draft-ietf-softwire-mesh-multicast-22.txt   draft-ietf-softwire-mesh-multicast-23.txt 
Softwire WG M. Xu Softwire WG M. Xu
Internet-Draft Y. Cui Internet-Draft Y. Cui
Intended status: Standards Track J. Wu Intended status: Standards Track J. Wu
Expires: December 20, 2018 Tsinghua University Expires: March 19, 2019 Tsinghua University
S. Yang S. Yang
Oudmon Tech Shenzhen University
C. Metz C. Metz
Cisco Systems Cisco Systems
June 18, 2018 September 15, 2018
IPv4 Multicast over an IPv6 Multicast in Softwire Mesh Network IPv4 Multicast over an IPv6 Multicast in Softwire Mesh Network
draft-ietf-softwire-mesh-multicast-22 draft-ietf-softwire-mesh-multicast-23
Abstract Abstract
During the transition to IPv6, there will be scenarios where a During the transition to IPv6, there will be scenarios where a
backbone network internally running one IP address family (referred backbone network internally running one IP address family (referred
to as the internal IP or I-IP family), connects client networks to as the internal IP or I-IP family), connects client networks
running another IP address family (referred to as the external IP or running another IP address family (referred to as the external IP or
E-IP family). In such cases, the I-IP backbone needs to offer both E-IP family). In such cases, the I-IP backbone needs to offer both
unicast and multicast transit services to the client E-IP networks. unicast and multicast transit services to the client E-IP networks.
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 20, 2018. This Internet-Draft will expire on March 19, 2019.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 5 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 5
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 4. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5. Mesh Multicast Mechanism . . . . . . . . . . . . . . . . . . 7 5. Mesh Multicast Mechanism . . . . . . . . . . . . . . . . . . 7
5.1. Mechanism Overview . . . . . . . . . . . . . . . . . . . 7 5.1. Mechanism Overview . . . . . . . . . . . . . . . . . . . 8
5.2. Group Address Mapping . . . . . . . . . . . . . . . . . . 7 5.2. Group Address Mapping . . . . . . . . . . . . . . . . . . 8
5.3. Source Address Mapping . . . . . . . . . . . . . . . . . 8 5.3. Source Address Mapping . . . . . . . . . . . . . . . . . 9
5.4. Routing Mechanism . . . . . . . . . . . . . . . . . . . . 9 5.4. Routing Mechanism . . . . . . . . . . . . . . . . . . . . 9
6. Control Plane Functions of AFBR . . . . . . . . . . . . . . . 10 6. Control Plane Functions of AFBR . . . . . . . . . . . . . . . 10
6.1. E-IP (*,G) and (S,G) State Maintenance . . . . . . . . . 10 6.1. E-IP (*,G) and (S,G) State Maintenance . . . . . . . . . 10
6.2. I-IP (S',G') State Maintenance . . . . . . . . . . . . . 10 6.2. I-IP (S',G') State Maintenance . . . . . . . . . . . . . 10
6.3. E-IP (S,G,rpt) State Maintenance . . . . . . . . . . . . 10 6.3. E-IP (S,G,rpt) State Maintenance . . . . . . . . . . . . 11
6.4. Inter-AFBR Signaling . . . . . . . . . . . . . . . . . . 10 6.4. Inter-AFBR Signaling . . . . . . . . . . . . . . . . . . 11
6.5. SPT Switchover . . . . . . . . . . . . . . . . . . . . . 13 6.5. SPT Switchover . . . . . . . . . . . . . . . . . . . . . 13
6.6. Other PIM Message Types . . . . . . . . . . . . . . . . . 13 6.6. Other PIM Message Types . . . . . . . . . . . . . . . . . 13
6.7. Other PIM States Maintenance . . . . . . . . . . . . . . 13 6.7. Other PIM States Maintenance . . . . . . . . . . . . . . 13
7. Data Plane Functions of the AFBR . . . . . . . . . . . . . . 13 7. Data Plane Functions of the AFBR . . . . . . . . . . . . . . 13
7.1. Process and Forward Multicast Data . . . . . . . . . . . 13 7.1. Process and Forward Multicast Data . . . . . . . . . . . 14
7.2. TTL . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 7.2. TTL . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
7.3. Fragmentation . . . . . . . . . . . . . . . . . . . . . . 14 7.3. Fragmentation . . . . . . . . . . . . . . . . . . . . . . 14
8. Packet Format and Translation . . . . . . . . . . . . . . . . 14 8. Packet Format and Translation . . . . . . . . . . . . . . . . 14
9. Softwire Mesh Multicast Encapsulation . . . . . . . . . . . . 15 9. Softwire Mesh Multicast Encapsulation . . . . . . . . . . . . 15
10. Security Considerations . . . . . . . . . . . . . . . . . . . 16 10. Security Considerations . . . . . . . . . . . . . . . . . . . 16
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 16 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 16
12.1. Normative References . . . . . . . . . . . . . . . . . . 16 12.1. Normative References . . . . . . . . . . . . . . . . . . 16
12.2. Informative References . . . . . . . . . . . . . . . . . 17 12.2. Informative References . . . . . . . . . . . . . . . . . 17
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 17 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 17
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backbone network. backbone network.
