Networking Fundamentals Tom Brett

Transcription

1 Networking Fundamentals Tom Brett Data Before we look at networking, it is important for us to understand what Data is and how it is stored and represented Data According to Webopedia, data is distinct pieces of information, usually formatted in a special way. All software is divided into two general categories: data and programs. Programs are collections of instructions for manipulating data. Data can exist in a variety of forms as numbers or text on pieces of paper, as bits and bytes stored in electronic memory, or as facts stored in a person's mind. Webopedia Data Retrieved from 1

2 Data is information which is categorized. For example, an example of data is Red, 1998, 1900, Hatchback The give away here is hatchback, we can all see it is a car, so this data becomes information when we understand what it pertains to Red = colour, 1998 = year, 1900 = Engine CC Hatchback = Body type How is data stored and processed? Computers store data as 1 s/0 s or on / off. It is combinations of these 1 s and 0 s which represent the data to be held or read. Different devices / components store data differently. Some store as electrical charges, some store as different magnetic states etc. Bit Each possible storage value consisting of these two states (1/0) is known as a bit. 2

3 Byte A byte is 8 bits Data bits are generally grouped together into bytes, this is for historical reasons (8bit processors) 8 bits can also be used to identify nearly all of the English characters etc (ASCII Character Set) Bytes, Bits are all known as Binary numbers We generally work in decimal numbers Examples of bytes If the byte starts off with 0 s we simply drop them so would be read as Binary to decimal Insert Binary Value Here Decimal Value

4 The Binary value = 5 Insert Binary Value Here Decimal Value Decimal Value What is the decimal values of the following? = = 17 4

5 Can we convert from Decimal to Binary Yes, simple Use the same table Insert Binary Value Here Decimal Value This time, find the highest decimal value which is equal or lower than the decimal value to compute, and add a 1 for it in the binary value, then do the same with the remainder etc.. What is the value 15 in Binary Insert Binary Value Here Decimal Value The highest value which goes into 15 is 8, so add from 15 leaves 7. The highest value which goes into 7 is 4 Add 1 to 4 Insert Binary Value Here This leaves Decimal Value 5

6 Highest value which goes into 3 is 2 leaving 1 remaining which is then 1/ Insert Binary Value Here Decimal Value So the decimal value of 15 is 1111 in Binary Hexadecimal Numbering Hexadecimal numbering is another method of representing decimal values, Hexadecimal numbering is a base 16 numbering set and uses a combination of letters and numbers Common areas where hexadecimal numbering can be seen used is in memory areas, error codes, colour representations etc. Hexadecimal to Decimal Conversion Hexadecimal uses 16 symbols 0 9 and A F 6

7 Networks A network is a group of two or more systems. The purpose of any network is to share resources (Hardware, Software and resources) Another feature (which becomes more important) is the central administration of these systems The Setting up of a network requires computers with network adapters, central connecting devices (hubs or switches) to connect these computers together, and a identification scheme (IP addresses) to differentiate one computer from the next. 7

8 Local Area Networks A local area network (LAN) is a group of computers that are confined to a small geographic area, usually a single building or small geographic area Local area networks (LANs) are used by just about every organization and many homes have them as well LAN requires computers with network adapters, central connecting devices, and some type of medium to tie it all together, be it cabled or wireless connections 8

9 Network Documentation In order to understand LANs better, it helps to write out the structure of a LAN in other words, to document it. Network documentation is any information that helps describe, define, and otherwise explain how computers are connected in a physical and logical way. The documentation phase occurs before a network is built, as well as whenever changes or additions are made to the network. Hub A hub is the most basic of central connecting devices. It connects each of the networked computers, known as hosts, to one another by way of copperbased cables. Any host that sends data must first send that data to the hub, where it is amplified and broadcast to the rest of the network. Hub types Passive Just passes on the signal Active Regenerates the signal (acts as a repeater) Switching Intelligent 9

10 Switch Network switches are capable of inspecting data packets as they are received, determining the source and destination device of each packet, and forwarding them appropriately. By delivering messages only to the connected device intended, a network switch conserves network bandwidth and offers generally better performance than a hub. Switch Benefits Each port is a separate collision domain Can direct traffic only to the port to which the destination computer is attached Can connect dissimilar network architectures Router A router is adevicethat forwards data packets along networks. A router is connected to at least two networks, commonly two LANs or WANs or a LAN and its ISP's network. In a TCP/IP network a router is commonly referred to as a Default Gateway, in that it acts as a doorway from one network to another. 10

