© NOKIADEFAULT.PPT / / AO page: 1 IP in LANs

© NOKIADEFAULT.PPT / / AO page: 2 LAN Technologies Ethernet - 10 Mbps, 100Mbps Fast Ethernet, Gigabit Ethernet Cable TV LANs Wireless LANs Token Ring, Token Bus FDDI ATM LANE, MPOA

© NOKIADEFAULT.PPT / / AO page: 3 Ethernet Principles Originally utilized shared media Operates on almost any media: IEEE physical layer specifications 10BASE5 Thick Coax 10BASE2 Thin Coax 10BASE-T Twisted Pair 10BROAD35 CATV wire 10BASE-F Fibers

© NOKIADEFAULT.PPT / / AO page: 4 Ethernet medium specifications 10BASE5, 0.5" coax bus transceiver and drop cable required Max length of the bus is 500 meters

© NOKIADEFAULT.PPT / / AO page: 5 Ethernet Medium Specifications - cont 10BASE2, thin 0.25" coax Hosts are connected directly to the thin coax bus Bus max. 200 meters long susceptible to any faults in the cable or hosts' network equipment

© NOKIADEFAULT.PPT / / AO page: 6 Ethernet Medium Specifications - cont 10BASE-T twisted pair cable Hosts connected to a HUB At present most popular installation

© NOKIADEFAULT.PPT / / AO page: 7 Ethernet Medium Specifications - cont 10BASE-F Fibers especially used between HUBs and LAN core 2km link length in Point-to-Point connections A pair of fibers needed for single link - one for transmission and other for receiving Star topology: Up to 33 stations with 1 km link length

© NOKIADEFAULT.PPT / / AO page: 8 Ethernet IEEE frame format Ethernet is connectionless, frame exchange protocol Each station has unique 6 octet long address Frame Size max octets min 512 bits |Preamble(7)|SFD(1)|Destination addr(6)|Source addr (6)|Length(2)|Data(<1500)|Pad|CRC(4) |

© NOKIADEFAULT.PPT / / AO page: 9 Ethernet CSMA/CD IEEE Medim Access Control (MAC) CSMA/CD Carrier Sense Multiple Access / Collision Detection Fairly simple algorithm: Listen to the network - wait until media is free Wait interframe gap time If still free, start sending - simultaneously monitor received signal If collision is detected, transmit jam sequence, wait random time and re- start algorithm Min. packet size and max. link length defined so that collisions detected

© NOKIADEFAULT.PPT / / AO page: 10 Ethernet LAN architecture Bridge - a transparent layer 2 device that interconnects several segments Many benefits Security Performance Reliability Structure

© NOKIADEFAULT.PPT / / AO page: 11 Ethernet Hubs 10BASET twisted pair from host to hub Usually Fiber link from hub to LAN backplane Better structureand security easier to install and maintain

© NOKIADEFAULT.PPT / / AO page: 12 Ethernet Switching Switching HUB - a HUB operating like learning bridge FIFO-buffered backplane bus: Hub is able to transmit several frames through the hub concurrently Usually dual-speed: Configurable 10Mbps and 100Mbps ports Dedicated 10Mbps

© NOKIADEFAULT.PPT / / AO page: 13 Ethernet Switching Ethernet Switches used increasingly to replace routers Switching much faster than routing Also Routing Switches available that combine Router and Switch functionality Route once, switch following frames

© NOKIADEFAULT.PPT / / AO page: 14 Address Resolution Protocols Underlying network is not aware of IP ARP used to bind IP addresses to MAC addresses RFC826: ARP protocol for Ethernet ARP Solves MAC addresses by broadcasting a ARP request: source IP address source MAC address destination IP address empty space for destination MAC address Reverse ARP - diskless host wants to know its IP address

© NOKIADEFAULT.PPT / / AO page: 15 DHCP Used for similar operation as RARP Supports three IP address mechanisms: automatic dynamic manual Decreases amount of IP-addresses needed in LAN

© NOKIADEFAULT.PPT / / AO page: 16 DHCP - cont Messages: DHCPDISCOVER - Client broadcast to locate available servers. DHCPOFFER - Server to client in response to DHCPDISCOVER with offer of configuration parameters. DHCPREQUEST - Client broadcast to servers requesting offered parameters from one server and implicitly declining offers from all others. DHCPACK - Server to client with configuration parameters, including committed network address. DHCPNAK - Server to client refusing request for configuration parameters (e.g., requested network address already allocated). DHCPDECLINE - Client to server indicating configuration parameters (e.g., network address) invalid. DHCPRELEASE - Client to server relinquishing network address and cancelling remaining lease.

© NOKIADEFAULT.PPT / / AO page: 17 applied ARP usage A Proxy-host that is attached to LAN and replies to ARP request targeted to hosts attached behind the Proxy can be utilized in simple Firewalls to create private local sub-net without need to allocate "real" IP-addresses by a host that tunnels IP packets through some other network technology

© NOKIADEFAULT.PPT / / AO page: 18 LAN development and markets 100 Mbps Fast Ethernet, included in IEEE compatible with 10Mbps Ethernet compatible with 10Mbps Cabling link lengths reduced Gigabit Ethernet, IEEE 802.3z standardization in process especially to be used on fiber links LAN backplane Compatible with 10Mbps frames

© NOKIADEFAULT.PPT / / AO page: 19 Markets

© NOKIADEFAULT.PPT / / AO page: 20 LAN Markets