This could be accomplished by re-using the multicast VPN approach This could be accomplished by re-using the multicast VPN approach
outlined in [RFC6513]. MVPN-like schemes can support the softwire outlined in [RFC6513]. MVPN-like schemes can support the softwire
mesh scenario and achieve a "many-to-one" mapping between the E-IP mesh scenario and achieve a "many-to-one" mapping between the E-IP
client multicast trees and the transit core multicast trees. The client multicast trees and the transit core multicast trees. The
advantage of this approach is that the number of trees in the I-IP advantage of this approach is that the number of trees in the I-IP
backbone network scales less than linearly with the number of E-IP backbone network scales less than linearly with the number of E-IP
client trees. Corporate enterprise networks, and by extension client trees. Corporate enterprise networks, and by extension
multicast VPNs, have been known to run applications that create too multicast VPNs, have been known to run applications that create too
many (S,G) states [RFC7899]. Aggregation at the edge contains the many (S,G) states [RFC7761][RFC7899]. Aggregation at the edge
(S,G) states for customer's VPNs and these need to be maintained by contains the (S,G) states for customer's VPNs and these need to be
the network operator. The disadvantage of this approach is the maintained by the network operator. The disadvantage of this
possibility of inefficient bandwidth and resource utilization when approach is the possibility of inefficient bandwidth and resource
multicast packets are delivered to a receiving AFBR with no attached utilization when multicast packets are delivered to a receiving AFBR
E-IP receivers. with no attached E-IP receivers.
[RFC8114] provides a solution for delivering IPv4 multicast services [RFC8114] provides a solution for delivering IPv4 multicast services
over an IPv6 network. But it mainly focuses on the DS-lite [RFC6333] over an IPv6 network. But it mainly focuses on the DS-lite [RFC6333]
scenario. This document describes a detailed solution for the IPv4- scenario, where IPv4 addresses assigned by a broadband service
over-IPv6 softwire mesh scenario, where client networks run IPv4 and provider are shared among customers. This document describes a
the backbone network runs IPv6. detailed solution for the IPv4-over-IPv6 softwire mesh scenario,
where client networks run IPv4 and the backbone network runs IPv6.
Internet-style multicast is somewhat different to the [RFC8114] Internet-style multicast is somewhat different to the [RFC8114]
scenario in that the trees are source-rooted and relatively sparse. scenario in that the trees are source-rooted and relatively sparse.
The need for multicast aggregation at the edge (where many customer The need for multicast aggregation at the edge (where many customer
multicast trees are mapped into one or more backbone multicast trees) multicast trees are mapped into one or more backbone multicast trees)
does not exist and to date has not been identified. Thus the need does not exist and to date has not been identified. Thus the need
for alignment between the E-IP and I-IP multicast mechanisms emerges. for alignment between the E-IP and I-IP multicast mechanisms emerges.
[RFC5565] describes the "Softwire Mesh Framework". This document [RFC5565] describes the "Softwire Mesh Framework". This document
provides a more detailed description of how one-to-one mapping provides a more detailed description of how one-to-one mapping
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multicast data flow. multicast data flow.
o Downstream AFBR: An AFBR that is located on the lower reaches of a o Downstream AFBR: An AFBR that is located on the lower reaches of a
multicast data flow. multicast data flow.
o I-IP (Internal IP): This refers to IP address family that is o I-IP (Internal IP): This refers to IP address family that is
supported by the core network. In this document, the I-IP is IPv6. supported by the core network. In this document, the I-IP is IPv6.
o E-IP (External IP): This refers to the IP address family that is o E-IP (External IP): This refers to the IP address family that is
supported by the client network(s) attached to the I-IP transit core. supported by the client network(s) attached to the I-IP transit core.
