Why Use a Computer Network? Sharing information (or data) Sharing hardware and software Centralizing administration and support

The sneakernet

Sharing Hardware and Software

Network Configuration Overview Servers—Computers that provide shared resources to network users. Clients—Computers that access shared network resources provided by a server. Media—The wires that make the physical connections. Shared data—Files provided to clients by servers across the network.

Network Topology A network's topology affects its capabilities Type of equipment the network needs. Capabilities of the equipment. Growth of the network. Way the network is managed.

Standard Topologies Bus Star Ring Mesh All network designs stem from four basic topologies: Bus Star Ring Mesh

Bus topology network

Communication on the Bus Sending the signal Signal bounce Terminator

The following are affect the network performance Number of computer in the network Hardware capabilities of computers on the network Total number of queued commands waiting to be executed Types of applications (client-server or file system sharing, for example) being run on the network Types of cable used on the network Distances between computers on the network

Terminator

Star

Ring

Token Passing One method of transmitting data around a ring is called token passing

Mesh

Variations on the Standard Topologies Many working topologies are hybrid combinations of the bus, star, ring, and mesh topologies

Star Bus

Star Ring

Network interface card Protocols – Ethernet, Token Ring, or FDDI Types of media – Twisted-pair, coaxial, wireless, or fiber-optic Type of system bus – PCI or ISA

Situations that require NIC installation include the following Installation of a NIC on a PC that does not already have one Replacement of a malfunctioning or damaged NIC Upgrade from a 10-Mbps NIC to a 10/100/1000-Mbps NIC Change to a different type of NIC, such as wireless Installation of a secondary, or backup, NIC for network security reasons

The following are some of the factors that determine throughput: Internetworking devices Type of data being transferred Network topology Number of users on the network User computer Server computer Power conditions Using the formula transfer time = size of file / bandwidth (T=S/BW)

Network Cabling Coaxial cable Twisted-pair (unshielded and shielded) cable Fiber-optic cable Wireless

Cable specification

Coaxial Cable

There are two types of coaxial cable: Thin (thinnet) cable Thick (thicknet) cable The thicker the copper core, the farther the cable can carry signals

Coaxial-Cable Connection Hardware

Twisted-Pair Cable Types of twisted-pair cable Unshielded Twisted-Pair (UTP) Cable Shielded Twisted-Pair (STP) Cable

RJ-45 connector

UTP cabling wire colors are two types

UTP cable

Straight through

Use straight-through cables for the following connections: Switch to router Switch to PC or server Hub to PC or server

Straight through

Straight through

Cross over

Use crossover cables for the following connections Switch to switch Switch to hub Hub to hub Router to router PC to PC Router to PC

Cross over

Cross over

Roll over

Roll over

Roll over

Fiber-optic cable

Wireless

Wireless

Single wire punch

PART TWO

Types of Networking Peer-to-peer Server based

Peer to peer versus client-server

OSI MODELS

Networking Models

Dividing the network into seven layers provides the following advantages: It breaks network communication into smaller, more manageable parts. It standardizes network components to allow multiple vendor development and support. It allows different types of network hardware and software to communicate with each other. It prevents changes in one layer from affecting other layers. It divides network communication into smaller parts to make learning it easier to understand.

Peer-to-peer communications

Cabling LAN Materials used in networking LAN REPEATERS HUBS BRIDGE SWITCH ROUTERS

REPEATERS Is two port (for signal i/o) It simply give strength for signal

HUBS Hubs are actually multiport repeaters Passive: used only to share the physical media (It does not boost or clean the signal ) Active: it needs power to amplify Intelligent: microprocessor chips and diagnostic capabilities

Hub

Five segments of network media Four repeaters or hubs The 5-4-3-2-1 rule requires that the following guidelines should not be exceeded: Five segments of network media Four repeaters or hubs Three host segments of the network Two link sections with no hosts One large collision domain

BRIDGE Used to segment a large LAN to smaller. decreases the amount of traffic on a single LAN bridges operate at the data link layer of the OSI model The function of the bridge is to make intelligent decisions about whether or not to pass signals on to the next segment of a network.

BRIDGE When a bridge receives a frame on the network, the destination MAC address is looked up in the bridge table to determine whether to:- Filter Flood Copy the frame onto another segment

Filter If the destination device is on the same segment as the frame, the bridge will not send the frame onto other segments. This process is known as filtering

Flood If the destination address is unknown to the bridge, the bridge forwards the frame to all segments except the one on which it was received. This process is known as flooding.

Copy the frame onto another segment If the destination device is on a different segment, the bridge forwards the frame to the appropriate segment.

SWITCH A switch is sometimes described as a multiport bridge Switches reduce traffic and increase bandwidth Switches operate at much higher speeds than bridges and can support new functionality, such as virtual LANs.

ROUTERS Routers are responsible for routing data packets from source to destination within the LAN, and for providing connectivity to the WAN. The DTE is the endpoint of the user’s device on the WAN link. The DCE is typically the point where responsibility for delivering data passes into the hands of the service provider.

