On Thursday 18 September 2008 13:54:34 [EMAIL PROTECTED] wrote: > Though if you looked at the white papers, you will notice > that there are some areas where extreme seems a few steps > ahead. > > - Back plane capacity
Well, this depends on your applications and budget. It's quite easy to get a 1U or 2U switch today that will support from as little as 32Gbps to as high as 320Gbps, over 48 ports. Depending on the requirements (i.e., number of ports needed), the switch could be oversubscribed or not. Oversubscription assumes all ports will be occupied and that all customers will be running at line rate, i.e., 1Gbps. This is quite rare for circumstances where 1U switches are used. Where you need this kind of throughput without dropping frames, you'd be looking at slightly bigger switches that have an independent switch fabric that is field-upgradeable - meaning you can start low and upgrade up to the switch's maximum capacity. > - Number of Vlans supported. What has your experience been? > - Size of Jumbo frames supported etc. The big names today all support jumbo frames (Cisco, Foundry, Force10, Extreme, Juniper, e.t.c.). The problem I have with Cisco is that they don't support jumbo frames in switches that only provide 10/100Mbps ports - it only applies to their 10/100/1000Mbps port switches. The same goes for their routers, but with the exception of the larger routers, i.e., 7600, XR 12000, CRS-1. > Not all these have been practical to us yet though we are > heading there. My advice would be (on the 3 issues you mention, above): * 1U switches are good enough for most applications with regard to switching capacity - if you need more growth, consider kit that has a field-upgradeable swith fabric, e.g., Cisco 6500 series, Juniper MX series, Foundry MLX series, e.t.c. * Depending on your design, you'll probably run out of ports before you do VLAN ID's, unless you do a lot of trunking. VLAN ID exhaustion is a problem you can fix with Q-in-Q, or my personal favorite, EoMPLS. 802.1Q doesn't scale for Metro-E environments, which is where VLAN ID runout is a big problem. * Be sure to find kit that will support jumbo frames, i.e., 9,216 bytes. If your customers can push it, jumbo frames help use more bandwidth for less CPU (more data carried in each frame). You also have the freedom of adding services and eating more into the Ethernet frame without worrying about it. This is quite helpful if you look at MPLS' advanced features. We do this also for our SDH-based WAN links (4,470 to 9,000 bytes). Cheers, Mark.
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