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IP in LANs

IP in LANs. LAN Technologies . Ethernet - 10 Mbps, 100Mbps Fast Ethernet, Gigabit Ethernet Cable TV LANs Wireless LANs Token Ring, Token Bus FDDI ATM LANE, MPOA. Ethernet Principles. Originally utilized shared media Operates on almost any media: IEEE 802.3 physical layer specifications

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IP in LANs

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  1. IP in LANs

  2. LAN Technologies • Ethernet - 10 Mbps, 100Mbps Fast Ethernet, Gigabit Ethernet • Cable TV LANs • Wireless LANs • Token Ring, Token Bus • FDDI • ATM LANE, MPOA

  3. Ethernet Principles • Originally utilized shared media • Operates on almost any media: • IEEE 802.3 physical layer specifications • 10BASE5 Thick Coax • 10BASE2 Thin Coax • 10BASE-T Twisted Pair • 10BROAD35 CATV wire • 10BASE-F Fibers

  4. Ethernet medium specifications • 10BASE5, 0.5" coax bus • transceiver and drop cable required • Max length of the bus is 500 meters

  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

  6. Ethernet Medium Specifications - cont • 10BASE-T twisted pair cable • Hosts connected to a HUB • At present most popular installation

  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

  8. Ethernet IEEE 802.3 frame format • Ethernet is connectionless, frame exchange protocol • Each station has unique 6 octet long address • Frame Size • max. 1518 octets • min 512 bits +-------------+--------+----------------------+------------------+-----------+--------------+---+---------+ |Preamble(7)|SFD(1)|Destination addr(6)|Source addr (6)|Length(2)|Data(<1500)|Pad|CRC(4) | +-------------+--------+----------------------+------------------+-----------+--------------+---+---------+

  9. Ethernet CSMA/CD • IEEE 802.3 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

  10. Ethernet LAN architecture • Bridge - a transparent layer 2 device that interconnects several segments • Many benefits • Security • Performance • Reliability • Structure

  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

  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

  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

  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

  15. DHCP • Used for similar operation as RARP • Supports three IP address mechanisms: • automatic • dynamic • manual • Decreases amount of IP-addresses needed in LAN

  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.

  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

  18. LAN development and markets • 100 Mbps Fast Ethernet, included in IEEE 802.3 • 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

  19. Markets

  20. LAN Markets

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