NetworkRoutingI

NetworkRoutingI - Switching and Forwarding Switching and...

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1 Csci 232: Computer Networks Forwarding and Routing Network Layer Part I 1 Switching and Forwarding Network Layer Part I Switching and Forwarding Generic Router Architecture –F o r w a r d i n g T a b l e s : Bridges/Layer 2 Switches; VLAN Routers and Layer 3 Switches Forwarding in Layer 3 (Network Layer) Network Layer Functions Network Service Models: VC vs. Datagram ATM and IP Datagram Forwarding IP Addressing Network vs. host: address blocks, longest prefix matching Address allocation and DHCP IP Datagram Forwarding Model and ARP Protocol IP and ICMP Protocols, IP Fragmentation and Re-assembly Readings: Textbook: Chapter 4: Section 4.1; Csci 232: Computer Networks Forwarding and Routing Network Layer Part I 2 Logical View of a Router A E D C B F 2 2 1 3 1 1 2 5 3 5 Csci 232: Computer Networks Forwarding and Routing Network Layer Part I 3 IP Addressing: Basics • Globally unique (for “public” IP addresses) • IP address: 32-bit identifier for host, router interface Interface: connection between host/router and physical link – router’s typically have multiple interfaces – host may have multiple interfaces – IP addresses associated with each interface • Dot notation (for ease of human reading) 223.1.1.1 = 11011111 00000001 00000001 00000001 223 11 1 Csci 232: Computer Networks Forwarding and Routing Network Layer Part I 4 IP Addressing: Network vs. Host • Two-level hierarchy – network part (high order bits) – host part (low order bits) What’s a network ? (from IP address perspective) – device interfaces with same network part of IP address – can physically reach each other without intervening router 223.1.1.1 223.1.1.3 223.1.1.4 223.1.2.2 223.1.2.1 223.1.2.6 223.1.3.2 223.1.3.1 223.1.3.27 223.1.1.2 223.1.7.0 223.1.7.1 223.1.8.0 223.1.8.1 223.1.9.1 223.1.9.2 multi-access LAN point-to-point link Csci 232: Computer Networks Forwarding and Routing Network Layer Part I 5 “Classful” IP Addressing 32 bits 0network host 10 network host 110 network host 1110 multicast address A B C D class 1.0.0.0 to 127.255.255.255 128.0.0.0 to 191.255.255.255 192.0.0.0 to 223.255.255.255 224.0.0.0 to 239.255.255.255 7 71 5 2 33 1 • Disadvantage: inefficient use of address space; address space exhaustion • e.g., class B net allocated enough addresses for 65K hosts, even if only 2K hosts in that network Csci 232: Computer Networks Forwarding and Routing Network Layer Part I 6 Classless Addressing: CIDR CIDR: C lassless I nter D omain R outing • Network portion of address is of arbitrary length • Addresses allocated in contiguous blocks – Number of addresses assigned always power of 2
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2 Csci 232: Computer Networks Forwarding and Routing Network Layer Part I 7 Representation of Address Blocks • “Human Readable” address format:
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This note was uploaded on 10/25/2009 for the course CS 232 taught by Professor Susan during the Fall '09 term at GWU.

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NetworkRoutingI - Switching and Forwarding Switching and...

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