Chapter 11 - Configuring the Server-to-Server Option
This chapter discusses the Manage Server-to-Server Connections menu. This menu allows you to perform the following operations:
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Specify another server with which you will establish a server-to-server connection. ![]()
Modify server entries that appear on the Manage Server-to-Server Connections screen. ![]()
Delete server entries that appear on the Manage Server-to-Server Connections screen. ![]()
Enable or disable entries that appear on the Manage Server-to-Server Connections screen. ![]()
Automatically establish server-to-server connections. ![]()
Display the status of all currently operating connections.
This chapter describes how to perform each of these configuration tasks.
In this chapter, information on the sample TCP/IP Server Information Worksheet from Chapter 6 is used in examples. This worksheet is repeated in Figure 11-1.
Accessing Server-to-Server Functions
The Manage Server-to-Server Connections menu allows you to establish connections with other VINES servers through a foreign host gateway. To display this menu, choose Manage Server-to-Server Connections from the TCP/IP selection of the Manage Communications main menu.
The Manage Server-to-Server Connections menu lists the servers with which you have manually configured a connection. Each entry contains the following fields:
Server - The name of the server. If the name is not yet known, the field displays a question mark (?).
Serial No. - The serial number of the server.
IP Address - The IP address of the target server's interface. This interface is the one that connects the target server to the foreign host gateway through which you are establishing the connection.
Subnetwork Mask - The subnetwork mask corresponding to the IP address.
Metric - This is an approximation of the amount of time (in 200-millisecond increments) required by the network to move a packet from your server to the target server. This setting is dependent on the type of physical media in your network.
MPS - Maximum packet size. This is usually the largest packet size supported by the media in your network. A setting of zero allows the system to use a default setting that corresponds to the physical media of the interface. Also referred to as MTU (Maximum Transfer Unit).
Sts - The status of the connection between your server and the target server, either E (enabled) or D (disabled), and the type of encapsulation used on the connection, either I (IP) or U (UDP).
Server-to-Server Management Tasks
The sections that follow explain how to add, modify, delete, and enable or disable server entries.
To add a server entry, follow these steps:
1. At the Manage Server-to-Server Connections menu, choose Add a server entry. The Add a server entry screen appears.
Only those servers that have recently communicated with the server being configured are listed.
Note: Servers configured through the Manage Routing through VINES Networks option do not appear on this list.
2. Choose a server from the list. If the server with which you want to establish a connection is not in the list, press F2 and enter the serial number of the target server.
If you choose a server from the list, the Configure a Server Entry screen appears.
If you chose the server from the list, its name is shown. Otherwise, a question mark (?) appears in the Server Name field.
3. Enter the IP address of the VINES server with which you want to communicate. When you press ENTER at the IP Address field, the Specify Subnetwork Mask screen appears.
4. Specify the appropriate subnetwork mask. When you press ENTER, the Specify Server-to-Server Configuration screen appears.
5. Enter the appropriate values for the routing metric, the maximum IP packet size, and the type of encapsulation. The next three sections provide guidelines for determining these values. If you use the default value (0) for the Maximum IP Packet Size, the configuration program uses a packet size that corresponds to the physical interface of the server. For example, if the server uses an Ethernet interface, the packet size will be 1500. The default encapsulation type is IP.
When you have finished entering the information for a server connection, the Manage Server-to-Server Connections screen appears.
Determining the Routing Metric
The routing metric should be the sum of the metrics of all links between the server you are configuring and the target server. Use Table 11-1 as a guide.
Caution: Changing the Routing Metric setting from the Specify Server-to-Server configuration screen may adversely affect the VINES network topology.
As an example, suppose you want to determine the routing metric for the connection illustrated in Figure 11-2.
The routing metric for a server-to-server connection between Server 2 and Server 1 in Figure 11-2 is the sum of the metrics of the intervening links. The routing metric you should specify is 51, which is the total of the three links:
Metric = 45 + 4 + 2 = 51
Determining the Maximum IP Packet Size
The maximum IP packet size (MPS) parameter is set according to the physical media and routing capabilities of your network.
Before you determine this setting, consider the following factors:
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What is the packet size supported on the media in your network? Some media, such as ProNET, support packet sizes larger than 1500 bytes. ![]()
If you are establishing a default gateway, what is the supported packet size of the media you use to reach that default gateway? ![]()
If you have routers and gateways in your IP network, what packet sizes do they support?
If you specify the default of zero, the system will use a maximum packet size appropriate to the interface you are using for the connection.
If you specify an MPS larger than your outgoing interface can support, the system will automatically adjust the MPS so that it is appropriate to your interface. For example, if you specify an MPS of 5000 bytes for an Ethernet interface, the system will use an MPS of 1500 bytes. You can, however, enter any packet size lower than that which is supported by your interface. In some cases, setting a lower MPS improves performance by reducing or eliminating the need for fragmentation by gateways, as explained in a following section.
Deciding Which Encapsulation Type to Use
You can use IP or UDP encapsulation. On a StreetTalk for Windows NT server, you must use UDP encapsulation. On a VINES server, you can use either UDP or IP encapsulation.
