3tier vs 2 tier architecture

[eng.bandar]

what most diff.

and what is the best

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[vmiller]

2 tier: core and access. distribution functionality is split between the two.

3 tier: core, access & distribution.

the best depends on all sorts of things, size, age/functionality of hardware.....no simple answer.

[damisco2000]

I think you need to revisit your post on 3 tier vs 2 tier.

2 Tier architecture is Access and distribution layer as the core is collapsed into the distribution layer. Not many companies can afford the Core infrastructure so its collapsed into the distribution layer.

[Joseph W. Doherty]

I'm not so sure it's a question of companies cannot afford 3 tier, but possible more a question of the march/progress of technology. Today's L3 switches can provide very large port counts while often providing full wire speed for all ports. Today's 2 tier can easily support a port count that would have, years ago, required 3 tier (again to support the same number of edge ports).

Today you might also see a 1 tier architecture handling a port count that would have required a 3 tier architecture back a couple of decades ago. Consider the number of ports a 6800 with IA or a Nexus with FEX can support.

[damisco2000]

Yes, you are right, guess that was wrong choice of word/analysis.

My issue was actually with this "2 tier: core and access. distribution functionality is split between the two." 

I thought core functionalities are collapsed into distribution so we have

tier 2 as just the access and distribution functionalities and not the other way round as its been put above

core and access???.