Network Working Group Y. Cui Internet-Draft J. Wu Intended status: Standards Track P. Wu Expires: May 2, 2012 Tsinghua University Q. Sun C. Xie China Telecom C. Zhou Huawei Technologies Y. Lee Comcast T. Tsou Huawei Technologies (USA) October 30, 2011 Lightweight 4over6 in access network draft-cui-softwire-b4-translated-ds-lite-04 Abstract The dual-stack lite mechanism provide an IPv4 access method over IPv6 ISP network for end users. Dual-Stack Lite enables an IPv6 provider to share IPv4 addresses among customers by combining IPv4-in-IPv6 tunnel and Carrier Grade NAT. However, in dual-stack lite, CGN has to maintain active NAT sessions, which could become the performance bottom-neck due to high dynamics of NAT entries, memory cost and log issue. This document propose the lightweight 4over6 mechanism which moves the translation function from tunnel concentrator (AFTR) to initiators (B4s), and hence reduces the mapping scale on the concentrator to per-customer level. For NAT44 translation usage, the mechanism allocates port restricted IPv4 addresses to initiators in a flexible way independent of IPv6 network in the middle. 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 working documents as Internet-Drafts. The list of current Internet- 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." Cui, et al. Expires May 2, 2012 [Page 1] Internet-Draft B4-translated ds-lite October 2011 This Internet-Draft will expire on May 2, 2012. Copyright Notice Copyright (c) 2011 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 publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Cui, et al. Expires May 2, 2012 [Page 2] Internet-Draft B4-translated ds-lite October 2011 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 6 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 7 4. Lightweight 4over6 Overview . . . . . . . . . . . . . . . . . 8 5. Port Restricted IPv4 Address Allocation . . . . . . . . . . . 9 6. Lightweight 4over6 Initiator Behavior . . . . . . . . . . . . 10 7. Lightweight 4over6 Concentrator Behavior . . . . . . . . . . . 11 8. Fragmentation and Reassembly . . . . . . . . . . . . . . . . . 12 9. DNS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 10. ICMP processing . . . . . . . . . . . . . . . . . . . . . . . 14 11. Mechanism Analysis . . . . . . . . . . . . . . . . . . . . . . 15 12. Security Consideration . . . . . . . . . . . . . . . . . . . . 16 13. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 17 14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Appendix 1. Appendix:Experimental Result . . . . . . . . . . . . 20 1.1. Experimental environment . . . . . . . . . . . . . . . . . 20 1.2. Experimental results . . . . . . . . . . . . . . . . . . . 21 1.3. Coexistent test with DS-Lite . . . . . . . . . . . . . . . 22 1.4. Conclusions . . . . . . . . . . . . . . . . . . . . . . . 22 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 23 Cui, et al. Expires May 2, 2012 [Page 3] Internet-Draft B4-translated ds-lite October 2011 1. Introduction Dual-stack lite technology[RFC6333] provides IPv4 access over IPv6 access network. Dual-Stack lite (DS-lite) also mitigates IPv4 address exhaustion by sharing public IPv4 addresses amongst users. The B4 element establishes an IPv4-in-IPv6 softwire to the AFTR and encapsulates the IPv4 packets into the softwire. When AFTR receives the IPv6 packets, it will decapsulate them and perform NAT-44 on the packets. This procedure allows AFTR to dynamically assign sessions to users when needed; hence, increases port-sharing radio and utilization. There is a trade-off, though. The AFTR is required to maintain active NAT sessions. In the centralized deployment model where one AFTR serves thousands of users, the large numbers of NAT sessions may become performance bottom-neck. First, maintaining active NAT sessions requires AFTR constantly creating and purging NAT sessions. Second, a large NAT table demands more processing power for searching and more memory space. In addition, dynamic session- based NAT will create large number of log entries, which will also be a challenging problem. To address these issues, we propose an extension to DS-lite. We propose to create rule mapping in the AFTR and distributes the dynamic NAT table into B4 elements. The B4 element will be provisioned with an IPv6 address, an IPv4 address and a port-set. The IPv6 address will be used to create the Softwire. The IPv4 address and port-set will be used for NAT-44 in the home gateway(CPE). Most CPE have been performing NAT-44 today. The CPE will perform PAT on user's packets with the IPv4 address and port-set provisioned by the ISP. The packets are forwarded between the CPE and the AFTR by IPv6 encapsulation over the tunnel. The AFTR will maintain a mapping entry with the IPv6 address, IPv4 address and port set per user. For inbound IPv4 packet on AFTR, it would use the IPv4 destination address and port as the index and use the forwarding rule in the mapping table to encapsulate the packets to the destination CPE. The AFTR would not create NAT entry per sessions. This will significantly reduce the AFTR's NAT table size. Compared to DS-lite, this extension reduces the AFTR NAT table size. Each entry represents a B4 element. This also relaxes the requirement