Lesson 1:Understanding the TCPIP Protocol Suite | MCSE Training Kit(c) Microsoft Windows XP Professional (Exam 70-270 2001)

TCP/IP provides communication across networks of computers with various hardware architectures and operating systems. Microsoft's implementation of TCP/IP enables enterprise networking and connectivity on computers running Windows XP Professional.

After this lesson, you will be able to

Describe the TCP/IP protocol suite and the TCP/IP tools that ship with Windows XP Professional

Estimated lesson time: 25 minutes

The TCP/IP Protocol Suite

TCP/IP is an industry-standard suite of protocols that enables enterprise networking and connectivity on Windows XP Professional-based computers. Adding TCP/IP to a Windows XP Professional configuration offers the following advantages:

A routable networking protocol supported by most operating systems. Most large networks rely on TCP/IP.
A technology for connecting dissimilar systems. You can use many standard connectivity tools to access and transfer data across dissimilar systems. Windows XP Professional includes several of these standard tools.
A robust, scalable, cross-platform client/server framework. TCP/IP supports the Microsoft Windows Sockets (Winsock) interface, which is ideal for developing client/server applications for Winsock-compliant stacks.
A method of gaining access to Internet resources.

The TCP/IP suite of protocols provides a set of standards for how computers communicate and how networks are interconnected. The TCP/IP suite of protocols maps to a four-layer conceptual model: network interface, Internet, transport, and application. These layers can be seen in Figure 4.1.

Figure 4.1 The TCP/IP suite of protocols within four layers

Network Interface Layer

At the base of the model is the network interface layer, which puts frames on the wire and pulls frames off the wire.

Internet Layer

Internet layer protocols encapsulate packets into Internet datagrams and run all the necessary routing algorithms. The four Internet layer protocols are Internet Protocol (IP), Address Resolution Protocol (ARP), Internet Control Message Protocol (ICMP), and Internet Group Management Protocol (IGMP). Table 4.1 describes these four Internet layer protocols.

Table 4.1 Protocols Included in the Internet Layer


Protocol	Description
IP	Provides connectionless packet delivery for all other protocols in the suite. Does not guarantee packet arrival or correct packet sequence. Does not try to recover from errors such as lost packets, packets delivered out of sequence, duplicated packets, or delayed packets. Packet acknowledgment and the recovery of lost packets are the responsibility of a higher layer protocol, such as TCP. IP is primarily responsible for addressing and routing packets between hosts.
ARP	Provides IP address mapping to the media access control (MAC) sublayer address to acquire the physical MAC control address of the destination. IP address resolution is required when IP packets are sent on shared access, broadcast-based networking technology, such as Ethernet. IP broadcasts a special ARP inquiry packet containing the IP address of the destination system. The system that owns the IP address replies by sending its physical address to the requester. The MAC sublayer communicates directly with the network adapter card and is responsible for delivering error-free data between two computers on a network.
ICMP	Provides special communication between hosts, allowing them to share status and error information. Higher level protocols use this information to recover from transmission problems. Network administrators use this information to detect network trouble. The Ping tool uses ICMP packets to determine whether a particular IP device on a network is functional. One instance in which ICMP provides special communication between hosts occurs when IP is unable to deliver a packet to the destination host; ICMP sends a Destination Unreachable message to the source host.
IGMP	Provides multicasting, which is a limited form of broadcasting, to communicate and manage information between all member devices in an IP multicast group. An IP multicast group is a set of hosts that listen for IP traffic destined for a specific IP multicast address. IP multicast traffic is sent to a single MAC address but is processed by multiple hosts. IGMP informs neighboring multicast routers of the host group memberships present on a particular network. Windows XP Professional supports multicast capabilities that allow developers to create multicast programs, such as Microsoft Windows 2000 Server NetShow Services.

Transport Layer

Transport layer protocols provide communication sessions between computers. The desired method of data delivery determines the transport protocol. The two transport layer protocols, described in Table 4.2, are Transmission Control Protocol (TCP) and User Datagram Protocol (UDP).

