InformIT: Mac OS X Unleashed > The Network Control Pane

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The Network Control Pane

The Network control pane, already introduced during the installation, is the GUI brain center of the OS X interface to TCP/IP. This control pane, in actuality, just provides a series of hints to the underlying Unix TCP/IP control software, but it does so in a much more elegant fashion than twiddling configuration parameters at the command line. The primary control with which you should familiarize yourself is the Configuration menu. In previous versions of Mac OS, various portions of the networking software were configured by separate control panels, and each panel was controlled by its own independent saved configuration setting. Mac OS X has instead placed all network configurations under a single parent control pane, with an umbrella configuration setting that covers TCP/IP, modem control, AppleTalk, and location settings. By default, under the Configurations menu you have options for PPP (dialup), Ethernet, AirPort (if your machine has an AirPort), and Advanced.

The Advanced Subpane

The available selections in the Configure menu switch between a number of subpane groups for the Network control pane. The Advanced subpane, doesn't provide advanced network configuration, but allows you to enable and disable already existing configurations, and create new configuration sets. Figure 9.2 shows the Advanced subpane of the Network control pane. OS X, to make network configuration as easy as possible, attempts to automatically detect and select the correct network configuration for any given situation. This convenience comes at a slight cost in startup time, so unless you actually intend to use all the available configurations, we don't recommend leaving all the configurations enabled as shown in the figure.

Figure 9.2 The Advanced subpane of the Network control pane.

If you've already experimented enough to find the location settings, the capability to save additional configurations might seem redundant. It becomes useful, however, in situations where you have multiple IP addresses at the same location, on a single network interface. Without iterating through different location settings, setting up several different configurations would allow the system to automatically search through each until it found a working set of parameters. This might occur if you have multiple in-building networks with different IP ranges on each, but with each connected to share resources.

Another possible use is if you have a number of different dialup service providers, and want your machine to try each until it finds an open one.

Modem

Under the Modem Configuration menu option, you can configure the settings required to establish a dialup connection. The subpanes available enable the configuration of how TCP/IP gets its settings, the PPP (Point to Point Protocol, carried over a dialup connection) configuration parameters, modem settings, and network proxy server settings.

Under the TCP/IP subpane, shown in Figure 9.3, you can configure how your TCP/IP stack gets its control and configuration information. The manual configuration settings, shown in the figure, allow you to configure individual options by hand, but it would be unusual if an ISP (Internet Service Provider) did not provide the information for these settings automatically, using PPP.

Figure 9.3 The TCP/IP subpane, showing available options for the dialup (Modem) configuration set.

If you need to provide manual configuration information, you will need to know and fill in the following information—you should be able to get this information from your network administrator:

IP Address— Your computer's IP address. This should be four sets of digits, separated by periods, like 192.168.1.21.
Subnet Mask— This should be four sets of numbers separated by periods, as well. Most likely it will be 255.255.255.0, or 255.255.0.0.
Router— The machine that your machine must contact to reach the outside network world. This will frequently (but not always) be similar to your IP address, only with the final number replaced by a 1. Your network administrator might also call this machine a gateway.
Domain Name Servers— The IP addresses of machines that will translate between IP addresses and fully qualified domain names (FQDNs) such as www.apple.com.
Search Domains— Partial domain names to append to machine names, if you give less than an FQDN. For example, you might frequently work with machines on the domains osxunleashed.com and apple.com. If you want your machine to try to connect to info.osxunleashed.com or info.apple.com whenever you ask it to connect to info, you can enter the domains here. Your machine will try them both when it discovers that you've asked for a name that does not resolve as an FQDN.

Under the PPP subpane, shown in Figure 9.4, you can configure how to connect to your ISP. Almost all ISPs use PPP to provide TCP/IP over dialup connections. If yours does not, you will need to follow its instructions, which will probably include installation of some custom software.

Figure 9.4 The PPP subpane of the Modem configuration allows you to specify your dialup account information.

The PPP subpane has the following fields:

Service Provider— An optional field where you can specify a name for the service provider. This option will be useful if you have multiple providers that your machine needs to dial, and you need a better way to keep track of them than just by phone number.
Telephone Number— The telephone number to dial.
Alternate Number— An alternative number to dial for the same service provider. If your ISP doesn't have alternative dial-in numbers, leave this blank.
Account Name— The username or account name that you have with this ISP.
Password— The password for this account and ISP.
Save Password— If your machine is going to be used by multiple users, and you don't want them to be able to connect to the Internet using your account information and password, don't check this box.

The PPP panel also has a PPP Options button and corresponding drop-down pane that enables you to configure several other options with respect to the dialup connection, as shown in Figure 9.5.

Figure 9.5 The Session and Advanced dialup options drop-down pane for dialup connections.

The pane enables you to configure

Whether to automatically dial and make a connection when an application starts that needs TCP/IP services.
Whether, and how frequently, to prompt you to stay connected, if there hasn't been any recent network activity.
How long to wait before disconnecting when there's no network activity.
Whether to disconnect when there's no user logged in on the console.
Whether to, how many times to, and how rapidly to redial the phone if the ISP is busy.
Whether to send PPP echo packets. Some ISPs periodically send little "are you really there?" messages to connected computers to make sure that everything is working properly—this option controls whether to respond. Unless you have been told by your ISP to do otherwise, leave this option checked.
Whether to compress TCP header information. TCP/IP information is carried in packets, with a significant amount of meta-information about the contents of the packet. Compressing this information can speed your network connection, but requires processor power. On a fast machine, you'll probably get a network speedup from compressing headers, unless your ISP is using some ancient hardware that takes more time to perform the compression/decompression than the savings in transmission time.
Whether to use a manual terminal window for connection. If your ISP doesn't use a standard PPP server, you might need to carry on some textual dialog with the server during connection. Selecting this option will open a terminal for you to interact with the host during connection.
The verbose logging option will increase the amount of information regarding dialup connections stored in the system logs.

