Network Working Group X. Li
Internet-Draft C. Bao
Intended status: Informational H. Zhang
Expires: April 29, 2010 CERNET Center/Tsinghua University
October 26, 2009
Address-sharing stateless double IVI
draft-xli-behave-divi-01
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Abstract
This document presents the concepts and the implementations of
address-sharing stateless IVI (stateless 1:N IVI) and the address-
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sharing stateless double IVI (stateless 1:N dIVI).
The stateless 1:N IVI keeps the features of stateless, end-to-end
address transparency and bidirectional-initiated communications of
the original stateless 1:1 IVI, while it can utilize the IPv4
addresses more effectively. The stateless 1:N dIVI has above
features and it does not require the DNS64/DNS46 and ALG supports.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminologies . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Stateless 1:N IVI . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Address-sharing algorithm . . . . . . . . . . . . . . . . 5
3.2. Extended address format . . . . . . . . . . . . . . . . . 5
3.3. Protocol translation . . . . . . . . . . . . . . . . . . . 7
3.4. Routing . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.5. DNS . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.6. ALG . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.7. The translator behavior and the IPv6 end system
requirements . . . . . . . . . . . . . . . . . . . . . . . 7
4. Stateless 1:N double IVI . . . . . . . . . . . . . . . . . . . 8
4.1. Port number mapping algorithm . . . . . . . . . . . . . . 8
4.2. Double IVI . . . . . . . . . . . . . . . . . . . . . . . . 9
4.3. Protocol translation . . . . . . . . . . . . . . . . . . . 10
4.4. Home gateway implementation . . . . . . . . . . . . . . . 10
4.5. End system implementation . . . . . . . . . . . . . . . . 10
5. Security Considerations . . . . . . . . . . . . . . . . . . . 11
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 11
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
8.1. Normative References . . . . . . . . . . . . . . . . . . . 12
8.2. Informative References . . . . . . . . . . . . . . . . . . 12
Appendix A. Testing environment and workflow examples . . . . . . 13
A.1. The host on the IPv4 Internet initiats communication . . . 14
A.2. The address-sharing end system on an IPv6 network
initiats communication . . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15
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1. Introduction
The experiences for the IPv6 deployment in the past 10 years strongly
indicate that for a successful transition, the communication between
IPv4 and IPv6 address families should be supported.
Recently, the stateless and stateful IPv4/IPv6 translation methods
are developed and becoming the IETF standards
[I-D.ietf-behave-v6v4-framework], [I-D.ietf-behave-v6v4-xlate],
[I-D.ietf-behave-v6v4-xlate-stateful]. The original stateless IPv4/
IPv6 translation (stateless 1:1 IVI) is scalable, maintains the end-
to-end address transparency and support both IPv6 initiated and IPv4
initiated communications [I-D.ietf-behave-v6v4-framework],
[I-D.ietf-behave-v6v4-xlate], [I-D.xli-behave-ivi]. But it can not
use the IPv4 addresses effectively. The IPv4 address depletion
problem makes the deployment of the 1:1 IVI stateless IVI difficult.
The stateful IPv4/IPv6 translation can share the IPv4 addresses among
IPv6 hosts, but it only supports IPv6 initiated communication
[I-D.ietf-behave-v6v4-framework],
[I-D.ietf-behave-v6v4-xlate-stateful]. Rely on session initiated
states, the stateful translation cannot support the end-to-end
address transparency and costs more compared with the stateless
translation.
In this document, we present concepts and the implementations of the
address-sharing stateless IVI (stateless 1:N IVI) and the address-
sharing stateless double IVI (stateless 1:N dIVI). The basic
concepts of these techniques are the combination of "Address plus
port addressing" (A+P) and the IPv4/IPv6 stateless translation (IVI).
