Network Performance Measurement for IPsec
draft-ietf-ippm-ipsec-03
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 7717.
|
|
|---|---|---|---|
| Authors | Kostas Pentikousis , Yang Cui , Emma Zhang | ||
| Last updated | 2014-06-05 | ||
| Replaces | draft-bi-ippm-ipsec | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Reviews | |||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | In WG Last Call | |
| Document shepherd | Brian Trammell | ||
| IESG | IESG state | Became RFC 7717 (Proposed Standard) | |
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | (None) |
draft-ietf-ippm-ipsec-03
IPPM WG K. Pentikousis, Ed.
Internet-Draft EICT
Intended status: Standards Track Y. Cui
Expires: December 7, 2014 E. Zhang
Huawei Technologies
June 5, 2014
Network Performance Measurement for IPsec
draft-ietf-ippm-ipsec-03
Abstract
The O/TWAMP security mechanism requires that both the client and
server endpoints possess a shared secret. Since the currently-
standardized O/TWAMP security mechanism only supports a pre-shared
key mode, large scale deployment of O/TWAMP is hindered
significantly. At the same time, recent trends point to wider IKEv2
deployment which, in turn, calls for mechanisms and methods that
enable tunnel end-users, as well as operators, to measure one-way and
two-way network performance in a standardized manner. This document
discusses the use of keys derived from an IKEv2 SA as the shared key
in O/TWAMP. If the shared key can be derived from the IKEv2 SA, O/
TWAMP can support certificate-based key exchange, which would allow
for more operational flexibility and efficiency. The key derivation
presented in this document can also facilitate automatic key
management.
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
Task Force (IETF). Note that other groups may also distribute
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Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 7, 2014.
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Copyright Notice
Copyright (c) 2014 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
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
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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 . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. O/TWAMP Security . . . . . . . . . . . . . . . . . . . . . . 3
3.1. O/TWAMP-Control Security . . . . . . . . . . . . . . . . 4
3.2. O/TWAMP-Test Security . . . . . . . . . . . . . . . . . . 5
3.3. O/TWAMP Security Root . . . . . . . . . . . . . . . . . . 6
4. O/TWAMP for IPsec Networks . . . . . . . . . . . . . . . . . 6
4.1. Shared Key Derivation . . . . . . . . . . . . . . . . . . 6
4.2. Server Greeting Message Update . . . . . . . . . . . . . 7
4.3. Set-Up-Response Update . . . . . . . . . . . . . . . . . 9
4.4. O/TWAMP over an IPsec tunnel . . . . . . . . . . . . . . 10
5. Security Considerations . . . . . . . . . . . . . . . . . . . 10
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
8.1. Normative References . . . . . . . . . . . . . . . . . . 11
8.2. Informative References . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
The One-way Active Measurement Protocol (OWAMP) [RFC4656] and the
Two-Way Active Measurement Protocol (TWAMP) [RFC5357] can be used to
measure network performance parameters, such as latency, bandwidth,
and packet loss by sending probe packets and monitoring their
experience in the network. In order to guarantee the accuracy of
network measurement results, security aspects must be considered.
Otherwise, attacks may occur and the authenticity of the measurement
results may be violated. For example, if no protection is provided,
an adversary in the middle may modify packet timestamps, thus
altering the measurement results.
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The currently-standardized O/TWAMP security mechanism [RFC4656]
[RFC5357] requires that endpoints (i.e. both the client and the
server) possess a shared secret. In today's network deployments,
however, the use of pre-shared keys is far from optimal. For
example, in wireless infrastructure networks, certain network
elements, which can be seen as the two endpoints from an O/TWAMP
perspective, support certificate-based security. For instance,
consider the case in which one wants to measure IP performance
between an eNB and SeGW. Both eNB and SeGW are 3GPP LTE nodes and
support certificate mode and IKEv2. Since the currently standardized
O/TWAMP security mechanism only supports pre-shared key mode, large
scale deployment of O/TWAMP is hindered significantly. Furthermore,
deployment and management of "shared secrets" for massive equipment
installation consumes a tremendous amount of effort and is prone to
human error.
With IKEv2 widely used, employing keys derived from IKEv2 SA as
shared key can be considered as a viable alternative. In mobile
telecommunication networks, the deployment rate of IPsec exceeds 95%
with respect to the LTE serving network. In older-technology
cellular networks, such as UMTS and GSM, IPsec use penetration is
lower, but still quite significant. If the shared key can be derived
from the IKEv2 SA, O/TWAMP can support cert-based key exchange and
make it more flexible in practice and more efficient. The use of
IKEv2 also makes it easier to extend automatic key management. In
general, O/TWAMP measurement packets can be transmitted inside the
IPsec tunnel, as it occurs with typical user traffic, or transmitted
outside the IPsec tunnel. This may depend on the operator's policy
and is orthogonal to the mechanism described in this document.
