1. Computing: Computer Networking Fundamentals Ian Eyre Part 4 Data Transmission

2. Revision What is a LAN? What is a WAN? Why do we use networks?

3. 1 2 3 4 5 Revision

5. What is a Wiring Closet ? What is an Equipment Rack ? What is a Patch Panel ? What is Trunking ? What is a Wall Socket ? Revision

6. Which type of cable uses these ? Revision

7. What is Attenuation ?

8. Data Transmission DATA TRANSMISSION is the method we use to make sure that data is successfully transferred from one computer to another across a network CORRECTLY. SenderReceiver Network

9. Things the computer must think about before sending data across a network: How do I know that all the sent data will be received? How do I know where the receiving computer is? How do I know that the sent data arrived without error? What happens if another PC sends data at the same time as me? Do I send all the data at once? What’s the fastest route to send the data? Data Transmission ? Will the other PC understand me?

10. Organising Data Transmission To organise data transmission, we use something called The TCP/IP Model of Data Communications. This organises the answers to the questions into 4 easy chunks! APPLICATION LAYER TRANSPORT LAYER INTERNET LAYER NETWORK ACCESS LAYER 1 2 3 4

11. The TCP/IP Model of Data Communications How it works APPLICATION LAYER Data (E-Mail, Web ) The Application Layer takes data from applications that need to use the network & formats it for sending across the network. Formatting data means CHANGING it to make it easier to send. Examples: Compression & Encryption The APPLICATION LAYER then sends the formatted data down to the TRANSPORT LAYER. The Application layer is responsible for formatting data to make it easier to send.

12. The TCP/IP Model of Data Communications How it works Data must be sent in chunks called SEGMENTS. Data must arrive in the correct order. Data must be sent at the correct speed. Data must be sent to the correct application program. Any data lost/damaged during transmission must be resent. APPLICATION LAYER TRANSPORT LAYER Data The Transport layer is responsible for making sure that the data is transmitted safely & arrives safely. The TRANSPORT LAYER then sends the data down to the INTERNET LAYER.

13. APPLICATION LAYER TRANSPORT LAYER Data INTERNET LAYER The Internet (Inter-Network) layer is responsible for addressing the data to make sure it gets to its destination network. The TCP/IP Model of Data Communications How it works The INTERNET LAYER then sends the data down to the NETWORK ACCESS LAYER.

14. APPLICATION LAYER TRANSPORT LAYER Data INTERNET LAYER The Network Access layer is responsible for passing the data onto the network & into the next router in the transmission path. The TCP/IP Model of Data Communications How it works The NETWORK ACCESS LAYER then sends the data across the network. NETWORK ACCESS LAYER Data is converted to electric signals. It can then pass to the next device. Data cannot crash into any other data.

15. The TCP/IP Model of Data Communications The Big Picture Sending PC Receiving PC Transmission Media

16. A TIN 1 2 3 4 The TCP/IP Model of Data Communications How To Remember The Layers

17. PROTOCOLS A PROTOCOL IS A SET OF RULES THAT BOTH THE SENDING & RECEIVING COMPUTER MUST OBEY TO MAKE SURE THEY CAN COMMUNICATE SUCCESSFULLY. A computer network uses many protocols. Each protocol helps the data transmission occur successfully.

18. NETWORK PROTOCOLS Transmission Control Protocol (TCP) Works in the TRANSPORT LAYER Makes sure data arrives safely Resends any data that doesn’t arrive safely Splits data into chunks (SEGMENTS) It puts sequence numbers into each chunk. Internet Protocol (IP) Works in the INTERNETWORK LAYER Makes sure data is addressed correctly Sends data to the correct network Uses Internet Protocol Address (IP Address) to identify each pc.

