Internet DRAFT - draft-kiesel-alto-ip-based-srv-disc
draft-kiesel-alto-ip-based-srv-disc
ALTO S. Kiesel
Internet-Draft University of Stuttgart
Intended status: Standards Track R. Penno
Expires: January 2, 2015 Cisco Systems
July 1, 2014
Application-Layer Traffic Optimization (ALTO) Anycast Address
draft-kiesel-alto-ip-based-srv-disc-03
Abstract
The goal of Application-Layer Traffic Optimization (ALTO) is to
provide guidance to applications that have to select one or several
hosts from a set of candidates capable of providing a desired
resource. ALTO is realized by a client-server protocol.
This document establishes a well-known IP address for the ALTO
service and specifies how ALTO clients embedded in the resource
consumer can use it to access the ALTO service.
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Terminology and Requirements Language
This document makes use of the ALTO terminology defined in RFC 5693
[RFC5693].
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 [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
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 2, 2015.
Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. ALTO Server Discovery based on well-known IP Address . . . . . 5
2.1. ALTO Anycast IP Address (AAIPA) . . . . . . . . . . . . . 5
2.2. ALTO Anycast Uniform Resource Identificator (AAURI) . . . 5
2.3. ALTO Anycast Client Behavior . . . . . . . . . . . . . . . 5
2.4. ALTO Anycast Server Behavior . . . . . . . . . . . . . . . 6
3. Deployment Considerations . . . . . . . . . . . . . . . . . . 8
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
4.1. Registration of IPv4 Special Purpose Address . . . . . . . 9
4.2. Registration of IPv6 Special Purpose Address . . . . . . . 10
5. Security Considerations . . . . . . . . . . . . . . . . . . . 12
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
6.1. Normative References . . . . . . . . . . . . . . . . . . . 13
6.2. Informative References . . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15
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1. Introduction
The goal of Application-Layer Traffic Optimization (ALTO) is to
provide guidance to applications that have to select one or several
hosts from a set of candidates capable of providing a desired
resource [RFC5693]. The ALTO requirements are itemized in [RFC6708].
The ALTO protocol [RFC7285] is a client-server protocol, which uses
HTTP [RFC7230] for message transport.
Before an ALTO client can ask for guidance, it needs to discover one
or more ALTO servers that can provide suitable guidance. Several
procedures have been specified that produce a suitable HTTP URI for a
given ALTO client (i.e., the URI may vary for different clients or
different points of network attachment, etc.). These approaches are
based on user input or DHCP [RFC7286], a "reverse DNS" (PTR) lookup
[I-D.kist-alto-3pdisc], or redirection within the application
protocol [I-D.kiesel-alto-alto4alto]. However, each of this
approaches has technical or operational issues that will hinder the
fast deployment of ALTO.
This document follows a different approach: it establishes a well-
known address for the ALTO service to be used as application-layer
anycast address. All ALTO clients seeking ALTO guidance are expected
to send requests to this address. It is then the duty of "the
network" to direct the query to a suitable server. This
(re-)directing could be done on several layers, e.g., by resolving a
well-known DNS domain name to different IP addresses (DNS split
horizon), or by routing IP packets with the well-known IP address to
different servers. This document follows the second option, as ALTO
is closely related to IP routing and routing costs.
This document specifies a procedure that can be used if the ALTO
client is embedded in the resource consumer. In other words, this
document tries to meet requirement AR-32 in [RFC6708] while AR-33 is
out of scope. Note that AR-20 mandates that "an ALTO client protocol
must be designed in a way that the ALTO service can be provided by an
entity that is not the operator of the underlying IP network."
Though not violating said requirement, the procedure specified here
is not helpful to fulfill it.
A more detailed discussion of various options where to place the
functional entities comprising the overall ALTO architecture can be
found in [I-D.ietf-alto-deployments].
Comments and discussions about this memo should be directed to the
ALTO working group: alto@ietf.org.
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2. ALTO Server Discovery based on well-known IP Address
2.1. ALTO Anycast IP Address (AAIPA)
IANA is requested to register (see Section 4) a single IPv4 address
192.0.0.X (TBD) and a single IPv6 address 2001:YYYY::ZZZZ (TBD)
within the respective Special Purpose Address Registries as the well-
known IP anycast addresses for the ALTO service. These addresses are
called AAIPA (ALTO Anycast IP Address(es)) in this document.
2.2. ALTO Anycast Uniform Resource Identificator (AAURI)
The ALTO Anycast Uniform Resource Identificators (AAURIs) are formed
using the HTTP or HTTPS protocol identifier, the AAIPA in their
literal forms (for literal IPv6 addresses in URIs see [RFC2732]), and
a constant suffix. That is, there are four AAURIs (TBD: replace X,
Y, Z with real values assigned by IANA):
http://192.0.0.X/alto
https://192.0.0.X/alto
http://[2001:YYYY::ZZZZ]/alto
https://[2001:YYYY::ZZZZ]/alto
2.3. ALTO Anycast Client Behavior
ALTO Clients that need to discover an ALTO server use the HTTP GET
method [RFC7231] to access one AAURI, e.g.