The remainder of this document is organized as follows. Section 3
summarizes O/TWAMP protocol operation with respect to security.
Section 4 presents a method of binding O/TWAMP and IKEv2 for network
measurements between the client and the server which both support
IKEv2. Finally, Section 5 discusses the security considerations
arising from the proposed mechanisms.
2. Terminology
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. O/TWAMP Security
Security for O/TWAMP-Control and O/TWAMP-Test are briefly reviewed in
the following subsections.
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3.1. O/TWAMP-Control Security
O/TWAMP uses a simple cryptographic protocol which relies on
o AES in Cipher Block Chaining (AES-CBC) for confidentiality
o HMAC-SHA1 truncated to 128 bits for message authentication
Three modes of operation are supported in the OWAMP-Control protocol:
unauthenticated, authenticated, and encrypted. In addition to these
modes, the TWAMP-Control protocol also supports a mixed mode, i.e.
the TWAMP-Control protocol operates in encrypted mode while TWAMP-
Test protocol operates in unauthenticated mode. The authenticated,
encrypted and mixed modes require that endpoints possess a shared
secret, typically a passphrase. The secret key is derived from the
passphrase using a password-based key derivation function PBKDF2
(PKCS#5) [RFC2898].
In the unauthenticated mode, the security parameters are left unused.
In the authenticated, encrypted and mixed modes, the security
parameters are negotiated during the control connection
establishment.
Figure 1 illustrates the initiation stage of the O/TWAMP-Control
protocol between a client and the server. In short, the client opens
a TCP connection to the server in order to be able to send O/TWAMP-
Control commands. The server responds with a Server Greeting, which
contains the Modes, Challenge, Salt, Count, and MBZ fields (see
Section 3.1 of [RFC4656]). If the client-preferred mode is
available, the client responds with a Set-Up- Response message,
wherein the selected Mode, as well as the KeyID, Token and Client IV
are included. The Token is the concatenation of a 16-octet
Challenge, a 16-octet AES Session-key used for encryption, and a
32-octet HMAC-SHA1 Session-key used for authentication. The Token is
encrypted using AES-CBC.
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+--------+ +--------+
| Client | | Server |
+--------+ +--------+
| |
|<---- TCP Connection ----->|
| |
|<---- Greeting message ----|
| |
|----- Set-Up-Response ---->|
| |
|<---- Server-Start --------|
| |
Figure 1: Initiation of O/TWAMP-Control
Encryption uses a key derived from the shared secret associated with
KeyID. In the authenticated, encrypted and mixed modes, all further
communication is encrypted using the AES Session-key and
authenticated with the HMAC Session-key. After receiving Set-Up-
Response the server responds with a Server-Start message containing
Server-IV. The client encrypts everything it transmits through the
just-established O/TWAMP-Control connection using stream encryption
with Client- IV as the IV. Correspondingly, the server encrypts its
side of the connection using Server-IV as the IV. The IVs themselves
are transmitted in cleartext. Encryption starts with the block
immediately following that containing the IV.
The AES Session-key and HMAC Session-key are generated randomly by
the client. The HMAC Session-key is communicated along with the AES
Session-key during O/TWAMP-Control connection setup. The HMAC
Session-key is derived independently of the AES Session-key.
3.2. O/TWAMP-Test Security
The O/TWAMP-Test protocol runs over UDP, using the client and server
IP and port numbers that were negotiated during the Request-Session
exchange. O/TWAMP- Test has the same mode with O/TWAMP-Control and
all O/TWAMP-Test sessions inherit the corresponding O/TWAMP-Control
session mode except when operating in mixed mode.
The O/TWAMP-Test packet format is the same in authenticated and
encrypted modes. The encryption and authentication operations are,
however, different. Similarly with the respective O/TWAMP-Control
session, each O/TWAMP-Test session has two keys: an AES Session-key
and an HMAC Session-key. However, there is a difference in how the
keys are obtained:
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O/TWAMP-Control: the keys are generated by the client and
communicated to the server during the control connection
establishment with the Set-Up-Response message (as part of
the Token).
O/TWAMP-Test: the keys are derived from the O/TWAMP-Control keys and
the session identifier (SID), which serve as inputs of the
key derivation function (KDF). The O/TWAMP-Test AES Session-
key is generated using the O/TWAMP- Control AES Session-key,
with the 16-octet session identifier (SID), for encrypting
and decrypting the packets of the particular O/TWAMP-Test
session. The O/TWAMP-Test HMAC Session-key is generated
using the O/TWAMP-Control HMAC Session-key, with the 16-octet
session identifier (SID), for authenticating the packets of
the particular O/TWAMP-Test session.