19. NETWORK ADDRESSING Each computer in a modern network normally has TWO addresses. The purpose of a computer’s address is to make sure other machines can communicate with it. The two addresses are :- IP ADDRESSES MAC ADDRESSES &

20. A Media Access Control (MAC address is the address of the network card in a computer.) MAC addresses are put into cards when they are made - & normally cannot be changed. Every computer has a UNIQUE MAC address. The MAC address is hence sometimes called a PHYSICAL ADDRESS. 00-0C-76-6E-F0-38 A MAC Address is 48 bits long.

21. MAC Addresses Ethernet adapter Wireless Network Connection: Connection-specific DNS Suffix. : Description........... : NETGEAR WG111v2 54Mbps Wireless NIC Physical Address.... : 00-0F-B5-CD-54-D1 Dhcp Enabled........... : Yes Autoconfiguration Enabled.... : Yes IP Address................. : 192.168.0.2 Subnet Mask.............. : 255.255.255.0 Default Gateway............ : 192.168.0.1 DHCP Server.............. : 192.168.0.1 DNS Servers............... : 192.168.0.1 Lease Obtained............. : 16 September 2007 09:34:14 Lease Expires.............. : 17 September 2007 09:34:14 Find the MAC address of your pc? Type ipconfig /all at a command prompt

22. IP ADDRESSES An Internet Protocol (IP) Address is an address given to a computer by a network administrator. An IP Address identifies a computer on a network. Every computer on a network has a UNIQUE IP address. The IP address is sometimes called a LOGICAL ADDRESS. Each IP address contains 4 numbers between 0 & 255. 192.168.0.3 An IP Address is 32 bits long.

23. IP Addresses Ethernet adapter Wireless Network Connection: Connection-specific DNS Suffix. : Description........... : NETGEAR WG111v2 54Mbps Wireless NIC Physical Address....... : 00-0F-B5-CD-54-D1 Dhcp Enabled........... : Yes Autoconfiguration Enabled.... : Yes IP Address...... : 192.168.0.2 Subnet Mask.............. : 255.255.255.0 Default Gateway............ : 192.168.0.1 DHCP Server.............. : 192.168.0.1 DNS Servers............... : 192.168.0.1 Lease Obtained............. : 16 September 2007 09:34:14 Lease Expires.............. : 17 September 2007 09:34:14 Find the IP address of your pc? Type ipconfig /all at a command prompt

24. IP Addressing (v4) Address Classes IP addresses consist of FOUR OCTETS (0 – 255) IP Addresses are divided into CLASSES. The value of the addresses FIRST NUMBER determines its CLASS First NumberAddress Class 0 - 127 128 - 191 192 - 223 A B C

25. IP Addressing Example 110.3.14.2 is address class A 192.165.10.2 is address class C 172.168.0.4 is address class B

26. IP Addressing Address Structure An IP address consists of 2 parts : 172.126.30.56 Network PartHost Part The NETWORK PART identifies the network. Every machine on a network has the SAME network address. The HOST PART UNIQUELY identifies each machine on the network. Every machine on the same network has a DIFFERENT host address.

27. IP Addressing Networks & Hosts The ‘Class’ of an IP address also determines which of its numbers describe the network portion & the host portion. 1 st OCTET2 nd OCTET3 rd OCTET4 th OCTET Network Host Class A Class B Class C

28. IP Addressing 192.126.30.56 Network PartHost Part 172.126.30.56 Network Part Host Part Class A Class B Class C 110.3.14.2 Network Part Host Part

29. IP Addressing In a Network Each PC has the same NETWORK ADDRESS. Each PC has a different HOST ADDRESS. Each PC has a different IP ADDRESS.

30. How NOT to send data across a Network. If we sent a message across a network in one large piece, all other messages would have to wait. Next message must wait Network Data Transmission

31. How to send data across a Network. By splitting data up into blocks, more than one message can be sent along the same route. Parts of a message may take different routes as it travels. These blocks are called PROTOCOL DATA UNITS or PDUs. Network Data Transmission

32. How to send data across a Network. The messages may arrive out of sequence, but TCP will re-sequence them. Network Data Transmission

33. Any Questions