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TCP/IP Design Overview. objectives. Describe aspects of design relating to TCP/IP networks Understand limitations inherent in IP addressing Distinguish private from public network addressing Describe the purpose of IP subnetting Describe the function of internet routing protocols.
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objectives • Describe aspects of design relating to TCP/IP networks • Understand limitations inherent in IP addressing • Distinguish private from public network addressing • Describe the purpose of IP subnetting • Describe the function of internet routing protocols
Design Overview • Physical network • Logical network • Every physical network requires at least one logical network number to allow hosts on other networks to locate and identify this segment Logical Network 10.1.0.0 Logical Network 10.2.0.0
IP Addressing • IP addresses are 4-byte logical representations written in dotted-decimal notation • Each address contains a network part and a host part • Public IP addresses are licensed and private IP address ranges are universally available IP address Network Host 10.16.127.104 10. 16.127.104 131.16.82.97 131.16. 82.97 195.31.72.123 195.31.72. 123
IP addresses • 4 classes of IP address • (netid, hostid) pair; 32 bit • Class A : 128 network, 16M hosts • Class B : 64K networks, 64K hosts • Class C : 2M networks, 254 hosts • Class D : multicast (basically not used) • public IP addresses to be assigned by NIC
IP Subnetting • Subnetting involves borrowing bits from the host part to expand the network part • A subnetting policy is locally administered to provide greater traffic control IP address Network Host 10.16.127.104 10. 16 . 127.104 131.16.82.97 131.16. 82 . 97 131.16.82.97 131.16. 82.96 1
Addressing Considerations • Choice of addresses • Public (InterNIC assigned) • Private (RFC 1918/1597) • Address translation • Automatic address assignment • - DHCP/DNS servers • Address organization to support scalable networks • - Address summarization and CIDR blocks
Routing Protocols • Routers are packet switches that forward traffic based on Layer 3 logical addresses • Routing protocol updates are exchanged by routers to learn about paths to other logical networks • Each routing protocol offers features that can make it desirable as part of an internetwork design I know about: I know about: Network A Network X X A Network B Network Y Network C Network Z Routing update B Y Exchanges network knowledge C Z
Types of Routing Protocols • Routing protocols function as • Gateway discovery • Interior routing • Exterior routing • Path determination is based on • Distance vector • Link state • Path modification is based on • Static • Dynamic
Types of Routing protocols • 2 types - distance vector and link vector • distance vector routing protocol, e.g., RIP • each router periodically transmit its routing table to all neigbours, normally every 30s • upon receiving routing table, neighbour routers recalculate their own routing tables • route selected based on the minimum number of hops between 2 routers • create heavy traffic & converge slowly if link fails
Types of Routing protocols (Cont.) • link state routing protocol; e.g. OSPF • based on link state, i.e., status of router interfaces • routers discover neighbours by sending HELLO packets every 10 sec • link state advertisement (LSA) sent when link state changes, i.e.,new router, new route, link failure etc. • small packets; converge quickly on link failure • cost-based; consider distance and bandwidth • better scalability and stability
Routing Considerations • Protocol selection based on conversion complexity • Convergence time and bandwidth consumption • Addressing flexibility (support of VLSM and route summarization) • Open standard vs proprietary • Route redistribution between different protocols
