SMI Tutorial > SMI-S 1.1.0 Overview > SMI-S 1.1.0 Requirements > SLP
The SMI-S 1.1.0 requires the use of the Service Location Protocol (SLP) version 2 to allow Clients to discover SMI Agents on a Storage Area Network (SAN). SLP is defined by IETF RFC 2608. The DMTF defines the use of the SLP by a SMI Agent in DSP0205. The DMTF defines a SLP Template in DSP0206. The SLP Template contains information about the capabilities of the SMI Agent. By examining the SLP Template, a Client can determine the capabilities of a SMI Agent such as which storage devices it supports.
The SLP defines the following three roles:
- Service Agent (SA) - represents the resource that advertises the capabilities of SMI Agents.
- Directory Agent (DA) - represents the resource that acts as a centralized network repository for SMI Agent advertisements.
- User Agent (UA) - represents the Client that wants to discover SMI Agents and to determine the capabilities of a SMI Agent.
A SMI Agent registers its SLP Template with a SA or DA. A Client broadcasts a request to listening SA's or DA's for available advertisements. The default reserved listening port for SLP is 427. An SA sends back its SLP Template. A DA sends back all the SLP Templates it has collected. A Client then examines the SLP Templates to discover which SMI Agents are available and to discover the capabilities of each discovered SMI Agent. Based on information collected, the Client decides which SMI Agent to connect to and manage. The SLP Template contains information that allows a Client to make their decision. The most important information is as follows:
- The address of the SMI Agent (e.g., http://192.168.0.200:5988)
- The communication mechanisms supported by the SMI Agent (e.g., CIM-XML)
- The types of HTTP authentication supported by the SMI Agent (e.g., Digest)
- The WBEM operations supported by the SMI Agent. For example, some SMI Agents may only be capable of read operations. Some may not support schema manipulation.
- The Namespaces available on the SMI Agent
- The name of the interop Namespace on the SMI Agent. The interop Namespace contains the Classes needed by the SMI Agent to manage itself.
- The Registered Profiles supported by the SMI Agent. For example, if a SMI Agent supports the SMI-S management of a disk array, then the "SNIA:Array" Profile would be advertised in its SLP Template.