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Unformatted text preview: icted with bridges: a spanning tree must be built to avoid cycles - Bridges work under a ﬂat address space (IEEE 802.x), no reachability aggregation => does not scale well - Bridges do not offer protection from broadcast storms (endless broadcasting by a host will be forwarded by a bridge) Routers + and Routers + Arbitrary topologies can be supported, cycling is limited by TTL counters in the IP header + Provide ﬁrewall protection against broadcast storms - Require IP address conﬁguration (not plug and play) - Require higher processing bandwidth Bridges do well in small (few hundred hosts) while routers are Bridges required in large networks (thousands of hosts) Ethernet Switches
Essentially a multi-interface Essentially bridge layer 2 (frame) forwarding, layer ﬁltering using LAN addresses large number of interfaces large often:individual hosts, staroften:individual connected into switch, each via a dedicated point-to-point connection; will always sense the medium as idle; no collisions ever! (so-called full-duplex ethernet switching) Switching: A-to-A and B-toSwitching: and B simultaneously, no simultaneously, collisions Ethernet Switches (cont d)
Ethernet Switches provide a combinations of shared/dedicated, Ethernet 10/100/1000 Mbps connections, Ethernet switches vary in size, with the largest ones incorporating a Ethernet high bandwidth interconnection network 10Gbps Ethernet (over ﬁber) already in work, key features include 10Gbps
support ONLY full-duplex, i.e. NO more collision resolution needed support a WAN form compatible with OC192 SONET => target low-cost SONET WAN replacement in Metro-applications !! (see www.lightreading.com for tradenews , industrial trend) Not an atypical LAN (IP network)
Dedicated Shared Summary comparison
Collision domain isolation bridges yes yes no routers yes no yes switches yes yes no no yes no plug & play optimal routing...
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This note was uploaded on 12/08/2010 for the course IEG IEG3310 taught by Professor Wingc.lau during the Spring '10 term at CUHK.
- Spring '10