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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: exchange point media
>>>>> "ma" == Mikael Abrahamsson <[email protected]> writes: > I was under the impression that there is nothing magical about jumbo > frames and that there are no interoperational problems with them as long > as they're supported at all. Please correct me if I am wrong. I'm afraid you are wrong... all interfaces connected to a logical IP subnetwork should have the same MTU. For most Layers-2 there is a pretty well-established default such as 1500 for Ethernet, 4470 for FDDI (well for ATM many people use 4470 rather than the IETF suggestion of 9180). But for Gigabit Ethernet the only standard MTU is the Ethernet MTU (1500). For a new exchange point built on Gigabit Ethernet, it could be worthwhile to postulate a larger MTU such as 8192 or 9180 and make sure every participant actually uses exactly that. But most exchange points supporting GigE still provide bridging to legacy (Fast) Ethernet, on which larger MTUs are uncommon or not supported at all. And bridging between Layer-2s is similarly problematic to having different MTUs in a LIS, although I'm well aware that such configurations are being used in many places, and thanks to bridges that do clever stuff besides bridging this may even work more or less reliably. -- Simon.
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