11 Router Routers use headers and forwarding tables to determine the best path for forwarding the packets, and they use protocols such as ICMP to communicate with each other and configure the best route between any two hosts. Router Router connects 2 or more subnetworks Router can be configured to support single protocol or multiple protocols Router processes only packets specifically addressing it as a destination Packets destined for locally connected subnetwork are passed to that network Packets destined for remote subnetwork are passed to next router in path Router that resides in same subnet as host can be configured as default gateway 4 port Router The router acts as a central connecting device, but it also has a special communications link to the Internet, thereby allowing the hosts to send data to and receive data from computers on the Internet. This communications link between the router and the Internet is where the LAN ends. 11

12 NAT (Network Address Translation) Because Routers connect (and separate) networks,private IP address ranges can be re used, this generally allows to increase the address availability of depleting(depleted ) IPv4 addresses. Routers combined with Private address ranges can also be used to hide internal machines from the external world therefore increasing security. To allow connectivity forwarders can be set on the router to point to specific internal (private addresses) Types of Transfers Broadcast has data sent to every other host on the network. Unicast has data sent to one host only. Data Transfer Rate Data transfer rate, otherwise known as bit rate defines the maximum bits per second (bps) that can be transmitted over a network. As mentioned, this value is rated in bits, and it is signified with a lowercase b (for example, 10 Mbps). The lowercase b helps differentiate this amount from data that is stored on a hard drive, which uses an upper case B that stands for bytes (for example 10 MB). 12

13 Network Interface Card (NIC) A network Interface Card (NIC) also known as a Network Adapter, is used to connect devices to the network medium and send / receive data. Some NIC s are integrated directly onto the mainboard within the PC, others are added on by the use of an adapter card. Network Medium There are several types of network medium, each offering different bandwidth (capacity of data throughput at any given time) and distances available. We have Wired, and Wireless types available The NIC chosen must be compatible with the medium being used. Viewing NIC properties within Windows This will depend on the OS in question.. Click Start, Right Click on My Computer Select Manage 13

14 The computer management console appears Click Device Manager The device manager opens showing all of the devices within the system broken up into categories Expanding the Network adapters category will show all of the network adapters within the system 14

15 Right click on the network adapter and choose properties A properties dialog box appears similar to the one listed below The properties dialog box is split into categories which appear in Tabs along the top. Different NICs and OS s may have different options see images below The options will vary depending on the NIC In question The following slide depicts the Link status You can tell that the card is active if the Link Status field has a green light. It also indicates that the card is connected at 1 Gbps Note the options for Full Duplex and Half Duplex Full Duplex = Communicates in both directions at the same time Half duplex = Can communicate in both directions, but only one direction at any particular time. 15

16 Network Properties Every network adapter will have a logical name. By default, the network adapter is known as the Local Area Connection, although you can change the name if you desire. The Local Area Connection has its own properties page and status page. To view these: Right click Network and select Properties. This will display the Network and Sharing Center window. If you don t have this option, you can click the windows key + x to show the administrative menu From here choose network connections In the Network Connections window, you should see the Local Area Connection icons. Right click the icon and select Properties 16

17 Using Network and Sharing center to view network properties Start Right click Network and select Properties. This will display the Network and Sharing Center window. If you don t have the Network option in your Start menu, you can add it from the Taskbar and Start Menu Properties dialog box, which can be accessed by right clicking the taskbar and selecting Properties. An alternate way to access the Network and Sharing Center is to go to Start > Control Panel > Network and Internet. Once in the Network and Internet window, select the Network and Sharing Center link. Click Change adapter settings This will bring up the Network Connections window. (Navigation to this window will be slightly different in other versions of Windows.) In the Network Connections window, you should see the Local Area Connection icon as well as any other connections. Right click the icon and select Properties. 17

18 The properties dialog box appears From here, you can configure Internet Protocol (IP), bind new protocols to the network adapter Double clicking on the connection icon (as long as it is connected) will bring you up the connection properties This dialog box displays the type of connectivity, speed, and how long the adapter has been connected; it also shows the total bytes sent and received. You can also get to the Properties window from here and diagnose the network adapter if necessary. 18

