Network Working Group R. Penno
Internet-Draft J. Medved
Intended status: Informational Juniper Networks
Expires: December 18, 2010 June 16, 2010
ALTO and IPv4/IPv6 Co-existence and Transition
draft-penno-alto-ipv4v6-00
Abstract
IPv4/IPv6 co-existence and transition is topic or great discussion
and interest. In order to deal with IPv4 depletion ISPs have some
techniques at their disposal such as Carrier Grade NAT , DS-Lite and
6rd.
As this techniques get deployed, they change the topology of the
network by creating gateways or overlays which in the end affect how
ALTO might work. This draft discusses such impacts and possible
solutions.
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 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
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This Internet-Draft will expire on December 18, 2010.
Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Landscape . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
5. Carrier Grade NAT . . . . . . . . . . . . . . . . . . . . . . . 4
5.1. Assumptions . . . . . . . . . . . . . . . . . . . . . . . . 5
5.2. Endpoint Property Service . . . . . . . . . . . . . . . . . 6
5.3. Endpoint Cost Service . . . . . . . . . . . . . . . . . . . 6
5.4. ALTO Server in ISP's Public Network . . . . . . . . . . . . 6
5.5. ALTO Server in ISP's Private Network . . . . . . . . . . . 6
6. Softwires . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
7. ALTO and CDNs . . . . . . . . . . . . . . . . . . . . . . . . . 7
7.1. Same Administrator Domain . . . . . . . . . . . . . . . . . 7
7.2. Different Administrator Domains . . . . . . . . . . . . . . 7
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 8
9. Security Considerations . . . . . . . . . . . . . . . . . . . . 8
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 8
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8
11.1. Normative References . . . . . . . . . . . . . . . . . . . 8
11.2. Informative References . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9
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1. Introduction
IPv4/IPv6 co-existence and transition is topic or great discussion
and interest. In order to deal with IPv4 depletion ISPs have some
techniques at their disposal, one of which, Carrier Grade NAT, is
probably the most popular due to the fact it requires no changes in
the infrastructure or end hosts. Other techniques based on Softwires
such as DS-Lite help with IPv4 depletion IPv6 introduction. 6rd helps
IPv6 introduction and leverages existing IPv4 access networks.
As this techniques get deployed, they change the topology of the
network by creating gateways or overlays which in the end affect how
ALTO might work. This draft discussed such impacts and possible
solutions.
2. Scope
This document discusses how the issues that IPv4/IPv6 co-existence
and transition brings to ALTO and how to possibly solve them. This
draft is a work in progress and will be updates based on feedback and
discussions.
3. Terminology
The reader should be familiar with terminology introduced by RFC 2663
[RFC2663], RFC 4787 [RFC4787], NAT64 [I-D.ietf-behave-v6v4-xlate],
DS-Lite [I-D.ietf-softwire-dual-stack-lite] and Carrier Grade NAT
[I-D.nishitani-cgn]
4. Landscape
During the co-existence period there will be three address 'families'
on the Internet: private IPv4, public IPv4 and IPv6. The same host
could be using one or more IP address from each of the families and
certainly different hosts within a home or enterprise could be
accessing the network using different address families. In this
context, ALTO clients and servers still need to a consistent and
deterministic view of the network. But this co-existence brings some
pitfalls that should be avoided, for example:
o An ALTO Client with only a public IPv4 has no use of a cost map
that contains private IPv4 addresses.
o An ALTO Client with only an IPv6 address has no use for a IPv4
cost map, whether private or public.
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Furthermore, with NAT migrating from the user CPE to the network and
the creation of overlays, the impact on the network and cost maps and
the associated placement of the ALTO Server needs to be evaluated.
In the next sections we will discuss some of these scenarios, their
implications and possible solutions.
5. Carrier Grade NAT
In the case of CGN, a NAT device is deployed in the edge of the
network instead of (or in addition to ) the NAT at the CPE. In this
scenario the placement of the ALTO Server and Client(s) becomes
specially important. If the Alto Server in on the private network,
the network and cost maps built from such data are not of use to
clients on the Internet or on the ISP's public network. If on the
other hand the ALTO Server is on the ISP's public network and the
ALTO Clients reside on end hosts (P2P case), the cost between
endpoints becomes the cost between CGN boxes.