In a mixed network having both VINES and StreetTalk for Windows NT servers, use UDP encapsulation to allow all servers to communicate. In a network of VINES servers only, IP encapsulation involves less overhead but you can use UDP.
Fragmentation
When a TCP/IP router or gateway encounters a packet that is too large for the media on which it is to be sent, the packet is:
1. Broken into smaller packets
2. Transmitted
3. Reassembled when it is received at its destination
This process is called fragmentation. Fragmenting and reassembling packets is time-consuming. Therefore, minimizing the amount of fragmentation is important for the performance of your network.
If you cannot avoid fragmentation, you can control where the fragmentation occurs. The proper location for fragmentation is dependent on the types of servers and gateways in your network. Some trial-and-error testing may be necessary to determine the best settings for your network.
For example, Figure 11-3 shows a network with two servers connected by a gateway. The gateway handles packets up to 500 bytes in length only, whereas the network's Ethernet media supports packets up to 1500 bytes. If you configure the server-to-server connection with an MPS of 500 bytes, all the fragmentation and reassembly is performed by the VINES servers. The gateway is not required to perform any fragmentation or reassembly.
In contrast, if you set the MPS for the VINES servers to 1500 bytes, the VINES servers fragment only those packets that are larger than 1500 bytes. The gateway, which supports only 500-byte packets, must then fragment each of the 1500-byte packets it receives from the VINES servers. This can lead to slower response time in the network.
Before you modify any of the parameters that make up a server entry, carefully consider whether your changes will adversely affect communications between your server and other servers. For example, changing the IP address of another server may make it unreachable.
When you modify a server entry, the configuration program steps you through the same series of screens that were used to add the entry. Perform the following steps:
1. At the Manage Server-to-Server Connections menu, choose MODIFY a Server Entry.
2. Select the entry you wish to modify. Display the screens that contain server information, and modify the information accordingly. See "Adding a Server Entry" earlier in this chapter if you need information on these screens.
3. When you have finished modifying information, return to the Manage Server-to-Server Connections screen. This screen shows the new information you entered for the server.
Note: Changing the metric will affect the server's view of the network topology and force both ends of the connection to re-synchronize their routing table entries based on the new metric.
To delete a server entry, follow these steps.
Caution: Deleting a server entry may make that server, and all servers you access through that server, unreachable.
1. At the Manage Server-to-Server Connections menu, choose DELETE a Server Entry.
2. Select the entry you wish to delete.
3. The configuration program prompts you for confirmation. Specify YES to delete the entry, or NO to cancel the deletion. YES is the default.
Enabling and Disabling a Server Entry
You can enable or disable a particular server-to-server link. To do this, follow these steps.
Caution: Disabling a server entry may make that server and all servers you access through that server unreachable.
1. At the Manage Server-to-Server Connections menu, choose ENABLE/DISABLE a Server Entry.
2. Select the entry you wish to enable or disable.
3. The configuration program prompts you for confirmation. Specify YES to complete the operation, or NO to cancel the operation. YES is the default.
Server-to-Server Management Options
This section describes the following topics:
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Enabling and Disabling Automatic Connectivity ![]()
Displaying the Status of Connections
Enabling and Disabling Automatic Connectivity
If you enable automatic connectivity, a server-to-server connection will be established with any server that has your server's name, serial number, and IP address in its TCP/IP configuration, and attempts to communicate with your server.
Caution: Your server does not have any control over which server attaches to it. Therefore, you should carefully set up your network security. Refer to Managing VINES Security for more information.
To enable or disable automatic connectivity, follow these steps:
1. At the Manage Server-to-Server Connections menu, choose ENABLE/DISABLE Automatic Connectivity.
2. The configuration program prompts you for confirmation. Specify YES to complete the operation, or NO to cancel the operation. YES is the default.
Caution: Disabling automatic connectivity removes any automatically configured server entries, as well as any VINES routes associated with these server entries. This could adversely affect the VINES network topology.
Once another server has established a connection with your server, the configuration information appears on the Manage Server-to-Server Connections screen.
Displaying the Status of Connections
When you choose Display Status of Connections from the Manage Server-to-Server Connections menu, the Display Status of Connections screen appears.
An asterisk ( * ) beside an entry on this screen indicates that the server was not manually configured, but was automatically configured.
This screen shows each server-to-server connection configured for this server, and the status of that connection. The status is indicated by the value in the Flags field. Table 11-2 shows all the possible values that may appear in the Flags field, and the meaning of each value.
Flag | Meaning |
0 | No connection has been established. If this connection is not disabled, the server with which you are trying communicate has not responded, still in request mode |
1 | Server is connected. A VINES routing packet has been received from this routing server. Use MNET to verify whether full routing information has been exchanged. |
2 | This server-to-server connection has been automatically established. This server is not locally configured but it has been able to establish a connection to your server because automatic connectivity is enabled. |
8 | This connection was manually disabled. If this flag is set, flag 1 will not be set. |
20 | This server-to-server connection has been established as a result of a UDP redirect. If this flag is set, flag 2 will not be set. |