GET http://192.0.0.X/alto
They MUST be prepared to receive an HTTP 307 temporary redirect to
the ALTO server's Information Resource Directory URI (Sec. 9 of
[RFC7285]).
For hosts equipped with multiple interfaces and/or using IPv4/v6 dual
stack, this discovery method might yield different Information
Resource Directory URIs for each interface and address familly (i.e.,
IPv4/v6). In general, if a client wishes to communicate using one of
its interfaces and using a specific IP address familiy, it SHOULD use
this interface and the IP address associated with this interface to
access the AAURI of the corresponding IP address family. Selecting
an interface and IP address family, as well as comparing results
returned from different ALTO servers, is out of the scope of this
document.
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TBD: rules for retrying (timers, etc.) in case of failure.
TBD: rules for caching discovery results.
A change of the IP address at an interface invalidates the result of
the ALTO server discovery procedure. For instance, if the IP address
assigned to a mobile host changes due to host mobility, it is
required to re-run the ALTO server discovery procedure without
relying on earlier gained information.
2.4. ALTO Anycast Server Behavior
ALTO anycast servers MUST listen on the IPv4 and/or IPv6 AAIPA(s) on
the HTTPS ports for incoming HTTPS requests and they SHOULD listen on
these AAIPA(S) on the HTTP port for incoming HTTP requests. They
MUST answer GET requests to AAURI using the 307 (Temporary Redirect)
status code and redirect to an ALTO server's Information Resource
Directory URI.
The Information Resource Directory itself MUST NOT reside on a AAIPA,
and it MUST NOT reside on an URI that resolves via DNS to a AAIPA.
After issuing the 307 status code ALTO anycast servers MUST close the
HTTP(S) connection.
Rationale for the requirements in the previous paragraph: The goal
is to keep the TCP connection to the AAIPA as short as possible.
When using anycast routing, IP packets belonging to an established
TCP connection could be diverted to another ALTO anycast server
due to state changes in the routing protocol or due to scheduled
maintenance. Keeping the connection duration as short as possible
reduces the risk of stalled or aborted connections. A UDP based
lookup using one query packet and one reply packet (e.g., based on
httpu) would eliminate that risk. However, there seems not to be
a well-standardized candidate protocol and studies [Levine2006]
suggest that short-lived TCP connections work well enough with
anycast routing.
An ALTO anycast server MUST redirect an HTTPS request for an HTTPS
AAURI to an HTTPS IRD URI. It MAY redirect an HTTP request for an
HTTP AAURI to an HTTP IRD URI, but it MAY also redirect it to an
HTTPS IRD URI.
The ALTO anycast server MAY consider the client's address and other
information when generating the reply, in order to redirect to
different ALTO servers depending on the client's identity or location
within the network topology.
TBD: do we need some URI such as http://192.0.0.X/server-identity in
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order to be able to identify the (misbehaving) ALTO anycast server
that currently serves us?
TBD: how should the ALTO anycast server handle GET requests to other
URIs or other HTTP methods?
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3. Deployment Considerations
Network operators have to install one or more ALTO anycast servers as
specified above. Depending on the the network deployment scenario
they may use IP routing tables, HTTP proxies with URI rewriting, or
other suitable mechanisms to direct GET-requests for a AAURI to one
of these servers.
[TBD: explain in more detail] This works fine even with cascaded
access routers with NATs. After each router hop the operator may
decide whether to handle the discovery requests, e.g., using a static
routing table entry, or whether let them flow "automatically" towards
the internet backbones using the default routing table entry.
TBD: what happens if an operator does not deploy these scheme?
Requests could be dropped at administrative borders. As an
alternative, there could be "public" ALTO anycast servers to answer
all queries that had not been answered in the respective originating
access network. These servers could use the third-party ALTO server
discovery procedure [I-D.kist-alto-3pdisc] to find the redirection
target based on the client's IP address.
[TBD: explain in more detail] The advantage of this scheme is that it
does not need support in home gateways, which would harm quick
deployment. This scheme also doesn't need new interfaces between the
operating system and applications, e.g., for passing DHCP options
from the operating system to the application.
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4. IANA Considerations
4.1. Registration of IPv4 Special Purpose Address
IANA is requested to register a single IPv4 address in the IANA IPv4
Special Purpose Address Registry [RFC5736].
[RFC5736] itemizes some information to be recorded for all
designations:
1. The designated address prefix.
Prefix: TBD by IANA. Prefix length: /32
2. The RFC that called for the IANA address designation.
This document.
3. The date the designation was made.
TBD.
4. The date the use designation is to be terminated (if specified
as a limited-use designation).
Unlimited. No termination date.
