Ip1

Lecture 8 Network Protocols - TCP/IP

1

Importance of Protocols ✘ Standards define how devices communicate with each other and access media ✘ Once a standard is implemented in software it becomes a protocol ✘ Protocols define how devices and applications communicate ✘ The protocols on a network affects the way in which it functions and its ability to interface with other networks CP2077 - Networking

2

Protocol Suites ✘ Transmission Control Protocol/Internet Protocol (TCP/IP) – the most common of all network protocol suites, is the ‘standard’ in modern networks, used for communication on the Internet ✘ Internet Packet eXchange/Sequence Packet eXchange (IPX/SPX) – developed by Novell, ensures communication between Netware operating systems, provides similar functionality to TCP/IP, can be routed but only to communicate with other Netware networks ✘ AppleTalk – popular networking protocol in American educational establishments, used for communicating between devices using the Mac OS CP2077 - Networking

3

TCP/IP Suite ✘ Developed for use on the Internet for the American Department of Defence ✘ Two Parts: ✘ TCP – responsible for connection oriented communication using error checking ✘ IP – implemented in the addressing system used to identify devices

✘ Although designed for the Internet it is used to build LANs, WANs and MANs ✘ Most widely used protocol suite, used within Unix, Windows and Macintosh platforms CP2077 - Networking

4

TCP/IP Protocol Suite

Telnet

FTP (File Transfer Protocol)

SNMP TFTP SMTP LPD NFS (Simple (Trivial (Simple (Line (Network Network X File Mail Printer File Managem Window Transfer Transfer Daemon) System) ent Protocol) Protocol) Protocol)

Others

UDP (User Datagram Protocol)

Network

TCP (Transmission Control Protocol)

ICMP (Internet Control Message Protocol)

BootP (Bootstrap Protocol)

IP (Internet Protocol)

Physical Data Link

Transport

Session Presentation Application

OSI

Ethernet

Token Ring

FDDI (Fibre Distributed Data Interface)

CP2077 - Networking

ARP RARP (Address Resolution (Reverse Address Protocol) Resolution Protocol)

Frame Relay

Others

5

Features of TCP/IP ✘ Interoperability – has become the industry ‘standard’, Netware have replaced two of its proprietary protocols (IPX and SPX) with TCP and IP ✘ Flexibility – the multiple protocols within the suite allow a variety of implementations, eg the use of either TCP (reliable but slow) or UDP (fast and efficient, but not as reliable) ✘ Multivendor Support – almost all network software supports it, eg Apple, DEC, IBM, Novell, Microsoft and Sun

CP2077 - Networking

6

Internet Protocol ✘ One of the most important protocols ✘ Developed to function within a UNIX environment in the days of ARPAnet ✘ Uses connectionless delivery – it does not guarantee delivery ✘ Main purpose is to provide logical addressing through the use of an IP address ✘ Uses IP address to route information between networks, therefore every device requires a unique address CP2077 - Networking

7

Understanding IP Addressing ✘ Address consists of 4 bytes = 32 bits ✘ Address is quoted as four dotted decimal numbers such as 134.220.198.170 = 10000110.11011100.11000110.10101010

✘ IP address consists of two parts the network portion, and the host portion ✘ The network portion is used to route packets between networks ✘ The host portion identifies the particular device on the host network CP2077 - Networking

8

Class Addresses ✘ There are five classes of IP address ✘ The class of address is identified by the first bits of the address ✘ Three classes are used for networks. The last two are reserved for special purposes (Class D is for multicast, and Class E is for experimentation and future use) ✘ See following diagram for Classes A to C CP2077 - Networking

9

Class A to Class C Byte 1

Byte 2

Byte 3

Byte 4

Class A 0 Network

Host

Class B 10 Network

Host

Class C 110 Network

Host

Class A – First eight bits identify network, the first bit is fixed at 0, giving 27 (128) networks, and 224 (16,777,316) hosts Class B – First 16 bits identify network, the first two bits are fixed at 10, giving 214 (16,384) networks, and 216 (65,536) hosts Class C – First 21 bits identify network, the first three bits are fixed at 110, giving 221 (2,097,152) networks and 28 (256) hosts CP2077 - Networking

10

Understanding IP Addressing (2) ✘ For any organisation the Network portion of the address remains fixed, the network administrator can assign the host address ✘ Assignment can be manual or through Dynamic Host Configuration ✘ The total number of addresses in this system is a mathematical possible 4,294,467,295 ✘ However, wastage in Class B (networks not using all the hosts numbers they could – this problem partially solved through ‘Ciderised’ addressing) plus proliferation of the Internet means we are running out of IP addresses CP2077 - Networking

