CSC 412 – Networking Scott Heggen. Agenda Today The Network Layer (Chapter 5) Discussion on A2: The Data Link Layer Thursday Q2: The Networking Layer.

CSC 412 – Networking

Scott Heggen

Agenda

Today The Network Layer (Chapter 5) Discussion on A2: The Data Link Layer

Thursday Q2: The Networking Layer A2: The Data Link Layer Due

Navigating a Network

Say you want to drive from Berea, KY to Beverly Hills, CA. How would you get there?

Networks use much of the same process: Data is passed around the local network To leave the network, data must reach the gateway

router The gateway router decides which route is best to

reach the destination, and forwards the packet to the next router

The process continues from router to router until the packet reaches it’s destination’s gateway router

The packet is passed around the receiver’s local network until it reaches it’s destination

Routing

Routing is the process by which data is passed through specific networks until it reaches the destination computer’s network (and eventually, the destination computer)

The Postmaster General

Every mailing address in the U.S. has a unique address, consisting of a zip code, state, city, and address

In a network, every device has a unique address, known as an Internet Protocol (IP) Address

The IP protocol defines addressing, as well as routing

IP Header

IP defines a 20-byte long header 4 bytes are used for the source IP address 4 bytes are used for the destination IP address The other 12 bytes are used for other

functions, which we will cover later

Comparing Protocols

HTML Data

HTTP Header Data

DataTCP Header

DataIP Header

DataEthernet Header

Layer 4: TransportSegment

Layer 3: NetworkPacket

Layer 2: Data LinkFrame

IP routing

What kind of addresses does OSI Layer 2 use?

What kind of addresses does OSI Layer 3 use?

When do we actually use these addresses?

MAC vs. IP

Why not use MAC addresses for everything?

IP Addresses

An IP address consists of 32 bits: 00001000 00101000 00011101 01110000

To make it easier to read, IP addresses are typically expressed in dotted decimal format: 8.40.29.112

Each decimal value in an IP address is called an octet; one IP address consists of 4 octets

For now, IP addresses will be in dotted decimal form; later, you will need to be able to convert between dotted decimal and binary

Binary / Decimal Conversions

Let’s practice. Convert the following binary values to dotted decimal: 01001010 . 11000101 . 00100010 . 10000010 11010011 . 01010101 . 10101010 . 11111011 11001100 . 00110011 . 00011100 . 11100011

And dotted decimal to binary: 123.45.67.89 254.0.12.99 99.100.128.129

IP Networks

All devices in a LAN should have the same network numbers

This allows routers to easily identify where sets of IP addresses are located

IP Routing

Does a router need to know where every unique IP address is located?

A router only needs to know where to forward a packet destined for each set of addresses

These groups of addresses are known as IP Networks

Network Numbers

A portion of an IP address defines the IP network

This portion, followed by binary zeros, is known as the network number I.E. IP Address 3.3.3.3 belongs to the network

number 3.0.0.0

Classes of Networking

Three classes of networks:

10 . 20 . 30 . 40

Classful IP Addressing

Classful IP Addressing

Routing

R1 and R2 need to know: How to route a packet to the network

8.0.0.0 How to route a packet to the network

130.4.0.0 How to route a packet to the network

199.1.1.0

Classful IP Addressing

What if one network was a Class A network with a network address of 8.0.0.0, and another network was a Class B network with a network address of 8.1.0.0?

The IP protocol defines a range of network numbers for each class, to avoid overlaps

00…

10…

11…

IP addresses

Identify the Class, Network number, and range of IP addresses:

192.168.1.1 10.1.4.3 126.0.0.0 255.255.255.255

Reserved Classes

IP Addressing Fundamentals

Rules Concerning IP Addresses They must be unique inside a particular network They are 32-bit numbers They are typically written and displayed as

dotted-decimal numbers (e.g., 192.168.1.2) Each decimal number in a dotted-decimal IP

address represents 8 bits of the IP address (often called an octet)

Each of the four octets in an IP address are between decimal 0 and 255

IP Addressing Fundamentals

IP Network Rules: Devices on the same LAN should use IP

addresses in the same group; the group is called an IP network

Devices on different LANs that are separated by at least one router should use IP addresses in different IP networks

IP addresses must be individually unique inside the same IP network

IP Networks

IP Classes

Three networks: What class is each? Is this a legal network?

Network and Broadcast Address

When all the host numbers are binary 0’s, the address is considered the network address

When all the host numbers are binary 1’s, the address is considered the broadcast address

All the values between the network and broadcast addresses are considered valid, usable IP addresses for that network

Network address: 192.168.1.0Broadcast address: 192.168.1.255

IP Addressing

Determine the network address, broadcast address, and valid range of IP addresses for each IP address: 24.92.0.0 203.0.0.255 1.1.1.1 142.255.255.255 222.255.255.0 100.0.0.0

IP Addressing

Determine: The number and location of each network The network number for each network The broadcast IP address for each network The range of valid IP addresses in each network

192.168.7.254135.16.65.254

F0/1192.168.7.2

F0/2135.16.8.33

F0/2222.130.6.2

F0/1222.130.6.9

F0/2101.1.10.4

F0/1101.7.10.4

IP Addressing

Determine what is wrong with the following network:

192.168.7.255135.16.8.33

F0/1192.168.7.2

F0/2135.16.8.33

F0/2222.130.6.2

F0/1222.130.6.0

F0/2101.1.10.4

F0/1101.7.10.4