5. The nature of the purpose of the designated address (e.g.,
unicast experiment or protocol service anycast).
protocol service anycast.
6. For experimental unicast applications and otherwise as
appropriate, the registry will also identify the entity and
related contact details to whom the address designation has been
made.
N/A.
7. The registry will also note, for each designation, the
intended routing scope of the address, indicating whether the
address is intended to be routable only in scoped, local, or
private contexts, or whether the address prefix is intended to be
routed globally.
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Typically used within a network operator's network domain, but in
principle globally routable.
8. The date in the IANA registry is the date of the IANA action,
i.e., the day IANA records the allocation.
TBD.
4.2. Registration of IPv6 Special Purpose Address
IANA is requested to register a single IPv6 address in the IANA IPv6
Special Purpose Address Block [RFC4773].
[RFC4773] itemizes some information to be recorded for all
designations:
1. The designated address prefix.
Prefix: TBD by IANA. Prefix length: /128
2. The RFC that called for the IANA address designation.
This document.
3. The date the designation was made.
TBD.
4. The date the use designation is to be terminated (if specified
as a limited-use designation).
Unlimited. No termination date.
5. The nature of the purpose of the designated address (e.g.,
unicast experiment or protocol service anycast).
protocol service anycast.
6. For experimental unicast applications and otherwise as
appropriate, the registry will also identify the entity and
related contact details to whom the address designation has been
made.
N/A.
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7. The registry will also note, for each designation, the
intended routing scope of the address, indicating whether the
address is intended to be routable only in scoped, local, or
private contexts, or whether the address prefix is intended to be
routed globally.
Typically used within a network operator's network domain, but in
principle globally routable.
8. The date in the IANA registry is the date of the IANA action,
i.e., the day IANA records the allocation.
TBD.
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5. Security Considerations
TBD
Issue: how to deal with TLS certificates for HTTPS?
TBD: rules for filtering route at administrative boundaries
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6. References
6.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2732] Hinden, R., Carpenter, B., and L. Masinter, "Format for
Literal IPv6 Addresses in URL's", RFC 2732, December 1999.
[RFC4773] Huston, G., "Administration of the IANA Special Purpose
IPv6 Address Block", RFC 4773, December 2006.
[RFC5736] Huston, G., Cotton, M., and L. Vegoda, "IANA IPv4 Special
Purpose Address Registry", RFC 5736, January 2010.
[RFC7230] Fielding, R. and J. Reschke, "Hypertext Transfer Protocol
(HTTP/1.1): Message Syntax and Routing", RFC 7230,
June 2014.
[RFC7231] Fielding, R. and J. Reschke, "Hypertext Transfer Protocol
(HTTP/1.1): Semantics and Content", RFC 7231, June 2014.
6.2. Informative References
[I-D.ietf-alto-deployments]
Stiemerling, M., Kiesel, S., Previdi, S., and M. Scharf,
"ALTO Deployment Considerations",
draft-ietf-alto-deployments-09 (work in progress),
February 2014.
[I-D.kiesel-alto-alto4alto]
Kiesel, S., "Using ALTO for ALTO server selection",
draft-kiesel-alto-alto4alto-00 (work in progress),
July 2010.
[I-D.kist-alto-3pdisc]
Kiesel, S., Krause, K., and M. Stiemerling, "Third-Party
ALTO Server Discovery (3pdisc)", draft-kist-alto-3pdisc-05
(work in progress), January 2014.
[Levine2006]
Levine, M., Lyon, B., and T. Underwood, "TCP Anycast -
Don't believe the FUD. Operational experience with TCP and
Anycast.", Presentation at NANOG37 http://www.nanog.org/
meetings/nanog37/presentations/matt.levine.pdf, June 2006.
[RFC5693] Seedorf, J. and E. Burger, "Application-Layer Traffic
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Optimization (ALTO) Problem Statement", RFC 5693,
October 2009.
[RFC6708] Kiesel, S., Previdi, S., Stiemerling, M., Woundy, R., and
Y. Yang, "Application-Layer Traffic Optimization (ALTO)
Requirements", RFC 6708, September 2012.
[RFC7285] Alimi, R., Penno, R., and Y. Yang, "Application-Layer
Traffic Optimization (ALTO) Protocol", RFC 7285,
June 2014.
[RFC7286] Kiesel, S., Stiemerling, M., Schwan, N., Scharf, M., and
H. Song, "Application-Layer Traffic Optimization (ALTO)
Server Discovery", RFC 7286, June 2014.
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Authors' Addresses
Sebastian Kiesel
University of Stuttgart Information Center
Allmandring 30
Stuttgart 70550
Germany
Email: ietf-alto@skiesel.de
URI: http://www.rus.uni-stuttgart.de/nks/
Reinaldo Penno
Cisco Systems
170 West Tasman Dr
San Jose CA
USA
Email: repenno@cisco.com
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