In this document, the I-IP is IPv6. In this document, the E-IP is IPv4.
o I-IP core tree: A distribution tree rooted at one or more AFBR o I-IP core tree: A distribution tree rooted at one or more AFBR
source nodes and branched out to one or more AFBR leaf nodes. An source nodes and branched out to one or more AFBR leaf nodes. An
I-IP core tree is built using standard IP or MPLS multicast signaling I-IP core tree is built using standard IP or MPLS multicast signaling
protocols operating exclusively inside the I-IP core network. An protocols (in this document, we focus on IP multicast) operating
I-IP core tree is used to forward E-IP multicast packets belonging to exclusively inside the I-IP core network. An I-IP core tree is used
E-IP trees across the I-IP core. Another name for an I-IP core tree to forward E-IP multicast packets belonging to E-IP trees across the
is multicast or multipoint softwire. I-IP core. Another name for an I-IP core tree is multicast or
multipoint softwire.
o E-IP client tree: A distribution tree rooted at one or more hosts o E-IP client tree: A distribution tree rooted at one or more hosts
or routers located inside a client E-IP network and branched out to or routers located inside a client E-IP network and branched out to
one or more leaf nodes located in the same or different client E-IP one or more leaf nodes located in the same or different client E-IP
networks. networks.
o uPrefix46: The /96 unicast IPv6 prefix for constructing an o uPrefix46: The /96 unicast IPv6 prefix for constructing an
IPv4-embedded IPv6 unicast address [RFC6052]. IPv4-embedded IPv6 unicast address [RFC6052].
o mPrefix46: The /96 multicast IPv6 prefix for constructing an o mPrefix46: The /96 multicast IPv6 prefix for constructing an
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map an IPv4 group/source address to an IPv6 group/source address and map an IPv4 group/source address to an IPv6 group/source address and
vice-versa. vice-versa.
The IPv4-over-IPv6 scenario is an emerging requirement as network The IPv4-over-IPv6 scenario is an emerging requirement as network
operators build out native IPv6 backbone networks. These networks operators build out native IPv6 backbone networks. These networks
support native IPv6 services and applications but in many cases, support native IPv6 services and applications but in many cases,
support for legacy IPv4 unicast and multicast services will also need support for legacy IPv4 unicast and multicast services will also need
to be accommodated. to be accommodated.
5. Mesh Multicast Mechanism 5. Mesh Multicast Mechanism
5.1. Mechanism Overview 5.1. Mechanism Overview
Routers in the client E-IP networks have routes to all other client Routers in the client E-IP networks have routes to all other client
E-IP networks. Through PIMv4 messages, E-IP hosts and routers have E-IP networks. Through PIMv4 messages, E-IP hosts and routers have
discovered or learnt of (S,G) or (*,G) IPv4 addresses. Any I-IP discovered or learnt of (S,G) or (*,G)[RFC7761] IPv4 addresses. Any
multicast state instantiated in the core is referred to as (S',G') or I-IP multicast state instantiated in the core is referred to as
(*,G') and is separated from E-IP multicast state. (S',G') or (*,G') and is separated from E-IP multicast state.
Suppose a downstream AFBR receives an E-IP PIM Join/Prune message Suppose a downstream AFBR receives an E-IP PIM Join/Prune message
from the E-IP network for either an (S,G) tree or a (*,G) tree. The from the E-IP network for either an (S,G) tree or a (*,G) tree. The
AFBR translates the PIMv4 message into an PIMv6 message with the AFBR translates the PIMv4 message into an PIMv6 message with the
latter being directed towards the I-IP IPv6 address of the upstream latter being directed towards the I-IP IPv6 address of the upstream
AFBR. When the PIMv6 message arrives at the upstream AFBR, it is AFBR. When the PIMv6 message arrives at the upstream AFBR, it is
translated back into an PIMv4 message. The result of these actions translated back into an PIMv4 message. The result of these actions
is the construction of E-IP trees and a corresponding I-IP tree in is the construction of E-IP trees and a corresponding I-IP tree in
the I-IP network. An example of the packet format and translation is the I-IP network. An example of the packet format and translation is
provided in Section 8. provided in Section 8.
