One document matched: draft-wu-pce-dns-pce-discovery-00.xml
<?xml version="1.0" encoding="UTF-8"?>
<!-- edited with XMLSPY v5 rel. 3 U (http://www.xmlspy.com)
by Daniel M Kohn (private) -->
<!DOCTYPE rfc SYSTEM "rfc2629.dtd" [
<!ENTITY rfc2119 PUBLIC "" "http://xml.resource.org/public/rfc/bibxml/reference.RFC.2119.xml">
]>
<rfc category="std" docName="draft-wu-pce-dns-pce-discovery-00"
ipr="trust200902">
<?xml-stylesheet type='text/xsl' href='rfc2629.xslt' ?>
<?rfc toc="yes" ?>
<?rfc symrefs="yes" ?>
<?rfc sortrefs="yes"?>
<?rfc iprnotified="no" ?>
<?rfc strict="yes" ?>
<front>
<title abbrev="DNS based PCED">Path Computation Element (PCE) Discovery
using DNS</title>
<author fullname="Qin Wu" initials="Q." surname="Wu">
<organization>Huawei</organization>
<address>
<postal>
<street>101 Software Avenue, Yuhua District</street>
<city>Nanjing</city>
<region>Jiangsu</region>
<code>210012</code>
<country>China</country>
</postal>
<email>sunseawq@huawei.com</email>
</address>
</author>
<date year="2013" />
<area>Routing Area</area>
<workgroup>Path Computation Element Working Group</workgroup>
<keyword>RFC</keyword>
<keyword>Request for Comments</keyword>
<keyword>I-D</keyword>
<keyword>Internet-Draft</keyword>
<keyword>Path Computation Element</keyword>
<abstract>
<t>Discovery of the (Path Computation Element (PCE) within an IGP area
or domain is possible using OSPF [RFC5088] and IS-IS [RFC5089]. However,
in some deployment scenarios PCEs may not wish, or be able, to
participate within the IGP process. Therefore it would be beneficial for
the Path Computation Client (PCC) to discover PCEs via an alternative
mechanism to those proposed in [RFC5088] and [RFC5089].</t>
<t>This document specifies the requirements, use cases, procedures and
extensions to support DNS for PCE discovery.</t>
</abstract>
</front>
<middle>
<section anchor="intro" title="Introduction">
<t>The Path Computation Element Communication Protocol (PCEP) is a
transaction-based protocol carried over TCP. In order to be able to
direct path computation requests to the Path Computation Element (PCE),
a Path Computation Client (PCC) needs to know the location and
capability of a PCE.</t>
<t>In a network where an IGP is used and where the PCE participates in
the IGP, discovery mechanisms exist for PCC to learn the identify and
capability of each PCE. [RFC5088] defines a PCE Discovery (PCED) TLV
carried in an OSPF Router LSA. Similarly, [RFC5089] defines the PCED
sub-TLV for use in PCE Discovery using IS-IS.</t>
<t>However in certain scenarios not all PCEs will participate in the IGP
instance, section 3 (Motivation) outlines a number of use cases. In
these cases, current PCE Discovery mechanisms are therefore not
appropriate and another PCE announcement and discovery function would be
required.</t>
<section title="Requirements">
<t>As described in [RFC4674], the PCE Discovery information should at
least be composed of: <list style="symbols">
<t>The PCE location: an IPv4 and/or IPv6 address that is used to
reach the PCE. It is RECOMMENDED to use an address that is always
reachable if there is any connectivity to the PCE;</t>
<t>The PCE path computation scope (i.e., intra-layer, inter-area,
inter-AS, or inter-layer);</t>
<t>The set of one or more PCE-Domain(s) into which the PCE has
visibility and for which the PCE can compute paths;</t>
<t>The set of zero, one, or more neighbor PCE-Domain(s) toward
which the PCE can compute paths;</t>
</list></t>
<t>that allows PCCs to select appropriate PCEs:</t>
<t>This document specifies an extension to DNS for the above PCE
information discovery, which is complimentary to IS-IS extension and
OSPF extension that describe the support of PCE discovery.</t>
</section>
</section>
<section title="Conventions used in this document">
<t>The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in <xref
target="RFC2119">RFC2119</xref>.</t>
</section>
<section title="Motivation">
<t>This section discusses in more detail the motivation and use cases
for an alternative DNS based PCE discovery mechanism.</t>
<section title="Load Sharing of Path Computation Requests">
<t>Inherent DNS based load balancing may be used for inbound load
balancing and implemented at the application level in both servers and
clients. Multiple host IP addresses are configured in DNS for a single
host server name. Also DNS is capable of automatically detecting and
reacting to errors. These allow you to provide load balancing across
two separate Systems and facilitate PCE system failover and
recovery.</t>
</section>
<section title="Network Address Translation Gateway">
<t>Network address translation breaks end-to-end connectivity. The
internal network devices communicate with hosts on the external
network by changing the source address of outgoing requests to that of
the NAT device and relaying replies back to the originating device.
