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.
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:
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
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 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 |
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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 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 |
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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. |
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 |
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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. |
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."