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with the unique "Well-Known" prefix or the ISP-defined prefix that with the unique "Well-Known" prefix or the ISP-defined prefix that
MUST NOT be used by another service provider, mesh multicast will not MUST NOT be used by another service provider, mesh multicast will not
influence non-transit PIM-SSM multicast at all. When an AFBR influence non-transit PIM-SSM multicast at all. When an AFBR
receives an I-IP (S',G') message, it MUST check S'. If S' starts receives an I-IP (S',G') message, it MUST check S'. If S' starts
with the unique prefix, then the message is actually a translated with the unique prefix, then the message is actually a translated
E-IP (S,G) or (*,G) message, and the AFBR translate this message back E-IP (S,G) or (*,G) message, and the AFBR translate this message back
to a PIMv4 message and process it. to a PIMv4 message and process it.
6.3. E-IP (S,G,rpt) State Maintenance 6.3. E-IP (S,G,rpt) State Maintenance
When an AFBR wishes to propagate a Join/Prune(S,G,rpt) message to an When an AFBR wishes to propagate a Join/Prune(S,G,rpt)[RFC7761]
I-IP upstream router, the AFBR MUST operate as specified in message to an I-IP upstream router, the AFBR MUST operate as
Section 6.5 and Section 6.6. specified in Section 6.5 and Section 6.6.
6.4. Inter-AFBR Signaling 6.4. Inter-AFBR Signaling
Assume that one downstream AFBR has joined an RPT of (*,G) and an SPT Assume that one downstream AFBR has joined an RPT of (*,G) and an SPT
of (S,G), and decided to perform an SPT switchover. According to of (S,G), and decided to perform an SPT switchover. According to
[RFC7761], it SHOULD propagate a Prune(S,G,rpt) message along with [RFC7761], it SHOULD propagate a Prune(S,G,rpt) message along with
the periodical Join(*,G) message upstream towards the RP. However, the periodical Join(*,G) message upstream towards the RP. However,
routers in the I-IP transit core do not process (S,G,rpt) messages routers in the I-IP transit core do not process (S,G,rpt) messages
since the I-IP transit core is treated as SSM-only. As a result, the since the I-IP transit core is treated as SSM-only. As a result, the
downstream AFBR is unable to prune S from this RPT, so it will downstream AFBR is unable to prune S from this RPT, so it will
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Refer to Section 7.4 of [RFC8114]. If there is at least one outgoing Refer to Section 7.4 of [RFC8114]. If there is at least one outgoing
interface whose IP address family is different from the incoming interface whose IP address family is different from the incoming
interface, the AFBR MUST encapsulate this packet with interface, the AFBR MUST encapsulate this packet with
mPrefix46-derived and uPrefix46-derived IPv6 address to form an IPv6 mPrefix46-derived and uPrefix46-derived IPv6 address to form an IPv6
multicast packet. multicast packet.
7.2. TTL 7.2. TTL
Processing of TTL information in protocol headers depends on the Processing of TTL information in protocol headers depends on the
tunneling technology, and it is out of scope of this document. tunneling technology [I-D.ietf-intarea-tunnels], and it is out of
scope of this document.
7.3. Fragmentation 7.3. Fragmentation
The encapsulation performed by an upstream AFBR will increase the The encapsulation performed by an upstream AFBR will increase the
size of packets. As a result, the outgoing I-IP link MTU may not size of packets. As a result, the outgoing I-IP link MTU may not
accommodate the larger packet size. As it is not always possible for accommodate the larger packet size. It is not always possible for
core operators to increase the MTU of every link. Fragmentation core operators to increase the MTU of every link, thus fragmentation
after encapsulation and reassembling of encapsulated packets MUST be after encapsulation and reassembling of encapsulated packets MUST be
supported by AFBRs [RFC5565]. supported by AFBRs [RFC5565]. The specific requirements for
fragmentation and tunnel configuration COULD be referred to in
[I-D.ietf-intarea-tunnels], which is under revision currently.
8. Packet Format and Translation 8. Packet Format and Translation
Because the PIM-SM Specification is independent of the underlying Because the PIM-SM Specification is independent of the underlying
unicast routing protocol, the packet format in Section 4.9 of unicast routing protocol, the packet format in Section 4.9 of
[RFC7761] remains the same, except that the group address and source [RFC7761] remains the same, except that the group address and source
address MUST be translated when traversing an AFBR. address MUST be translated when traversing an AFBR.
For example, Figure 5 shows the register-stop message format in the For example, Figure 5 shows the register-stop message format in the
IPv4 and IPv6 address families. IPv4 and IPv6 address families.
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IPv6 Source Address (Encoded-Group format): The encoded-unicast IPv6 Source Address (Encoded-Group format): The encoded-unicast
format of the IPv6 source address described in Section 4.3. format of the IPv6 source address described in Section 4.3.
