Cabletron Systems MMAC-5FNB Networking Manual

Also see for MMAC-5FNB: Overview and setup guide

Contents

Cabletron Systems MMAC-5FNB Networking Manual Manual pdf 96 page image

Ethernet5-16SegmentationWe may also segment the network logically by geographic location. This makes iteasier to troubleshoot and expand existing networks. Geographic segmentation isusually an inferior segmentation solution in comparison with segmentation byrelated function or access. The increase in logical layout that can be accomplishedusing this method is frequently overshadowed by decreased networkperformance as a higher percentage of traffic is sent through bridges.Now that you have learned the basics of single-level repeated Ethernet, we canprogress to the next level of expertise, Bridged Ethernet. Bridges are network“traffic control” devices which affect the way that information moves from onenetwork to another. Bridges segment networks, while still allowing traffic thatneeds to pass between two networks to pass. By doing this, bridges keep trafficlocal, freeing a bridged network from the effects of traffic on its distant neighbors.A bridge connects networks in a similar fashion to a repeater, but a bridge goes afew steps further, monitoring the individual data packets to determine if theyneed to be sent to other segments or not, and regenerating, retiming, andreclocking the signal to increase its ability to be retransmitted.BridgesA bridge is a device that can be added to a network to allow expansion beyondthe limitations of IEEE 802.3. If an Ethernet network has a repeater hop of fourrepeaters or a round trip propagation delay near the 51.2μs maximum, a bridgecan be used to build an extended network. Ethernet bridges read in packets anddecide to filter, discard, or forward based on the destination address of the packet.The simple forward/filter decision process allows a bridge to segment trafficbetween two networks, keeping local traffic local. This process increases theavailability of each network while still allowing traffic destined for the oppositeside of the bridge to pass.When multiple Ethernet networks are created within a single chassis, they alloperate as separate networks. Although a configuration may support threeEthernet networks in a single modular chassis, they are considered separate fromone another and do not exchange information. This effectively means that anEthernet station on Ethernet Channel A is not able to communicate with anEthernet station on Ethernet Channel B in the same chassis.It is the function of bridges to connect separate networks while maintaining theseparation between them. An Ethernet bridge acts in much the same way as abridge in the physical world. It provides a single point of access between bothnetworks, allowing traffic which must cross to the other network to do so, whilekeeping unrelated network activity on one side of the bridge from impacting theoperation of the network on the other side of the bridge.