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... administrators to use several servers for a single
domain, to move services from host to host with little fuss, and to
designate some hosts ...
... single
domain, to move services from host to host with little fuss, and to
designate some hosts as primary servers for a service ...
... host to host with little fuss, and to
designate some hosts as primary servers for a service and others as
backups.
...
... Priority
As for MX, the priority of this target host. A client MUST
attempt to contact the target host ...
... target host. A client MUST
attempt to contact the target host with the lowest-numbered
priority it can reach; target hosts ...
... target host with the lowest-numbered
priority it can reach; target hosts with the same priority
SHOULD be tried in pseudorandom order. The range ...
... Weight
Load balancing mechanism. When selecting a target host among
the those that have the same priority, the chance of trying this
...
... Target
As for MX, the domain name of the target host. There MUST be
one or more A records for this name. Implementors ...
... services for a single domain are spread over several
hosts, it seems advisable to have a list of A RRs at the same
DNS ...
... node as the SRV RR, listing reasonable (if perhaps
suboptimal) fallback hosts for Telnet, NNTP and other protocols
...
...
- Where one service is provided by several hosts, one can either
provide A records for all the hosts ...
... hosts, one can either
provide A records for all the hosts (in which case the round-
robin mechanism, where available, will share the load equally)
or just for one (presumably the fastest).
...
... or just for one (presumably the fastest).
- 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 A
records ...
... A
records.
- Hosts that are referenced by backup A records must use the port
number specified in Assigned Numbers for the service ...
... telnet.tcp.asdf.com" for instance); each SRV RR adds
20 bytes plus the name of the target host; each NS RR in the NS ...
... NS
section is 15 bytes plus the name of the name server host; and
finally each A RR in the additional data section is 20 bytes or so,
...
...
- A client MAY use means other than Weight to choose among target
hosts with equal Priority.
...
... the SRV RR's and the client may want to connect to the target
host(s) involved, the client MUST look up the A RR(s). (This
...
... telnet.tcp.asdf.com." and possibly A lookups of "new-
fast-box.asdf.com." and/or the other hosts named. The size of the
SRV reply is approximately 365 bytes:
...
... DNS operations personnel to cooperate.
- There is no way a site can keep its hosts from being referenced
as servers (as, indeed, some sites become unwilling secondary
MXes today). This could lead to denial of service ...
... DNS spoofers can supply false port numbers, as well as
host names and addresses. The authors do not see any practical
effect of this.
...