Is the Distribution Layer Still Needed?

arnie_apesacrappin wonders: "I'm in the process of designing the network for a new building in what I would consider a small to medium sized company. It is on the scale of tens of access layer switches, not hundreds. There is a ongoing argument about the need for a distribution layer. My position is that with today's layer 2/3 switches in the core, the distribution layer is outdated for a network of this size. The layer 2/3 core can provide all the aggregation services of the old distribution layer and the routing/filtering functionality of the core with better price and performance. My opponents can only argue that having a distribution layer is the standard. So, are there good reasons for having a distribution layer in a small to medium network? If you were going to argue against the distribution layer, what points would you make?"

Comments

Glad you don't work here.

[grub]

Quit trying to be clever. Proper use of L3 equipment around the LAN and judicious use of VLANs is smart. Current equipment will let you design in redundencies for failed hardware so trying to aggregate all your networking smarts to a central point of failure is not cool. Frankly it sounds like you're trying to impress management without thinking of the ramifications.

Re:It can be done.

[Kaamoss]

That's the real key, if the network can't be scalable then you're not setting your self up to do further work for the company. When you give someone a solution it should have the ability to grow with them. In the end it's almost allways cheaper to go with the more complete solution than the simple one.

Spoken like a true CCNA

[Schezar]

The very concept was never spoken of at university (Rochester Institute of Technology), nor has it ever come up in work (IBM).

Those three "layers" are abstractions, nothing more. The "distribution" layer is simply a term for traffic shaping and optimization. It's very useful in eliminating excess resource use on beleagured routers. Eliminating the layer is nothing more than simplifying your backbone architecture. There is no "layer" to eliminate except the theoretical one.

It always amazes me how Cisco-certified (not making any acusations here) network techs speak an entirely different language from university-educated ones. They talk about Cisco-specific concepts like they're set in stone universally, and use Cisco jargon for common and/or basic concepts.

There are other options besides Cisco, and not every network fits within the nomenclature of Cisco Jargon. You'd do yourself an immense favour to lean more about generic architecture concepts.

I don't want to sound mean, but a Cisco cert is about as useful as an MSCE.

Re:Spoken like a true CCNA

[brunson]

I love the fact that the very next posting after this one starts with "To preface, I am a CCIE, so I know a little about these things."

To the CCIE's defense, he gave a balanced and reasoned opinion that was not rife with Cisco jargon.

I, on the other had, find it interesting to talk to university educated CS majors (I graduated with a BA in Math, but have worked as an SA and programmer for 17 years) who use lingo (especially pattern nomenclature) and discuss concepts (stateless session beans, oooooooooh) on a level that makes it clear that they a) have never written code in the real world and b) don't have a clue about the mechanics of how things actually work (what do you mean I can telnet to an SMTP port and send mail)?

Re:Spoken like a true CCNA

[prof.morbius]

I think you're underrating the value of a CCNA, but you're right that the program doesn't present alternatives and uses different terminology than the Real World. That's what bugged me about it while I was taking the program; the education was OK, the indoctrination was a pain. Of course, the real problem is folks who (like those the original poster is arguing against) accept the Cisco Gospel at the expense of actual needs analysis.

Re:It can be done.

[Anonymous Coward]

Smaller layer 3 devices around the LAN allows for more scalability than a central beast.

Re:Layer 3 Switch?

[rf600r]

I was taught that hubs work on Layer 1 (physical), switches on Layer 2 (data link layer - i.e. dealing with MAC addresses) and...

You were taught incorrectly, or, perhaps a more plausible possibility is that you learned incorrectly. Ethernet hubs and switches are both Layer 2 devices. Your best bet is to read /. for a while and resist posting. You may learn something from this very thread.

Re:It can be done.

[Anonymous Coward]

...and less total cost on the cisco P.O.

Your budget is too big

[fred fleenblat]

Count your blessings. You'd be amazed at how many small to medium sized companies (2000+ employees) have one Cisco router in a rack somewhere and use consumer grade linksys or d-link 10/100 switches everywhere else.

For sending email and word docs around, you really don't need the whole Cisco hierarchy. On the other hand, If you're sending uncompressed production video around, it's not enough.

Distribution layer exists only in the Ciscoland

[wikinerd]

The term "distribution layer" is defined by Cisco, which is just a corporation. There is no standard where you will encounter this term.

The most well-known networking standards are the OSI model and the TCP/IP model. Neither of these standard models include the term "distribution layer", which means nothing by itself: Is it about physical-electrical distribution, data distribution or information distribution?

I personally dislike "standards" or tech-speak set by corporations and I believe international bodies and computer scientists should be preferred when it comes to standards and technical jargon: Imagine two computer scientists, one using Cisco-speak and the other knowing only Microsoft-speak, how are they going to communicate? It's impossible! - unless they both adopt a common language like these proposed in the OSI or TCP/IP model.

I personally can communicate network concepts using the OSI model, and I am completely unaware of Cisco-speak. In an attempt to answer your question, I will assume that by "distribution" Cisco means "routing", which translates to "Internet layer" in TCP/IP-speak and is related to the Internet Protocol, while in ISO-speak it translates to "Network layer". If my understanding is correct, then the answer is that no matter how small your network is, you will want to use routing, for example for connecting your small network to the Internet. Even if the routing functionality is included in a device of another layer, or even when it is implemented in software, it will always be there, no matter whether the users or even the administrator can see it, especially if you are going to use the TCP/IP protocol suite.