This poses a problem for PCEs that is behind the NAT devices, as PCE
information carried by PCE that is behind NAT devices in the outgoing
IGP advertisement doesn't require substitution or special traversal
techniques for NAT traversal and can not be used by PCC that is on the
external network to reach the PCE.</t>
</section>
<section title="Multiple-Provider Domains">
<t>In the case of multiple ASes within different service provider
networks, the H-PCE [RFC6805] architecture does not require disclosure
of internals of a child domain to the parent PCE. It may be necessary
for a third party to manage the parent PCEs according to commercial
and policy agreements from each of the participating service
providers.</t>
<t>[RFC6805] specifies that a child PCE must be configured with the
address of its parent PCE in order for it to interact with its parent
PCE. However handling changes in parent PCE identities and coping with
failure events would be an issue for a configured system.</t>
<t>There is no scope for parent PCEs to advertise their presence,
however there is potential for directory systems (such as DNS
[RFC4848] as used in the ALTO discovery function [I-D.ietf-alto-
server-discovery]).</t>
</section>
</section>
<section title="Discovering a Path Computation Element">
<t>The Dynamic Delegation Discovery System (DDDS) [RFC3401] is used to
implement lazy binding of strings to data, in order to support
dynamically configured delegation systems. The DDDS functions by mapping
some unique string to data stored within a DDDS database by iteratively
applying string transformation rules until a terminal condition is
reached. When DDDS uses DNS as a distributed database of rules, these
rules are encoded using the Naming Authority Pointer (NAPTR) Resource
Record (RR). One of these rules is the First Well Known Rule, which says
where the process starts.</t>
<t>In current specifications, the First Well Known Rule in a DDDS
application [RFC3403] is assumed to be fixed, i.e., the domain in the
tree where the lookups are to be routed to, is known. This document
proposes the input to the First Well Known Rule to be dynamic, based on
the search path the resolver discovers or is configured to use.</t>
<t>The search path of the resolver can either be pre-configured, or
discovered using DHCP.</t>
<t>When the PCC needs to discover PCEs in the domain into which the PCC
has visibility (e.g.,local domain), the input to the First Well Known
Rule MUST be the domain the PCC knows, which is assumed to be
pre-configured in the PCC or discovered using DHCP.</t>
<t>When the PCC needs to discover PCE in the other domain (e.g., Parent
PCE in the parent domain)into which the PCC has no visibility, it SHOULD
know the domain name of that domain and use DHCP to discover IP address
of the PCE in that domain that provides path computation service along
with some PCE location information useful to a PCC for PCE selection,
and contact it directly. In some instances, the discovery may result in
a per protocol/application list of domain names that are then used as
starting points for the subsequent NAPTR lookups. If neither the IP
address or PCE location information can be discovered with the above
procedure, the PCC MAY request a domain search list, as described in
[RFC3397] and [RFC3646], and use it as input to the DDDS application.
