Chapter 2 - StreetTalk Naming Service
The StreetTalk Naming service is a Banyan service that allows you to assign unique names and attributes to users and resources (printers, servers, services, and so on) in the network in order to easily find and manage them. Attributes describe and categorize properties of the resource. A later section contains examples of attributes.
Every Banyan server has its own StreetTalk Naming service identified as ST@servername@Servers, where servername is the name of the server. The organization Servers is automatically created. Server names are used to create groups within the Servers organization. A network composed of servers USCHI001 and USCH002 automatically defines groups called USCHI001@Servers and USCHI002@Servers.
StreetTalk runs on VINES servers and StreetTalk for Windows NT servers.
Individual users, groups of users, and resources are added to the server and given names in the StreetTalk service located on that server. Unless the administrator later moves them, each resource remains on the server and is "owned" by the StreetTalk service on that server. The server on which a user's StreetTalk service resides is that user's home server.
Every StreetTalk service maintains a database on the server on which it runs. The database contains detailed information about:
Groups physically located on the server Items in each group All name and attribute information associated with items in the groups The location of other groups on different servers in the network stored in group tables
Access to resources is always consistent because detailed, item-level information is updated and shared among servers. (Organizations, in contrast to groups, exist only logically as a way of associating groups together. Individual servers do not maintain organizations.)
In a single-server network, the StreetTalk directory is this database. In a multi-server network, the directory is distributed among servers and there is no single point of failure. Services regularly share information, indicating their own database changes to all StreetTalk services in the network. Thus, StreetTalk services maintain a complete and up-to-date picture of resources available on the network. The network does not have a centralized naming server, which, if not available, could limit the network's ability to function. In a Banyan network, names are accessible to the entire network even if a server fails. You can relocate or replace resources without directly impacting users.
Tracking all resources in this way eliminates the need for complex addressing schemes and allows network users to find resources using natural and logical names consistent with their workplace. Users do not need to know where a resource is located; they only need to know a resource name. If a user knows the name, StreetTalk can find the resource if it is currently available.
Group Tables
Every server has an internal group table that maps group names to server names. When one StreetTalk service needs to query information about a group that it does not maintain, it can quickly connect to the appropriate StreetTalk service based on its internal group table. StreetTalk services cooperate to provide comprehensive directory management to the network. For example, if a Banyan program running on server Maple requests information maintained on server Birch, the StreetTalk service on Maple (ST@Maple@Servers) immediately issues a query to ST@Birch@Servers.
Distributing Information
In a multi-server network, the StreetTalk service periodically distributes information contained in the StreetTalk directory. Servers update one another whenever a new server is added or a group is added or deleted.
When you add a group, you choose a server to maintain that group. (Chapter 5 describes StreetTalk groups.) The server then notifies other servers that it is responsible for that group. The StreetTalk directory is also updated automatically at set intervals. If you shut down the server for maintenance, only the resources in the groups that the server maintains are affected.
StreetTalk's distribution of information is transparent to network users. Their view of StreetTalk is the same in both single-server and multi-server networks.
StreetTalk Guaranteed Login (SGL) is a feature that enables you to log in even when your home server - the server on which your StreetTalk login information resides - is not available. SGL guarantees that you can log in because it allows you to replicate the necessary StreetTalk information on servers other than your home server. This replication is done on a group by group basis. Each group can exist on up to two other servers besides the home server.
Note: StreetTalk Guaranteed Login is supported only for groups on a server running VINES 6.0 or greater or StreetTalk for Windows NT 7.5 or greater.
StreetTalk Guaranteed Login requires that you set up shadow groups, which are described in Chapter 5.
Calculating Disk Space Requirements
StreetTalk databases dynamically adjust their disk space requirements based on the number of resources you create as well as the number and size of attributes associated with them. Chapter 15 and Chapter 16 describe attributes.
As a rule, the database of each StreetTalk service requires the following amounts of disk space:
You must reserve 800 bytes of disk space to store each database entry (name). For each attribute established for a user, allocate an additional 180 bytes of disk space plus the size of the attribute itself.
These figures are approximate, representing maximum rather than average requirements. Use them to calculate rough disk space requirements based on the number of users and the average number of attributes for each user. Information on combined StreetTalk and STDA disk space requirements can be found in Chapter 10.
As groups and organizations are added to the network, the memory needs of each StreetTalk service in the network increases and can adversely affect the performance of a server. If you cannot group all users and services together on the same server, try to create a scheme that makes your network both responsive and easy to use.
If memory usage becomes a concern, it is possible to monitor the amount of memory that StreetTalk requires for organization and group entries. For more information, see Monitoring and Optimizing Servers.
Note: StreetTalk Directory Assistance services also have disk space requirements. For more information on STDA disk space requirements, see Chapter 10.
