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sroylance · Tue Apr 09, 2002 8:34 am

(perpetual post your campus network thread?)

I see a lot of home network topics, but it doesn't look like anyone is discussing larger networks. I remember the big-lan FAQ that had a wealth of knowledge about large LANs, but the mailing list was dead by the time I subscribed to it in '98.

The network I help support has about 45,000 nodes, 200 routers and 700 switches. We use ATM OC-3 for the wide area core and GigE and FastE for everything else.

Cyklopz · Tue Apr 09, 2002 9:38 am

Ours is not a large network at about 45 nodes. FastE for everything through 4 switches and a redundant firewall/router/proxy.

Cy

mattsteg · Tue Apr 09, 2002 10:35 am

Damn. Only 10 nodes on my network right now.

zgirl · Tue Apr 09, 2002 10:52 am

I cast for 100-999, since that is the current network size that I work on. I have, however, done work for Ford Motor Co, Lear and others well over the 10000 range. All depends on where and when I've been.

Despite · Tue Apr 09, 2002 1:10 pm

at this point I'd like to recommend everybody here make sure they're current on the definition of "LAN"

sroylance · Tue Apr 09, 2002 1:20 pm

Despite wrote:
at this point I'd like to recommend everybody here make sure they're current on the definition of "LAN"

<sarcasm>Great, could you please post the URL to the cannonical definition of LAN?</sarcasm>

I think LAN, WAN, MAN etc are difficult to pin down terms. Do you define a WAN by how far apart the subnetworks are? Do you define LAN by end-to-end latency?

Campus networks seem to sit outside of the usual classifications, IMO. My network has LAN-like throughput and latency, but the major sites are miles apart, what kind of Area Network is it?

absurdity · Tue Apr 09, 2002 5:40 pm

sroylance wrote:
My network has LAN-like throughput and latency, but the major sites are miles apart, what kind of Area Network is it?

I believe that'd be a WAN, being you have 2 areas of it or more seperated by a significant geographical distance. I don't quite have the definition of a MAN pinned down, but I'm pretty sure what you've got is a WAN.

Here where I am, I only work on the computer helpdesk end, but the campus has roughly 2200 nodes, I believe.

Speed · Tue Apr 09, 2002 6:42 pm

I work on the Internet, so I guess my network is the biggest.

sroylance, those terms have been defined:

LAN = Local Area Network
MAN = Metropolitan Area Network
WAN = Wide Area Network

A local area network is just that -- local. If it crosses someone else's property, it ain't local. A metropolitan network is just that -- metropolitan. Local governments and large local businesses use these. A wide area network is pretty much everything that's not a LAN. As a rule of thumb, if you're using microwave, SONET or "T" lines, it's probably a WAN. Yes, a MAN is also a WAN.

zgirl · Tue Apr 09, 2002 7:07 pm

Right, LAN, you need to see the Ford world HQ building planted right next to the Ford credit building, they share the same parking lot and are connected by a nuke proof tunnel. Were talking 20 stories in the HQ building not to mention the primary datacenter in the credit building. Hell the credit building had 1500 people in it and was only two stories. Yes, their were a lot of T1s conntecting the other buildings up, but these two were huge and all self contained.

Not that I'm there anymore I work elsewhere now.

Speed · Tue Apr 09, 2002 8:00 pm

Just out of curiosity, what's the point of a nuke-proof tunnel? If the buildings are vaporized, does it really matter if the wires connecting them remain?

sroylance · Tue Apr 09, 2002 9:15 pm

Speed wrote:
sroylance, those terms have been defined:

I know what the acronyms stand for, but I do not believe that any of the terms have unambiguous universally accepted definitions. I, personally, like to refer to campus networks as 'extended LANs'.
Campus networks blur the lines:
We have a fiber run to the parking office which crosses over the street (city owned) on a connecting bridge (owned by us). It kinda leaves our property, but Its only a few hundred feet from my office, is it WAN?
We have data closets in a building around the corner from the parking garage. We own enough dark single-mode fiber from my building to that one that each closet gets its own GigE trunk back to the core in my building. We own the fiber, but probably not even the conduit it runs through.
Latency and throughput through the ATM core are similar to latency and throughput in the 'local' paths through the network, that certainly is not a characteristic of a classic WAN.
I have most often heard the term MAN to refer to networks like mine, too large (geographicly) to be consider strictly local, but not quite what could be considered wide area, I wouldn't say they are restricted to large companies and municipalities.

This entry was interesting, and led to some other interesting definitions as well.
http://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci214083,00.html
All the *AN definitions are somewhat ambiguous.

If you asked 10 networkers what LAN means as opposed to WAN or MAN you would get 10 different answers.

Speed · Tue Apr 09, 2002 9:58 pm

Just because people can be imprecise in day to day conversation doesn't mean that a precise definition doesn't exist.

