Internet DRAFT - draft-wu-softwire-public4over6-deployment
draft-wu-softwire-public4over6-deployment
Network Working Group P. Wu
Internet-Draft Q. Sun
Intended status: Informational Tsinghua University
Expires: January 10, 2013 July 9, 2012
Deployment Considerations for Public 4over6
draft-wu-softwire-public4over6-deployment-00
Abstract
Public 4over6 is a stateful transition mechanism which assigns public
IPv4 address to CPE/host and uses IPv4-in-IPv6 tunnel. It doesn't
involve CGN as in DS-lite and reduces the mapping scale on the
Concentrator to per-subscriber level. This document describers
deployment models for Public 4over6, and the deployment
considerations of the Public 4over6 architecture.
Status of This Memo
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This Internet-Draft will expire on January 10, 2013.
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements Language . . . . . . . . . . . . . . . . . . . . . 3
3. Concentrator Deployment Considerations . . . . . . . . . . . . 3
3.1. Interface Consideration . . . . . . . . . . . . . . . . . . 3
3.2. MTU Consideration . . . . . . . . . . . . . . . . . . . . . 3
3.3. Fragmentation . . . . . . . . . . . . . . . . . . . . . . . 3
3.4. Logging at Concentrator . . . . . . . . . . . . . . . . . . 3
3.5. Reliability Considerations of Concentrator . . . . . . . . 4
3.6. Placement of Concentrator . . . . . . . . . . . . . . . . . 4
3.7. Considerations for Geographically Aware Services . . . . . 4
4. Initiator Deployment Considerations . . . . . . . . . . . . . . 4
4.1. Concentrator Discovery Considerations . . . . . . . . . . . 4
4.2. DNS Deployment Considerations . . . . . . . . . . . . . . . 4
4.3. Optional NAT44 Functionality on Initiator . . . . . . . . . 5
5. Deployment Experience . . . . . . . . . . . . . . . . . . . . . 5
6. IDC Transition Usage . . . . . . . . . . . . . . . . . . . . . 5
7. Security Consideration . . . . . . . . . . . . . . . . . . . . 5
8. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . . 5
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5
9.1. Normative References . . . . . . . . . . . . . . . . . . . 5
9.2. Informative References . . . . . . . . . . . . . . . . . . 6
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1. Introduction
Public 4over6 [I-D.ietf-softwire-public-4over6] is a transition
mechanism that enables operators to assign public IPv4 addresses to
end users over IPv6. Public 4over6 uses IPv4-in-IPv6 softwire to
provide IPv4 connectivity between users in IPv6 access networks and
IPv4 Internet.This document discuss various Public 4over6 deployment
considerations for operators.
Terminology of this document follows the definitions and
abbreviations of [I-D.ietf-softwire-public-4over6] .
2. 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].
3. Concentrator Deployment Considerations
Public 4over6 and DS-Lite [RFC6333] shares some deployment
considerations, while Concentrator and Initiator of Public 4over6
play a similar role to AFTR and B4 of DS-Lite.
3.1. Interface Consideration
Tunnel Concentrator is deployed at the IPv4-IPv6 network border where
the tunnel interface is IPv6 and the external interface is IPv4. It
shares the same deployment considerations with
[I-D.ietf-softwire-dslite-deployment].
3.2. MTU Consideration
Same with [I-D.ietf-softwire-dslite-deployment].
3.3. Fragmentation
Same with [I-D.ietf-softwire-dslite-deployment].
3.4. Logging at Concentrator
Timestamped logging is essential for back tracking specific users
when a problem is identified with one of the assigned public IPv4
address. Operators only log one entry per subscriber. The log
should include the subscriber's IPv6 address and the public IPv4
address.
3.5. Reliability Considerations of Concentrator
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For redundancy, the backup Concentrator should apply either of the
following types. One is that a dedicated DHCP server synchronizes
mapping entries with all Concentrators considering that the DHCP
server is responsible for IPv4 address allocation. Each Concentrator
maintain per-subscriber mapping table accordingly. Once the working
Concentrator is down, subscribers will switch to the backup
Concentrator using technologies like anycast etc.
The other method is that Initiators PING the Concentrator
periodically to check the status of the Concentrator. If the PING
test fails for a specific number of times, Initiators should release
the current public IPv4 address and require for another public IPv4
address from the backup Concentrator.