19 DATA TRANSFER ON A LAN When data is transferred on a LAN, it is sent in a serial fashion over twisted pair cabling. Serial data transfer means the transfer of one bit at a time A Simple Example Moving a text file across a LAN First, the text file is packaged by the operating system into what is known as a packet. The packet will be slightly larger than the original file. The packet is then sent to the network adapter. The network adapter takes the packet and places it inside a frame, which is slightly larger than a packet. (Usually, this will be an Ethernet frame LANs utilize one of several Ethernet standards. Ethernet is a set of rules that govern the transmission of data between network adapters and various central connecting devices). The frame of information needs to be sent to the physical media the cabling. The network adapter breaks down the frame of information into a serial data stream that is sent one bit at a time across the cables to the other computer. The receiving computer takes the single bit stream and recreates the frame of data. After analyzing the frame and verifying that it is indeed the intended recipient, the computer strips the frame information so that only the packet remains. The packet is sent to the operating system, and ultimately, the text file shows up on the computer s hard drive, available to the user through Windows Explorer. Ethernet In this type of network, when a computer sends data, that data is broadcast to every other host on the network by default. The problem with this method is that usually there is only one intended recipient for the data, so the rest of the computers will simply drop the data packets Ethernet switching was developed to combat this wastage, Switching has many advantages, one of which is that the switch only sends unicast traffic. Unicast describes the situation in which information is sent to one host only. This reduces network traffic greatly, and it also helps with packet loss and duplication. 19

20 Data Transfer Rate A more accurate term for network speed would be data transfer rate, otherwise known as bit rate. This is defined as the maximum bits per second (bps) that can be transmitted over a network. This value is rated in bits, and it is signified with a lowercase b (for example, 10 Mbps). The lowercase b helps differentiate this amount from data that is stored on a hard drive, which uses an upper case B that stands for bytes (for example 10 MB). Types of Transfers Broadcast has data sent to every other host on the network. Unicast has data sent to one host only. Internet Protocol Internet Protocol, or IP, is the part of TCP/IP suite of protocols which is used to allocate addresses to identify machines and devices connectable/addressable on a network An IP address allows a computer to send data to another computer. A Network device which has an IP address is known as a node. The IP address is what distinguishes one node from another on a network There are two versions of IP address IPv4 and IPv6 20

21 IPv4 is the original address system, with IPv6 being a replacement. IPv6 supports a larger address space which is needed because of the sheer amount of devices being used. An example of a IPv4 address is An example of a IPv6 address is 4051:0db8:88a3:0042:1000:8a2e:0370:7b34 According to Wikipedia, IPv4 still carries the vast majority of Internet traffic as of As of September 2013, the percentage of users reaching Google services over IPv6 surpassed 2% for the first time Wikipedia.org IPv6 Retrieved from IPv4 IPv4 Addresses are 32 bits long (they are comprised of 4 x 8 bit parts) Largest binary = 255 Smallest binary = 0 Although we represent IPv4 addresses in decimal, they are derived from binary notation. 4.3 billion potential IP addresses Every IP address is broken down into two parts: The network portion, which identifies the network that your computer is a member of, The host portion, which identifies each individual node on the network uniquely The subnet mask is part of the IPv4 setup which is used to identify the network and host portion Subnet Mask The subnet mask is a group of four numbers that define what IP network the computer is a member of. An example of the a subnet mask is All of the 255s in a subnet mask collectively refer to the network portion, whereas the 0s refer to the host portion The subnet mask above ( ) tells us that the first 3 parts (octets) represent the network address and the last octet represents the node address or identifier. 21

22 IPv4 Address Classes Class Addresses Description A B C D E First octet: network ID Last 3 octets: host ID Default subnet mask: First 2 octets: network ID Last 3 octets: host ID Default subnet mask: First 3 octets: network ID Last octet: host ID Default subnet mask: Multicasting addresses Experimental use Configuring a Class C IPv4 Address A Class C IPv4 Address is in the range to A Class C is the most common address range to be used based on the amount of machines supported per network The first part is to identify a network address to be used by all machines in the network The second part is to identify a unique address per machine to be used. Configuring a Class C IPv4 Address Access the Local Area Connection Properties dialog box once again. Click Internet Protocol Version 4, then click the Properties button. This displays the Internet Protocol Version 4 Properties dialog box. (Write down the current settings (if there are any) so that you can return the computer to these settings at the end of the exercise). 22