The stateless 1:N IVI is the extensions of the stateless 1:1 IVI. It
is the solution for the following scenarios
[I-D.ietf-behave-v6v4-framework].
o Scenario 1: An IPv6 network to the IPv4 Internet.
o Scenario 2: The IPv4 Internet to an IPv6 network.
o Scenario 5: An IPv6 network to an IPv4 network.
o Scenario 6: An IPv4 network to an IPv6 network.
The stateless 1:N IVI and the stateless 1:N dIVI keep all the
advantages of stateless 1:1 IVI and can use the IPv4 addresses more
effectively. In addition, stateless 1:N dIVI can work without DNS64/
DNS46 and ALG.
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2. Terminologies
This document uses the terminologies defined in
[I-D.ietf-behave-v6v4-framework].
The key words MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,
SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this
document, are to be interpreted as described in [RFC2119].
3. Stateless 1:N IVI
The stateless 1:N IVI is shown in the following figure.
--------
// \\ -----------
/ \ // \\
/ +----+ \ ------------
| |XLAT| |------ End System 1
| The IPv4 +----+ An IPv6 | ------------
| Internet +----+ Network | ------------
| |DNS | (address |------ End System N
\ +----+ subset) / ------------
\ / \\ //
\\ // ----------
--------
<====>
Figure 1: Stateless 1:N IVI
Where the XLATE is the IPv4/IPv6 translator perform 1:N translation
between IPv4 and IPv6; DNS is the DNS46 and DNS64 for providing the
authoritative and resolving services; the End System 1 and End System
N, etc are the IPv6-only hosts which can restrict their transport-
layer number port range when communicating with the IPv4 Internet.
In order to share the IPv4 address among IPv6 hosts, the port number
multiplexing technique is used [I-D.xli-behave-ivi]. The basic idea
is similar to the ones used in NAT and A+P. This is to say that a
single IPv4 address can be shared for multiple IPv6 hosts under the
condition that these individual hosts can only use a subset of the
65,536 port numbers when communicating with the IPv4 Internet. For
example, if the port multiplexing ratio is 128, each host with IPv4-
translatable address can use 512 concurrent port numbers when
communicating with IPv4 Internet. Note that there is no port number
restriction when these IPv6 hosts communicate with the IPv6 Internet.
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3.1. Address-sharing algorithm
The stateless 1:N IVI is shown in the following figure.
.-------|Host0| A1/(P%N)+0
/
------ ----- |
/ The \ ------ / An \ |
| IPv4 |--|1:N |---| IPv6 |------------|Host1| A1/(P%N)+1
\Internet/ |XLATE | \Network/ |
------ ------ ----- |
|\
| -------|Host2| A1/(P%N)+2
|
|
\
-------|HostK| A1/(P%N)+K
Figure 2: Stateless 1:N IVI
In the above figure, the Host0, Host1, Host2, ..., HostK are sharing
the same IPv4 address A1, but port number range for different hosts
are not overlapped. Therefore, when these IPv6 hosts communicate
with the IPv4 Internet via the translator, it looks like a single
host with IPv4 address A1 communicating with the IPv4 Internet.
We use the Modulus Operator to define the port number range. If the
multiplexing ratio is N, then:
o For host K, the allowed port number (P) are P=j*N + K (j=0, 1,
..., N-1).
o For the destination port number (P), the packets will be sent to
host K=(P%N) (% is the Modulus Operator).
For example: If N=256, then host K=5 is only allowed to use port
numbers 5, 261, 517, 773, ..., 65,285 as the source port, while the
packets with these port numbers as the destination port number will
be send to host K=5.
3.2. Extended address format
In order to perform the stateless translation (IVI) between the IPv4
and IPv6, both IPv4-mapped and IPv4-translatable address are required
[I-D.ietf-behave-v6v4-framework]. We use the reserved 16-bits to
encode the range of the port number [I-D.ietf-behave-address-format].