</t>
<t>When the PCC does not find valid domain names using the procedures
above, it MUST stop the attempt to discover any PCE.</t>
<t>The dynamic rule described above SHOULD NOT be used for discovering
services other than Path computation services described in this
document, unless stated otherwise by a future specification.</t>
<t>The procedures defined here result in an IP address, PCE domain,
neighboring PCE domain and PCE Computation Scope where the PCC can
contact the PCC that hosts the service the PCC is looking for.</t>
<section title="Determining the PCE Service and transport protocol">
<t>The PCC should know the service identifier for the Path Computation
Discovery service. The service identifier for the Path Computation
Discovery service is defined as "PCED", The PCE supporting "PCED"
service MUST support only TCP as transport, as described in
[RFC5440].</t>
<t>The services relevant for the task of transport protocol selection
are those with NAPTR service fields with values "ID+M2X", where ID is
the service identifier defined in the previous section, and X is a
letter that corresponds to a transport protocol supported by the
domain. This specification only defines M2T for TCP. This document
also establishes an IANA registry for mappings of NAPTR service name
to transport protocol.</t>
<t>These NAPTR [RFC3403] records provide a mapping from a domain to
the SRV [RFC2782] record for contacting a PCE with the specific
transport protocol in the NAPTR services field. The resource record
MUST contain an empty regular expression and a replacement value,
which indicates the domain name where the SRV record for that
particular transport protocol can be found. As per [RFC3403], the
client discards any records whose services fields are not
applicable.</t>
<t>The PCC MUST discard any service fields that identify a resolution
service whose value is not "M2T", for values of T that indicate TCP
transport protocols supported by the client. The NAPTR processing as
described in RFC 3403 will result in the discovery of the most
preferred transport protocol of the PCE that is supported by the
client, as well as an SRV record for the PCE.</t>
</section>
<section title="Determining the IP Address of the PCE">
<t>As an example, consider a client that wishes to find “PCED” service
in the example.com domain. The client performs a NAPTR query for that
domain, and the following NAPTR records are returned: <figure>
<artwork>
Order Pref Flags Service Regexp Replacement
IN NAPTR 50 50 "s" "PCED" ""
_PCED._tcp.example.com
IN NAPTR 90 50 "s" "PCED+M2T" ""
_PCED._udp.example.com
</artwork>
</figure></t>
<t>This indicates that the domain does have a PCE providing Path
Computation services over TCP, in that order of preference. Since the
client only supports TCP, TCP will be used, targeted to a host
determined by an SRV lookup of _PCED._tcp.example.com. That lookup
would return: <figure>
<artwork>
;; Priority Weight Port Target
IN SRV 0 1 XXXX server1.example.com
IN SRV 0 2 XXXX server2.example.com
</artwork>
</figure></t>
<t>where XXXX represents the port number at which the service is
reachable.</t>
<t>Note that the regexp field in the NAPTR example above is empty. The
regexp field MUST NOT be used when discovering path computation
services, as its usage can be complex and error prone. Also, the
discovery of the path computation service does not require the
flexibility provided by this field over a static target present in the
TARGET field.</t>
<t>If the client is already configured with the information about
which transport protocol is used for a path computation service in a
particular domain, it can directly perform an SRV query for that
specific transport using the service identifier of the path
computation Service. For example, if the client knows that it should
be using TCP for path computation service, it can perform a SRV query
directly for_PCED._tcp.example.com.</t>
<t>Once the server providing the desired service and the transport
protocol has been determined, the next step is to determine the IP
address.</t>
<t>According to the specification of SRV RRs in [RFC2782], the TARGET
field is a fully qualified domain name (FQDN) that MUST have one or
more address records; the FQDN must not be an alias, i.e., there MUST
NOT be a CNAME or DNAME RR at this name. Unless the SRV DNS query
already has reported a sufficient number of these address records in
the Additional Data section of the DNS response (as recommended by
[RFC2782]), the PCC needs to perform A and/or AAAA record lookup(s) of
the domain name, as appropriate. The result will be a list of IP
addresses, each of which can be contacted using the transport protocol
determined previously.</t>
</section>
<section title="Determining path computation scope,the PCE domains and Neighbor PCE domains">
<t>DNS servers MAY add new RRsets to the additional information
section that are relevant to the answer and have the same authenticity
as the data (the IP Address of the PCE)in the answer section. RRsets
include path computation scope, the PCE domains and Neighbor PCE
domains associated with. path information Applications on the PCC MAY
inspect those Additional Information section and be capable of
handling responses from nameservers that never fill in the Additional
Information part of a response.</t>
</section>
</section>
<section title="IANA Considerations">
<t>The usage of NAPTR records described here requires well-known values
for the service fields for the transport supported by Path Computation
Services. The table of mappings from service field values to transport
protocols is to be maintained by IANA.</t>
<t>The registration in the RFC MUST include the following
information:<figure>
<artwork>
Service Field: The service field being registered.
Protocol: The specific transport protocol associated with that
service field. This MUST include the name and acronym for the
protocol, along with reference to a document that describes the
transport protocol.
Name and Contact Information: The name, address, email address,
and telephone number for the person performing the registration.
</artwork>
</figure></t>
<t>The following values have been placed into the registry:<figure>
<artwork>
Service Fields Protocol
PCED+M2T TCP
</artwork>
</figure></t>
<t>New Service Fields are to be added via Standards Action as defined in
[RFC5226].</t>
<t>IANA is also requested to register PCED as service name in the
Protocol and Service Names registry.</t>
</section>
<section title="Security Considerations">
<t>It is believed that this proposed DNS extension introduces no new
security considerations (i.e., A list of known threats to services using
DNS) beyond those described in [RFC3833]. For most of those identified
threats, the DNS Security Extensions [RFC4033] does provide protection.