3.3. O/TWAMP Security Root
As discussed above, the AES Session-key and HMAC Session-key used by
the O/TWAMP-Test protocol are derived from the AES Session-key and
HMAC Session-key which are used in O/TWAMP-Control protocol. The AES
Session-key and HMAC Session-key used in the O/TWAMP-Control protocol
are generated randomly by the client, and encrypted with the shared
secret associated with KeyID. Therefore, the security root is the
shared secret key. Thus, for large deployments, key provision and
management may become overly complicated. Comparatively, a
certificate-based approach using IKEv2 can automatically manage the
security root and solve this problem, as we explain in Section 4.
4. O/TWAMP for IPsec Networks
This section presents a method of binding O/TWAMP and IKEv2 for
network measurements between a client and a server which both support
IPsec. In short, the shared key used for securing O/TWAMP traffic is
derived using IKEv2 [RFC5996].
4.1. Shared Key Derivation
In the authenticated, encrypted and mixed modes, the shared secret
key can be derived from the IKEv2 Security Association (SA). Note
that we explicitly opt to derive the shared secret key from the IKEv2
SA, rather than the child SA, since the use case whereby an IKEv2 SA
can be created without generating any child SA is possible [RFC6023].
If the shared secret key is derived from the IKEv2 SA, SKEYSEED must
be generated first. SKEYSEED and its derivatives MUST be computed as
per [RFC5996], where prf is a pseudorandom function:
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SKEYSEED = prf( Ni | Nr, g^ir )
Ni and Nr are, respectively, the initiator and responder nonces,
which are negotiated during the initial exchange (see Section 1.2 of
[RFC5996]). g^ir is the shared secret from the ephemeral Diffie-
Hellman exchange and is represented as a string of octets.
The shared secret key MUST be generated as follows:
Shared secret key = PRF( SKEYSEED, "IPPM" )
Wherein the string "IPPM" comprises four ASCII characters. It is
recommended that the shared secret key is derived in the IPsec layer.
This way, the IPsec keying material is not exposed to the O/TWAMP
client. Note, however, that the interaction between the O/TWAMP and
IPsec layers is host-internal and implementation-specific.
Therefore, this is clearly outside the scope of this document, which
focuses on the interaction between the O/TWAMP client and server.
That said, one possible way could be the following: at the client
side, the IPSec layer can perform a lookup in the Security
Association Database (SAD) using the IP address of the server and
thus match the corresponding IKEv2 SA. At the server side, the IPSec
layer can look up the corresponding IKEv2 SA by using the SPIs sent
by the client, and therefore extract the shared secret key. In case
that both client and server do support IKEv2 but there is no current
IKEv2 SA, two alternative ways could be considered. First, the O/
TWAMP client initiates the establishment of the IKEv2 SA, logs this
operation, and selects the mode which supports IKEv2. Alternatively,
the O/TWAMP client does not initiate the establishment of the IKEv2
SA, logs an error for operational management purposes, and proceeds
with the modes defined in [RFC4656][RFC5618]. Again, although both
alternatives are feasible, they are in fact implementation-specific.
If rekeying for the IKEv2 SA or deletion of the IKEv2 SA occurs, the
corresponding shared secret key generated from the SA can continue to
be used until the lifetime of the shared secret key expires.
4.2. Server Greeting Message Update
To achieve a binding association between the key generated from IKEv2
and the O/TWAMP shared secret key, Server Greeting Message should be
updated as in Figure 2.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Unused (12 octets) |
| |
|+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Modes |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Challenge (16 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Salt (16 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Count (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| MBZ (12 octets) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Server Greeting format
The Modes field in Figure 2 will need to allow for support of key
derivation as discussed in Section 4.1. As such, the Modes value
extension MUST be supported by implementations compatible with this
document, indicating support for deriving shared key from IKEv2 SA.
Three new Modes including authenticated mode over IKEv2(IANA.TBA.O/
TWAMP.IKEAuth),encrypted mode over IKEv2(IANA.TBA.O/TWAMP.IKEEnc) and
mixed mode over IKEv2(IANA.TBA.TWAMP.IKEMix) are proposed.
Authenticated mode over IKEv2 means that the client and server
operate in authenticated mode with the shared secret key derived from
IKEv2 SA. Encrypted mode over IKEv2 means that the client and server
operate in encrypted mode with the shared secret key derived from
IKEv2 SA. Mixed mode over IKEv2 means that the client and server
operate in encrypted mode for the O/TWAMP-Control protocol while
operating in unauthenticated mode for the O/TWAMP-Test protocol with
shared secret key derived from IKEv2 SA.
The choice of this set of Modes values poses the least backwards
compatibility problems to existing O/TWAMP clients. Robust client
implementations of [RFC4656] would disregard the fact that the first
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29 Modes bits in the Server Greeting is set. If the server supports
other Modes, as one would assume, the client would then indicate any
of the Modes defined in [RFC4656] and effectively indicate that it
does not support key derivation from IKEv2. At this point, the
Server would need to use the Modes defined in [RFC4656] only.
