Chapter 4 Introduction to TCP/IP Protocols

This chapter is all about “Protocol”. As we have learned Protocol is the rule that governs computers and the exchange of data on the network. The protocol suite which is virtually on all networks today is Transmission Control Protocol/Internet Protocol. (TCP/IP) It is not just one protocol rather a suite of specialized protocols, including TCP, IP, UDP, ARP, and many others called subprotocols. TCP/IP has become the standard based on the following advantages:

• It is open rather than proprietary – not owned by any company.
• It is flexibly – can run on virtually any platform.
• It is routable – can be interpreted by routers.

The following diagram depicts the TCP/IP model. It is essentially four layers that correspond to seven of the OSI model.

The OSI model is considered more theoretical whereas the TCP/IP is considered more practical. Understanding what functions belong to each layer of the model will be beneficial when analyzing problems.

The following is a list of subprotocols of the TCP/IP suite.  These core TCP/IP protocols operate in the transport or network layers of the OSI model and provide basic services to protocols in other layers.

• TCP - Transmission Control Protocol provides reliable data delivery services.
• UDP – User Datagram Protocol is a connectionless transport service.
• IP – Internet Protocol provides how and where data should be delivered.
• IGMP – Internet Group Management Protocol manages multicasting on networks running IPv4.
• ARP – Address Resolution Protocol creates a database that maps the MAC address to the IP address.
• ICMP – Internet Control Message Protocol reports on success or failure of data delivery.

The following list application layer protocols translate user requests into a format the network can read.

• Telnet- is a terminal emulation protocol used to log on to remote hosts using TCP/IP suite.
• FTP – File transfer Protocol is used to send and receive files via TCP/IP using ports 20 and 21.
• TFTP - Trivial file transfer protocol that enables file transfers between computers but is simpler.
• NTP – Network time protocol is used to synchronize clocks of computers on a network.
• Ping – Packet Internet Groper is a utility that can verify that TCP/IP is installed.

 The most common way to express an IP addresses is the Dotted decimal notation. This refers to the shorthand convention used to represent IP addresses and makes it easy for people to read. An example of a dotted decimal IP address is 121.44.12.18. In addition to an IP address that is running IPv4, a subnet mask is assigned. A subnet mask is a special 32 bit number that when combined with the device’s IP address informs the rest of network about the segment or network to which the device is attached.

The chapter covers the assigning of IP address and DHCP (Dynamic Host Configuration Protocol) which is an automated means of assigning a unique IP address to devices on the network. It explains DHCP leasing and terminating lease process. It also, briefly talks about “private and link-local addresses” which is a means to extend the number of available addresses along with some other features.

The text also talks about Host names and DNS (Domain Name System) and sockets and ports.

There was a great deal of material in this chapter which helped provide a good understanding of Protocols and the OSI model and the TCP/IP model. This will be a good reference chapter for future use.