It is therefore recommended to consider the usage of DNSSEC [RFC4033]
and the aspects of DNSSEC Operational Practices [RFC4641] when deploying
Path Computation Services.</t>
<t>In deployments where DNSSEC usage is not feasible, measures should be
taken to protect against forged DNS responses and cache poisoning as
much as possible. Efforts in this direction are documented in
[RFC5452].</t>
<t>Where inputs to the procedure described in this document are fed via
DHCP, DHCP vulnerabilities can also cause issues. For instance, the
inability to authenticate DHCP discovery results may lead to the Path
Computation service results also being incorrect, even if the DNS
process was secured.</t>
</section>
</middle>
<back>
<references title="Normative References">
<reference anchor="RFC2119">
<front>
<title abbrev="RFC Key Words">Key words for use in RFCs to Indicate
Requirement Levels</title>
<author fullname="Scott Bradner" initials="S." surname="Bradner">
<organization>Harvard University</organization>
<address>
<postal>
<street>1350 Mass. Ave.</street>
<street>Cambridge</street>
<street>MA 02138</street>
</postal>
<phone>- +1 617 495 3864</phone>
<email>sob@harvard.edu</email>
</address>
</author>
<date month="March" year="1997" />
<area>General</area>
<keyword>keyword</keyword>
<abstract>
<t>In many standards track documents several words are used to
signify the requirements in the specification. These words are
often capitalized. This document defines these words as they
should be interpreted in IETF documents. Authors who follow these
guidelines should incorporate this phrase near the beginning of
their document: <list>
<t>The key words "MUST", "MUST NOT", "REQUIRED", "SHALL",
"SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described
in RFC 2119.</t>
</list></t>
<t>Note that the force of these words is modified by the
requirement level of the document in which they are used.</t>
</abstract>
</front>
</reference>
<reference anchor="RFC2782">
<front>
<title>A DNS RR for specifying the location of services (DNS
SRV)</title>
<author fullname="A.Gulbrandsen" initials="A." surname="Gulbrandsen">
<organization></organization>
</author>
<date month="February" year="2000" />
</front>
<seriesInfo name="RFC" value="2782" />
<format target="http://www.rfc-editor.org/rfc/rfc2782.txt" type="TXT" />
</reference>
<reference anchor="RFC3397">
<front>
<title>Dynamic Host Configuration Protocol (DHCP) Domain Search
Option</title>
<author fullname="B.Aboba" initials="B." surname="Aboba">
<organization></organization>
</author>
<date month="November" year="2002" />
</front>
<seriesInfo name="RFC" value="3397" />
<format target="http://www.rfc-editor.org/rfc/rfc3397.txt" type="TXT" />
</reference>
<reference anchor="RFC3403">
<front>
<title>Dynamic Delegation Discovery System (DDDS) Part Three: The
Domain Name System (DNS) Database</title>
<author fullname="M.Mealling" initials="M." surname="Mealling">
<organization></organization>
</author>
<date month="October" year="2002" />
</front>
<seriesInfo name="RFC" value="3403" />
<format target="http://www.rfc-editor.org/rfc/rfc3403.txt" type="TXT" />
</reference>
<reference anchor="RFC3646">
<front>
<title>DNS Configuration options for Dynamic Host Configuration
Protocol for IPv6 (DHCPv6)</title>
<author fullname="R.Droms" initials="R." surname="Droms">
<organization></organization>
</author>
<date month="December" year="2003" />
</front>
<seriesInfo name="RFC" value="3646" />
<format target="http://www.rfc-editor.org/rfc/rfc3646.txt" type="TXT" />
</reference>
<reference anchor="RFC5226">
<front>
<title>Guidelines for Writing an IANA Considerations Section in
RFCs</title>
<author fullname="T.Narten" initials="T." surname="Narten">
<organization></organization>
</author>
<date month="May" year="2008" />
</front>
<seriesInfo name="RFC" value="5226" />
<format target="http://www.rfc-editor.org/rfc/rfc5226.txt" type="TXT" />
</reference>
<reference anchor="RFC4674">
<front>
<title>Requirements for Path Computation Element (PCE)
Discovery</title>
<author fullname="R.Droms" initials="R." surname="Droms">
<organization></organization>
</author>
<date month="December" year="2003" />
</front>
<seriesInfo name="RFC" value="4674" />
<format target="http://www.rfc-editor.org/rfc/rfc4674.txt" type="TXT" />
</reference>
<reference anchor="RFC6805">
<front>
<title>The Application of the Path Computation Element Architecture
