DNS
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... Service
Location Protocol (SLP) [RFC2608] via DNS SRV [RFC2782]. We consider
remote service discovery ...
... service discovery as discovering desired services in given
remote DNS domains, and local service discovery as discovering
...
... multicast).
DNS SRV provides good support for remote service discovery. However,
if multiple servers are discovered via DNS SRV ...
... DNS SRV provides good support for remote service discovery. However,
if multiple servers are discovered via DNS SRV for a service, only
priority ...
... service properties (such as cost, speed and service quality) need to
be considered in the selection process, DNS SRV becomes insufficient.
We propose that using SLP ...
...
We propose that using SLP and DNS SRV together can provide better
support for remote service discovery. First, a UA ...
... support for remote service discovery. First, a UA uses DNS SRV to
find SLP DAs at a remote DNS ...
... services. In this way, we can
avoid the limitations in using SLP and DNS SRV separately. On one
hand, without DNS SRV, an SLP ...
... SLP and DNS SRV separately. On one
hand, without DNS SRV, an SLP UA needs to depend on static
...
... administrative domain. On the other hand, without SLP, DNS SRV has
limited support for service selection.
...
... SLP DA services, which are used to map a given DNS domain to
remotely accessible (i.e., accessible from the Internet ...
... domain. Then, we discuss various issues in using SLP and DNS SRV
together for remote service discovery. Finally, we give the steps
...
... service discovery. Finally, we give the steps
for discovering services in remote DNS domains.
...
... Next we show an example of using DNS SRV RRs to map a given DNS
domain to remotely accessible DAs in that domain ...
... domain (say, example.com), a UA
makes a DNS query [RFC1034,RFC1035] for QNAME=_slpda._tcp.example.com
...
... UA will receive a list of DNS SRV RRs in a DNS reply, which gives
all remotely accessible DAs in the domain example.com, such as:
...
... SLP DAs can be discovered in two ways: (1) using the mechanisms
described in RFC 2608, and (2) using DNS SRV RRs as described in this
document. The second approach is useful for UAs ...
... document. The second approach is useful for UAs to acquire service
information for remote DNS domains. For example, a mobile node
...
... SLP DAs are registered. For remote service discovery,
it is assumed that the DNS domain of interest is known via a priori
knowledge. For example, a UA ...
...
Note that there is no implied "search order" of DNS domains in
finding remote DAs. For instance, if a UA ...
... A UA discovers desired services in a given remote DNS domain by
unicasting requests to DAs in that domain ...
... UA uses remote DAs
according to these prioritized rules: (1) using DAs which it has been
configured with, and (2) using DAs which it has discovered via DNS
SRV.
...
... service MUST be
registered in the "default" scope, but it MAY be registered in other
scopes at the same time. Similarly, all DAs advertised via DNS SRV
MUST serve the "default" scope, but they MAY serve other scopes at
the same time. As a result, users wishing to discover services ...
... the same time. As a result, users wishing to discover services at a
remote DNS domain SHOULD only search the "default" scope.
...
... domain D are as follows.
(1) U makes a DNS query for QNAME=_slpda._tcp.D (or
QNAME=_slpda._udp.D), QCLASS=IN, and QTYPE=SRV ...
... IN, and QTYPE=SRV. Then, U gets a
list of DNS SRV RRs (referred to as L) in a DNS reply, which
...
... list of DNS SRV RRs (referred to as L) in a DNS reply, which
gives all remotely accessible DAs in D.
...
... queries that are not in the "default" scope. In addition, the
security considerations for DNS SRV [RFC2782] apply to this document.
Also, the DNS security extensions ...
... DNS SRV [RFC2782] apply to this document.
Also, the DNS security extensions [RFC 2535(-> 4035prop | 4034prop | 4033prop)] SHOULD be used to
provide origin authentication and integrity ...
... 2535(-> 4035prop | 4034prop | 4033prop)] SHOULD be used to
provide origin authentication and integrity protection for DNS data.
...
... This specification describes remote service discovery in SLP via DNS
SRV. It facilitates discovering services at a remote DNS domain ...
... SLP via DNS
SRV. It facilitates discovering services at a remote DNS domain if
the domain name ...
...
Users should be aware of two constraints in using DNS SRV to discover
SLP DAs: (1) they SHOULD only use DNS SRV ...
... DNS SRV to discover
SLP DAs: (1) they SHOULD only use DNS SRV to discover DAs in the
"default" scope, and (2) an administrator may choose to register ...
... administrator may choose to register only
a subset of all DAs in the "default" scope via DNS SRV. Thus, to
discover local DAs, implementations MUST use the standard SLP
...
... mechanisms per RFC 2608. In addition, implementations supporting
this specification MAY use DNS SRV to discover local DAs in the
"default" scope.
...
...
Note that the services discovered via DNS SRV and remote SLP DAs may
not necessarily be remotely accessible.
...
... Gulbrandsen, A., Vixie, P. and L. Esibov, "A DNS RR for specifying the location of services (DNS SRV ...