acceptable (TCP directly over ATM) if ATM can comprehensively taken over the world .... which given the dominance of Ethernet for desktop is extremely unlikely. As long as there are multiple transport network technologies in a (most) path, IP routing will be required. John
I've noticed that several of the larger networks use frame-relay.
What technical advantages does a frame-relay network have over an IP routed network?
It's not so much the frame relay itself which gives an advantage, but they can bring in many more customers per router via the switches than via direct T1's, plus the switches allow them to control customer usage a lot more closely. Steve Mansfield steve@nwnet.net NorthWestNet Network Engineer 425-649-7467
participants (11)
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Alex Rubenstein -
Ben Black -
Dorian R. Kim -
Ehud Gavron -
Joe McGuckin -
leongļ¼ inversenet.com -
Martin J. Hannigan -
Nathan Stratton -
Paul Ferguson -
Robert Bowman -
Steve Mansfield