to the Determination of a Sequence of Domains in MPLS and
GMPLS</title>
<author fullname="D.King" initials="D." surname="King">
<organization></organization>
</author>
<author fullname="A.Farrel " initials="A." surname="Farrel">
<organization></organization>
</author>
<date month="November" year="2012" />
</front>
<seriesInfo name="RFC" value="6805" />
<format target="http://www.rfc-editor.org/rfc/rfc6805.txt" type="TXT" />
</reference>
<reference anchor="RFC4848">
<front>
<title>Domain-Based Application Service Location Using URIs and the
Dynamic Delegation Discovery Service (DDDS)</title>
<author fullname="L. Daigle" initials="D." surname="Daigle">
<organization></organization>
</author>
<date month="April" year="2007" />
</front>
<seriesInfo name="RFC" value="4848" />
<format target="http://www.rfc-editor.org/rfc/rfc4848.txt" type="TXT" />
</reference>
<reference anchor="RFC5440">
<front>
<title>Path Computation Element (PCE) Communication Protocol
(PCEP)</title>
<author fullname="JL. Le Roux" initials="JL." surname="Le Roux">
<organization></organization>
</author>
<date month="April" year="2007" />
</front>
<seriesInfo name="RFC" value="5440" />
<format target="http://www.rfc-editor.org/rfc/rfc5440.txt" type="TXT" />
</reference>
<reference anchor="RFC4641">
<front>
<title>DNSSEC Operational Practices</title>
<author fullname="O. Kolkman" initials="O." surname="Kolkman">
<organization></organization>
</author>
<date month="September" year="2006" />
</front>
<seriesInfo name="RFC" value="4641" />
<format target="http://www.rfc-editor.org/rfc/rfc4641.txt" type="TXT" />
</reference>
<reference anchor="RFC4033">
<front>
<title>DNS Security Introduction and Requirements</title>
<author fullname="R. Arends" initials="R." surname="Arends">
<organization></organization>
</author>
<date month="March" year="2005" />
</front>
<seriesInfo name="RFC" value="4033" />
<format target="http://www.rfc-editor.org/rfc/rfc4033.txt" type="TXT" />
</reference>
</references>
<references title="Informative References">
<reference anchor="RFC5088">
<front>
<title>OSPF Protocol Extensions for Path Computation Element (PCE)
Discovery</title>
<author fullname="JL. Le Roux" initials="JL." surname="Le Roux">
<organization></organization>
</author>
<date month="January" year="2008" />
</front>
<seriesInfo name="RFC" value="5088" />
<format target="http://www.rfc-editor.org/rfc/rfc5088.txt" type="TXT" />
</reference>
<reference anchor="RFC5089">
<front>
<title>IS-IS Protocol Extensions for Path Computation Element (PCE)
Discovery</title>
<author fullname="JL. Le Roux" initials="JL." surname="Le Roux">
<organization></organization>
</author>
<date month="January" year="2008" />
</front>
<seriesInfo name="RFC" value="5089" />
<format target="http://www.rfc-editor.org/rfc/rfc5089.txt" type="TXT" />
</reference>
<reference anchor="RFC3401">
<front>
<title>Dynamic Delegation Discovery System (DDDS) Part One: The
Comprehensive DDDS</title>
<author fullname="M.Mealling" initials="M." surname="Mealling">
<organization></organization>
</author>
<date month="October" year="2002" />
</front>
<seriesInfo name="RFC" value="3401" />
<format target="http://www.rfc-editor.org/rfc/rfc3401.txt" type="TXT" />
</reference>
<reference anchor="RFC3833">
<front>
<title>Threat Analysis of the Domain Name System (DNS)</title>
<author fullname="D.Atkins" initials="D." surname="Atkins">
<organization></organization>
</author>
<date month="August" year="2004" />
</front>
<seriesInfo name="RFC" value="3833" />
<format target="http://www.rfc-editor.org/rfc/rfc3833.txt" type="TXT" />
</reference>
<reference anchor="RFC5452">
<front>
<title>Measures for Making DNS More Resilient against Forged
Answers</title>
<author fullname="A.Hubert" initials="A." surname="Hubert">
<organization></organization>
</author>
<date month="January" year="2009" />
</front>
<seriesInfo name="RFC" value="5452" />
<format target="http://www.rfc-editor.org/rfc/rfc5452.txt" type="TXT" />
</reference>
<reference anchor="ALTO">
<front>
<title>ALTO Server Discovery</title>
<author fullname="S. Kiesel" initials="S." surname="Kiesel">
<organization></organization>
</author>
<date month="March" year="2013" />
</front>
<seriesInfo name="ID" value="draft-ietf-alto-server-discovery-08" />
</reference>
</references>
</back>
</rfc>
| PAFTECH AB 2003-2026 | 2026-04-23 20:48:53 |