Overview of Windows XP Professional TCPIP

Overview of Windows XP Professional TCP/IP

TCP/IP provides communication across interconnected networks that use diverse hardware architectures and various operating systems. TCP/IP can communicate with computers running Windows XP Professional and other Microsoft operating systems, or non-Microsoft systems such as UNIX.

TCP/IP in Windows XP Professional builds upon the Microsoft Windows 2000 TCP/IP implementation, which in itself is an improvement over the TCP/IP functionality found in Microsoft Windows NT Workstation version 4.0. Table 21-1 shows some of the features of the TCP/IP implementation in Windows XP Professional.

Table 21-1: Features of TCP/IP in Windows XP Professional

Feature	Description
Logical and physical multihoming	Allows association of multiple IP addresses to single or multiple network adapters for internetwork connectivity.
Internal IP routing capability	Allows a Windows XP Professional based computer to route packets between multiple network adapters.
Multiple configurable default gateways	Allows configuring multiple default gateways to improve network reliability and availability.
Virtual private networking	Permits secured transmission of data across public networks through encapsulated and encrypted packets.
Windows Sockets Version 2 (Winsock2) interface	Standard application programming interface (API) permits access to networking features.
NetBIOS interface	Allows the use of NetBIOS sessions, datagrams, and name management over TCP/IP.
My Network Places browsing support	Lists of network resources for My Network Places can span a TCP/IP internetwork.
Simple Network Management Protocol (SNMP) agent	Permits performance and resource monitoring of a TCP/IP host.
TCP/IP connectivity tools	Command-line tools such as Finger, Ftp, Rcp, Rexec, Rsh, Telnet, and Tftp allow access to heterogeneous hosts across a TCP/IP-based network.
Simple TCP/IP tools	Chargen, Daytime, Discard, Echo, and Quote of the Day client and server tools.
TCP/IP management and diagnostic tools	Command-line tools such as Arp, Ipconfig, Nbtstat, Ping, Netsh, Route, Nslookup, Tracert, and PathPing provide maintenance and diagnostic features.
TCP/IP network printing	Permits printing on other-connected devices, such as UNIX-connected devices.

Defining TCP/IP

TCP/IP is a suite of interconnected protocols, which has evolved with the Internet as its communications standard. Because Internet connectivity is now a dominant force in networking, TCP/IP has all but eclipsed other networking protocols. All other protocols in the TCP/IP suite rely on the basic services provided by the following protocols: Internet Protocol (IP), Address Resolution Protocol (ARP), Internet Control Message Protocol (ICMP), Internet Group Management Protocol (IGMP), Transmission Control Protocol (TCP), and User Datagram Protocol (UDP).

TCP/IP in Windows XP Professional offers the following advantages:

• A standard, routable enterprise networking protocol that is the most complete and accepted networking protocol suite available.

• All current network operating systems offer TCP/IP support, and most large networks rely on TCP/IP for much of their network traffic.

• A technology for connecting dissimilar systems.

• A number of protocols in the TCP/IP suite are available to access and transfer data between dissimilar systems, including File Transfer Protocol (FTP) and Telnet, a terminal emulation protocol. Several of these standard tools are included with Windows XP Professional.

• A dependable, scalable, cross-platform client/server framework.

• TCP/IP in Windows XP Professional uses the Windows Sockets interface, which is ideal for developing client/server applications that can run on Windows Sockets compliant stacks from other vendors.

• A method of gaining access to the Internet.

• The Internet is a world-wide collaboration of networks, connecting research facilities, universities, libraries, private companies, and individuals.

TCP/IP Features in Windows XP Professional

The following features are part of the TCP/IP implementation in the Windows XP Professional operating system.

Automatic determination of interface based metrics for default gateway assignment

Every computer that runs TCP/IP makes routing decisions. These decisions are controlled by the IP routing table. The routing table is built automatically, based on the current TCP/IP configuration of your computer. Each route occupies a single line in the displayed table. The routing table is searched by your computer for an entry that is the most specific match to the destination IP address.