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The IPv4-mapped addresses are used to represent IPv4 addresses in
IPv6, as shown in the following figure.
| 0 |32 |40 |72 |88 127|
-----------------------------------------------------------------
| LIR |FF | IPv4 addr | all 0 |
-----------------------------------------------------------------
Figure 3: IPv4-mapped address format
Note that we use the address format and the prefix (e.g. 2001:db8:
ff00::/40) defined in [I-D.xli-behave-ivi]. There is no port number
coding required for the IPv4-mapped address.
The IPv4-translatable addresses are used to represent IPv6 addresses
in IPv4, we defined the extended IPv4-translatable as shown in the
following figure.
| 0 |32 |40 |72 |88 127|
-----------------------------------------------------------------
| LIR |FF | IPv4 addr |Port Coding| all 0 |
-----------------------------------------------------------------
Figure 4: Extended IPv4-translatable address format
Where, we use reserved 16-bits to encode the port number range based
on the Modulus Operator.
The most significant 4 bits define the multiplexing ratio and the
least significant 12 bits define the index of the host, as shown in
the following figure.
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(4 bits) | Index Range(12 bits) | Multx ratio | # of Ports
-----------------------------------------------------------------
0 000-000 1 65,536
1 000-001 2 32,768
2 000-003 4 16,384
3 000-007 8 8,192
4 000-00f 16 4,096
5 000-01f 32 2,048
6 000-03f 64 1,024
7 000-07f 128 512
8 000-0ff 256 256
9 000-1ff 512 128
A 000-3ff 1,024 64
B 000-7ff 2,048 32
C 000-fff 4,096 16
-----------------------------------------------------------------
Figure 5: Transport layer port number coding
3.3. Protocol translation
The protocol translation is defined in [I-D.ietf-behave-v6v4-xlate].
3.4. Routing
The routing follows the general IPv4/IPv6 routing principle, i.e.
"more specifics win", same as the original stateless 1:1 IVI.
[I-D.xli-behave-ivi].
3.5. DNS
The DNS handling is referring to DNS64 [I-D.ietf-behave-dns64] and
DNS46 [I-D.xli-behave-ivi].
3.6. ALG
The ALG related issue is discussed in
[I-D.ietf-behave-v6v4-framework].
3.7. The translator behavior and the IPv6 end system requirements
For the stateless 1:N IVI, the IPv6 end systems are required to
follow the port number range defined by the extended IPv4-
translatable address format when communicating with the IPv4
Internet. The behaviors of the stateless 1:N translator are:
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o If the packets are from the IPv4 Internet to an IPv6 network, the
IPv4 source addresses are translated to the IPv4-mapped addresses
and the source port numbers are unchanged; the IPv4 destination
addresses are translated to the extended IPv4-translatable
addresses based on the destination port number and the destination
port numbers are unchanged.
o If the packets are from an IPv6 network to the IPv4 Internet, the
IPv6 source addresses and the source port numbers are checked, if
the source port number matches the port number range defined by
the extended IPv4-translatable address format, the IPv6 source
addresses (which are the IPv4-translatable addresses) are
translated to the IPv4 addresses and the source port numbers are
unchanged; the destination IPv6 addresses (which are the IPv4-
mapped addresses) are translated to the IPv4 destination addresses
and the destination port numbers are unchanged. However, if the
source port numbers do not match the port number range defined by
the extended IPv4-translatable address format, the packets will be
dropped.
Therefore, the IPv6 end systems must follow the port number range
defined by the extended IPv4-translatable addresses. The behavior of
the IPv6 end system when communicating with the IPv4 Internet are:
o If the IPv6 end system is used as a server, different well-known
ports will be served by different IPv6 hosts.
o If the IPv6 end system is used as a client, the end system must
generate the source port numbers in the range defined by the
extended IPv4-translatable address format. This can be done by
modification of the end system, or via a port number mapping
device (home gateway).
4. Stateless 1:N double IVI
In general, it is not a good idea to modify the end system in order
to meet the IPv6 end system requirements of the stateless 1:N IVI.
Alternatively, we can use the home gateway to map the randomly
generated source port number to the port number range defined by
extended IPv4-translatable address format.
