rfc2614.txt

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RFC 2614                  Service Location API                 June 1999


2.1.5. Network Configuration Properties

   The properties in this section allow various network configuration
   properties to be set.

      net.slp.isBroadcastOnly

         A boolean indicating if broadcast should be used instead of
         multicast.  Like the net.slp.useScopes and net.slp.DAAddresses
         properties, this property is "read-only", so attempts to change
         it after the configuration file has been read are ignored.
         Default is false.

      net.slp.passiveDADetection

         A boolean indicating whether passive DA detection should be
         used.  Default is true.

      net.slp.multicastTTL

         A positive integer less than or equal to 255, giving the
         multicast TTL. Default is 255.

      net.slp.DAActiveDiscoveryInterval

         A 16 bit positive integer giving the number of seconds
         between DA active discovery queries.  Default is 900 seconds
         (15 minutes).  This property corresponds to the protocol
         specification parameter CONFIG_DA_FIND [7].  If the property is
         set to zero, active discovery is turned off.  This is useful
         when the DAs available are explicitly restricted to those
         obtained from DHCP or the net.slp.DAAddresses property.

      net.slp.multicastMaximumWait

         A 32 bit integer giving the maximum amount of time to perform
         multicast, in milliseconds.  Default is 15000 ms (15 sec.).
         This property corresponds to the CONFIG_MC_MAX parameter in the
         protocol specification [7].

      net.slp.multicastTimeouts

         A value-list of 32 bit integers used as timeouts, in
         milliseconds, to implement the multicast convergence
         algorithm.  Each value specifies the time to wait before
         sending the next request, or until nothing new has
         been learned from two successive requests.  Default
         is:  3000,3000,3000,3000,3000.  In a fast network the



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         aggressive values of 1000,1250,1500,2000,4000 allow better
         performance.  This property corresponds to the CONFIG_MC_RETRY
         parameter in the protocol specification [7].  Note that the
         net.slp.DADiscoveryTimeouts property must be used for active DA
         discovery.

      net.slp.DADiscoveryTimeouts

         A value-list of 32 bit integers used as timeouts, in
         milliseconds, to implement the multicast convergence algorithm
         during active DA discovery.  Each value specifies the time
         to wait before sending the next request, or until nothing
         new has been learned from two successive requests.  This
         property corresponds to the protocol specification parameter
         CONFIG_RETRY [7].  Default is:  2000,2000,2000,2000,3000,4000.

      net.slp.datagramTimeouts

         A value-list of 32 bit integers used as timeouts, in
         milliseconds, to implement unicast datagram transmission to
         DAs.  The nth value gives the time to block waiting for a reply
         on the nth try to contact the DA. The sum of these values is
         the protocol specification property CONFIG_RETRY_MAX [7].

      net.slp.randomWaitBound

         A 32 bit integer giving the maximum value for all random
         wait parameters, in milliseconds.  Default is 1000 (1
         sec.).  This value corresponds to the protocol specification
         parameters CONFIG_START_WAIT, CONFIG_REG_PASSIVE, and
         CONFIG_REG_ACTIVE [7].

      net.slp.MTU

         A 16 bit integer giving the network packet MTU, in bytes.
         This is the maximum size of any datagram to send, but the
         implementation might receive a larger datagram.  The maximum
         size includes IP, and UDP or TCP headers.  Default is 1400.

      net.slp.interfaces

         Value-list of strings giving the IP addresses of network
         interfaces on which the DA or SA should listen on port 427 for
         multicast, unicast UDP, and TCP messages.  Default is empty,
         i.e.  use the default network interface.  The grammar for this
         property is:





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               addr-list     =  hostnumber / hostnumber "," addr-list
               hostnumber    =  1*3DIGIT 3("." 1*3DIGIT)


         An example is:


                  195.42.42.42,195.42.142.1,195.42.120.1


         The example machine has three interfaces on which the DA should
         listen.

         Note that since this property only takes IP addresses, it will
         need to be changed if the network is renumbered.

2.1.6. SA Configuration

   This section contains configuration properties for the SA. These
   properties are typically set programmatically by the SA, since they
   are specific to each SA.

      net.slp.SAAttributes

         A comma-separated list of parenthesized attribute/value list
         pairs that the SA must advertise in SAAdverts.  The property
         must be in the SLP attribute list wire format, including
         escapes for reserved characters. [7]

2.1.7. UA Configuration

   This section contains configuration properties for the UA. These
   properties can be set either programmatically by the UA or in the
   configuration file.

      net.slp.locale

         A RFC 1766 Language Tag [6] for the language locale.  Setting
         this property causes the property value to become the default
         locale for SLP messages.  Default is "en".  This property is
         also used for SA and DA configuration.

      net.slp.maxResults

         A 32 bit integer giving the maximum number of results to
         accumulate and return for a synchronous request before the
         timeout, or the maximum number of results to return through a
         callback if the request results are reported asynchronously.



