SLP Architecture
This section outlines the fundamental operation of SLP and describes agents and processes
that are used in SLP administration.
SLP provides all of the following services automatically, with little or no configuration.
Client application requests for information that is required to access a service
Advertisement of services on network hardware devices or software servers; for example, printers, file servers, video cameras, and HTTP servers
Managed recovery from primary server failures
In addition, you can do the following to administer and tune SLP operation
if necessary.
Organize services and users into scopes that are composed of logical or functional groups
Enable SLP logging to monitor and troubleshoot the SLP operation on your network
Adjust SLP timing parameters to enhance performance and scalability
Configure SLP not to send and not to process multicast messages when SLP is deployed on networks that lack support for multicast routing
Deploy SLP Directory Agents to improve scalability and performance
Summary of the SLP Design
SLP libraries inform network-aware agents that advertise services in order for those services
to be discovered over a network. SLP agents maintain up-to-date information on the
type and location of services. These agents can also use proxy registrations to
advertise services that are not directly SLP enabled. For more information, see Chapter 10, Incorporating Legacy Services.
Client applications rely on SLP libraries that make requests directly to the agents
that advertise services.
SLP Agents and Processes
The following table describes the SLP agents. For expanded definitions of these terms
and other terms that are used in this volume, refer to the
Glossary.
Table 7-1 SLP Agents
SLP Agent |
Description |
|
|---|
Directory Agent (DA) |
Process that caches SLP advertisements that are registered by
Service Agents (SAs). The DA forwards service advertisements to User Agents (UAs) on demand. |
|
Service
Agent (SA) |
SLP agent that acts on behalf of a service to distribute
service advertisements and to register the service with Directory Agents (DAs). |
|
User Agent (UA) |
SLP
agent that acts on behalf of a user or application to obtain
service advertisement information. |
|
scope |
An administrative or logical grouping of services. |
|
The following figure shows the basic agents and processes that implement the SLP
architecture. The figure represents a default deployment of SLP. No special configuration has
been done. Only two agents are required: the UA and SA. The SLP
framework allows the UA to multicast requests for services to the SA. The
SA unicasts a reply to the UA. For example, when the UA
sends a service request message, the SA responds with a service reply message.
The service reply contains the location of services that match the client's requirements. Other
requests and replies are possible for attributes and service types. For more information,
see Chapter 11, SLP (Reference).
Figure 7-1 SLP Basic Agents and Processes
The following figure shows the basic agents and processes that implement the SLP
architecture when a DA is deployed in the framework.
Figure 7-2 SLP Architectural Agents and Processes Implemented With a DA
When you deploy DAs, fewer messages are sent in the network and
UAs can retrieve information much faster. DAs are essential when the size of
a network increases or for situations in which there is no support for
multicast routing. The DA serves as a cache for registered service advertisements. SAs send
register messages (SrvReg) that list all the services they advertise to DAs. SAs
then receive acknowledgments (SrvAck) in reply. The service advertisements are refreshed with the
DA, or they expire according to the lifetime that is set for the
advertisement. After a UA discovers a DA, the UA unicasts a request to
the DA rather than multicasting requests to SAs.
For more information about Solaris SLP messages, refer to Chapter 11, SLP (Reference).