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(preamble)
ISP Private ISP Public Internet
,-. ,-. ,-.
+---+ / \ / \ ; :
|CPE| / \ / \ ; :
+---+ ; +-----+ ; +-----+ ; :
; | | ; | | ; :
; | CGN |; | BR | ; :
+---+ | | || | | | |
|CPE| | +-----+| +-----+ ; :
+---+ ; | ; | ; :
; : ; : | |
| +-----+ +-----+| |
+---+ | | | | || |
|CPE| | | CGN | | BR || |
+---+ | | | | || |
. | +-----+ +-----+| |
| | | | | | |
| | | | | | |
| : ; : ; | |
: +-----+: +-----+: ;
+---+ __________ | || | | : ;
|CPE|()_________)| CGN || | BR | | |
+---+ : | |: | | : ;
: +-----+ : +-----+ : ;
: ; : ; : ;
\ / \ / : ;
\ / \ / : ;
`-' `-' `-'
(postamble)
5.1. Assumptions
The following assumptions are common for all Alto Server - CGN
interworking use cases:
o In absence of failures, any given CPE always uses the same CGN.
All sessions from the CPE pass through that CGN.
o The assignment of CPEs to CGN is determined by a policy specified
by the provider. The assignment does not change while both the
CPE and the CGN are alive
o A Content Origin Server will typically reside in a public network,
since all its clients will connect to it at Port 80, which can not
be translated by the NAT.
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5.2. Endpoint Property Service
The Endpoint Property Lookup query allows an ALTO Client to lookup
properties of Endpoints known to the ALTO Server. In the case where
the ALTO Server is on the ISP's public network, the 'pid' property
remains as is since a public IPv4 address belongs to a PID. On the
other hand, properties that are different across endpoints such as
bandwidth and access type need modification.
In other to make use of this service to query properties associated
exclusively with an endpoint, the query would need to be extended to
include a public transport port associated with the private IP
address. This stems from the fact that many private IPv4 addresses
are mapped to the same public IPv4 address.
5.3. Endpoint Cost Service
The endpoint cost service does not need modification. The cost might
have different semantics but the query can be used as specified in
the ALTO protocol.
5.4. ALTO Server in ISP's Public Network
In this case the network and cost map are built based on NAT pool
addresses configured at each CGN. If the architecture is distributed
such that the cost from endpoints to the CGN does not vary
significantly, the ALTO Service should not be impacted. In fact,
having an anchor point such as a CGN might present some advantages
such as a natural mapping between PID and CGN and deterministic
traffic flow and therefore cost map.
5.5. ALTO Server in ISP's Private Network
If the ALTO Server and associated network and cost maps are based on
the private network they might provide more fine granular guidance
but such maps could not be used by outside parties. One way to solve
this problem is to have another ALTO Server on the public side and
provide two network and cost maps to clients.
6. Softwires
Softwires create a overlay on top of the current IP infrastructure.
Everything between the Softwire Initiator and Concentrator is seen as
a 'single-hop' or virtual link from the network users point of view.
Therefore, the network and cost maps should be built similar to the
CGN case where the ALTO Server is place in the ISP's public network.
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In the case of 6rd which is based on stateless IP anycast operation,
there is no way to know a priori which border relay will be used by a
CPE. This makes computation of network maps and consequently cost
maps problematic.
DS-Lite requires NAPT44 and therefore traffic from and endhost is
expected to flow drought the same NAPT device consistently. IP
anycast could be used with DS-Lite as well but NAPT44 requires
traffic flows to be more deterministic.
7. ALTO and CDNs
For CDN use cases, we have to differentiate whether the CDN is in the
same administrative domain as the CPE's Network Provider or not.
7.1. Same Administrator Domain
The network provider may want to place cache nodes as close to the
CPE as possible, i.e., in the private network.
Alto Server HTTP Redirector / DNS Redirector all in the private
network. We are optimizing the traffic through the private network,
choosing a cache node in the private network which is the closest to
the CPE.
Assume the Cache Node also goes though its own CGN, so we must
optimize the whole path CPE->Cache->CGN->Origin Server.