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         Positive integers and -1 are legal values.  If -1, indicates
         that all results should be returned.  Default value is -1.

         DAs and SAs always return all results that match the
         request.  This configuration value applies only to UAs, that
         filter incoming results and only return as many values as
         net.slp.maxResults indicates.

      net.slp.typeHint

         A value-list of service type names.  In the absence of any
         DAs, UAs perform SA discovery for finding scopes.  These SA
         discovery requests may contain a request for service types as
         an attribute.

         The API implementation will use the service type names supplied
         by this property to discover only those SAs (and their scopes)
         which support the desired service type or types.  For example,
         if net.slp.typeHint is set to "service:imap,service:pop3" then
         SA discovery requests will include the search filter:


         (|(service-type=service:imap)(service-type=service:pop3))


         The API library can also use unicast to contact the discovered
         SAs for subsequent requests for these service types, to
         optimize network access.

2.1.8. Security

   The property in this section allows security for all agents to be set
   on or off.  When the property is true, then the agent must include
   security information on all SLP messages transacted by that agent.
   Since security policy must be set network wide to be effective, a
   single property controls security for all agents.  Key management and
   management of SLP SPI strings [7] are implementation and policy
   dependent.

      net.slp.securityEnabled

         A boolean indicating whether the agent should enable
         security for URLs, attribute lists, DAAdverts, and SAAdverts.
         Each agent is responsible for interpreting the property
         appropriately.  Default is false.






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2.2. Multihomed Machines

   On multihomed machines, the bandwidth and latency characteristics on
   different network interfaces may differ considerably, to the point
   where different configuration properties are necessary to achieve
   optimal performance.  The net.slp.interfaces property indicates which
   network interfaces are SLP enabled.  An API library implementation
   may support configuration customization on a per network interface
   basis by allowing the interface IP address to be appended to the
   property name.  In that case, the values of the property are only
   used for that particular interface, the generic property (or defaults
   if no generic property is set) applies to all others.

   For example, if a configuration has the following properties:


      net.slp.interfaces=125.196.42.41,125.196.42.42,125.196.42.43
      net.slp.multicastTTL.125.196.42.42=1


   then the network interface on subnet 42 is restricted to a TTL of 1,
   while the interfaces on the other subnets have the default multicast
   radius, 255.

   The net.slp.interfaces property must only be set if there is no
   routing between the interfaces.  If the property is set, the DA (if
   any) and SAs should advertise with the IP address or host name
   appropriate to the interface on the interfaces in the list.  If
   packets are routed between the interfaces, then the DA and SAs should
   only advertise on the default interface.  The property should also be
   set if broadcast is used rather than multicast on the subnets
   connected to the interfaces.  Note that even if unicast packets are
   not routed between the interfaces, multicast may be routed through
   another router.  The danger in listening for multicast on multiple
   interfaces when multicast packets are routed is that the DA or SA may
   receive the same multicast request via more than one interface.
   Since the IP address is different on each interface, the DA or SA
   cannot identify the request as having already being answered via the
   previous responder's list.  The requesting agent will end up getting
   URLs that refer to the same DA or service but have different
   addresses or host names.

2.3. Serialized Registration File

   The serialized registration file contains a group of registrations
   that a DA or SA server (if one exists) registers when it starts up.
   These registrations are primarily for older service programs that do
   not internally support SLP and cannot be converted, and for portably



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   exchanging registrations between SLP implementations.  The character
   encoding of the registrations is required to be UTF-8.

   The syntax of the serialized registration file, in ABNF format [5],
   is as follows:


      ser-file      =  reg-list
      reg-list      =  reg / reg reg-list
      reg           =  creg / ser-reg
      creg          =  comment-line ser-reg
      comment-line  =  ( "#" / ";" ) 1*allchar newline
      ser-reg       =  url-props [slist] [attr-list] newline
      url-props     =  surl "," lang "," ltime [ "," type ] newline
      surl          =  ;The registration's URL. See
                       ; [8] for syntax.
      lang          =  1*8ALPHA [ "-" 1*8ALPHA ]
                       ;RFC 1766 Language Tag see [6].
      ltime         =  1*5DIGIT
                       ; A positive 16-bit integer
                       ; giving the lifetime
                       ; of the registration.
      type          =  ; The service type name, see [7]
                       ; and [8] for syntax.
      slist         =  "scopes" "=" scope-list newline