Ch 3: Underlying Technologies (remainder) Lecture #5 Reminder - Exam 1 on Tuesday Dr. Clincy Lecture

CONNECTING DEVICES Dr. Clincy Lecture

Repeater Operates at the physical layer – layer 1 Receives the signal and regenerates the signal in it’s original pattern A repeater forwards every bit; it has no filtering capability Is there a difference between a regen or repeater and an amp ?? Dr. Clincy Lecture

Repeaters d For the architecture above, will a signal ever traverse through more than 2 repeaters ? Dr. Clincy Lecture

Hubs Hub – multi-port repeater Typically used to create a physical star topology Also used to create multiple levels of hierarchy For bus technology type networks, hubs can be used to increase the collision domain Dr. Clincy Lecture

Bridge Operates at both the physical and data link layers At layer 1, it regenerates the signal. At layer 2, it checks the Tx/Rx physical address (using a bridge table) Example Below: If packet arrives to bridge-interface #1 for either of the 71….. stations, the packet is dropped because the 71…. Stations will see the packet If packet arrives to bridge-interface #2 for either of the 71….. stations, the packet is forwarded to bridge-interface #1 With such an approach, the “bridged” network segments will acted as a single larger network What is a “smart” bridge ?? Dr. Clincy Lecture

Routers Show example where a decision is needed d d Is a 3-layer device: (1) at layer 1, regen the signals, (2) at layer 2, check physical address and (3) at layer 3, check network addresses Routers are internetworking devices Routers contain a physical and logical/IP address for it’s interfaces (repeaters/bridges don’t) Routers only act on the packets needing to pass through Routers change the physical address of the packets needing to pass through (repeaters/bridges don’t change physical addresses) Show example where a decision is needed d d Dr. Clincy Lecture

Routing example LAN 1 LAN2 Routers can change the physical address of a packet Example: as a packet flow from LAN 1 to LAN 2 In LAN 1, the source address is the Tx’s address and the destination address is the Router’s interface address In LAN 2, the source address is the Router’s interface address and the destination address is the Rx’s address LAN 1 LAN2 Dr. Clincy Lecture

You are a High Priced Network Consultant Marketing Dept Engineering Dept (Super Computer) Manufacturing Dept (Robots) d They want all departments to communicate with one another; you want the network to maintain top performance – which design would you recommend ? Which devices would you recommend for empty circles ? – the least cost solution is the best solution Dr. Clincy Lecture

Note: Lectures for Exam 1 just ended. We now start lectures for Exam 2 Dr. Clincy Lecture

Chapters 4 & 5 Addressing Dr. Clincy Lecture

IP ADDRESSING (Ch 4) Dr. Clincy Lecture

IP Addresses Internetworking Protocol (IP) of the Network Layer is responsible for uniquely identifying all devices and connections on the Internet The unique identifier is called an IP address IP address consist of 32 bits (for version 4) Keep in mind that, if a single device had multiple connections to the Internet, you would need an IP address for each connection Address space is 232 = 4,294,967,296 32-bit addresses In theoretical terms, 4,294,967,296 connections can be made to the Internet (not really true in real life) Dr. Clincy Lecture

IP Addresses The IP Address has 3 notations: Binary, Dotted-decimal and Hexadecimal Binary: 4 Octets: 01110101 10010101 00011101 11101010 Dotted-Decimal (or dot notation): For Dotted-Decimal, each number can range from 0 to 255 Hexadecimal: 0111 0101 1001 0101 0001 1101 1110 1010 75 95 1D EA 75951DEA Dr. Clincy Lecture

EXAMPLES Change the following IP address from binary notation to dotted-decimal notation: 10000001 00001011 00001011 11101111 Solution 129.11.11.239 Change the following IP address from dotted-decimal notation to binary notation: 111.56.45.78 Solution 01101111 00111000 00101101 01001110 Find the error, if any, in the following IP address: 111.56.045.78 Solution There are no leading zeroes in dotted-decimal notation (045). Change the following IP addresses from binary notation to hexadecimal notation: 10000001 00001011 00001011 11101111 810B0BEF16 Solution Dr. Clincy Lecture

IP Addresses: Classful Addressing When IP addressing was first started, it used a concept called “classful addressing”. A newer concept called “classless addressing” is slowly replacing it though. Regarding “classful addressing”, the address space is divided into five classes: A, B, C, D and E. Class # of addresses Percent of the Space A 231=2147483648 50% B 230=1073741824 25% C 229=536870912 12.5% D 228=268435456 6.25% E Dr. Clincy Lecture

Finding the class in binary notation Finding the class in decimal notation Dr. Clincy Lecture

EXAMPLES Solution Find the class of the address: 00000001 00001011 00001011 11101111 The first bit is 0. This is a class A address. Solution Find the class of the address: 11000001 10000011 00011011 11111111 The first 2 bits are 1; the third bit is 0. This is a class C address. Solution Find the class of the address: 227.12.14.87 The first byte is 227 (between 224 and 239); the class is D. Dr. Clincy Lecture