23 Configuring a Class C IPv4 Address Usually, by default, the dialog box options will be configured as Obtain an IP address automatically and Obtain DNS server address automatically, This means that the network adapter will attempt to get all of its IP information from a DHCP server or other device like a SOHO 4 port router. For this lab we wish to configure the adapter statically. Tick the radio button for Use the following IP address where we will enter the addresses accordingly. Configuring a Class C IPv4 Address Enter the following: For the IP address, enter x where x is a unique number which assigned to you This last octet will identify your node uniquely on the network For the Subnet mask, enter This identifies the first 3 octets ( ) as being the network portion of the address Configuring a Class C IPv4 Address Leave the Default gateway and the Preferred DNS server fields blank. The Default gateway is the address of the device which allows connectivity to remote networks (usually the internet) The DNS server is the address of a machine which can resolve (identify) Web addresses to machine IP addresses. Click OK. Then, in the Local Area Connection Properties dialog box, click OK. This will bind the configuration to the network adapter. 23

24 Testing IP configuration There are several methods to check and test your configuration. The best and most common methods are to use the ipconfig command, and the ping command. IPCONFIG Open a command prompt. Do this by pressing the Windows + R keys and typing cmd in the open field. The command prompt is a TUI interface which we can use to run commands IPCONFIG Type ipconfig and press Enter The screenshot bellows show both a IPv6 and IPv4 address. 24

25 Ping You can Ping a computer on the same network. If there are no other computers, you can ping your own IP address. Type the following command: ping This command sends requests out to the other IP address. If the other computer is running and configured properly, it should reply back as follows. Ping If for some reason you do not get a reply or you get another message like request timed out, you should check the IP configuration again to make sure that the other computer you are trying to ping is configured properly. Also make sure that all involved computers are wired to the network. Ping Command There are several useful names used to test your own connections ping loopback ping localhost ping

26 Ping Localhost You can also ping your own computer using the loopback address, also known as the local loopback. Every Windows computer automatically gets this address; it is This address exists is in addition to the logical address that you assigned earlier. Try the command ping loopback and check your results. You can also try ping localhost and ping This never places any packets on to the network so it is a solid way to test whether TCP/IP is installed correctly to a network adapter, even if you aren t physically connected to a network. Types Of LANS One of the first decisions organizations must make now is whether to use wired or wireless LANs There are benefits and disadvantages to each. 26

27 Wired LAN s Most computers and other devices are wired together using copper based twisted pair cables. These cables have RJ45 plugs on each end, which make the actual connection to the RJ45 ports that reside on the computer s network adapter and on hubs, switches, or routers. Other forms of cables and connectors exist, offering different bandwidths, Coax and Fiber Optic. Wired LAN using a Switch / HUB Wired Connections Generally, the connection from PCs to the switch will be either 100 Mbps or 1 Gbps. To achieve a speed, each device and cable must support the same speed. To accomplish gigabit network speeds, the cables used would have to be Category 5e or greater If you are connecting computers to a server the server should always have greater bandwidth then the other machines where possible. 27

28 Wireless Connections Wired networks were significantly faster than wireless networks. Now, the speed difference between the two is much smaller due to the fact that wireless networking technology has progressed in giant leaps over the past decade or so A wireless local area network (WLAN) has many advantages, the most obvious of which is the ability to roam. This is where the person connected does not need to be physically connected to the network. This same advantage is also a disadvantage causing a major security concern, as hackers may not even need to be within the building to connect to the companies network. 2 Types of Wireless Network Ad hoc Where computers connect directly to one another Infrastructure Uses a WAP (Wireless Access Point) This allows several advantages Security (MAC Address Filtering, Encryption etc) Allows the Wireless network to connect to the wired network Wireless Local Area Network (WLAN) A wireless local area network (WLAN) has many advantages, the most obvious of which is the ability to roam. 28

29 Wireless Access Point The wireless access point (WAP) acts as the central connecting device for the network. Today, such networks can consist of many types of devices other than traditional PCs, including smart phones, PDAs, tablet computers, and micro computers. Not to mention the fact that PCs and laptops equipped with wireless network adapters can connect to these networks as well. Router Emulators Virtual LAN A virtual LAN (VLAN )is a group of hosts with a common set of requirements that communicate as if they were connected together in a normal fashion on one switch, regardless of their physical location. A VLAN is implemented to segment a network, reduce collisions, organize the network, boost performance, and increase security. Switches usually control the VLAN. A VLAN compartmentalizes a network and can isolate traffic. 29