The Protocols of the TCP/IP Model Each layer of the TCP/IP model adheres to a different set of rules for communication. These are the protocols that are used at each of the layers to ensure that peer-to-peer communication occurs correctly between hosts . This section lists the protocols that are in operation for each of the layers. Network Interface Layer Protocols Protocols of the Network Interface layer also include those of the Hardware layer because the Hardware layer is seen as being incorporated into the Network Interface layer. The following protocols operate at the Network Interface layer: -
IEEE 802.3 Ethernet including CSMA/CD ” The standard network access method used in Ethernet networks. -
IEEE 802.4 Token Bus ” A network access method used in a bus topology, which also utilizes a token passing mechanism. -
IEEE 802.5 Token Ring ” A network access method used primarily in a ring topology, which utilizes a token passing mechanism. -
Serial Line Internet Protocol (SLIP) ” A protocol used for serial communication between two machines that have been configured to talk to each other, such as a dialup connection to an Internet service provider (ISP). -
Point-to-Point Protocol (PPP) ” A protocol used for serial communication, such as a dialup connection to an ISP. PPP is preferred over SLIP because it can share a line with other users and provides error detection ”facilities not provided with SLIP. Internet Layer Protocols Protocols in use at the Internet layer include the following: -
Address Resolution Protocol (ARP) ” A protocol used to map a 32-bit IP address to a 48-bit Ethernet address. -
Reverse Address Resolution Protocol (RARP) ” A protocol used to map a 48-bit Ethernet address to a 32-bit IP address. -
Internet Protocol (IP) ” A protocol that handles connectionless delivery of datagrams across the network. -
Internet Control Message Protocol (ICMP) ” An integral part of IP that is used to send error and control messages to other hosts on the network. -
Various Internet Security protocols (IPSEC) ” A collection of protocols that provides additional security to data traveling across networks.  | Each of the protocols listed here are discussed in more detail in Chapters 3 and 4. |
 | ARP and RARP are protocols that actually operate between the Network Interface layer and the Internet layer, but are generally described as Internet layer protocols. |
Transport Layer Protocols The Transport layer includes the following two protocols: -
Transmission Control Protocol (TCP) ” A connection-oriented, stateful, and reliable protocol used to exchange data between hosts on a network. -
User Datagram Protocol (UDP) ” A connectionless, stateless, and unreliable protocol used to exchange data between hosts on a network ”the reliability is provided by the network itself or the application. | | TCP and UDP are discussed in more detail in Chapter 9. |
Application Layer Protocols A number of protocols are in use at the Application layer, some of which are listed here: -
Telnet ” Terminal communication between two hosts on a network. -
FTP ” The File Transfer Protocol, used for copying files between two hosts on a network. -
SMTP ” Simple Mail Transfer Protocol, used for email transfer. -
POP3 ” Post Office Protocol version 3, used to allow the remote retrieval of email, from the Internet for example. -
DNS ” Domain Name System, used to resolve addresses to hostnames. DNS is discussed in Chapter 10, "Domain Name System (DNS)." -
DHCP ” Dynamic Host Configuration Protocol, used to assign IP addresses to hosts automatically. DHCP is discussed in Chapter 11, "Basic DHCP." -
HTTP ” Hypertext Transfer Protocol, used to access data via a Web browser.  |