Your computer uses the default route if no other host or network route matches the destination address included in an IP datagram. The default route typically forwards an IP datagram (for which there is no matching or explicit local route) to a default gateway address for a router on the local subnet.

Because the router that corresponds to the default gateway contains information about the network IDs of the other IP subnets within the larger TCP/IP internet, it forwards the datagram to other routers until the datagram is eventually delivered to an IP router that is connected to the specified destination host or subnet within the larger network.

A metric allows you to select the best path to a destination by indicating the cost or logical distance to a specific address. In this instance, it allows your computer to choose, as your default gateway, the router interface that is the shortest distance (or has the lowest metric cost) from your computer. In the case of the Routing Information Protocol (RIP), the metric indicates the number of hops to the destination.

If your default gateway has been automatically assigned, you can use the Advanced TCP/IP Settings dialog box to indicate whether you want that automatically assigned default gateway to have an automatically assigned or a static metric. If you choose a static metric, you are able to specify that metric in a text box.

If you have multiple interfaces and you configure a default gateway for each interface, TCP/IP by default automatically calculates an interface metric that is based on the speed of the interface. The interface metric becomes the metric of the default route in the routing table for the configured default gateway. The interface with the highest speed has the lowest metric for its default route. The result is that whenever multiple default gateways are configured on multiple interfaces, the fastest interface will be the one used to forward traffic to its default gateway.

In previous implementations of TCP/IP in Windows, multiple default gateways all had a default route metric set to 1, and the default gateway used depended on the order of the interfaces. This sometimes caused difficulty in determining which default gateway the TCP/IP protocol was using.

On Windows XP Professional based computers, the automatic determination of the interface metric is enabled by default through the Automatic metric check box on the IP Settings tab on the advanced properties of the Internet Protocol (TCP/IP) protocol.

You can disable the automatic determination of the interface metric and type a new value for the interface metric. If multiple interfaces have the same lowest interface metric, the default gateway of the first network adapter is used. The default gateway for the second network adapter is used when the first is unavailable.

To access the Advanced TCP/IP Settings dialog box

In Control Panel (default view), click Network and Internet Connections.

1. Click Network Connections.

2. In Network Connections, right-click the local area connection you want to modify, and then click Properties.

3. In the Local Area Connection Properties dialog box, select Internet Protocol (TCP/IP), then click Properties.

4. In the Internet Protocol (TCP/IP) Properties dialog box, click Advanced.

5. The Advanced TCP/IP Settings dialog box appears.

If you plan instead to assign one or more static default gateways to an interface, you can use the Advanced TCP/IP Settings dialog box to do so by selecting Add beneath Default gateways. When you enter the static address of a default gateway, you can also indicate if you want that static default gateway to have an automatically assigned or a static metric. If you want a static metric, you can specify that metric in a text box.

For more information about configuring default gateways and interface-based metrics, see Configuring IP Address and Name Resolution in this book.

Alternate Configuration

Laptops that participate on more than one network often use a static IP address at home and a dynamically assigned IP address at the office. In earlier versions of Windows, this required reconfiguration of TCP/IP settings. By configuring an alternate configuration, you can configure TCP/IP to first try Dynamic Host Configuration Protocol (DHCP), and then configure an alternate static IP address setting if a DHCP configuration is not received. For more information about alternate configuration, see Configuring IP Address and Name Resolution in this book.

IGMP v3

Multicast is communication between a single sender and multiple receivers on a network. Internet Group Management Protocol (IGMP) is used to exchange membership status data between members of multicast groups and neighboring IP routers that support multicast forwarding.

Earlier versions of Windows support only IGMP version 1 and version 2. IGMP Version 3 (IGMPv3) adds support for source filtering, which enables a multicast group member to specify that they want to receive multicast traffic from specified sources or from all but a specific set of sources.

Network Diagnostics

Network Diagnostics provides improved network and connectivity testing and validation. Network Diagnostics is a feature of the new Help and Support Center in Windows XP. To run Network Diagnostics, click Start, then click Help and Support. Under Pick a Task, click Use Tools to view your computer information and diagnose problems, and then click Network Diagnostics.