One document matched: draft-zhou-softwire-ds-lite-p2p-00.txt
Softwires C. Zhou
Internet-Draft T. Tsou
Intended status: Standards Track Huawei Technologies
Expires: December 3, 2010 Y. Lee
Comcast
June 1, 2010
Deployment DS-lite in Point-to-Point Access Network
draft-zhou-softwire-ds-lite-p2p-00
Abstract
Gateway-Initiated Dual-Stack lite (GI-DS-lite) is a proposal to
logically extend existing access tunnels beyond the access gateway to
AFTR using softwires with an embedded context identifier. This memo
describes a deployment model using GI-DS-lite in Point-to-Point
access network.
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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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 December 3, 2010.
Copyright Notice
Copyright (c) 2010 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.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Scope and Requirements . . . . . . . . . . . . . . . . . . . . 3
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Current Deployment . . . . . . . . . . . . . . . . . . . . 4
3.2. DS-lite in Point-to-Point Access Network . . . . . . . . . 5
4. Requirements Language . . . . . . . . . . . . . . . . . . . . . 6
5. Proposed Alternative Context Identifier . . . . . . . . . . . . 6
6. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . 7
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
9. Security Considerations . . . . . . . . . . . . . . . . . . . . 7
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
10.1. Normative References . . . . . . . . . . . . . . . . . . . 7
10.2. Informative References . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8
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1. Introduction
GI-DS-lite [I-D.ietf-softwire-gateway-init-ds-lite] describes the use
of Gateway-Initiated softwire tunnels operating between the Gateway
and the Address Family Transition Router (AFTR) to conserve IPv4
addresses. Flows from multiple access devices (CPEs) can be
distinguished through use of Context Identifiers (CID). GI-DS-lite
describes an architecture where each CPE is a single device. It does
not cover the case where each CPE manages multiple hosts. This is
common in fixed network deployment and home network deployment over
air.
GI-DS-lite proposes few tunnel modes used for CID. One option is to
use Plain IP-in-IP. In this mode, a unique IPv4 address must be
assigned for each CPE from the gateway. As such, it does not support
CPEs using overlapped address. To support overlapped address space,
stateful tunnel (eg. GRE) is required between gateway and AFTR. It
is expensive to create one stateful tunnel per CPE especially in
fixed network non-mobility deployment.
DS-Extra-lite [I-D.arkko-dual-stack-extra-lite] describes that when
the CPE is connected to the gateway by point-to-point link rather
than shared media connection, it is unnecessary for the CID to be an
IP address. If another identifier with the required uniqueness
properties can be found (eg. VLAN and ATM PVC), the gateway can use
the per-interface identity to uniquely identify the CPE. This
relaxes the contraint of using CPE's IPv4 address for uniqueness.
This memo describes a framework to use the point-to-point identifier
and the IPv6 Flow Label [RFC3697] to create a unique binding in the
AFTR for CPEs using overlapped address space in the point-to-point
access network.
2. Scope and Requirements
This specification focuses on the point-to-point access network
deployment using GI-DS-lite. Other deployment scenarios are out of
scope. These are the assumptions of the network:
1. The access network is point-to-point.
2. The access network is not yet IPv6 enabled.
3. Avoid double-NAT.
4. Edge router does not perform NAT.
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5. Edge router uses plain IP-in-IPv6 to connect to AFTR.
6. Extend the point-to-point mapping to AFTR.
3. Overview
3.1. Current Deployment
Many operators use point-to-point (eg. PPP) to connect to their
customers. The operators give each customer a public IPv4 address.
Many customers also have a gateway (managed or unmanaged) which is a
NAT device managing the customer's internal network. Figure 1 shows
a common deployment architecture.
|
| IPv4 Internet
|
+------+------+
| Gateway |
+-------------+
/ \
Layer-3 / \ Layer-3
+----+ +----+
| ER | | ER |
+----+ +----+
/\ /\
/ \ / \ Pt-to-Pt
NAT/ \NAT NAT/ \NAT
+===+ +===+ +===+ +===+
| A | | B | | C | | D |
+===+ +===+ +===+ +===+
| | | |
--+-- --+-- --+-- --+--
| | | | | | | |
H1 H2 H3 H4 H5 H6 H7 H8
Access CPEs A,B,C,D all use 192.168.1.0/24
for their internal network.
Figure 1
Each CPE has been assigned a unique global IPv4 address and performs
NAT for the hosts, so Edge Router (ER) can uniquely identify the CPEs
by their IP addresses.
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3.2. DS-lite in Point-to-Point Access Network
When IPv4 addresses are scarce, operators may want to increase the
IPv4 address utilization by sharing a single IPv4 address to multiple
users. [I-D.ietf-softwire-dual-stack-lite] describes a framework to
implement B4 element in the CPE and tunnel the IPv4-in-IPv6 packets
to AFTR element in the operator network for NAT-ing. The AFTR uses
the unique IPv6 address of the B4 to identify the CPE. This
framework works well for both shared media network and point-to-point
access network, but it requires the operator to upgrade the access
network to IPv6.