4.1. Port number mapping algorithm
The port number mapping algorithm is straightforward. The port
number mapping device maintains a database of allowed port numbers
defined by the extended IPv4-translatable address format. If the
packets from the end system contains the source port number which do
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not match the port number range defined by the extended IPv4-
translatable address format, the home gateway will translate the
source port number to an allowed one and keep the record in the
database for translating back the returning packets and all the
packets in the same session.
The port number database can be refreshed via the corresponding
transport layer flags for TCP or via timeout for UDP sessions.
4.2. Double IVI
If we can use the home gateway for the port number mapping, then we
can also use the home gateway (1:1 Xlate) to translate the IPv6
packets back to IPv4, as shown in the following figure.
------ -----
/ The \ ------ / An \ ----- -----
| IPv4 |--|1:N |---| IPv6 |------|1:1 |---|Host1|
\Internet/ |XLATE | \Network/ |XLATE| -----
------ ------ ----- -----
Figure 6: Double IVI (dIVI)
The advantage of double IVI is that the DNS64/DNS46 and ALG are not
required.
The first IPv4/IPv6 translator (1:N XLATE) is the core network
translator, the second IPv4/IPv6 translator (1:1 XLATE) is the home
gateway translator. The features of these translators are:
Core network translator: The core network translator (1:N XLATE) is
implemented in the border between the IPv6 core network and the
IPv4 Internet. It translates the packets between IPv4 and IPv6
with the 1:N stateless address mapping, same as the one used in
the stateless 1:N IVI.
Home gateway translator: The home gateway translator (1:1 XLATE) is
implemented between an IPv6 network and user's end system. It
translates the packets between IPv4 and IPv6 with 1:1 stateless
address mapping. In addition, the home gateway translator maps
random source port numbers to restricted port number based on the
extended IPv4-translatable address format and keeps the mapping
table in database for the port number mapping of the retuning
packets and all the packets in the same session. Note that the
1:1 XLATE is still stateless for the address mapping.
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4.3. Protocol translation
The protocol translation is referring to
[I-D.ietf-behave-v6v4-xlate]. Special MTU and fragmentation actions
must be taken, due to double translation (more details).
4.4. Home gateway implementation
The home gateway implementation is suitable for the ADSL environment,
as shown in the following figure.
---- -----
.-|hgw0|---|Host0| A1/(P%N)+0
/ ---- -----
------ ----- |
/ The \ ------ / An \ | ---- -----
| IPv4 |--|1:N |---| IPv6 |------|hgw1|---|Host1| A1/(P%N)+1
\Internet/ |XLATE | \Network/ | ---- -----
------ ------ ----- |
|\ ---- -----
| -|hgw2|---|Host2| A1/(P%N)+2
| ---- -----
|
\ ---- -----
-|hgwK|---|HostK| A1/(P%N)+K
---- -----
Figure 7: dIVI home gateway implementation
Where Xlate is the IPv4/IPv6 stateless 1:N IVI translator; hgw0,
hgw1, ..., hgwK are the home gateways performing the port number
mapping and the 1:1 IPv4/IPv6 translation function; Host0, Host1,
..., HostK are dual-stack hosts who share same IPv4 address (A1), and
have different non-IPv4-translatable IPv6 addresses.
4.5. End system implementation
For the wireless mobile Internet environment, it is not difficult to
modify the operating system of the mobile device, therefore it
possible to integrate the port number restriction and the IPv4/IPv6
translation function in the mobile device, which is an IPv6-only host
to the network and has a dual-stack socket API for the applications
running on this host.
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-----------
.-|Host0 (hgw)| A1/(P%N)+0
/ -----------
------ ----- |
/ The \ ------ / An \ | -----------
| IPv4 |--|1:N |---| IPv6 |------|Host1 (hgw)| A1/(P%N)+1
\Internet/ |XLATE | \Network/ | -----------
------ ------ ----- |
|\ -----------
| -|Host2 (hgw)| A1/(P%N)+2
| -----------
|
\ -----------
-|HostK (hgw)| A1/(P%N)+K
-----------
Figure 8: dIVI end system implementation
5. Security Considerations
There are no security considerations in this document.