Netid and hostid A, B and C class-addresses are divided into network id and host id For Class A, Netid=1 byte, Hostid = 3 bytes For Class B, Netid=2 bytes, Hostid = 2 bytes For Class C, Netid=3 bytes, Hostid = 1 byte Dr. Clincy Lecture

Blocks in class A Example Netid 73 is assigned Class A has 128 blocks or network ids First byte is the same (netid), the remaining 3 bytes can change (hostids) Network id 0 (first), Net id 127 (last) and Net id 10 are reserved – leaving 125 ids to be assigned to organizations/companies Each block contains 16,777,216 addresses – this block should be used by large organizations. How many Host can be addressed ???? The first address in the block is called the “network address” – defines the network of the organization Example Netid 73 is assigned Last address is reserved Recall: routers have addressees Dr. Clincy Lecture

Blocks in class B Example Netid 180.8 is assigned Class B is divided into 16,384 blocks (65,536 addresses each) 16 blocks are reserved First 2 bytes are the same (netid), the remaining 2 bytes can change (hostids) For example, Network id 128.0 covers addresses 128.0.0.0 to 128.0.255.255 Network id 191.225 is the last netid for this block Example Netid 180.8 is assigned Last address is reserved Recall: routers have addresses Dr. Clincy Lecture

Blocks in class C Class C is divided into 2,097,152 blocks (256 addresses each) 256 blocks are reserved First 3 bytes are the same (netid), the remaining 1 byte can change (hostids) For example, Network id 192.0.0 covers addresses 192.0.0.0 to 192.0.0.255 Dr. Clincy Lecture

Class D addresses are used for multicasting; there is only one block in this class. Class E addresses are reserved for special purposes; most of the block is wasted. Dr. Clincy Lecture

Network Addresses The network address is the first address. The network address defines the network to the rest of the Internet. Given the network address, we can find the class of the address, the block, and the range of the addresses in the block Given the network address 17.0.0.0, find the class, the block, and the range of the addresses. The class is A because the first byte is between 0 and 127. The block has a netid of 17. The addresses range from 17.0.0.0 to 17.255.255.255. Solution Given the network address 132.21.0.0, find the class, the block, and the range of the addresses. The class is B because the first byte is between 128 and 191. The block has a netid of 132.21. The addresses range from 132.21.0.0 to 132.21.255.255. Solution Given the network address 220.34.76.0, find the class, the block, and the range of the addresses. The class is C because the first byte is between 192 and 223. The block has a netid of 220.34.76. The addresses range from 220.34.76.0 to 220.34.76.255. Solution Dr. Clincy Lecture

REMINDER: Go Over Converting Binary to Decimal and Vice Versa Dr. Clincy Lecture

Converting Number Systems - Review   Base-10 The decimal number system is based on power of the base 10. For example, for the number 1259, the 9 is in the 10^0 column - 1s column the 5 is in the 10^1 column - 10s column the 2 is in the 10^2 column - 100s column the 1 is in the 10^3 column - 1000s column 1259 is 9 X 1 = 9 + 5 X 10 = 50 + 2 X 100 = 200 + 1 X 1000 = 1000 ----- 1259 Base-2 (Binary) The Binary number system uses the same mechanism and concept however, the base is 2 versus 10  The place values for binary are based on powers of the base 2: … 2^7 2^6 2^5 2^4 2^3 2^2 2^1 2^0 128 64 32 16 8 4 2 1 Dr. Clincy Lecture

Converting Number Systems - Review So, the binary number 10110011 can be converted to a decimal number   1 X 1 = 1 (right most bit or position) 1 X 2 = 2 0 X 4 = 0 0 X 8 = 0 1 X 16 = 16 1 X 32 = 32 0 X 64 = 0 1 X 128 = 128 (left most bit or position) ------ 179 in decimal To convert from decimal to binary requires a different method called the division/remainder method. The idea is to repeatedly divide the decimal number and resulting quotients by 2. The answer will be the remainders. Example: convert 155 to binary (Start from the top and work down) 155/2 Q = 77, R = 1 (Start) 77/2 Q = 38, R = 1 38/2 Q = 19, R = 0 19/2 Q = 9, R = 1 9/2 Q = 4, R = 1 4/2 Q = 2, R = 0 2/2 Q = 1, R = 0 1/2 Q = 0, R = 1 (Stop) Answer is 10011011. Be careful to place the digits in the correct order. Dr. Clincy Lecture

Converting Number Systems - Review Check the answer (10011011) :   1 X 1 = 1 1 X 2 = 2 0 X 4 = 0 1 X 8 = 8 1 X 16 = 16 0 X 32 = 0 0 X 64 = 0 1 X 128 = 128 ----- 155 Base-16 (Hex) The hexadecimal number system is based 16, and uses the same mechanisms and conversion routines we have already examined. The place values for hexadecimal are based on powers of the base 16 The digits for 10-15 are the letters A - F (A is 10, …….., F is 15) …….. 16^3 16^2 16^1 16^0 4096 256 16 1 The binary number 10110011 can be converted to hexadecimal by grouping bits into groups of 4 bits: 1011 0011 B 3 Dr. Clincy Lecture