11

IP Subnets ✘ Larger classes of networks (A and B) are usually divided in to smaller networks ✘ This is achieved by dividing up the host portion of the address ✘ This process is known as subnetting ✘ A ‘subnet mask’ uses some of the bits from the host address to create subnets ✘ The number of bits used determines the number of subnets which are generated ✘ The remaining bits in the host portion identify the number of host IP addresses in each subnet ✘ <subnet portion> CP2077 - Networking

12

IP Version 6 ✘ Current IP Address = 4 x 8-Bit 4,294,467,295 addresses ✘ Version 6 IP Address = 8 x 16-Bit 3 x1038 approx addresses ✘ This ‘should provide sufficient addresses for our future needs’ – however, it is suggested that before long even the light switches in our homes will need their own IP addresses ✘ Format – hexadecimal numbers separated by colons, 4718:25E1:4450:C287:0018:52F3:B5C2:001F CP2077 - Networking

13

Address Resolution Protocol ✘ Within an Ethernet network, the physical address (MAC address) is necessary to provide intercommunication between devices ✘ It is not always possible for a source device to know the physical address of a destination device ✘ ARP provides a service of matching an IP address to a MAC address ✘ ARP broadcasts a request for the NAC address of a device with a particular IP address, and that device responds by sending back its MAC address ✘ This allows the source device to send to a specific MAC address without having to broadcast all messages (and slowing down the network)

CP2077 - Networking

14

Reverse Address Resolution Protocol ✘ The opposite of the ARP – provides the IP address for a device whose MAC address is known ✘ Typically used in networks using diskless workstations, these devices can not store their IP address but have access to the MAC address ✘ A RARP Server responds to the RARP request and provides an IP address for the device to use ✘ Once the device is turned off the IP address is available for the RARP server to assign elsewhere CP2077 - Networking

15

Internet Control Message Protocol ✘ ICMP is implemented on all TCP/IP networks, providing messaging that can help with troubleshooting, including ✘ Destination unreachable ✘ Time exceeded ✘ Redirect ✘ Echo ✘ Echo reply ✘ Information request ✘ Information reply ✘ Address mask request CP2077 - Networking

16

Transport Protocols ✘ Transmission Control Protocol – TCP uses checksums which are added to data packets to aid error checking, also uses sequence numbering to identify the order in which packets were sent, destination devices acknowledges correct receipt (otherwise requests re-transmission), slows down the network ✘ User Datagram Protocol (UDP) – uses a connectionless transportation system, does not use error checking or sequence numbering, assumes that other protocols will handle the error checking, only concerned with getting the data to the Transport Layer of the destination device, as it does not use error checking it requires few network resources (uses less bandwidth than TCP) CP2077 - Networking

17

Application Layer Protocols ✘ File Transfer Protocol (FTP) – a protocol, a service and an application. Allows transfer of files between devices. One of the first protocols to be developed. ✘ Trivial File Transfer Protocol (TFTP) – works with UDP to transfer files across the Internet, requires an acknowledgement of receipt of each packet before the next is transmitted ✘ Simple Mail Transfer Protocol (SMTP) – transfers email between devices, uses connection-oriented services of TCP to send and receive, as it was designed for UNIX not all OS understand SMTP – SMTP gateways are required to provide translation services CP2077 - Networking

18

Application Layer Protocols (2) ✘ Hypertext Transfer Protocol (HTTP) – used to access HTNL files on the Internet, provides only two services (requests from client and response from server), SHTTP provides the encryption and security checks lacking from the original ✘ Domain Name System (DNS) – manages and centralises domain names on the Internet, matches a host name to the IP address of a server where the host is located ✘ Telnet – protocol and application, takes place over a telephone network (hence name), allows end user to use a computer as a terminal for a communication session on a remote host (as if they were physically at the same location), translates commands so that the server can understand CP2077 - Networking

19

Application Layer Protocols (3) ✘ Dynamic Host Configuration Protocol (DHCP) – dynamically provides IP addresses to devices on a network which do not have one, a DHCP server provides the address from a pool either for a limited time or the duration of the device’s use of the network, has become very useful as the demand for IP addresses has increased ✘ Simple Network Management Protocol (SNMP) – allows the configuration, monitoring and management of network resources and devices CP2077 - Networking

20

Summary ✘ Importance of Protocols ✘ Protocol Suites ✘ OSI model and TCP/IP ✘ IP Addressing (version 4 and 6) ✘ Address Classes and Subnetting ✘ Network Layer Protocols ✘ Transport Layer Protocols ✘ Application Layer Protocols CP2077 - Networking

21