3.6. Placement of Concentrator
Concentrator maintains a per-subscriber mapping table, smaller than
the per-session binding table on DS-Lite AFTR. As a result,
Concentrator can be deployed closer to core of the network to cover a
larger region. And the amount of subscribers and the capability of
devices should be taken into account.
3.7. Considerations for Geographically Aware Services
Even though Public 4over6 supports the assignment of public IPv4
address, identification by IP address is no easier than that in DS-
Lite. Thus applications that assume such geographic information may
not work as intended. In Public 4over6, each address represents a
single machine, a single household, or a single small office, but
it's hard to identify geographic information over IPv6 access
networks. The considerations are similar to section 2.11 of
[I-D.ietf-softwire-dslite-deployment]
4. Initiator Deployment Considerations
4.1. Concentrator Discovery Considerations
A public 4over6 Initiator must discover the Concentrator's IPv6
address before starting IPv4 connections. The IPv6 address can be
learned through out-of-band mechanism, manual configuration or DHCPv6
option. If an operator uses DHCPv6 for provision the Initiator,
DHCPv6 option defined in [RFC6334] must be implemented in the
Initiator.
4.2. DNS Deployment Considerations
The Initiator can implement a proxy resolver that will proxy DNS
query from IPv4 transport to the DNS server in the IPv6 network.
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Alternatively, the Initiator can tunnel IPv4 DNS query to an external
DNS server over IPv6 network.
4.3. Optional NAT44 Functionality on Initiator
The Initiator can be a host or a CPE device. If it's a host, the
host can get Public IPv4 address and does not need NAT44 function.
If it's a CPE, NAT44 function must be enabled for local private IPv4
Network.
5. Deployment Experience
Tsinghua University has deployed a Tunnel Concentrator in CERNET lab.
The DHCP server collocates on the same device with Tunnel
Concentrator. Public4over6 client software has also been released,
with Win7 version and Linux version. The system has provided IPv4
service over IPv6 access networks of universities from China.
The IPv4-over-IPv6 services Public 4over6 provided is transparent to
the upper layer applications. Even though in IPv6 networks, users
can also get access to IPv4 websites with no difference to native
IPv4. Because of assignment of public IPv4 address to Initiators,
users can experience P2P services. Public 4over6 is able to provide
qualified IPv4 services with no side impact on native IPv6.
6. IDC Transition Usage
IDC is responsible for steady service for users. And as a server, a
public IPv4 address does good to guarantee the IDC's QoS. Public
4over6 is able to provide service for IDC locating in an IPv6-only
network. As an Initiator, an IDC will get a public IPv4 address and
achieve "dual-stack" environment, which is essential for better
service.
7. Security Consideration
This specification raises no new security issues.
[I-D.ietf-softwire-public-4over6] discusses public 4over6 related
security issues.
8. Acknowledgement
TBD
9. References
9.1. Normative References
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[RFC2119] Bradner, S., "Key words for
use in RFCs to Indicate
Requirement Levels", BCP 14,
RFC 2119, March 1997.
[RFC6333] Durand, A., Droms, R.,
Woodyatt, J., and Y. Lee,
"Dual-Stack Lite Broadband
Deployments Following IPv4
Exhaustion", RFC 6333,
August 2011.
[RFC6334] Hankins, D. and T. Mrugalski,
"Dynamic Host Configuration
Protocol for IPv6 (DHCPv6)
Option for Dual-Stack Lite",
RFC 6334, August 2011.
9.2. Informative References
[I-D.ietf-softwire-dslite-deployment] Lee, Y., Maglione, R.,
Williams, C., Jacquenet, C.,
and M. Boucadair, "Deployment
Considerations for Dual-Stack
Lite", draft-ietf-softwire-
dslite-deployment-03 (work in
progress), March 2012.
[I-D.ietf-softwire-public-4over6] Cui, Y., Wu, J., Wu, P., Metz,
C., Vautrin, O., and Y. Lee,
"Public IPv4 over IPv6 Access
Network", draft-ietf-softwire-
public-4over6-01 (work in
progress), March 2012.
Authors' Addresses
Peng Wu
Tsinghua University
Department of Computer Science, Tsinghua University
Beijing 100084
P.R.China
Phone: +86-10-6278-5822
EMail: peng-wu@foxmail.com
Qi Sun
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Tsinghua University
Department of Computer Science, Tsinghua University
Beijing 100084
P.R.China
Phone: +86-10-6278-5822
EMail: sunqi@csnet1.cs.tsinghua.edu.cn
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