DTE & DCE

TCP-IP

TCP/IP MODEL

TCP/IP MODEL

TCP/IP MODEL

TCP/IP MODEL

TCP/IP MODEL

The OSI and TCP/IP models have many similarities: Both have layers. Both have application layers, though they include different services. Both have comparable transport and network layers. Both use packet-switched instead of circuit-switched technology. Networking professionals need to know both models.

Some differences of the OSI and TCP/IP models: TCP/IP combines the OSI application, presentation, and session layers into its application layer. TCP/IP combines the OSI data link and physical layers into its network access layer. TCP/IP appears simpler because it has fewer layers. When the TCP/IP transport layer uses UDP it does not provide reliable delivery of packets. The transport layer in the OSI model always does. The Internet was developed based on the standards of the TCP/IP protocols. The OSI model is not generally used to build networks. The OSI model is used as a guide to help students understand the communication process.

NETWORK ADDRESSING

IP Addressing The Hierarchical IP Addressing Scheme There are three types of IP addressing Dotted-decimal, as in 172.16.30.56 Binary, as in 10101100.00010000.00011110.00111000 Hexadecimal, as in AC.10.1E.38

Network Addressing called the network number uniquely identifies each network

Network Address Range: Class A 00000000 = 0 01111111 = 127 Network Address Range: Class B 10000000 = 128 10111111 = 191 Network Address Range: Class C 11000000 = 192 11011111 = 223 Network Address Ranges: Classes D and E Class D (224–239) Class E (240–255

Class A network.node.node.node In a Class A network address, the first byte is assigned to the network address, and the three remaining bytes are used for the node addresses: All host bits off is the network address: 10.0.0.0. All host bits on is the broadcast address: 10.255.255.255

Private IP Addresses (they’re not routable through the Internet) Reserved IP Address Space Address Class Reserved address space Class A 10.0.0.0 through 10.255.255.255 Class B 172.16.0.0 through 172.31.255.255 Class C 192.168.0.0 through 192.168.255.255

Introduction to Network Address Translation (NAT) to translate your private inside addresses to a global outside address by using NAT There are different flavors of NAT Static NAT Dynamic NAT Overloading

Classless Inter-Domain Routing (CIDR) It’s basically the method that ISPs (Internet Service Providers) use to allocate an amount of addresses to a company, a home—a customer When you receive a block of addresses from an ISP, what you get will look something like this: 192.168.10.32/28.(The slash notation (/) means how many bits are turned on (1s))

Broadcast Addresses Layer 2 broadcasts These are sent to all nodes on a LAN. Broadcasts (layer 3) These are sent to all nodes on the network. Unicast These are sent to a single destination host. Multicast These are packets sent from a single source, and transmitted to many devices on different networks

Subnetting Basics Reduced network traffic Optimized network performance Simplified management Facilitated spanning of large geographical distances

How to Create Subnets Follow these steps: 1.Determine the number of required network IDs: One for each subnet One for each wide area network connection 2.Determine the number of required host IDs per subnet: One for each TCP/IP host One for each router interface 3.Based on the above requirements, create the following: One subnet mask for your entire network A unique subnet ID for each physical segment A range of host IDs for each subnet

Subnetting

Subnetting a Class C Address Answer five simple questions: How many subnets does the chosen subnet mask produce? How many valid hosts per subnet are available? What are the valid subnets? What’s the broadcast address of each subnet? What are the valid hosts in each subnet?

Subnetting a Class C Address

How many subnets. 2^x = number of subnets How many subnets? 2^x = number of subnets. x is the number of masked bits, or the 1s How many hosts per subnet? 2^y – 2 = number of hosts per subnet. y is the number of unmasked bits, or the 0s. For example, in 11000000, the number of zeros gives us 26 – 2 hosts. In this example, there are 62 hosts per subnet What are the valid subnets? 256 – subnet mask = block size, or increment number. An example would be 256 – 192 = 64. The block size of a 192 mask is always 64. Start counting at zero in blocks of 64 until you reach the subnet mask value and these are your subnets. 0, 64, 128, 192. What’s the broadcast address for each subnet? the broadcast address is always the number right before the next subnet. What are the valid hosts? Valid hosts are the numbers between the subnets, omitting all the 0s and all 1s.

Practice Example #1: 255.255.255.192 (/26) Let’s use the Class C subnet mask from the preceding example, 255.255.255.192, to see how much simpler this method is than writing out the binary numbers. We’re going to subnet the network address 192.168.10.0 and subnet mask 255.255.255.192.

How many subnets? Since 192 is 2 bits on (11000000), the answer would be 22. How many hosts per subnet? We have 6 host bits off (11000000), so the equation would be 26 – 2 = 62 hosts. What are the valid subnets? 256 – 192 = 64. Remember, we start at zero and count in our block size, so our subnets are 0, 64, 128, and 192.

Practice Example #2: 255.255.255.224 (/27) This time, we’ll subnet the network address 192.168.10.0 and subnet mask 255.255.255.224.

How many subnets? 224 is 11100000, so our equation would be 23 = 8. How many hosts? 25 – 2 = 30. What are the valid subnets? 256 – 224 = 32. We just start at zero and count to the subnet mask value in blocks (increments) of 32: 0, 32, 64, 96, 128, 160, 192, 224.