The Modem subpane, shown in Figure 9.6, allows you to select your modem, configure the dialing type, and determine whether you want to hear your connections as they progress.

Figure 9.6 The Modem subpane of the Modem configuration.

If you're on a network segment where you must connect to proxy servers instead of directly to outside services such as FTP and Web servers, the Proxies subpane is the place to tell the system about the proxies. Shown in Figure 9.7, the Proxies subpane allows you to select what is needed and how to contact the proxy types.

Figure 9.7 The Proxies subpane of the Modem configuration option. This pane is identical to Modem, Ethernet, and AirPort configuration sets.

The Proxies submenu proxy types are

FTP Proxy— If you need to contact a proxy to use FTP, enter its IP address and the proxy port here.
Gopher Proxy— Gopher was an early browser-based way of serving data around the Internet, and has been all but completely supplanted by Web servers. If you've found one of the worlds' few remaining Gopher servers and need to access it through a proxy, this is where you tell the system about it.
SOCKS Firewall— The SOCKS firewall system can be used to proxy for a number of different network services. If your network uses a SOCKS-type firewall, enter its information here.
Streaming Proxy (RTSP)— Most types of proxy setups are designed to prevent a remote host from having any chance of connecting back to your machine. This makes it difficult for streaming services that need to send a lot of data as quickly as possible; hence, a specific proxy type for streaming data. If you're behind a firewall, you probably need to configure this—if your network services allow streaming data through at all.
Web Proxy (HTTP)— Configure this if you need to go through a proxy to access the Web. There are occasions where you might want to use a Web proxy even if you don't have to. For example, if you want to make your server connections anonymous by going through one of the Web's anonymous proxy servers.

You can also configure your machine to use PASV (passive) FTP mode for transferring data, an option that will probably be required if you are behind a firewall, or on a NAT (network address translation) private local network.

Finally, you can configure hosts and domains in which the proxy settings should be ignored. If you contact servers both inside and outside your local firewall, you might want to provide your local network information for this option. Therefore, your machine doesn't need to contact the proxy, and then reconnect inside your local network for interior connections.

Ethernet

If you are connected to your network via an Ethernet connection (a physical chunk of wire, typically twisted pair, which looks like a bulky phone cable), you'll need to configure your connection under the Ethernet configuration option. Because switching from one physical transport to another requires only changing a little bit in a few protocol layers, it's similar to dialup configurations you've already seen.

Again, under the TCP/IP subpane, you have the option of providing manual configuration settings or of getting your configuration parameters from a server. If you have a static IP address and configuration that you must supply manually, the options are identical to those discussed under the Modem configuration. In addition, you have the option of selecting from DHCP configuration of all options, DHCP configuration of all options except the IP address, and BootP configuration of all options.

Tip

Note that although there are essentially identical TCP/IP and other subpanes available under this and other configurations, the settings entered in each are specific to the interface configuration set in which they are entered. Information entered in one interface configuration set does not automatically become the default information for any other interface. Therefore, you might need to enter such things as proxies, for example, in more than one place, depending on how your network is set up.

As mentioned earlier, TCP/IP is just one of a number of communication protocols. It's actually possible to run multiple communication protocols over the same piece of wire at the same time. In a clever use of this capability, it's possible to establish a PPP connection via Ethernet wiring, instead of a phone line. If your service provider gives you this option, you can configure it with the subpane shown in Figure 9.9.

Figure 9.9 The PPPoE subpane of the Ethernet configuration set. The options available here are exactly analogous to the options under the dial-in PPP configuration.

Figure 9.8 The TCP/IP options for the Ethernet configuration are essentially identical to those for the Modem configuration.

In this subpane, you have the following fields to fill in:

Service Provider— An informational field similar to the service provider field for a dial-in connection.
PPPoE Service Name— Another informational field.
Account Name— The user or account name for your PPPoE ISP.
Password— The password for your account.
Save Password— Again, if you want this account to function automatically without needing to specify a password at each network connection, select this option.

The PPPoE subpane (like the PPP pane) has settings similar to the Dial-in/PPP configuration, in which you can specify options, such as how long to wait before disconnection. Click the PPPoE Options button to display the drop-down pane.

The Ethernet configuration setting set also includes a Proxies subpane identical to that under the Dialup configuration and an AppleTalk subpane. As mentioned previously, AppleTalk is a different communication protocol that is independent of TCP/IP, so this pane will be covered in a section dedicated to AppleTalk later in this chapter.

AirPort

The final default configuration type is the AirPort configuration set. This configuration has TCP/IP and Proxies subpanes with options that are identical to the Ethernet configuration settings. It also includes an AirPort subpane, shown in Figure 9.10, wherein you can choose your default AirPort network, and enter your network password if required.

Figure 9.10 The AirPort subpane of the AirPort configuration set.

If you have an AirPort card, an AirPort Dockling will appear in your dock. The AirPort Dockling provides a continuous display of your signal strength, and access to basic AirPort functionality such as disabling the card and choosing the network to connect to.

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