NETWORK LAYER IP Addressing 1

ANNOUNCEMENT: Rescheduled  NO PRACTICAL SESSIONS ON TUESDAY 22, November 2010  Rescheduled sessions: MONDAY: November 21, 2010, NW202  PRAC GROUP 1: –  PRAC GROUP 2: –  PRAC GROUP 3: –  PRAC GROUP 4: –

Review - Local Area Networks  So far, we have only discussed local area networks (LAN),  Underlying physical medium is shared.  Data sent to a LAN goes to ALL of the computers on that LAN.  The size of LANs is limited. An electrical signal can only travel a limited distance. LAN size can be extended by using Repeaters 3

Review - Wide Area Network (WAN)  Network that covers large geographic area  A Wide Area Network (WAN) is made up from interconnected LANs  Network devices such as Switches or Routers can be used to join LANs together to form a WAN  Any examples?  Internet… LAN Cat5 UTP WAN ISP Router

TCP/IP Protocol Stack  Two computers, anywhere in the world can communicate, even when not directly connected.  TCP/IP - a suite of protocols, is the reference model that provides specifications for the Internet  IP protocol operates at Layer 3 or Internet/ Network layer  TCP works at Layer 4 5 TCP IP Protocol

Network Layer  Network layer is responsible for moving data through a set of networks (Figure 1).  Router (R) helps to connect different networks together  A, B, C, D are different networks (Figure 1)  IP protocol operates at Network Layer  IP protocol uses IP Address to identify a PC uniquely in the Internet. 6 R R R - Router RR R R R Figure 1

Network Addressing: Analogy with telephone numbers 7  Network addresses are similar to Phone numbers  Area Code / Phone Number  831 –  Network address helps to identify path (route) through network cloud from start to destination.  Each network (red ring in the figure 2) has an address 1.0 as 1 is the common number between 1.1, 1.2, 1.3  Each host (PC) within the network has an address (blue ring), e.g., 1.3 Router Figure 2 Figure 1

Why two Addresses for computer on network? Both Layer 2 (Ethernet) and Layer 3 (IP) Addresses are needed:  Layer 2 / MAC address  Physically burned into the NIC  Doesn’t change  The device’s real identity  Layer 3 / Protocol address  Configurable Can be changed  The device’s “mailing” address  Needs to change when device is moved connected to a network having different network address 8

Review: What is the MAC and IP Address on my computer? 9

Flat versus Hierarchical 10  Layer 2 - Flat addressing schemes  Next available  Social Security Number  MAC addresses  Layer 3 - Hierarchical addressing schemes  Phone numbers  ZIP codes  IP addresses

IP Addresses 11  Older Technology - Classful IP Addressing  Defines IP address as belonging to one of the available five classes: Class A Class B Class C Class D Class E  Current technology - Classless IP Addressing

IP Address 12 IP Addresses are 32 bits. Divide into four 8 bit sections (octets). Convert from binary to decimal.

Classful IP Addressing 13  Five different classes of IP addresses  A, B, C, D, E  Class A, B and C are primary classes Used for assigning IP addresses  Class D, E used for special purposes  Class D for multicast E.g., Videoconferencing  Class E addresses are reserved for experimentation

IP Address Classes 14 Network ID Host ID Network IDHost ID 8 16 Class A 32 Class B 10 Class C 110 Multicast Addresses Class D 1110 Reserved for experiments Class E  Look at the first group of numbers in the dotted decimal notation  ClassRange  A0-127  B  C  D  E Which Class has the largest Host ID and how many bits long? Which class has the largest Network ID and how many bits long?

Subnet mask - NetID /HostID boundary  Every machine on the network must know which part of the host address will be used as netid and hostid.  Subnet mask identifies the boundary between netid and hostid  Which class has more hosts?  Which class supports more networks?  Default subnet masks are  Class A :  Class B :  Class C : Network Host Network Host Network Host 1st octet2nd octet3rd octet4th octet Class A Class B Class C

Find Network/Host ID from IP Address 16  Logical ‘AND’ IP address and subnet mask to get Net-ID.  E.g. IP address is , Find Network ID using default subnet mask of for class C Find the binary representation of IP address and subnet mask Logical ‘AND’ with subnet mask IP Address Subnet mask for Class C Network ID  Convert binary to decimal value  Network ID: AND

17 Hierarchy in IP addressing IP addresses are hierarchical. Conceptually each IP address is a pair Divided into a prefix and a suffix –Prefix (net-id) identifies network to which computers are attached. –Suffix (host-id) identifies computers within that network.

RD-CSY /08 18  Loopback address   Network address  IP address with all host bits set to 0 Example: , subnet mask:  Broadcast address  IP address with all host bits set to 1 Example: , subnet mask: Special IP Addresses

RD-CSY /0819 Private IP Addresses  Private IP Addresses cannot exist on the public Internet.  Name Address Translation (NAT) used to give data packets a “legitimate” IP source address. Class B: to (In the 3 rd Octet, the 128, 64, and 32 bit are off. The 16 bit is on.) Class C: to (256 separate Class C Addresses) Class A: (Favored by large enterprises because of its flexibility)

Grouping Devices into Networks and Hierarchical Addressing 20  Divide a large network into subnetworks  Geographical area  Functionality Departments Admin, HR…

IP addressing example What is the class of IP address in the figure? Which network device is connecting the two networks?

Subnet Masks – Your Turn! 22  Underline the network portion of each address: Network Address Subnet Mask / / /16  What is the other portion of the address?

Subnet Masks – Your Turn! 23  Underline the network portion of each address: Network Address Subnet Mask / / /16  What is the other portion of the address?  Host Addresses