SLP
The Service Location Protocol (SLP) discovers and selects services in IP networks. SLP Version 2 is specified in RFC 2608. RFC 3111 describes how SLPv2 can be used in IPv6 networks. SLP uses UDP and TCP, so only minor changes are necessary to use SLP on IPv6 networks. SLPv1, which was defined in RFC 2165, does not support IPv6. If you want to use SLP over IPv6, you have to use SLPv2.
Tip
For a detailed discussion of SLP concepts, refer to my book Guide to Service Location Protocol (podbooks.com) or to http://playground.sun.com/srvloc/slp_white_paper.html.
The changes made for SLPv2 can be summarized as follows:
The use for broadcasting of SLP requests was eliminated.
The format of SLP URLs (service entries) must be able to hold IPv6 addresses.
SLP must be able to use IPv6 multicast addresses and multicast scopes.
The propagation of Service Advertisements must be restricted.
When SLP is used over IPv4, it can be configured to use broadcasts for service requests, but this is not recommended. IPv6 no longer supports broadcasts, so if SLP is used over IPv6, it has to use multicast addresses to discover service or directory agents.
Table 9-2 shows the multicast addresses that have been defined for SLP over IPv6.
Table 9-2. Multicast addresses for SLP over IPv6
|
Multicast address |
Description |
|---|---|
|
FF0X:0:0:0:0:0:0:116 |
Service Agent (SA), used for Service Type and Attribute Request Messages. |
|
FF0X:0:0:0:0:0:0:123 |
Directory Agent (DA), used by User Agents (UA) and SAs to discover DAs. ... |