service
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... SRV RR allows administrators to use several servers for a single
domain, to move services from host to host with little fuss, and to
...
... host with little fuss, and to
designate some hosts as primary servers for a service and others as
backups.
...
... clients should use the SRV record. Such specification MUST
define the symbolic name to be used in the Service field of the SRV
record as described below. It also MUST include security
considerations. Service ...
... Service field of the SRV
record as described below. It also MUST include security
considerations. Service SRV records SHOULD NOT be used in the absence
of such specification.
...
... supports TCP protocol and provides LDAP service for the domain
example.com., it does a lookup ...
...
_Service._Proto.Name TTL Class SRV Priority Weight Port Target
...
... Service
The symbolic name of the desired service, as defined in Assigned
Numbers [STD 2] or locally. An underscore (_) is prepended to
...
... Numbers [STD 2] or locally. An underscore (_) is prepended to
the service identifier to avoid collisions with DNS labels that
...
... occur in nature.
Some widely used services, notably POP, don't have a single
universal name. If Assigned Numbers names the service ...
... 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
...
... 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.
...
... If a host is intended to provide a service only when the main
server(s) is/are down, it probably shouldn't be listed in
address ...
... are very round: A reply packet has a 30-byte overhead plus the name
of the service ("_ldap._tcp.example.com" for instance); each SRV RR
adds 20 bytes plus the name of the target host ...
... asking a separate server when the client selects a server and
contacts it. For short-lived services an extra step in the
connection establishment seems too expensive, and for long-lived
...
... connection establishment seems too expensive, and for long-lived
services, the load figure may well be thrown off a minute after the
connection is established when someone else starts ...
... network proximity estimation, available bandwidth estimation, and
similar services. Use of the SRV record with such facilities, and in
particular the interpretation of the Weight field when these
...
... update
these files on every single computer of the net every time a new
service is added, and makes it possible to move standard services out
of the "root ...
... these files on every single computer of the net every time a new
service is added, and makes it possible to move standard services out
of the "root-only" port range ...
... If the reply is NOERROR, ANCOUNT>0 and there is at least one
SRV RR which specifies the requested Service and Protocol in
the reply:
...
... Port numbers SHOULD NOT be used in place of the symbolic service
or protocol names (for the same reason why variant names cannot
be allowed: Applications would have to do two or more lookups ...
...
This example uses fictional service "foobar" as an aid in
understanding SRV records. If ever service ...
... service "foobar" as an aid in
understanding SRV records. If ever service "foobar" is implemented,
it is not intended that it will necessarily use SRV records. This is
...
... experimental, version of this specification is that now the
protocol and service labels are prepended with an underscore, to
lower the probability of an accidental clash with a similar name used
for unrelated purposes. Aside from that, changes are only intended
...
... to block internal clients from accessing specific external
services, slightly harder to block internal users from running
unauthorized services, and more important for the router ...
... services, slightly harder to block internal users from running
unauthorized services, and more important for the router
operations and DNS operations ...
... There is no way a site can keep its hosts from being referenced
as servers. This could lead to denial of service.
...
... Hamilton, M. and R. Wright, "Use of DNS Aliases for Network Services", BCP 17, RFC 2219, October 1997. ...
... Armijo, M., Esibov, L. and P. Leach, "Discovering LDAP Services with DNS", Work in Progress. ...