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Cisco Architectures for 2950/2960 Switches and 2800 Routers

marijaslash1
Level 1
Level 1

Hello,

I have a question regarding the architectures of these three series, i.e. the type of switch fabric they use and the general architecture (first, second, or third generation regarding the sharing of the bus, memory and the type of switch fabric). We have so far learned these three generation and our assumption is that the only generation being produced now is the third (crossbar) generation, but so far we have to information to back up this claim. We are doing a study on buffer sizing in edge routers/switches so knowing the exact architecture of each model is our priority.

 

Thank you for reading and thanks in advance for the answers. 

2 Replies 2

Joseph W. Doherty
Hall of Fame
Hall of Fame

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Exact details on Cisco switch and/or router architecture can be hard to come by, as much of the information, Cisco appears to consider proprietary.

Most switches have some kind of cross bar architecture.  Overall bandwidth tends to be higher in later variants (to support higher port densities and/or higher bandwidth ports).  Later switch architectures are less likely to block at ports.  However, there are often other architecture changes which may improve or worsen performance.  For example, 2960 tends to have more fabric bandwidth than the 2950, but the 2960 has different port buffer management (I believe) from the 2950, often resulting in more port drops with bursty traffic.

True routers, like the 2800 series, I believe use a PCI bus, with additional bandwidth restrictions to the modules.  They will well support the WAN bandwidths they are recommended for, but they do not well support LAN port bandwidths.  Again, specific architecture details can be hard to come by.

Thank you very much for answering. Well, we agree completely that router architecture is hard to come by. We have found some lectures that agree with your answer on the shared PCI bus, but nothing too conclusive. As for the 2950/2960 we have also seen that the buffering is done differently.

Thank you once again.

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