Mask Given the network address, we can easily determine the block and range of addresses Suppose given the IP address, can we determine the network address (beginning of the block) ? To route packets to the correct network, a router must extract the network address from the destination IP address For example, given 134.45.78.2, we know this is a class B, therefore 134.45 is the netid and 134.45.0.0 is the network address (starting address of the block) How would we EXTRACT the network address from the IP address? We would use a MASK. A mask is a 32-bit binary number that gives the first address in the block (the network address) when bitwise ANDed with an address in the block. Dr. Clincy Lecture

AND operation If bit is ANDed with 1, it’s preserved If bit is ANDed with 0, it’s changed to a 0. There are 3 default masks: one for each class. The default masks preserve the netid when ANDed with the addresses Class A Default Mask: 255.0.0.0 Class B Default Mask: 255.255.0.0 Class C Default Mask: 255.255.255.0 A simple way to determine the netid for un-subnetted cases: (1) if mask byte is 255, retain corresponding byte of the address, (2) if mask byte is 0, set corresponding address byte to 0. Dr. Clincy Lecture

Examples Given the address 23.56.7.91 and the default class A mask, find the beginning address (network address). The default mask is 255.0.0.0, which means that only the first byte is preserved and the other 3 bytes are set to 0s. The network address is 23.0.0.0. Solution Given the address 132.6.17.85 and the default class B mask, find the beginning address (network address). The default mask is 255.255.0.0, which means that the first 2 bytes are preserved and the other 2 bytes are set to 0s. The network address is 132.6.0.0. Solution Given the address 201.180.56.5 and the class C default mask, find the beginning address (network address). The default mask is 255.255.255.0, which means that the first 3 bytes are preserved and the last byte is set to 0. The network address is 201.180.56.0. Solution Dr. Clincy Lecture

5-bit Address Space Illustration No Netid case 32 addresses/block Number of blocks: 1 Address range per block: 0 to 31 Netids: N/A Network Addresses : 00000 Broadcast Addresses: 11111 Dr. Clincy Lecture

5-bit Address Space Illustration 1-bit Netid case 16 addresses/block Number of blocks: 2 Address range per block: 0 to 15 Netids: 0, 1 Network Addresses : 00000, 10000 Broadcast Addresses: 01111, 11111 Dr. Clincy Lecture

5-bit Address Space Illustration 2-bit Netid Case 8 addresses/block Number of blocks: 4 Address range per block: 0 to 7 Netids: 00, 01, 10, 11 Network Addresses : 00000, 01000, 10000, 11000 Broadcast Addresses: 00111, 01111, 10111, 11111 Dr. Clincy Lecture

5-bit Address Space Illustration 3-bit Netid Case 4 addresses/block Number of blocks: 8 Address range per block: 0 to 3 Netids: 000, 001, 010, 011, 100, 101, 110, 111 Network Addresses : 00000, 00100, 01000, 01100 10000, 10100, 11000, 11100 Broadcast Addresses: 00011, 00111, 01011, 01111 10011, 10111, 11011, 11111 Dr. Clincy Lecture

Mixing 3-bit & 2-bit Cases (think of the 32-bit case) 4 addresses/block and 8 addresses/block Number of blocks: 6 Address range per block: 0 to 3 and 0 to 7 Netids: 000, 001, 010, 011, 10, 11 Network Addresses : 00000, 00100, 01000, 01100 10000, 11000 Broadcast Addresses: 00011, 00111, 01011, 01111 10111, 11111 Dr. Clincy Lecture

Multihomed devices As we mentioned that, any device with one or more connections to the Internet will need an IP address for EACH connection – such devices are called “multihomed” devices. A Router could be a multihomed device Dr. Clincy Lecture

Example of direct broadcast address Router sending to all hosts on a network If the hostid is all 1’s, it’s called a “broadcast address” and the router use it to send a packet to all host in a specific network. In this case, hosts 20, 64, 126 and etc. will receive the packet from the router Example of limited broadcast address Host sending to all other hosts on a network If the hostid and netid are all 1’s, it’s called a “limited broadcast address”. If the host wants to send a packet to all host in a specific network, it would use this address. The router would block this address so that data stays contained within a specific network. Dr. Clincy Lecture

Example of this host on this address IPless Host sending message to bootstrap server An address of all 0’s is used during bootstrap time if the host doesn’t know it’s IP address. The un-named host sends an all 0 source address and limited broadcast (all 1’s) destination address to the bootstrap server. Example of specific host on this network Host sending to some other specific host on a network An address with a netid of all 0’s is used by a host or router to send another host with in the same network a message. Dr. Clincy Lecture

Example of loopback address The IP address with the 1st byte equal to 127 is used for the loop back address. Loopback address is used to test software on a machine – the packet never leaves the machine – it returns to the protocol software Example: a “ping” command can send a packet with a loopback address as the destination address to see if the IP software is capable of receiving and processing a packet. Dr. Clincy Lecture

Sample internet With your new found knowledge, think about Project 2 Ethernet ATM Token Ring Ethernet With your new found knowledge, think about Project 2 Dr. Clincy Lecture