System Administration Guide: Network Services

Analyzing a snoop slp Trace

In the following example, slpd runs on slphost1 in the default mode as an SA server. The SLP daemon initializes and registers slphost2 as an echo server. Then, the snoop slp process is invoked on slphost1.

Note –

To simplify the description of the trace results, the lines in the following snoop output are flagged with line numbers.

(1) slphost1 -> SLP V@ SrvRqst [24487] service:directory-agent []
(2) slphost2 -> slphost1 SLP V2 DAAdvert [24487] service:directory-agent://129
(3) slphost1 -> SLP V2 SrvRqst [24487] service:directory-agent []
(4) slphost1 -> SLP V2 SrvRqst [24487] service:directory-agent []
(5) slphost1 -> slphost2 SLP V2 SrvReg [24488/tcp]service:echo.sun:tcp://slphost1:
(6) slphost2 -> slphost1 SLP V2 SrvAck [24488/tcp] ok
(7) slphost1 -> slphost2 SLP V2 SrvDereg [24489/tcp] service:echo.sun:tcp://slphost1:
(8) slphost2 -> slphost1 SLP V2 SrvAck [24489/tcp] ok
  1. Shows slpd on slphost1 performing active directory agent discovery by multicasting to the SLP multicast group address in search of directory agents. The message number, 24487, for the active discovery is indicated in square brackets in the trace display.

  2. Indicates that the active discovery request 24487 from trace 1 is answered by slpd, which is running as a DA on the host slphost2. The service URL from slphost2 has been truncated to fit on a single line. The DA has sent a DA advertisement in reply to the multicast directory agent discovery message, as indicated by the matching message numbers in traces 1 and 2.

  3. Shows multicasts from the UAs on slphost1 for additional DAs. Because slphost2 has already answered the request, it refrains from responding again, and no other DAs reply.

  4. Repeats the multicast operation that is shown in the previous line.

  5. Shows a slpd on slphost1 forwarding SA client registrations to the DA on slphost2. A unicast service registration (SrvReg) for an echo server is made by slphost1 to the DA on slphost2.

  6. Shows slphost2 responding to the slphost1 SrvReg with a service acknowledgment (SrvAck) that indicates the registration is successful.

    Traffic between the echo server that runs the SA client and the SLP daemon on slphost1 does not appear in the snoop trace. This absence of information is because the snoop operation is performed over the network loopback.

  7. Shows the echo server on slphost1 deregistering the echo service advertisement. The SLP daemon on slphost1 forwards the deregistration to the DA on slphost2.

  8. Shows slphost2 responding to the slphost1 with a service acknowledgment (SrvAck) that indicates that the deregistration is successful.

    The /tcp parameter that is appended to the message number on lines 5, 6, 7, and 8 indicates that the message exchange occurred by TCP.

Where to Go From Here

After monitoring the SLP traffic, you can use the information that was collected from the snoop traces to help determine whether any reconfiguration of the SLP defaults is needed. Use the related information in Chapter 9, Administering SLP (Tasks) for configuring SLP property settings. For more information about SLP messaging and service registrations, refer to Chapter 11, SLP (Reference).