TCP/IP Architecture

In a Nutshell - CIW Course Section 1, Part C, Chapter 4

Internet Architecture

Here we shall look at how TCP/IP is used for the Internet. As with other protocols, the Internet Architecure is split into layers, with each layer corresponding with layers in the OSI/RM.

Network Access Layer: The Network Access Layer of the Internet Architecture corresponds to the physical and data link layers of the OSI model. The layer usually consists of: The OS device driver, the interface card and the physical connections.
Internet Layer: This layer corresponds to the network layer of the OSI model. Protocols used at the Internet Layer are: Internet Protocol (IP), Internet Control Message Protocol (ICMP), Internet Group Management Protocol (IGMP), Address Resolution Protocol (ARP) and the Reverse Address Resolution Protocol (RARP).
Transport Layer: The Transport layer corresponds to the transport and session layers of the OSI model. The transport layer accepts data from the application layer, splits it into packets and provides the flow of information between two hosts. Protocol used at this layer are: Transmission Control Protocol (TCP) and User Datagram Protocol (UDP).
Application Layer: The Application layer of the Internet Architecture relates to the presentation and application layers of the OSI model. Application programs such as remote terminal protocol (Telnet), File Transfer Protocol (FTP), Simple Mail Transfer Protocol (SMTP) can be invoked to access nodes on the network.

Internet Protocols

The diagram shows the protocols used in each layer of the Internet Architecture. Each protocol is listed below with it's respective RFC number.

Request for Comments (RFCS)

RFCs are published documents that include detailed information about standardised Internet Protocols. RFCs are identified by a number as will be seen shortly.

Before a protocol becomes a standard it goes through a number of acceptance stages and as it progresses through this acceptance it will be given a maturity level:

Experimental - Not intended for operational use.
Proposed - Under consideration and probably undergoing testing by various groups
Draft - Under serious consideration. testing continues and changes are referred back to the IESG. Any changes will require the status to be returned to Proposed
Standard - Protocols accepted and in use
Historic - No longer used
Informational - Protocols developed outwith the remit of the IETF/IESG

Internet Layer

Internet Protocol (IP) RFC 791

The Internet Protocol (IP) is the basic data transfer method used throughout the Internet. It is responsible for IP Addressing, and performs the routing function, which selects the path to send data to the destination IP Address.

Internet Control Message Protocol (ICMP) RFC 792

The Internet Control Message Protocol (ICMP) is the troubleshooting protocol of TCP/IP. It allows Internet hosts and gateways to report errors through ICMP messages.

Internet Group Management Protocol (IGMP) RFC 1112

The Internet Group Management Protocol (IGMP) is used for multicasting. In multicasting, one source sends a message to a group of subscribers (multicast groups). For multicast delivery to be successful, members must identify themselves and the groups that interest them to local multicast-enables routers.

Address Resolution Protocol (ARP) RFC 826

The Address Resolution Protocol (ARP) is used to translate Internet addresses to physical addresses, such as an ethernet network's 48-bit physical address.

Reverse Address Resolution Protocol (RARP) RFC 903

The Reverse Address Resolution Protocol (RARP) performs the reverse function of ASRP. It uses a node's hardware address to request an IP address. RARP is generally used for disl;ess workstations that do not have an IP address.

Transport Layer

Transport Control Protocol (TCP) RFC 793

The Transport Control Protocol (TCP) provides session management between the source and the destination systems. TCP is a stateful protocol, i.e. a session must be esatblished prior to transferring data.

User Datagram Protocol (UDP) RFC 768

The User Datagram Protocol (UDP) provides a simple datagram form of communication. One UDP packet is created for each output operation by an application, and a session is not necessary.

Application Layer

Hypertext Transfer Protocol (HTTP) RFC 1945 and 2616

The Hypertext Trnsfer Protocol (HTTP) is used to transport HTML documents (Web Pages) across the Internet. HTTP requires a client program (a browser) on one end and a server on the other, both running TCP/IP.

File Transfer Protocol (FTP) RFC 959

The File Transfer Protocol (FTP) is a system for transferring files between computers on a TCP/IP network. FTP is an efficient and quick way to transfer files as it does not have the overhead of encoding/decoding the data.

Trivial File Transfer Protocol (TFTP) RFC 1350

Trivial File Transfer Protocol (TFTP) is used for initialising diskless systems. It works with the BOOTstrap (BOOTP) protocol.

Chapter Continued . . .

SECTION 1