Novell EDIRECTORY 8.8 SP3, Administration Manual, Page: 397 / 634

Implementing the Service Location Protocol 397
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15.3.1 Central Repository
Directory Agents function as a centralized data store for service URLs that are registered by Service
Agents and solicited by User Agents. Because Directory Agents hold all the services for each
configured scope, User Agents can obtain all desired service information with a single request and
reply. By contrast, in networks without Directory Agents, User Agents issue a multicast request and
might receive many replies.
15.3.2 SLP Scopes
Directory Agents are configured to support one or more SLP scopes. (An unscoped operation is
similar to supporting a single scope.) Directory Agents collect and store service URLs and their
associated attributes according to the scope in which the services are registered. Service Agents and
User Agents obtain the scopes supported by a Directory Agent from a Directory Agent’s DA Advert
message. In this way, User Agents and Service Agents can dynamically detect and utilize the scopes
configured for each Directory Agent. In networks without Directory Agents, Service Agents and
User Agents must be configured with the SLP scopes they will use.
15.3.3 Customized Scopes
Novell Directory Agents allow the network administrator to create customized scopes by pulling
service information from one scope and storing it in a different scope. This is a variation of the scope
proxy feature because the custom scope name is different than the scope being proxied.
For example, if a network administrator wants to create a custom scope for a single group of users
containing only specific service URLs and attributes, the custom scope is configured on the local
Directory Agent and the address of the scope authority servicing a target scope and the target scope’s
name is configured as a proxy address for the custom scope. The content of the custom scope can be
further controlled by adding filters that apply only to the custom scope.
When the services are retrieved from the scope authority and registered in the custom scope, the
attributes of the service are modified to indicate that the service is now part of the custom scope. The
group of users can then be configured to use only the custom scope with the network administrator
controlling the service information available to them. Using this same technique, a hierarchy of
scopes can be created to reflect the administrative groupings of services that best fit your network
user’s needs.
15.3.4 Proxy Scopes
Novell Directory Agents can be configured to proxy scopes supported natively by other Directory
Agents, also referred to as scope authorities. Instead of having every Service Agent register with
every Directory Agent in the network, Service Agents can be configured to register with a single or
small subset of Directory Agents. The other Directory Agents in the network are then configured to
proxy the scopes of the central Directory Agents, which act as the authorities for the proxied scopes.
When a Directory Agent is configured to proxy a scope supported by another Directory Agent, the
proxy agent downloads the scope information at configured intervals and then acts as a local service
cache for that scope. This can be advantageous for remote sites reachable over WAN segments.
Rather than having User Agents in remote sites interacting with Directory Agents over the WAN, a
proxy Directory Agent can be deployed in the remote site, keeping all SLP service queries within
the local site’s network.