CPE->Cache->CGN can be optimized by the private network Redirector
using private network's Alto Server Network Maps. For CGN->Origin
Server optimization we need Network Maps from a public network Alto
Server - this is likely a similar situation as we had in the multi-
domain CDN case (the interesting part is that the model seems to be
similar to the multi-domain model, yet this is a single domain case,
but the public/private split makes it look like multi-domain.
7.2. Different Administrator Domains
In this case the CDN cache nodes will also reside in a public
network, and all traffic between the CPE and either the Origin Server
and/or the cache node will go through the CGN. Since the assignment
of CPEs to the CGN is static, we can only optimize traffic in the
public network by selecting a cache node that is closest to the CPE's
CGN.
This would work with both HTTP redirection and DNS redirection as
described in ALTO and CDNs [I-D.penno-alto-cdn]. The Alto Server in
the public network would provide network maps to either an HTTP
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Redirector or a DNS Redirectors, which would choose a cache node
closest to the CPE's CGN. Neither the Alto Server nor the HTTP
Redirector nor the DNS Redirector is aware of the private network and
that the CPE is behind a NAT. (Note that this would work pretty much
the same as CPE-based NATs today.)
8. IANA Considerations
This document makes no request of IANA.
Note to RFC Editor: this section may be removed on publication as an
RFC.
9. Security Considerations
10. Acknowledgements
TBD
11. References
11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
11.2. Informative References
[I-D.ietf-alto-protocol]
Alimi, R., Penno, R., and Y. Yang, "ALTO Protocol",
draft-ietf-alto-protocol-04 (work in progress), May 2010.
[I-D.ietf-behave-v6v4-xlate]
Li, X., Bao, C., and F. Baker, "IP/ICMP Translation
Algorithm", draft-ietf-behave-v6v4-xlate-20 (work in
progress), May 2010.
[I-D.ietf-behave-v6v4-xlate-stateful]
Bagnulo, M., Matthews, P., and I. Beijnum, "Stateful
NAT64: Network Address and Protocol Translation from IPv6
Clients to IPv4 Servers",
draft-ietf-behave-v6v4-xlate-stateful-11 (work in
progress), March 2010.
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[I-D.ietf-softwire-dual-stack-lite]
Durand, A., Droms, R., Haberman, B., Woodyatt, J., Lee,
Y., and R. Bush, "Dual-Stack Lite Broadband Deployments
Following IPv4 Exhaustion",
draft-ietf-softwire-dual-stack-lite-04 (work in progress),
March 2010.
[I-D.nishitani-cgn]
Yamagata, I., Nishitani, T., Miyakawa, S., Nakagawa, A.,
and H. Ashida, "Common requirements for IP address sharing
schemes", draft-nishitani-cgn-04 (work in progress),
March 2010.
[I-D.penno-alto-cdn]
Penno, R., Raghunath, S., Medved, J., Bakshi, M., Alimi,
R., and S. Previdi, "ALTO and Content Delivery Networks",
draft-penno-alto-cdn-00 (work in progress), June 2010.
[RFC2663] Srisuresh, P. and M. Holdrege, "IP Network Address
Translator (NAT) Terminology and Considerations",
RFC 2663, August 1999.
[RFC3022] Srisuresh, P. and K. Egevang, "Traditional IP Network
Address Translator (Traditional NAT)", RFC 3022,
January 2001.
[RFC3568] Barbir, A., Cain, B., Nair, R., and O. Spatscheck, "Known
Content Network (CN) Request-Routing Mechanisms",
RFC 3568, July 2003.
[RFC4787] Audet, F. and C. Jennings, "Network Address Translation
(NAT) Behavioral Requirements for Unicast UDP", BCP 127,
RFC 4787, January 2007.
[RFC5632] Griffiths, C., Livingood, J., Popkin, L., Woundy, R., and
Y. Yang, "Comcast's ISP Experiences in a Proactive Network
Provider Participation for P2P (P4P) Technical Trial",
RFC 5632, September 2009.
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Authors' Addresses
Reinaldo Penno
Juniper Networks
1194 N Mathilda Avenue
Sunnyvale
USA
Email: rpenno@juniper.net
Jan Medved
Juniper Networks
1194 N Mathilda Avenue
Sunnyvale
USA
Email: jmedved@juniper.net
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