Overview of Internet Technology

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Networking with TCP/IP

Client/Server Aspect of TCP/IP

	The server and the client are aware of each other and work together to coordinate service availability.
	TCP/IP uses the client/server model of communication in which a computer user (a client) requests and is provided a service (such as sending a Web page) by another computer (a server) in the network.
	TCP/IP communication is primarily point-to-point, meaning each communication is from one point (or host computer) in the network to another point or host computer.

What the TCP/IP Protocols Do

	Break data into small units that can be efficiently transmitted.
	Communicate the destination of the data to the network.
	Verify the receipt of the data on the other end of the transmission.
	Reconstruct the data in its original form.

Two Major Components of TCP/IP

	TCP (Transport Control Protocol)
	IP (Internet Protocol)

IP

Network Layer Protocol

Envelopes and addresses the data

	Specifies the data format
	Performs routing functions

Enables the network to read the envelope and forward the data to its destination

Defines how much data can fit in a single "envelope" (a packet)

IP defines the internet datagram as the unit of information passed across the internetwork.

Provides an unreliable, connectionless data delivery service on a "best effort basis."

RFC

http://www.cis.ohio-state.edu/htbin/rfc/rfc791.html

TCP

Breaks data up into packets that the network can handle efficiently

Verifies that all the packets arrive at their destination

Reassembles the data

RFC

http://www.cis.ohio-state.edu/htbin/rfc/rfc793.html

Reference

	http://www.scit.wlv.ac.uk/~jphb/comms/tcp.html
	TCP/IP 15 Minute Series

UDP - User Datagram Protocol

An alternative to the Transmission Control Protocol (TCP).

Like the Transmission Control Protocol, UDP uses the Internet Protocol to actually get a data unit (called a datagram) from one computer to another.

Unlike TCP, however, UDP does not provide the service of dividing a message into packets (datagrams) and reassembling it at the other end.

UDP doesn't provide sequencing of the packets that the data arrives in.

	This means that the application program that uses UDP must be able to make sure that the entire message has arrived and is in the right order.
	Used by Network applications to save processing time because they have very small data units to exchange (and therefore very little message reassembling to do) may prefer UDP to TCP.

The Trivial File Transfer Protocol (TFTP) uses UDP instead of TCP.

UDP provides two services not provided by the IP layer. It provides port numbers to help distinguish different user requests and, optionally, a checksum capability to verify that the data arrived intact.

RFC

http://www.cis.ohio-state.edu/htbin/rfc/rfc0768.html

ARP/RARP - Address Resolution Protocol

Low-level protocol that dynamically maps network layer addresses to physical media access control (MAC) addresses.

ARP allows the source host or router to find the MAC address of the destination host on the same network segment, given only the network layer address of the destination system.

For example, a router receives an IP packet destined for a host connected to one of its LANs. The packet only contains a 32-bit IP destination address. To construct the data link layer header, a router must acquire the physical MAC address of the destination host and map that address to the 32-bit IP address. This function is called address resolution.

RFC

	http://www.cis.ohio-state.edu/htbin/rfc/rfc0826.html
	reverse resolution - http://www.cis.ohio-state.edu/htbin/rfc/rfc0826.html

ICMP - Internet Control Message Protocol

ICMP is at the same relative layer as IP

Provide information about routes to destination addresses.

It's purpose is to transmit information needed to control IP traffic.

ICMP redirects messages to inform hosts about more accurate routes to other systems

ICMP unreachable messages indicate problems with a route.

ICMP can cause TCP connections to terminate ``gracefully'' if the route becomes unavailable.

Ping is a commonly-used ICMP-based service.

RFC

http://www.cis.ohio-state.edu/rfc/rfc0792.txt