6. IANA Considerations
This memo adds no new IANA considerations.
Note to RFC Editor: This section will have served its purpose if it
correctly tells IANA that no new assignments or registries are
required, or if those assignments or registries are created during
the RFC publication process. From the author's perspective, it may
therefore be removed upon publication as an RFC at the RFC Editor's
discretion.
7. Acknowledgments
The authors would like to acknowledge the following contributors in
the different phases of the address-sharing IVI and dIVI development:
Maoke Chen, Yu Zhai, Wentao Shang, Weifeng Jiang and Yuncehng Zhu.
The authors would like to acknowledge the following contributors who
provided helpful inputs: Dan Wing, Fred Baker, Dave Thaler, Randy
Bush and Kevin Yin.
8. References
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8.1. Normative References
[I-D.ietf-behave-address-format]
Huitema, C., Bao, C., Bagnulo, M., Boucadair, M., and X.
Li, "IPv6 Addressing of IPv4/IPv6 Translators",
draft-ietf-behave-address-format-00 (work in progress),
August 2009.
[I-D.ietf-behave-dns64]
Bagnulo, M., Sullivan, A., Matthews, P., and I. Beijnum,
"DNS64: DNS extensions for Network Address Translation
from IPv6 Clients to IPv4 Servers",
draft-ietf-behave-dns64-01 (work in progress),
October 2009.
[I-D.ietf-behave-v6v4-framework]
Baker, F., Li, X., Bao, C., and K. Yin, "Framework for
IPv4/IPv6 Translation",
draft-ietf-behave-v6v4-framework-03 (work in progress),
October 2009.
[I-D.ietf-behave-v6v4-xlate]
Li, X., Bao, C., and F. Baker, "IP/ICMP Translation
Algorithm", draft-ietf-behave-v6v4-xlate-03 (work in
progress), October 2009.
[I-D.ietf-behave-v6v4-xlate-stateful]
Bagnulo, M., Matthews, P., and I. Beijnum, "NAT64: Network
Address and Protocol Translation from IPv6 Clients to IPv4
Servers", draft-ietf-behave-v6v4-xlate-stateful-02 (work
in progress), October 2009.
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
8.2. Informative References
[CERNET] "CERNET Homepage:
http://www.edu.cn/english_1369/index.shtml".
[CNGI-CERNET2]
"CNGI-CERNET2 Homepage:
http://www.cernet2.edu.cn/index_en.htm".
[I-D.xli-behave-ivi]
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Li, X., Bao, C., Chen, M., Zhang, H., and J. Wu, "The
CERNET IVI Translation Design and Deployment for the IPv4/
IPv6 Coexistence and Transition", draft-xli-behave-ivi-02
(work in progress), June 2009.
[dIVI] "Test homepage for the dIVI:
http://202.38.97.114:8056/test.html".
Appendix A. Testing environment and workflow examples
We have a testing environment for the address-sharing stateless
double IVI with 1:N stateless core translator and 1:1 stateless home
gateway translators (or modified end systems) deployed in the
[CERNET] (IPv4) and [CNGI-CERNET2] (IPv6).
The current implementation of the core translator, home gateway
translator and the modified end systems are implemented in Linux OS,
with a slightly different Port Coding scheme, as shwon in the
following figure:
| 0 |32 |40 |72 |96 |112 127|
-----------------------------------------------------------------
| LIR |FF | IPv4 addr | zero | R |H index |
-----------------------------------------------------------------
R: Port multiplexing ratio
H index: Host Index
Figure 9: Extended IPv4-translatable address format (testing)
Where bit 96 to 111 is used to represnet the port multiplexing ratio,
for example, 0100 represents port multiplexing ratio 256; bit 112 to
127 is used to represent the host index starting from 0 to R-1.
