Internet DRAFT - draft-ma-softwire-dslite-test
draft-ma-softwire-dslite-test
Internet Engineering Task Force Q. Ma
Internet-Draft China Mobile
Intended status: Informational October 15, 2012
Expires: April 18, 2013
Test about deployment of dual-stack lite
draft-ma-softwire-dslite-test-00
Abstract
This document introduces the test about deployment of dual-stack lite
firstly，then describe two major problems about CPE devices in
the test,address assignment and packet fragmentation.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Test overview . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. test rusult of address assignment . . . . . . . . . . . . . . . 4
4. test result of fragmentation . . . . . . . . . . . . . . . . . 4
4.1. Test topology . . . . . . . . . . . . . . . . . . . . . . . 4
4.2. Result Description . . . . . . . . . . . . . . . . . . . . 4
4.3. Analysis . . . . . . . . . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
7. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 5
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1. Introduction
With the exhaust of IPv4 address space, the deployment of IPv6 became
imperative to the Internet service providers.Dual-Stack lite
technology which defined in RFC6333 has the potential to be widely
used in the IPv6 evoluation process. In order to verify whether the
existing equipments be able to support Dual-Stack lite technology,
and meet the operational needs of network operators, it is necessary
to test the various equipments and technical aspects involved in
Dual-Stack lite.
In this document, the content of Dual-stack deployment test is
introduced fristly, after that, two problems about CPE devices found
in the test are described, one is a few CPE devices's WAN interface
can not support to achieve 128bits IPv6 Address by DHCPv6-NA, another
is a few CPE devices handling jumbo frames with a different
fragmentation manner compare to the definiton of RFC6333.
2. Test overview
Through test the functionality, performance, reliability and other
aspects of B4, AFTR, CGN devices or function modules which invlved in
dual-stack lite technology, the service provider be able to
understand the technical maturity of the various equipment
manufacturers, obtain the crisis data and technical support to the
deployment of dual-stack lite.
The test mainly include the following aspects:
-functionality of dual-Stack lite, including obtain and distribute
addresses, IPv4-in-IPv6 tunnel, NAT ,application level gateway and
other tests.
- functionality of Radius, including authentication, accouting,
recording extended attributes of NAT,tracing and other tests;
- control policies, including the limit of ipv6 address ranges, limit
of NAT sessions and other tests;
- reliability test, including warm standy, hot standby of Address
Family Transition Routers;
- performance test, including the number of tunnels, the number of
NAT sessions, forwarding performance and other tests;
- DSLite+ NAT444 test,including deploy dual-stack lite and NAT444 at
the same time, switching between dual-stack lite and NAT444, and
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other tests;
3. test rusult of address assignment
A dual-stack lite CPE is an IPv6-aware CPE with a B4 interface
implemented in the WAN interface. The IPv6 address of B4 element can
be configured using several methods. In the test, we used methods of
neighbor discovery mechanism and DHCPv6 options. The B4 element gets
a 128-bit address by neighbor discovery negotiation, which is a
directed link address and is usually different from the IPv6 prefix
assigned by DHCPv6 prefix delegation (RFC 3633). The result shows
that all test equipment can support this function. In the method of
DHCPv6 options, the B4 element could directly get 128-bit global
address in IA_NA option, or auto-configures a 128-bit address with
the IPv6 prefix in the IA_PD option. A DS-Lite CPE could share the
same prefix pool with the hosts connecting the CPE. The test result
shows that some home gateways with FE ports cannot support the method
of DHCPv6 IA_NA option. That means some low-end CPEs don't support
DHCPv6 well.
4. test result of fragmentation
4.1. Test topology
|--------| |-----| |------------| |----------| |--------|
| Tester |--| CPE |---|Aggregation |---|BRAS/BNG |--| Tester |
| | | | | Device | | AFTR/CGN | | |
|--------| |-----| |------------| |----------| |--------|
Figure 1: Test topology
4.2. Result Description
Tester simulates end users which send IPv4 packets to remote, the CPE
device encapsulates these IPv4 packets into IPv4-in-IPv6 tunnel, then
AFTR device decapsulates them and send the IPv4 packets to their
destinations. In the test scenarios, if the original IPv4 frame is
larger than 1462bytes, it has to be fragmented when be transited in
the IPv4-in-IPv6 tunnel. We found that there are some problems about
a few provider's CPE devices, when the IPv4 larger than 1462bytes was
transited by AFTR, it had not been reassembled, but the fragmented
IPv4 packet were forwarded.
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4.3. Analysis
After analyse the mirroring packets, we realized that the reason of
the above phenomenon is a few CPE devices fragment the original IPv4
packet into two smaller IPv4 packets, then encapsulates these packets
into tunnel, and when those packets arrived at the AFTR, they were be
decapsulated and transfered as the normal process. The AFTR did not
know the decapsulated IPv4 packets need to be reassembled.
In the RFC6333 section 5.3, fragmentation and reassembly in the B4
element had be defined as follow: The inner IPv4 packet MUST NOT be
fragmented. Fragmentation MUST happen after the encapsulation of the
IPv6 packet. Reassembly MUST happen before the decapsulation of the
IPv4 packet.
A few CPE devices did not accomplish the fragmentation function
according the definition of RFC6333. The fragmented IPv4 packets
need to be reassembled by the final recipient, so an extra burden was
bringed to the recipient. Due to the fragmented IPv4 packet may be
smaller than the handling requirement of some device in the transfer
path, the packet could even be discarded.
5. Security Considerations
It needs to be further identified.
6. IANA Considerations
TBD
7. Acknowledgement
Thanks for the contributions from Tang Hao.
Author's Address
Ma Qiongfang
China Mobile
32, Xuanwumenxi Ave.
Xicheng District, Beijing 01719
China
Email: maqiongfang@chinamobile.com
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