I worked for a place that has a data center on one side of the street, and a skywalk carrying fiber to the main building. Sure the fiber ran contiguously across company property. In fact, the entire campus network was a huge nonsegmented network, in the logical sense. But if the fiber was cut, there would be two functioning LANs. Each building had its own core networking infrastructure. Each building was a LAN. The fact that the various LANs were fairly close to each other has nothing to do with it.

sroylance · Wed Apr 10, 2002 5:58 am

One of our main sites is too tight on space to have a datacenter. It has a network core in a glorified wiring closet, but no 'local' resources. All of their 'local' services are actually across the ATM a few miles away. It is our largest site and has something like 20,000 nodes.

What is the authoratative source book for networking jargon? I'll stop being imprecise when the unambiguous defintions are provided.

Speed · Wed Apr 10, 2002 7:59 am

I learned the finer points of networking jargon while sitting through a number of CS classes. If you have any universities nearby with good CS schools, you might look in the campus bookstore for a textbook or two. I specialize in network operating systems, so while I can recommend the seminal OS book (Modern Operating Systems, by Andy Tanenbaum), I'm at a loss to single out any one text for what you're looking for. Cisco dominates the networking field, so you might look for precise definitions on their website, or run down to the bookstore and look in their too expensive to actually buy books for the same.

The textbooks will get you to a certain point. Remember that plenty of networks have been erected without giving any thought to definitions. Back before the Internet was a necessity, the most common LAN would be isolated from all other networks. But nowadays the WAN is far more common, even for relatively tiny organizations. So if you spend much time looking at existing networks and try to figure out exactly what category they fit into, you could be making a lot of frustration for yourself, and little else.

It's important to recognize that networking technology is constantly advancing. The state of the art has changed radically since the time when the terms LAN MAN WAN were coined. If your vocation is data networking, then shouldn't the priority be knowing what to do with what you have now, and what's to come? Just a thought.

sroylance · Wed Apr 10, 2002 8:33 am

Speed wrote:
It's important to recognize that networking technology is constantly advancing. The state of the art has changed radically since the time when the terms LAN MAN WAN were coined. If your vocation is data networking, then shouldn't the priority be knowing what to do with what you have now, and what's to come?

Exactly.

IMO, the ?AN terms are not really useful for characterizing networks today. In the past a clear distinction between local and wide area had to be made becuase fast low-latency long-haul data transports were not widely available, or were too expensive to implement. Now there are many options for making traditionally 'wide-area' distances look 'local' from a network perspective.

Speed · Wed Apr 10, 2002 10:01 am

Interesting POV, sroylance. My last employer had an OC-3 MAN connecting all of its hospitals and HQ. It did feel very much like a traditional LAN, thanks to the high-quality WAN connections. Unfortunately the flipside of that coin was that the hospital LAN that I worked on was poorly designed, and had frightening latency and lots o' dropped packets. So when users couldn't tell if they were getting their data from down the hall, across town or Malvern, PA, it wasn't necessarily a Good Thing.

In that particular case, the problem was that the networking management and staff failed to understand what the "V" in "VLAN" meant. They spent millions for a brand-new Cisco infrastructure that gave them the ability to segment a 5000 node campus network (notice that I didn't say "LAN") and reduce broadcast domains. But they stopped short of actually doing it!

I have wandered off-topic; I guess I'm still fascinated by how easy it is to get corporate money without any accountability. Maybe I should start my own "IS Horror Stories" thread...

sroylance · Wed Apr 10, 2002 10:15 am

It's not unreasonably difficult to get money for infrastructure here, but not easy either. The network was all thicknet risers, hubs and routers. All that has been replaced with Catalyst switches in every closet with fiber back to the core. The routers remained but have recently been replaced by MSFC's (Cisco's layer-3 switching engine for the 6500 switch). It did take a few years to do becuase they wouldn't budget for the whole thing in one year.

Now there are groups asking for gig, so a lot of closets need to be upgraded.

Speed · Wed Apr 10, 2002 10:56 am

Sounds like a sweet setup! It looks like someone responsible is in charge of your shop, though. I can understand why stuff like that would be phased in. In my case it was more like a project that was abandoned the day the hardware was installed. We went from 10Base-T from the wiring closets to the desktop, to 10Base-T again! Our new network was strictly a plaything for the network people. I see a lot of that in IS -- people who are only interested in accumulating and playing with hardware. For those types, the goal is accomplished when the boxes arrive.

At my old workplace, they left the multimillion dollar network unfinished so they could focus on a multimillion dollar SAN that held a few user files for months and months. It took a corporate merger and another department eyeing the hardware before anybody thought of using the thing.

I have dozens of stories like that. :roll:

sroylance · Wed Apr 10, 2002 11:11 am

Speed wrote:
Sounds like a sweet setup! It looks like someone responsible is in charge of your shop, though.

Yea, there are a few guys with 10 years of solid networking experience. It's a little frustrating sometimes, I've been working in IS here for 5 years but haven't had the opportunity to make any contributions to the network design because the more senior people keep that for themselves.

It is rock solid though, because those people have been thorough and conservative.