9. Softwire Mesh Multicast Encapsulation 9. Softwire Mesh Multicast Encapsulation
Softwire mesh multicast encapsulation does not require the use of any Softwire mesh multicast encapsulation does not require the use of any
one particular encapsulation mechanism. Rather, it MUST accommodate one particular encapsulation mechanism. Rather, it MUST accommodate
a variety of different encapsulation mechanisms, and allow the use of a variety of different encapsulation mechanisms, and allow the use of
encapsulation mechanisms mentioned in [RFC4925]. Additionally, all encapsulation mechanisms mentioned in [RFC4925]. Additionally, all
of the AFBRs attached to the I-IP network MUST implement the same of the AFBRs attached to the I-IP network MUST implement the same
encapsulation mechanism. encapsulation mechanism, and follow the requirements mentioned in
[I-D.ietf-intarea-tunnels].
10. Security Considerations 10. Security Considerations
The security concerns raised in [RFC4925] and [RFC7761] are The security concerns raised in [RFC4925] and [RFC7761] are
applicable here. applicable here.
The additional workload associated with some schemes could be The additional workload associated with some schemes could be
exploited by an attacker to perform a DDoS attack. exploited by an attacker to perform a DDoS attack.
Compared with [RFC4925], the security concerns SHOULD be considered Compared with [RFC4925], the security concerns SHOULD be considered
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<https://www.rfc-editor.org/info/rfc7899>. <https://www.rfc-editor.org/info/rfc7899>.
[RFC8114] Boucadair, M., Qin, C., Jacquenet, C., Lee, Y., and Q. [RFC8114] Boucadair, M., Qin, C., Jacquenet, C., Lee, Y., and Q.
Wang, "Delivery of IPv4 Multicast Services to IPv4 Clients Wang, "Delivery of IPv4 Multicast Services to IPv4 Clients
over an IPv6 Multicast Network", RFC 8114, over an IPv6 Multicast Network", RFC 8114,
DOI 10.17487/RFC8114, March 2017, DOI 10.17487/RFC8114, March 2017,
<https://www.rfc-editor.org/info/rfc8114>. <https://www.rfc-editor.org/info/rfc8114>.
12.2. Informative References 12.2. Informative References
[I-D.ietf-intarea-tunnels]
Touch, J. and M. Townsley, "IP Tunnels in the Internet
Architecture", draft-ietf-intarea-tunnels-09 (work in
progress), July 2018.
[RFC4925] Li, X., Ed., Dawkins, S., Ed., Ward, D., Ed., and A. [RFC4925] Li, X., Ed., Dawkins, S., Ed., Ward, D., Ed., and A.
Durand, Ed., "Softwire Problem Statement", RFC 4925, Durand, Ed., "Softwire Problem Statement", RFC 4925,
DOI 10.17487/RFC4925, July 2007, DOI 10.17487/RFC4925, July 2007,
<https://www.rfc-editor.org/info/rfc4925>. <https://www.rfc-editor.org/info/rfc4925>.
Appendix A. Acknowledgements Appendix A. Acknowledgements
Wenlong Chen, Xuan Chen, Alain Durand, Yiu Lee, Jacni Qin and Stig Wenlong Chen, Xuan Chen, Alain Durand, Yiu Lee, Jacni Qin and Stig
Venaas provided useful input into this document. Venaas provided useful input into this document.
skipping to change at page 18, line 23 skipping to change at page 18, line 32
Jianping Wu Jianping Wu
Tsinghua University Tsinghua University
Department of Computer Science, Tsinghua University Department of Computer Science, Tsinghua University
Beijing 100084 Beijing 100084
P.R. China P.R. China
Phone: +86-10-6278-5983 Phone: +86-10-6278-5983
Email: jianping@cernet.edu.cn Email: jianping@cernet.edu.cn
Shu Yang Shu Yang
Oudmon Tech Shenzhen University
OUDMON Technology Co.,ltd South Campus, Shenzhen University
Shenzhen 518057 Shenzhen 518060
P.R. China P.R. China
Phone: +86-755-2601-3697 Phone: +86-755-2653-4078
Email: yangshu@oudmon.com Email: yang.shu@szu.edu.cn
Chris Metz Chris Metz
Cisco Systems Cisco Systems
170 West Tasman Drive 170 West Tasman Drive
San Jose, CA 95134 San Jose, CA 95134
USA USA
Phone: +1-408-525-3275 Phone: +1-408-525-3275
Email: chmetz@cisco.com Email: chmetz@cisco.com
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