In point-to-point access network, each CPE has a unique point-to-
point link. The operator can use this information to identify the
CPE. In this specification, the ER does not give any IPv4 address to
the CPE. Instead, each point-to-point interface is an unnumbered
interface. The CPE is still an IPv4 DHCP server for the LAN, it
continues to offer [RFC1918] addresses to its managed hosts. In this
memo, the CPE does not NAT the packets coming from its hosts.
Instead, the CPE simply puts the packets to the point-to-point link
and forward to the ER. When ER receives the packet, it maps the
point-to-point identifier to the IPv6 Flow Label [RFC3697] and send
to the AFTR for NAT. Figure 2 shows the architecture.
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|
| IPv4 Internet
+--------+
| DS-lite| NAT Mappings:
| AFTR | (Flow Label, TCP port1 <->
+---++---+ a.b.c.d, TCP port2)
||
IPv6 || Softwire Tunnel (IP-in-IPv6)
|| (CID is the Flow Label)
||
+-----++------+
| Edge Router | Map IPv6 Flow Label to CID
+-------------+
/ \ Pt-to-Pt
/ \ unnumbered I/F
+===+ +===+
| A | | B | Access CPE A and B
+===+ +===+ use 192.168.1.0/24
| |
--+-- --+--
| | | |
H1 H2 H3 H4
.5 .6 .5 .6
Figure 2
In Figure 2, H1 and H3, and H2 and H4 use duplicate IP addresses.
Since CPE A and B do not have IP address, the ER cannot use the IP
address to returned packets to the hosts behind CPE A and B.
Alternatively, ER creates a binding table to map the point-to-point
identifier to the CPEs. Then, ER uses the IPv6 Flow Label [RFC3697]
as the Context Identifier for the GI-DS-lite tunnel. No stateful
tunnel is required between AFTR and ER.
4. Requirements Language
This document uses no requirements language.
5. Proposed Alternative Context Identifier
This memo proposes that an additional type of context identifier be
added to the set identified in GI-DS-lite. Where the tunnel between
the Gateway and the AFTR is IP-in-IPv6, it is proposed to use the
IPv6 Flow Label as the context identifier.
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The Flow Label is 20 bits, where the Context ID in GI-DS-lite is 32
bits. Use of the Flow Label as the Context ID is therefore suitable
only for deployments not requiring the larger scale. To some extent
this limitation can be overcome by using multiple tunnels between the
Gateway and the AFTR.
6. Conclusion
We present a framework to deploy GI-DS-lite in point-to-point access
network. This framework promotes IPv6 deployment from the core to
the edge. When IPv6 is ready in the access network, the operators
can either upgrade the CPE to B4 element and migrate to classic DS-
lite deployment or provision dual-stack to the CPE and continue to
use GI-DS-lite.
7. Acknowledgements
TBD
8. IANA Considerations
This memo includes no request to IANA.
9. Security Considerations
See the security considerations for [RFC3697] and
[I-D.ietf-softwire-dual-stack-lite]. This proposal adds no further
security considerations.
10. References
10.1. Normative References
[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.ietf-softwire-gateway-init-ds-lite]
Brockners, F., Gundavelli, S., Speicher, S., and D. Ward,
"Gateway Initiated Dual-Stack Lite Deployment",
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draft-ietf-softwire-gateway-init-ds-lite-00 (work in
progress), May 2010.
[RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and
E. Lear, "Address Allocation for Private Internets",
BCP 5, RFC 1918, February 1996.
[RFC3697] Rajahalme, J., Conta, A., Carpenter, B., and S. Deering,
"IPv6 Flow Label Specification", RFC 3697, March 2004.
10.2. Informative References
[I-D.arkko-dual-stack-extra-lite]
Arkko, J. and L. Eggert, "Scalable Operation of Address
Translators with Per-Interface Bindings",
draft-arkko-dual-stack-extra-lite-00 (work in progress),
February 2010.
Authors' Addresses
Cathy Zhou
Huawei Technologies
Section B, Huawei Industrial Base
Bantian Longgang
Shenzhen 518129
P.R. China
Email: cathyzhou@huawei.com
URI: http://www.huawei.com
Tina Tsou
Huawei Technologies
Bantian, Longgang District
Shenzhen 518129
P.R. China
Email: tena@huawei.com
URI: http://www.huawei.com
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Yiu L. Lee
Comcast
One Comcast Center
Philadelphia 19103
U.S.A.
Email: yiu_lee@cable.comcast.com
URI: http://www.comcast.com
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