ES 101. Module 2 IP Addressing & Routing

Last Lecture Wide area networking Definition of “packets”

This Lecture TCP/IP Architecture Internetworking/routing Internet Protocol (IP)

History TCP/IP was first developed by the Advanced Research Projects Agency (ARPA) in 1969, and implemented as a test internetwork –Known as the “ARPANET” –ARPA is now known as DARPA The ARPANET was originally utilized to interconnect a small number of government agencies and universities ARPANET has evolved into what we now know as the Internet

Internetworking Definition Link multiple local area networks (LANs) together Route and deliver data between devices on different local area networks These mechanisms are provided by the TCP/IP protocols, which are divided into different protocol “layers”

TCP/IP Protocol Suite Layer 5 Layer 4 Layer 3

Internetworking The Internet is composed of a “network of networks” interconnected by routers Routers determine how to forward packets to the destination computer This routing is accomplished via two types of addressing: –Network Number –Computer (host) number on a given network

Internetworking Architecture

Internetworking Schematic PSTN

Internet Protocol (IP) IP Version 4 (IPv4) is utilized today Understanding IP addressing is fundamental to understanding routing We must understand network numbers, and IP addressing before we proceed any further

IP Address Format We will first review IP addressing in order to understand how the routing process works IP utilizes a 32 bit (4 octet) source and destination address IP addresses identify both the network number and the host address –This is accomplished via a “subnet mask” –More on this later…. IP addresses are commonly expressed in “dotted decimal” notation For humans, dotted decimal notation is easier to remember than a 32 bit binary number!!!

IPv4 Header

IP Address Usage IP addresses are global These IP addresses are managed by the Internet Assigned Number Authority (IANA) – Blocks of addresses are assigned to organizations like Vanderbilt This allows a unique IP address and network number to be assigned to each host and network on the Internet

Dotted Decimal Notation The 32 bit address is divided into four octets of 8 bits, with each octet written as a decimal number –Each octet can have a value from 0 to = 256, with numbers ranging from “0” decimal to “255” decimal –Example: Part of the binary IP address is utilized to define the Network ID The remainder of the binary address is utilized to indicate the Host ID The net mask defines the boundary between the Network ID and the Host ID

Net Masks It is necessary to determine where the network address ends, and the host address begins This is accomplished by the use of a net mask –Net masks are indicated by the use of “255” and “0” in dot-decimal notation “255” decimal equals “ ” binary “0” decimal equals “ ” binary –Example: This designation allows easy determination of network numbers and host IDs by a “bitwise and” mathematical operation

Subnet and Host ID Determination

Network Classes The IETF defined network address “classes” –Organizations originally registered for IP address space, and were assigned an address class, based on their anticipated IP usage –This is no longer the case, since IP addresses are becoming scarce This subject is beyond the scope of this class Default IP address classes: –Class A Subnet Mask = (3 octets for Hosts) –Class B Subnet Mask = (2 octets for Hosts) –Class C Subnet Mask = (1 octet for Hosts) Some bits in the host and network address space are reserved

Network Class Usage Classes A, B, and C are the most common Class D is reserved for multi-casting Class E is reserved for experimentation and development

Default Network Address Formats

Class Address Ranges First Octet of the Network Address Note: 0.X.Y.Z, 127.X.Y.Z, and 255.X.Y.Z are all reserved

Reserved IPv4 Address Values First Octet Decimal 255 (all binary 1s) is used for net masking as discussed previously Decimal 127 is used for the loopback, or localhost address –Helps in troubleshooting

Introduction to Routing Routers are essentially the “post office” of the Internet IP packets are best viewed as a “post card” –Source address –Destination address You drop your post card into a mailbox, and it comes out at the destination –You don’t care how it gets there –Routers determine where to send packets by “routing tables” The IP address is composed of two parts –Host ID (analogous to the street address) –Network number (analogous to the zip code)

Default Gateway Routers are sometimes known as “gateways” In order for your computer to transfer information to another machine, it must have a “default gateway” in the network settings If the computer needs to send info to foreign networks, it sends the info to the default gateway The network of routers handles everything from there

Internetwork Example

Routing Table Rules If a network is locally attached, no “Next Router” information is entered for that network number in the routing table If a network is not locally attached, the router must “know” what the next hop in the route is –This next hop IP address is entered into the routing table –This can be done automatically or dynamically Dynamic routing is beyond the scope of this class Each router has a routing table, which defines the next hop IP address for all network numbers on the Internet

Routing Table Example

Routing Tables - Router 1

Routing Tables - Router 2

Routing Tables - Router 3

Next Lecture(s) Domain Name System Higher layer protocols