3Com 3824 Implementation Manual

Also see for 3824 - SuperStack 3 Switch: Getting started guide

Contents

24 CHAPTER 2: OPTIMIZING B ANDWIDTH■ Before removing an entire aggregated link, you must disable all theaggregated link ports or disconnect all the links, except one — if youdo not, a loop may be created.■ When manually creating an aggregated link between two devices, theports in the aggregated link must not be physically connectedtogether until the aggregated link has been correctly configured atboth ends of the link. Failure to configure the aggregated link at bothends before physically connecting the ports can result in a number ofserious network issues such as lost packets and network loops.Traffic Distribution and Link Failure on Aggregated LinksTo maximize throughput, all traffic is distributed across the individual linksthat make up an aggregated link. Therefore, when a packet is madeavailable for transmission down an aggregated link, a hardware-basedtraffic distribution mechanism determines which particular port in the linkshould be used. The traffic is distributed among the member links asefficiently as possible.To avoid the potential problem of out-of-sequence packets (or “packetre-ordering”), the Switch ensures that all the conversations between agiven pair of endstations will pass through the same port in theaggregated link. Single-to-multiple endstation conversations, on theother hand, may still take place over different ports.If the link state on any of the ports in an aggregated link becomesinactive due to link failure, then the Switch will automatically redirect theaggregated link traffic to the remaining ports. Aggregated links thereforeprovide built-in resilience for your network.The Switch also has a mechanism to prevent the possible occurrence ofpacket re-ordering when a link recovers too soon after a failure.Aggregated Link —ManualConfigurationExampleThe example shown in Figure 6 illustrates an 8 Gbps aggregated linkbetween two Switch units, (that is, each port is operating at 1000 Mbps,full duplex).