3. The format of the SRV RR

   Here is the format of the SRV RR, whose DNS type code is 33:

        Service.Proto.Name TTL Class SRV Priority Weight Port Target

        (There is an example near the end of this document.)

   Service
        The symbolic name of the desired service, as defined in Assigned
        Numbers or locally.

        Some widely used services, notably POP, don't have a single
        universal name.  If Assigned Numbers names the service
        indicated, that name is the only name which is legal for SRV
        lookups.  Only locally defined services may be named locally.
        The Service is case insensitive.

   Proto
        TCP and UDP are at present the most useful values
        for this field, though any name defined by Assigned Numbers or
        locally may be used (as for Service).  The Proto is case
        insensitive.

   Name
        The domain this RR refers to.  The SRV RR is unique in that the
        name one searches for is not this name; the example near the end
        shows this clearly.

   TTL
        Standard DNS meaning.

   Class
        Standard DNS meaning.

   Priority
        As for MX, the priority of this target host.  A client MUST
        attempt to contact the target host with the lowest-numbered
        priority it can reach; target hosts with the same priority
        SHOULD be tried in pseudorandom order.  The range is 0-65535.

   Weight
        Load balancing mechanism.  When selecting a target host among
        the those that have the same priority, the chance of trying this
        one first SHOULD be proportional to its weight.  The range of
        this number is 1-65535.  Domain administrators are urged to use
        Weight 0 when there isn't any load balancing to do, to make the
        RR easier to read for humans (less noisy).

   Port
        The port on this target host of this service.  The range is
        0-65535.  This is often as specified in Assigned Numbers but
        need not be.

   Target
        As for MX, the domain name of the target host.  There MUST be
        one or more A records for this name. Implementors are urged, but
        not required, to return the A record(s) in the Additional Data
        section.  Name compression is to be used for this field.

        A Target of "." means that the service is decidedly not
        available at this domain.