The testing environment is shown in the following figure.
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[2001:DA9:FF3A:C8C0:A00:0:100:0] - 58.200.192.10:4096
---- -----
.-|hgw0|---|Host0|
/ ---- -----
------ ----- |
/ The \ ------ / An \ |
| IPv4 |--|1:N |---| IPv6 |--
\Internet/ |XLATE | \Network/ | ---- -----
------ ------ ----- \--|hgw1|---|Host1|
/ \ ---- -----
| \ [2001:DA9:FF3A:C8C0:A00:0:100:1] - 58.200.192.10:4097
| \
| \ --
| \ ----|S2|
-- --
|C1| 202.38.105.1:80 - [2001:252:ffca:2669:100::]
--
125.34.46.137 - [2001:DA9:ff7d:222e:8900::]
Figure 10: dIVI testing environment
In this testing environment, the LIR=2001DA9:ff00::/40 and the port
multiplexing ratio R=256. We only show two hosts here, Host0
(index=0) and Host1 (index=1). The core translator 1:N XLATE is
configured with LIR=2001DA9:ff00::/40 and R=256. The home gateway
(hgw1) is configured with LIR=2001DA9:ff00::/40, R=256 and index=0,
while the home gateway (hgw2) is configured with LIR=2001DA9:
ff00::/40, R=256 and index=1.
The testing homepage is at [dIVI]
A.1. The host on the IPv4 Internet initiats communication
Host C1 (125.34.46.137) in the IPv4 Internet initiates communication
with address-sharing end system Host0 (http://58.200.192.10:4096) in
an IPv6 network behind home gateway.
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On the IPv4 Internet
Src#p= 125.34.46.137#1856 (#random port)
Dst#p= 58.200.192.10:4096 (#server port)
On an IPv6 network
Src#p= [2001:DA9:ff7d:222e:8900::]#1856 (#random port)
Dst#p= [2001:DA9:FF3A:C8C0:A00:0:100:0]#4096 (#server port)
On the address-sharing end system Host0
Src#p= 125.34.46.137#1856 (#random port)
Dst#p= 58.200.192.10:4096 (#server port)
Figure 11: Example 1
The returning packets reverse the Src and Dst.
A.2. The address-sharing end system on an IPv6 network initiats
communication
An address-sharing end system Host0 (58.200.192.10) in an IPv6
network behind home gateway initiates communication with Host S2
(http://202.38.105.1:80) in the IPv4 Internet
On the end system Host0
Src#p= 58.200.192.10:1881 (random port)
Dst#p= 202.38.105.1:80#80 (server port)
On an IPv6 network
Src#p= [2001:DA9:FF3A:C8C0:A00:0:100:0]#8192 (home gateway mapped port)
Src#p= [2001:252:ffca:2669:100::]#80 (server port)
On the IPv4 Internet
Src#p= 58.200.192.10:8192 (home gateway mapped port)
Dst#p= 202.38.105.1:80#80 (server port)
Figure 12: Example 2
The returning packets reverse the Src and Dst, the home gateway maps
the "home gateway mapped port (8192)" back to the original "random
port (1881)".
Li, et al. Expires April 29, 2010 [Page 15]
Internet-Draft Address-sharing dIVI October 2009
Authors' Addresses
Xing Li
CERNET Center/Tsinghua University
Room 225, Main Building, Tsinghua University
Beijing 100084
CN
Phone: +86 10-62785983
Email: xing@cernet.edu.cn
Congxiao Bao
CERNET Center/Tsinghua University
Room 225, Main Building, Tsinghua University
Beijing 100084
CN
Phone: +86 10-62785983
Email: congxiao@cernet.edu.cn
Hong Zhang
CERNET Center/Tsinghua University
Room 225, Main Building, Tsinghua University
Beijing 100084
CN
Phone: +86 10-62785983
Email: neilzh@gmail.com
Li, et al. Expires April 29, 2010 [Page 16]