Table 4.2 Protocols Included in the Transport Layer


Protocol	Description
TCP	Provides connection-oriented, reliable communications for applications that typically transfer large amounts of data at once or require an acknowledgment for data received. TCP is connection-oriented, so a connection must be established before hosts can exchange data. TCP provides reliable communication by assigning a sequence number to each segment of data that is transmitted so that the receiving host can send an acknowledgment (ACK) to verify that the data was received. If an ACK is not received, the data is retransmitted. TCP guarantees the delivery of packets, ensures proper sequencing of the data, and provides a checksum feature that validates both the packet header and its data for accuracy.
UDP	Provides connectionless communications but does not guarantee the delivery or the correct sequence of packets. Applications that use UDP typically transfer small amounts of data at once. Reliable delivery is the responsibility of the application.

Application Layer

At the top of the model is the application layer, in which applications gain access to the network. There are many standard TCP/IP tools and services in the application layer, such as File Transfer Protocol (FTP), Telnet, Simple Network Management Protocol (SNMP), Domain Name System (DNS), and so on.

TCP/IP provides two interfaces for network applications to use the services of the TCP/IP protocol stack: Winsock and the NetBIOS over TCP/IP (NetBT) interface. Table 4.3 describes these two interfaces.

Table 4.3 Interfaces Through Which Applications Use TCP/IP Services


Interface	Description
Winsock	Serves as the standard interface between socket-based applications and TCP/IP protocols. An application specifies the protocol, the IP address of the destination host, and the port of the destination application. Winsock provides services that allow the application to bind to a particular port and IP address on a host, initiate and accept a connection, send and receive data, and close the connection.
NetBT	Serves as the standard interface for NetBIOS services, including name, datagram, and session services. It also provides a standard interface between NetBIOS-based applications and TCP/IP protocols.

Lesson Review

Here are some questions to help you determine whether you have learned enough to move on to the next lesson. If you have difficulty answering these questions, review the material in this lesson before beginning the next lesson. The answers are in Appendix A, "Questions and Answers."

What are the four layers to which the TCP/IP suite of protocols maps? What are the functions of the protocols that map to each layer?
Which of the following statements correctly describes IP? (Choose all answers that are correct.)
1. IP guarantees packet arrival and correct packet sequence.
2. IP provides connection-oriented, reliable communications for applications that typically transfer large amounts of data at one time.
3. IP is primarily responsible for addressing and routing packets between hosts.
4. IP provides connectionless packet delivery for all other protocols in the suite.
Which of the following statements correctly describes TCP? (Choose all answers that are correct.)
1. TCP provides connectionless communications but does not guarantee that packets will be delivered.
2. TCP provides connection-oriented, reliable communications for applications that typically transfer large amounts of data at one time.
3. TCP provides services that allow the application to bind to a particular port and IP address on a host.
4. TCP provides and assigns a sequence number to each segment of data that is transmitted.
Which of the four layers to which the TCP/IP suite of protocols maps does IGMP map to and what is IGMP used for?
What is multicasting?
The two transport layer protocols are ____________________________ and _______________________________________.
Which of the following statements correctly describes ARP? (Choose all answers that are correct.)
1. ARP is a protocol included in the Internet layer.
2. ARP is a protocol included in the transport layer.
3. ARP provides IP address mapping to the MAC sublayer address to acquire the physical MAC control address of the destination.
4. ARP is primarily responsible for addressing and routing packets between hosts.

Lesson Summary

Microsoft's implementation of TCP/IP provides a robust, scalable, cross-platform client/server framework that is supported by most large networks, including the Internet.
Windows XP Professional includes many standard connectivity tools to access and transfer data between dissimilar systems.
The TCP/IP suite of protocols maps to a four-layer conceptual model: network interface, Internet, transport, and application.
The four Internet layer protocols-IP, ARP, ICMP, and IGMP-encapsulate packets into Internet datagrams and run all the necessary routing algorithms.
IP provides connectionless, unreliable packet delivery for all other protocols in the TCP/IP suite and is primarily responsible for addressing and routing packets between hosts.
The two transport layer protocols-TCP and UDP-provide communication sessions between computers.
TCP provides connection-oriented, reliable communications for applications that typically transfer large amounts of data at once or require an acknowledgment for data received.
There are many standard TCP/IP tools and services in the application layer, such as FTP, Telnet, SNMP, DNS, and so on.
TCP/IP provides two interfaces for network applications to use the services of the TCP/IP protocol stack: Winsock and the NetBT interface.