4.3. Set-Up-Response Update
The Set-Up-Response Message should be updated as in Figure 3.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Mode |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Key ID (80 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Token (16 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Client-IV (12 octets) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Set-Up-Response Message
The Security Parameter Index (SPI)(see [RFC4301] [RFC5996]) can
uniquely identify the Security Association (SA). If the client
supports the derivation of shared secret key from IKEv2 SA, it will
choose the corresponding mode value and carry SPIi and SPIr in the
Key ID field. SPIi and SPIr are included in the Key ID field of Set-
Up- Response Message to indicate the IKEv2 SA from which the O/TWAMP
shared secret key derived from. The length of SPI is 4 octets.
Therefore, the first 4 octets of Key ID field carry SPIi and the
second 4 octets carry SPIr. The remaining bits of the Key ID field
are set to zero.
A O/TWAMP server which supports the specification of this document,
can obtain the SPIi and SPIr from the first 8 octets and ignore the
rest octets of the Key ID field. Then, the client and the server can
derive the shared secret key based on the mode value and SPI. If the
O/TWAMP server cannot find the IKEv2 SA corresponding to the SPIi and
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SPIr received, it MUST log the event for operational management
purposes. In addition, the O/TWAMP server SHOULD set the Accept
field of the Server-Start message to the value 6 to indicate that
server is not willing to conduct further transactions in this O/
TWAMP-Control session since it can not find the corresponding IKEv2
SA.
4.4. O/TWAMP over an IPsec tunnel
IPsec AH [RFC4302] and ESP [RFC4303] provide confidentiality and
data integrity to IP datagrams. Thus and IPsec tunnel can be used to
provide the protection needed for O/TWAMP Control and Test packets,
even if the peers choose the unauthenticated mode of operation. If
the two endpoints are already connected through an IPSec tunnel it is
RECOMMENDED that the O/TWAMP measurement packets are forwarded over
the IPSec tunnel if the peers choose the unauthenticated mode in
order to ensure authenticity and security.
5. Security Considerations
As the shared secret key is derived from the IKEv2 SA, the key
derivation algorithm strength and limitations are as per [RFC5996].
The strength of a key derived from a Diffie-Hellman exchange using
any of the groups defined here depends on the inherent strength of
the group, the size of the exponent used, and the entropy provided by
the random number generator employed. The strength of all keys and
implementation vulnerabilities, particularly Denial of Service (DoS)
attacks are as defined in [RFC5996].
As a more general note, the IPPM community may want to revisit the
arguments listed in [RFC4656], Sec. 6.6. Other widely-used Internet
security mechanisms, such as TLS and DTLS, may also be considered for
future use over and above of what is already specified in [RFC4656]
[RFC5357].
6. IANA Considerations
IANA will need to allocate additional values for the Modes options
presented in this document.
7. Acknowledgments
Emily Bi contributed to an earlier version of this document.
We thank Eric Chen, Yakov Stein, Brian Trammell, and John Mattsson
for their comments on this draft, and Al Morton for the discussion
and pointers to related earlier work in IPPM WG.
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8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4302] Kent, S., "IP Authentication Header", RFC 4302, December
2005.
[RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)", RFC
4303, December 2005.
[RFC4656] Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M.
Zekauskas, "A One-way Active Measurement Protocol
(OWAMP)", RFC 4656, September 2006.
[RFC5357] Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J.
Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)",
RFC 5357, October 2008.
[RFC5618] Morton, A. and K. Hedayat, "Mixed Security Mode for the
Two-Way Active Measurement Protocol (TWAMP)", RFC 5618,
August 2009.
[RFC5996] Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen,
"Internet Key Exchange Protocol Version 2 (IKEv2)", RFC
5996, September 2010.
8.2. Informative References
[RFC2898] Kaliski, B., "PKCS #5: Password-Based Cryptography
Specification Version 2.0", RFC 2898, September 2000.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, December 2005.
[RFC6023] Nir, Y., Tschofenig, H., Deng, H., and R. Singh, "A
Childless Initiation of the Internet Key Exchange Version
2 (IKEv2) Security Association (SA)", RFC 6023, October
2010.
Authors' Addresses
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Kostas Pentikousis (editor)
EICT GmbH
EUREF-Campus Haus 13
Torgauer Strasse 12-15
10829 Berlin
Germany
Email: k.pentikousis@eict.de
Yang Cui
Huawei Technologies
Otemachi First Square 1-5-1 Otemachi
Chiyoda-ku, Tokyo 100-0004
Japan
Email: cuiyang@huawei.com
Emma Zhang
Huawei Technologies
Huawei Building, Q20, No.156, Rd. BeiQing
Haidian District , Beijing 100095
P. R. China
Email: emma.zhanglijia@huawei.com
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