nanog mailing list archives
Re: switch speed question
From: Tom Storey <tom () snnap net>
Date: Thu, 26 Feb 2009 00:43:01 +1030
Were not considering anything other than basic switching in this scenario, as is my understanding.
2 hosts will create 2gbps of traffic as each host is inputting 1gbps into the switch (just multiply it by 12 to give you 24 ports). 3 hosts will create 3gbps of traffic as each inputs 1gbps into the switch (e.g. each host could be sending 500mbps to each of the other hosts). And thus and so forth. :-)
You can only input a maximum of 24gbps into the switch, which means that only 24gbps will cross the backplane.
Yes there is 48gbps if you combine tx and rx of each port, but traffic only has to cross the backplane once, from rx on one port to tx on another.
Sorry if I have hijacked this thread from the OP. :-) Tom On 26/02/2009, at 12:18 AM, David Barak wrote:
Doesn't that assume that the communicarion is unidirectional?If two hosts are exchanging 1Gbps flows, the traffic across the bus will be 2Gbps, right?And of course, this doesn't include any bus-intensive operations like multicast or things which require cpu processing - those can consume a lot more resources than the input rate of the port.-David Barak Tom Storey wrote:They were talking about a simple scenario where a bit that enters a port will leave a port. With 24 gigabit ports, for all intents and purposes, you will only ever have 24 gigabits at the most traversing the backplane.Not every bit in results in just one bit out. Broadcast, multicast, flooding for unknown MACs (or switching failures), ...
Current thread:
- Re: switch speed question, (continued)
- Re: switch speed question Brian Feeny (Feb 23)
- RE: switch speed question Bruce Grobler (Feb 24)
- Re: switch speed question Eric Gearhart (Feb 24)
- Re: switch speed question Tony Varriale (Feb 24)
- Re: switch speed question Roy (Feb 24)
- Re: switch speed question Chris Adams (Feb 24)
- Re: switch speed question Eric Gearhart (Feb 24)
- RE: switch speed question Holmes,David A (Feb 24)
- Re: switch speed question deleskie (Feb 24)
- Re: switch speed question Tom Storey (Feb 25)
- Re: switch speed question David Barak (Feb 25)
- Re: switch speed question Tom Storey (Feb 25)
- Re: switch speed question Nathan Ward (Feb 25)
- Re: switch speed question Dave Israel (Feb 25)
- Re: switch speed question David Barak (Feb 25)