to create a log entry per dynamic session. AFTR only needs to keep a log entry per B4 element. This is also an extended case which covers addressing sharing for [I-D.cui-softwire-host-4over6]. However, the extension will decrease IPv4 address utilization. Moreover, since port randomization algorithm must use ports within this port-set, it may cause the port randomization algorithm more predictable. Compared to stateless solutions with port set/set allocation such as Cui, et al. Expires May 2, 2012 [Page 4] Internet-Draft B4-translated ds-lite October 2011 4rd, this mechanism is suitable for operators who prefers to keep IPv6 and IPv4 addressing separated. For example, an operator may want to provide IPv4 with an on-demand way in its IPv6 network, the dynamic allocation of IPv4 address and port makes more efficient usage of IPv4 resource. Another example is that an operator may only have many small and discontinuous IPv4 blocks available to provide IPv4 over IPv6, rather than a few big IPv4 blocks. This mechanism keeps dynamic feature of IPv4-IPv6 address binding as in DS-Lite, so it won't require to administrate and manage many 4rd domains in the network and mapping rules in the CPEs. Cui, et al. Expires May 2, 2012 [Page 5] Internet-Draft B4-translated ds-lite October 2011 2. Requirements Language 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]. Cui, et al. Expires May 2, 2012 [Page 6] Internet-Draft B4-translated ds-lite October 2011 3. Terminology Starting from here, the document will use the terminologies of lightweight 4over6 instead of DS-lite for distinction. Lightweight 4over6: lightweight 4over6 is an IPv4-over-IPv6 hub and spoke mechanism proposed in this document, which supports address sharing to deal with IPv4 address exhaustion, and places the IPv4 translation on the initiator side. Lightweight 4over6 initiator (or "initiator" for short): the tunnel initiator in lightweight 4over6 mechanism. The lightweight 4over6 initiator could be a host directly connected to IPv6, or an dual- stack CPE in front of an IPv4 local network. It is responsible for IPv4 public-private translation besides tunnel encapsulation and decapsulation. Lightweight 4over6 concentrator (or "concentrator" for short): the tunnel concentrator in lightweight 4over6 mechanism. The lightweight 4over6 concentrator connects the ISP IPv6 network and IPv4 Internet. It provides tunnel encapsulation and decapsulation but no IPv4 public-private translation. Port Restricted IPv4 Address: A public IPv4 address with restricted port set. In lightweight 4over6, multiple initiators will share the same IPv4 address, while the port sets are disjoint from each other. Cui, et al. Expires May 2, 2012 [Page 7] Internet-Draft B4-translated ds-lite October 2011 4. Lightweight 4over6 Overview Figure 1 provides an overview of the lightweight 4over6 mechanism. A lightweight 4over6 initiator which can be either an IPv6 hosts or CPE, and the lightweight 4over6 concentrator are separated by the IPv6 network in the middle, so they use IPv4-in-IPv6 tunnel to build IPv4 connectivity. An initiator uses IPv4 address with restricted port set for this IPv4 connectivity, which is acquired through either DHCPv4 with the concentrator, or through PCP with the PCP server. The concentrator keeps the mapping between initiator's IPv6 address and the allocated IPv4 address + port set. +-------------------------+ | IPv6 ISP Network | | | +---------+ | |LW 4over6|Host | |Initiator|===============+---------+ +-----------+ +---------+ |LW 4over6| | IPv4 | +--------+ | IPv4-in-IPv6 |Concen- |---| Internet | | | +---------+ |trator | | | |IPv4 LAN|--|LW 4over6|===============+---------+ +-----------+ | | |Initiator|CPE |DHCPv4 +--------+ +---------+ +----------+ |Server(Relay) | |PCP Server| | | +----------+ | +-------------------------+ Figure 1 Lightweight 4over6 overview Cui, et al. Expires May 2, 2012 [Page 8] Internet-Draft B4-translated ds-lite October 2011 5. Port Restricted IPv4 Address Allocation As is described above, a lightweight 4over6 initiator needs the public address and port for stateful translation. This is achieved by basic PCP mechanism [I-D.ietf-pcp-base]. It's obvious that individual, realtime address + port allocation is not efficient due to round-trip time delay and high signaling volume caused. A practical manner would be allocating and address and a group ports at one time beforehand, i.e., allocating port restricted IPv4 address. To our knowledge there're two methods which are probably suitable for restricted address allocation from concentrator to initiator. One is extending DHCP to support address allocation with port set embedded. [I-D.bajko-pripaddrassign] discusses this DHCP usage. In this special context, we need to build the DHCPv4 procedure over IPv6 [I-D.cui-dhc-dhcpv4-over-ipv6]. The other is extending PCP to support port set control. See [I-D.tsou-pcp-natcoord] for details. Adopting either method, an initiator can get port restricted IPv4 address allocated dynamically from the concentrator. Meanwhile, the dynamic mapping rule between IPv4 address, port set and IPv6 address are recorded on the concentrator in the initiation phase. Unlike stateless 4over6 solutions such as [I-D.murakami-softwire-4rd], the port restricted