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 Layer 4: Transport Segment Layer 3: Network Packet Layer 2: Data Link Frame

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?

Network Interface Card (NIC) Every network interface in a computer needs an IP address to be allowed on the network Can a computer have more than one NIC? Does each NIC get it’s own IP address? Routers typically have multiple NICs Many servers come with multiple NICs also

IP Addresses An IP address consists of 32 bits: To make it easier to read, IP addresses are typically expressed in dotted decimal format: 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: And dotted decimal to binary:

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 belongs to the network number

Classes of Networking Three classes of networks:

Classful IP Addressing

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

Classful IP Addressing What if one network was a Class A network with a network address of , and another network was a Class B network with a network address of ? 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:

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., ) 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: Broadcast address:

IP Addressing Determine the network address, broadcast address, and valid range of IP addresses for each IP address:

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

IP Addressing Determine what is wrong with the following network: