2102473 Communication Engineering Laboratory

Computer Networking BasicsLAN Cable & IP Addresses

1

Common network cable types

• Coaxial cable

• Unshielded twisted pair

• Fiber optic

2

UTP categories

Category 1 Voice only (Telephone)

Category 2 Data to 4 Mbps (Localtalk)

Category 3 Data to 10Mbps (Ethernet)

Category 4 Data to 20Mbps (Token ring)

Category 5

Category 5e

Data to 100Mbps (Fast Ethernet)

Data to 1000Mbps (Gigabit Ethernet)

Category 6 Data to 2500Mbps (Gigabit Ethernet)3

Cat5e cable• 1000Mbps data capacity• For runs of up to 90 meters• Solid core cable ideal for structural installations

(PVC or Plenum)• Stranded cable ideal for patch cables• Terminated with RJ-45 connectors

4

RJ45 connector

5

Making connections ‐Tools

• Cat5e cable• RJ45 connectors• Cable stripper• Scissors• Crimping tool

6

Making connections ‐Steps

1. Strip cable end2. Untwist wire ends3. Arrange wires4. Trim wires to size5. Attach connector6. Check 7. Crimp8. Test

7

Step 1 – Strip cable end

• Strip 1 – 1½” of insulating sheath• Avoid cutting into conductor insulation

8

Step 2 – Untwist wire ends

• Sort wires by insulation colors

9

Step 3 – Arrange wires

• TIA/EIA 568A: GW-G OW-Bl BlW-O BrW-Br• TIA/EIA 568B: OW-O GW-Bl BlW-G BrW-Br

10

11

Step 4 – Trim wires to size

• Trim all wires evenly• Leave about ½” of wires exposed

12

Step 5 – Attach connector

• Maintain wire order, left-to-right, with RJ45 tab facing downward

13

Step 6 ‐ Check

• Do all wires extend to end?• Is sheath well inside connector?

14

15

Step 7 ‐ Crimp

• Squeeze firmly to crimp connecter onto cable end (8P)

16

Step 8 – Test

• Does the cable work?

17

IP Address v4 & Subnetting

18

Internet Addresses

• ICANN (Internet Corporation for Assigned Names and Numbers) manages the assignment of both IP and application layer name space, both directly and through authorized registrars around the world.

• ICANN manages some domains directly (e.g., .com, .org, .net) and authorizes private companies to become domain name registrars in other countries (e.g., .ca, .uk, .hk)

• Application layer and network layer addresses are assigned at the same time and in groups.

• For example, Indiana University uses application layer addresses that end in .indiana.edu and iu.edu and uses IP addresses in the 129.79.x.x range (where x is any number between 0 and 255). 19

IPv4 Addresses

• IPv4, uses 4 byte (32 bit) addresses which are really strings of 32 binary bits.

• To make IP addresses easier to understand for human readers, dotted decimal notation is used.

• Dotted decimal notation breaks the address into four bytes separated by periods and writes the digital equivalent for each byte.

• An example of an IP address in dotted decimal notation would be: 128.192.56.1

20

The Need for IPv6 Addressing

• IPv4’s 32 bit addresses correspond to a total of one billion possible addresses.

• Because IP addresses have been allocated in very large groups, giving out many numbers at a time, IPv4 address space has been used up quickly.

• For example, Indiana University was allocated a Class A IP address space which includes 65,000 addresses, many thousands more than the university needed.

• IPv6 uses 128 bit addresses, corresponding to 3.2 x 1038 possible addresses. Given how large a number this is, the problem of using up the huge IPv6 address space will likely not be an issue for some time, if ever.

21

An IPv4 address is 32 bits long.

Note

22

23

Change the following IPv4 addresses from binarynotation to dotted-decimal notation.

Example 19.1

SolutionWe replace each group of 8 bits with its equivalentdecimal number (see Appendix B) and add dots forseparation.

24

Change the following IPv4 addresses from dotted-decimalnotation to binary notation.

Example 19.2

SolutionWe replace each decimal number with its binaryequivalent (see Appendix B).

25

Find the error, if any, in the following IPv4 addresses.

Example 19.3

Solutiona. There must be no leading zero (045).b. There can be no more than four numbers.c. Each number needs to be less than or equal to 255.d. A mixture of binary notation and dotted-decimal

notation is not allowed.26

In classful addressing, the address space is divided into five classes:

A, B, C, D, and E.

Note

27

Subnets (see Figure 3‐11)• Computers on the same LAN are usually given IP numbers with

the same prefix, called a subnet. For example: o Computers in a University’s Business school might be given

addresses in the range: 128.192.56.x (where x is between 0 & 255)o While the Computer Science IP addresses could be: 128.192.55.x

• The above subnets are 128.192.56.x and 128.192.55.x, respectively. Subnets can also be assigned addresses that are more or less than eight bits in length.

• If 7 bits were used for a subnet, one subnet could have a range of 128.184.55.1-128 and the other 128.184.55.129-255.

• Subnet masks are used to make it easier to separate the subnet part of the address from the host part. In the 7 bit subnet example above, the subnet mask would be: 255.255.255.128 or, in binary: 11111111.11111111.11111111.10000000

28

IP Addresses ‐ Class A• 32 bit global internet address• Network part and host part• Few networks each with many hosts• Class A

o Start with binary 0o All 0 reservedo 01111111 (127) reserved for loopbacko Range 1.x.x.x to 126.x.x.xo All allocated

29

IP Addresses ‐ Class B• Medium number of networks, each with a medium

number of hosts• Start 10• Range 128.x.x.x to 191.x.x.x• Second Octet also included in network address• 214 = 16,384 class B addresses• All allocated

30

IP Addresses ‐ Class C• Many networks, each with a few hosts• Start 110• Range 192.x.x.x to 223.x.x.x• Second and third octet also part of network

address• 221 = 2,097,152 addresses• Nearly all allocated

o See IPv6

31

Subnets and Subnet Masks

• Allow arbitrary complexity of internetworked LANs within organization

• Insulate overall internet from growth of network numbers and routing complexity

• Site looks to rest of internet like single network• Each LAN assigned subnet number• Host portion of address partitioned into

subnet number and host number• Local routers route within subnetted network• Subnet mask indicates which bits are subnet

number and which are host number

32

IP Address & Subnet Mask

33

Binary representation Dotted Decimal

IP Address11000000.11100100.00010001.00111001 192.228.17.57

Subnet Mask11111111.11111111.11111111.11100000 255.255.255.224

Bitwise AND of address and mask

11000000.11100100.00010001.00100000 192.228.17.32

Subnet Number 001 1

Host Number11001 25

Default Subnet Masks

34

Binary Representation Dotted Decimal

Class A default mask11111111.00000000.00000000.00000000 255.0.0.0

Example Class A mask11111111.11000000.00000000.00000000 255.192.0.0

Class B default mask11111111.11111111.00000000.00000000 255.255.0.0

Example Class B mask11111111.11111111.11111000.00000000 255.255.248.0

Class C default mask11111111.11111111.11111111.00000000 255.255.255.0

Example Class C mask11111111.11111111.11111111.11111100 255.255.255.252

Routing Using Subnets

35

Address subnets36

• การเขา้สาย LAN (RJ-45)

37