<div>Drawback when stacking could be scalability (there is always a maximum number of switches that could be stacked), but is a nice solution for a limited number of nodes. Of course, this is not at all an HA approach.</div>
<div> </div>
<div>There is a network manufacturer that implements a couple of protocols that could be interesting for network redundancy and low-latency failover mechanisms, that can perfectly fit on that ring proposal you're doing. Those protocols are EAPSv2 (based in a set of rings) for L2 and ESRP for L3. Yet once again, propietary protocols, that's the drawback.
</div>
<div> </div>
<div>Spanning tree has some caveats and could make you to increase the number of hops when communicating two distant leafs. In this case there are some vendor-specific spanning tree implementations (i.e PVST+, EMISTP, etc...) but also a number of "standard" Spanning tree standard implementations (for instance the first definition of STP in
802.1D and its successors 802.1w, etc....)</div>
<div> </div>
<div>Anyway, hop latency in Ethernet is most of times just peanuts in terms of latency compared to TCP/IP stack overhead...</div>
<div> </div>
<div>Other option could be not to impement redundancy but of course this depends on the criticity of your cluster....<br><br> </div><br><br>
<div><span class="gmail_quote">2007/7/11, Mark Hahn <<a href="mailto:hahn@mcmaster.ca">hahn@mcmaster.ca</a>>:</span>
<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">>> my question is: do switches these days have smart protocols for mapping and<br>>> routing in such a configuration? I know that the original spanning
<br>><br>> That's 802.3ad. Quick pointer:<br>> <a href="http://en.wikipedia.org/wiki/Link_aggregation">http://en.wikipedia.org/wiki/Link_aggregation</a><br><br>I don't think that's what I meant. imagine instead that you have
<br>48pt GE switches, each of which has 4x 10G extra ports. now, take<br>5 such switches and fully connect them (each switch has a 10G link<br>to each of the other 4 switches). I don't think 802.3ad helps here,<br>since what you want is to _avoid_ a single spanning tree, which
<br>would necessarily have one root.<br><br>802.3ad is exactly the right thing if you simply want to stack<br>two such switches and want 4x10Gb inter-switch bandwidth.<br><br>I noticed that d-link appears to use 10G links for stacking, but
<br>has a route-discovery protocol that lets them structure the switches<br>into a ring. I'm not sure they use this to reduce hop-count, though -<br>perhaps just for reliability.<br>_______________________________________________
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