Communication Between Networks How the Internet Got Its Name

Addressing to get Out of Town MAC Addresses used for Local Traffic Hierarchical Addressing Needed for inter- network traffic. (Think Zip Codes or Phone #).Zip Codes Network Layer Protocols:  IP: Early 1980s, ARPANet, used with TCP  IPX: Late 1980s to 90s. 32-bits for network + MAC  Routing Layer in DECnet: 1975 –  Path Control Layer in SNA

Internet Protocol Version 4 (IPv4) What’s in a Name?  All Internet Names (i.e. alllinksvt.com) convert IP Address (using Domain Name Service) 32-bit address, divided into 4 8-bit sections  A.B.C.D (i.e )  Numbers can be between 0 and 255 (8-bits)  Part of the address identifies the Network, the other part identifies the host.

Networks and Hosts IP Network Addresses are assigned using IP Address and Subnet mask. Subnet mask defines network and host portions. Example: IP Addr Netmask255 0O Network Host

Special IP Addresses Private IP Addresses:  Do not Route on Internet /8 (i.e. netmask= ) /16 (i.e. netmask= ) x.x/24 (i.e. netmask= ) These Addresses are used on LANS. Routers translate these to routable IP Addresses using Network Address Translation Without Private Address we would be out of IP Addr. Without Private Address we would be out of IP Addr

Network Address Translation Router translates internal (private) address to external (public) IP Address. Typically this is a many to one translation.  All external communication uses Routers WAN Address.  Router keeps a table of connections in order to route correctly.  Helps security by obscuring LAN IP Addresses  You can’t attack what you can’t see.

Where do IP Addresses Come From? Globally: Internet Assigned Numbers Authority (IANA)Internet Assigned Numbers Authority Regional:  American Registry for Internet Numbers (ARIN) for North America and parts of the Caribbean American Registry for Internet Numbers  RIPE Network Coordination Centre (RIPE NCC) for Europe, the Middle East and Central Asia RIPE Network Coordination Centre  Asia-Pacific Network Information Centre (APNIC) for Asia and the Pacific region Asia-Pacific Network Information Centre  Latin American and Caribbean Internet Addresses Registry (LACNIC) for Latin America and parts of the Caribbean region Latin American and Caribbean Internet Addresses Registry  African Network Information Centre (AfriNIC) for Africa African Network Information Centre

Configuring IP Addresses Can be Set Manually  IP Address  Subnet Mask  Default Gateway  DNS 1, DNS2 Can be set by Dynamic Host Configuration Protocol Server.  A range of LAN addresses is set aside  DHCP Server “Leases” these out.

Host-Based Routing Decision

Routers: Getting There from Here Hop by Hop Routing Routers Build Routing Tables  Network ID  Cost  Next Hop  Quality of Service  Filtering  Interface

Routed vs Routing Protocols Routed Protocols are protocols that get routed.  Web   IPX Routing Protocols define how and what routers share  Routing Information Protocol (RIP)  Open Shortest Path First (OSP)  Cisco Proprietary: IGRP, EIGRP, BRP

What do Routers Do? Operational  Forward Packets towards destination  Access Control (Firewall Functions) Types of Routes  Static: non-adaptive, created manually.  Distance-Vector RP: Cost calculated for each path  Link-State: creates a (flood) map of network  Path-Vector Protocol: Good for large inter-domain routing

Routing Table