Speed · Wed Apr 10, 2002 11:16 am

LOL, yeah, networking guys can be a little clannish. If you can get hooked up with a group that really knows their stuff, it's worth it to stick your neck out and get noticed. Networking is where it's at these days, unless you write good code.

zgirl · Wed Apr 10, 2002 11:26 am

I have no idea why it was a nuke proof tunnel. That's just what I was told. Then if you consider the fact that since there is all these manufacturing facilities here in southeast MI, the whole damn lower part of the state would be a tactical target. Wouldn't have been much left if Russia had decided to nuke us. To me the fact that they had a separate data center running idle 12 miles away made no sense either. It would all be gone. All I do know was there where some massive conduit pipes running down that tunnel.

They did have some parts VLAN'd and other segments on separate switching gear by floor or dept. I was there near the end of a token ring to ethernet conversion. I would consider it all one big fubared LAN, simply because we supported it no matter which of the two buildings it was in. Also I wouldn't be surprised if I didn't have access to everything that was there.

Also I don't feel that a VLAN separates a LAN in to two. Nodes are still connected to the same equipment. It's just a logical division to keep traffic separate. Then you consider the fact that some departments had people in both buildings who could access the same servers or services. It was all one big poorly laid out LAN.

Speed · Wed Apr 10, 2002 12:20 pm

Heh. I can imagine that some defense pork was responsible for the nuke tunnel. Go figure.

I suppose that per the above conversation that VLAN is something of a misnomer, since there's nothing preventing them from crossing WANs. It's a neat concept in theory. But so far I haven't seen any evidence that it's really worth the cost. The main headache that VLANs bring is this unexplained desire to segment departments. Peer to peer "workgroup" networking has gone the way of the Dodo, so why bother? IME, the people who plan VLANs come up with these Baroque schemes that ironically take more effort to implement than physical subnetting would!

Seems to me that you might as well VLAN arbitrarily, assigning n MACs to each VLAN, and let the enterprise switch sort it all out. That way there's a minimum of planning and execution, and a maximum of flexibility. Broadcast domains are kept in check simply by limiting the size of n. Make the server farm VLAN a member of all the other VLANs, and you're done. I mean, the whole point is supposed to be making administration easier, right?

zgirl · Wed Apr 10, 2002 12:40 pm

Absolutely right, just remember that I was there back in '95 and '96 for almost two years, so things that were being done might have been decided on, because this was the considered the latest and greatest. Don't forget some managers, VPs, who ever, loved the latest buzz words. VLANs yeah let's do that! Never mind if the idea made sense or not.

sroylance · Wed Apr 10, 2002 12:49 pm

VLANs are a neat technology with some important applications. The whole VLAN for a workgroup idea is dead at this point, but VLANs are still important. We use VLANs to create separate subnets on one switch or to separate secure from insecure traffic.

zgirl · Wed Apr 10, 2002 1:10 pm

Never said they weren't, but implementing them just for the sake of implementing them isn't a good reason. I've used them in a few situations for separating traffic without having to buy a bunch of new network equipment to do it physically.

Speed · Wed Apr 10, 2002 2:12 pm

I'm guessing that sroylance was probably responding to what I wrote about VLANs above, and wasn't being critical of you, z-man.

I do agree that VLAN has legitimate benefits when executed properly. It's just that I don't get to see the good implementations very often (he says ruefully). Too many of those buzzword-happy managers in my career lately.

:evil:

<-- (pointy-haired boss)

zgirl · Wed Apr 10, 2002 4:00 pm

I wasn't sure, but I wasn't taking offense to it. Just stating my opinion.

Red 6 · Fri Apr 12, 2002 8:50 pm

I'm not sure about the whole VLAN buzz either. The only true use I've ever seen implemented was traffic seperation. You keep hearing about how you can build workgroups into the same vlan even if they are spread across the whole campus. Who cares. If they have IP addresses and the network is setup correctly they can still communicate no matter what VLAN they are on.

The only practical use I've seen and used VLANs in is splitting a large switch, like a Black Diamond 6808 or Catalyst 6509 into smaller virtual switches to reduce broadcast domains. We use vlans that way and have seperated our campus network so that we know what part of the campus something is happening by the IP address. Good use, I don't know but it's as good as any I've seen in my five years doing this.

As for the LAN>WAN>MAN debate, I just call it the network and avoid the confusion as those terms have blurred with the availability of quality high speed links to the point of being somewhat overlapping.

Speed · Sat Apr 13, 2002 6:32 am

I agree with you, Red 6. Reducing broadcast domains can be done easily. VLANing together all computers in a department gains nothing, because a VLAN doesn't offer the same latency advantage that the router and hub paradigm did. Duh! I have no sympathy for networking managers who pull 6-figure salaries and can't grasp this basic fact.

I wouldn't mind having one of those 6-figure jobs myself, but I'm just not clueless enough.

sroylance · Sat Apr 13, 2002 7:00 am

Cisco doesn't even recommend using VLANs for workgroups anymore. Their current design recommendation for campus networks is 'one closet (switch) per VLAN'.
Of course this is because they now sell the 6500 switch where every port can be a layer 3 interface, and so every closet can get its own, but it does have advantages. Spanning tree redundancy is difficult to configure and even more difficult to troubleshoot. Doing everything at layer 3 is easier, you can use HSRP (or VRRP on non-cisco equipment).

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