Internet DRAFT - draft-xu-dnssd-sf-update
draft-xu-dnssd-sf-update
Dnssd Working Group X. Xu
Internet-Draft Huawei
Intended status: Informational May 16, 2014
Expires: November 17, 2014
DNS Update Based Service Function Update
draft-xu-dnssd-sf-update-00
Abstract
In a Service Function Chaining (SFC)-enabled domain, the Domain Name
System (DNS) can be used as a mechanism for Service Function (SF)
auto-discovery [I-D.xu-dnssd-sf-discovery]. Since the information
associated with SF instances (e.g., capacity and current load) would
change dynamically, the information associated with SF instances
which is stored in the DNS sever needs to be updated accordingly.
This document describes how to use the DNS UPDATE mechanism [RFC2136]
to dynamically update the corresponding Resource Records (RRs) for SF
instances.
Requirements Language
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 [RFC2119].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on November 17, 2014.
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Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Updating SF-Specific RRs . . . . . . . . . . . . . . . . . . 3
3.1. RR Format . . . . . . . . . . . . . . . . . . . . . . . . 3
3.2. Updating SRV RR . . . . . . . . . . . . . . . . . . . . . 4
3.3. Updating TXT RR . . . . . . . . . . . . . . . . . . . . . 5
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
5. Security considerations . . . . . . . . . . . . . . . . . . . 6
6. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 6
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
7.1. Normative References . . . . . . . . . . . . . . . . . . 6
7.2. Informative References . . . . . . . . . . . . . . . . . 7
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
In a Service Function Chaining (SFC)-enabled domain, the Domain Name
System (DNS) can be used as a mechanism for Service Function (SF)
auto-discovery [I-D.xu-dnssd-sf-discovery]. Since the information
associated with SF instances (e.g., capacity and current load) would
change dynamically, the information associated with SF instances
which is stored in the DNS needs to be updated accordingly.
Specifically, the SRV [RFC2782] and TXT [RFC1035] records containing
the information associated with SF instances need to be updated
accordingly.
This document describes how to use the DNS update mechanism as
described in [RFC2136] to dynamically update the corresponding SRV
and TXT RRs for SF instances.
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2. Terminology
This section contains definitions for terms used frequently
throughout this document. However, many additional definitions can
be found in [I-D.xu-dnssd-sf-discovery], [RFC2136] and
[I-D.quinn-sfc-arch].
Service Function (SF): A function that is responsible for specific
treatment of received packets. A Service Function can act at the
network layer or other OSI layers. A Service Function can be a
virtual instance or be embedded in a physical network element.
One of multiple Service Functions can be embedded in the same
network element. Multiple instances of the Service Function can
be enabled in the same administrative domain. A non-exhaustive
list of Service Functions includes: firewalls, WAN and application
acceleration, Deep Packet Inspection (DPI), server load balancers,
NAT44 [RFC3022], NAT64 [RFC6146], HOST_ID injection, HTTP Header
Enrichment functions, TCP optimizer, etc.
Service Function Chain (SFC): A service function chain defines an
ordered set of service functions that must be applied to packets
and/or frames selected as a result of classification.
SF Identifier (SF ID): A unique identifier that represents a
service function within an SFC-enabled domain.
Service Node (SN): Physical or virtual element that hosts one or
more service functions and has one or more network locators
associated with it for reachability and service delivery.
SID: Segment Identifier
Service SID: A locally unique SID indicating a particular service
function on a service node.
3. Updating SF-Specific RRs
3.1. RR Format
All RRs as defined in [RFC1035] have the same top level format shown
below:
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1 1 1 1 1 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| |
/ /
/ NAME /
| |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| |
| TYPE |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| |
| CLASS |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| |
| TTL |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| |
| RDLENGTH |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
/ /
/ RDATA /
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
o NAME: a domain name to which this resource record pertains.
o TYPE: two octets containing one of the RR type codes. This
field specifies the meaning of the data in the RDATA field.
o CLASS: two octets which specify the class of the data in the
RDATA field.
o TTL: a 32 bit signed integer that specifies the time interval
that the resource record may be cached before the source of the
information should again be consulted.
o RDLENGTH: an unsigned 16 bit integer that specifies the length
in octets of the RDATA field.
o RDATA: a variable length string of octets that describes the
resource. The format of this information varies according to the
TYPE and CLASS of the resource record.
3.2. Updating SRV RR
The SF-specific SRV record has a name of the form
"<Instance>.<Service>.<Domain>" and gives the target host
(representing the Service Node) where the SF instance can be reached
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(Note that the port number given by the SRV record is meaningless in
the SFC case). When a particular SF instance is moved from one
service node to another, the Target field within the corresponding
SRV RR for that SF instance needs to be updated accordingly. The
following is an example:
Table 1: SRV RR
+------------------------+-----------------------------+
| SRV Name | SRV Data |
+------------------------|-----------------------------+
|<instance1>.<firewall>. |Target:FQDN of Service Node 2|
|<sfc.example.com> | |
| |Priority: Not Available |
| | |
| |Weight: Not Available |
| | |
| |Port: Not Available |
| | |
+------------------------+-----------------------------+
3.3. Updating TXT RR
The TXT record is used to contain additional information (such as
capacity, current load, service SID) associated with an SF instance.
Once any information (e.g., current load) is changed, the
corresponding key/value pair within the TXT record for that SF
instance needs to be updated accordingly. The following is an
example:
Table 1: TXT RR
+------------------------+-----------------------+
| TXT Name | TXT Data |
+------------------------+-----------------------+
|<instance1>.<firewall>. |0x09 ssid=1000 |
|<sfc.example.com> | |
| |0x0D capacity=1024 |
| | |
| |0x08 load=80% |
| | |
+------------------------+-----------------------+
o ssid=1000: The Service SID for the named SF instance.
o capacity=1024: The capacity of the named SF instance. For
example, this information can refer to the maximum number of
entries that can be supported by a firewall SF.
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o load=80%: The current load of the named SF instance. This
information may be used for load-balancing purposes for instance.
This parameter may reflect the amount of active entries vs. the
total amount of entries.
4. IANA Considerations
TBD.
5. Security considerations
The security considerations described in [RFC3007] is applicable to
this document. No additional security measure is required.
6. Acknowledgement
TBD.
7. References
7.1. Normative References
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2136] Vixie, P., Thomson, S., Rekhter, Y., and J. Bound,
"Dynamic Updates in the Domain Name System (DNS UPDATE)",
RFC 2136, April 1997.
[RFC2782] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for
specifying the location of services (DNS SRV)", RFC 2782,
February 2000.
[RFC3007] Wellington, B., "Secure Domain Name System (DNS) Dynamic
Update", RFC 3007, November 2000.
[RFC3022] Srisuresh, P. and K. Egevang, "Traditional IP Network
Address Translator (Traditional NAT)", RFC 3022, January
2001.
[RFC6146] Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful
NAT64: Network Address and Protocol Translation from IPv6
Clients to IPv4 Servers", RFC 6146, April 2011.
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7.2. Informative References
[I-D.quinn-sfc-arch]
Quinn, P. and J. Halpern, "Service Function Chaining (SFC)
Architecture", draft-quinn-sfc-arch-05 (work in progress),
May 2014.
[I-D.xu-dnssd-sf-discovery]
Xu, X., "DNS-SD Extensions for Service Function
Discovery", draft-xu-dnssd-sf-discovery-00 (work in
progress), May 2014.
Author's Address
Xiaohu Xu
Huawei
Email: xuxiaohu@huawei.com
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