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Unformatted text preview: in a token bus conﬁguration). Still, elaborate procedures to recover from lost token, etc. lost etc. LAN technologies
MAC protocols used in LANs, to control access to the channel MAC Token Rings: IEEE 802.5 (IBM token ring), for computer room, Token or Department connectivity, up to 16Mbps; FDDI (Fiber Distributed Data Interface), for Campus and Metro connectivity, up to 200 stations, at 100Mbps. Ethernets: employ the CSMA/CD protocol; 10Mbps (IEEE Ethernets 802.3), Fast Ethernet (100Mbps), Gigabit Ethernet (1,000 Mbps); by far the most popular LAN technology LAN Addresses and ARP
IP address: drives the packet to destination network IP network LAN (or MAC or Physical) address: drives the packet to the LAN (or address destination node s LAN interface card (adapter card) on the LAN local LAN 48 bit MAC address (for most LANs); burned in the adapter 48 (for ROM LAN Address (cont d)
MAC address allocation administered by IEEE MAC A manufacturer buys a portion of the address space (to assure manufacturer uniqueness) Analogy: Analogy: (a) MAC address: like ID card # (b) IP address: like postal address MAC ﬂat address => portability MAC IP hierarchical address NOT portable (need mobile IP) IP Broadcast LAN address: 1111………….1111 Broadcast ARP: Address Resolution Protocol
Each IP node (Host, Router) on the LAN has ARP module and Each ARP module Table (aka ARP cache) ARP Table: IP/MAC address mappings for some LAN nodes ARP some LAN < IP address; MAC address; TTL> < ………………………….. > TTL (Time To Live): timer, typically 20 min TTL ARP (cont d)
Host A wants to send packet to destination IP addr XYZ on Host same LAN, (A knows the dest. is in the same LAN by comparing the subnet mask with the dest. IP addr.) Source Host ﬁrst checks own ARP Table for IP addr XYZ Source If XYZ not in the ARP Table, ARP module broadcasts ARP pkt: If not in broadcasts ARP < XYZ, MAC (?) > ALL nodes on the LAN accept and inspect the ARP pkt ALL Node XYZ responds with unicast ARP pkt carrying own MAC Node unicast ARP addr: < XYZ, MAC (XYZ) > MAC address cached in ARP Table MAC cached in Routing Packet to another LAN
Say, route packet from source IP addr <126.96.36.199> to Say, destination addr <188.8.131.52> By consulting its subnet mask, the source host determines that By the dest. belongs to a...
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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