address allocation in lightweight 4over6 has no requirement on careful planning of the IPv6 domain range, IPv4/IPv6 mapping relationship, prefix length and multiplex ratio, etc. Cui, et al. Expires May 2, 2012 [Page 9] Internet-Draft B4-translated ds-lite October 2011 6. Lightweight 4over6 Initiator Behavior A lightweight 4over6 initiator should discover the concentrator's IPv6 address during startup. This IPv6 address can be learned through a variety of methods, ranging from an out-of-band mechanism, manual configuration, or a DHCPv6 option. For DHCPv6 case, the DHCPv6 option should carry the concentrator's IPv6 address information. The AFTR-Name option [RFC6334] can be applied here; however, using the same option may cause confusion when both lightweight 4over6 and dual-stack lite are deployed in one network. In that case, it is better we define a new DHCPv6 option for lightweight 4over6 concentrator discovery. A lightweight 4over6 initiator should support either extended DHCP client, or extended PCP client, as is described above. When requiring IPv4 access, the initiator runs either client(according to the support of the concentrator) to get a port restricted IPv4 address, and renew/extend it when the lease/lifetime is about to expire. The data plane functions of the initiator includes translation and encapsulation/decapsulation. For CPE initiator case, the initiator runs a standard local NAT44 with the address pool consisting of the allocated port restricted address. When receiving an IPv4 packet with private source address from its end hosts, it performs NAT44 function and translates the source address into public. Then it encapsulates the packet with the concentrator's IPv6 address as destination IPv6 address, and forwards it to the concentrator. When receiving an IPv4-in-IPv6 packet from the concentrator, the initiator decapsulates the IPv6 packet to get the IPv4 packet with public destination IPv4 address. Then it performs NAT44 function and translates the destination address into private. For host initiator case, end host gets public address directly. It is also suggested that the host run a local NAT to map randomly generated ports into the restricted, valid port set. Private-public address translation would not be needed in this NAT. Another solution is to have the IP stack to only assign ports within the restricted, valid range to applications. Either way the host guarantees that every source port number in the packets sent out by itself falls into the allocated port set. Cui, et al. Expires May 2, 2012 [Page 10] Internet-Draft B4-translated ds-lite October 2011 7. Lightweight 4over6 Concentrator Behavior The lightweight 4over6 concentrator should either allocate port restricted addresses directly(by performing an extended DHCPv4 server, or an extended PCP server), or leave the allocation to dedicated DHCP/PCP server(and perform a relay in DHCP case). When accomplishing one such allocation, the concentrator simultaneously install a mapping entry into the mapping table. This entry consists of the public IPv4 address, the port set and initiator's IPv6 address. Its lifetime is set according to the allocation. It'll be used for encapsulation of inbound packets. This mapping entry will be deleted when the lifetime expires. The lifetime of the mapping entry will be refreshed when the initiator renews/extends the allocation. The data plane functions of the concentrator is purely encapsulation and decapsulation. When receiving an IPv4-in-IPv6 packet from an initiator, the concentrator decapsulates it and forwards it to IPv4 Internet. When receiving an IPv4 packet from the Internet, it uses the destination address and port from this packet to lookup the destination initiator's IPv6 address in the mapping table. Then the concentrator encapsulates this packet using the IPv6 address found in the table as IPv6 destination address, and forwards it to the correct initiator based on native IPv6 routing. Hence there is no port-set routing in IPv6 network anymore. Cui, et al. Expires May 2, 2012 [Page 11] Internet-Draft B4-translated ds-lite October 2011 8. Fragmentation and Reassembly There is no change to section 5.3 and section 6.3 of [RFC6333] in fragmentation and reassembly behavior, on either side of the tunnel. Cui, et al. Expires May 2, 2012 [Page 12] Internet-Draft B4-translated ds-lite October 2011 9. DNS The DNS consideration is also the same to section 5.5 and section 6.4 in [RFC6333]. Cui, et al. Expires May 2, 2012 [Page 13] Internet-Draft B4-translated ds-lite October 2011 10. ICMP processing ICMP availability would become a challenge in port restricted address environment. To support ICMP "session" initiated from a lightweight 4over6 initiator, the mechanism divides ICMP id field in the same way with dividing port space, i.e. each initiator will get the ICMP id range which is identical to the allocated port set. An initiator only uses the allocated address and restricted id range when send out an ICMP request. Hence the concentrator can encapsulate the corresponding ICMP reply correctly according to the ICMP id field. The inbound ICMP request would be left unsupported on the concentrator, which is the similar behavior of NAT/CGN. See details about ICMP processing in section 4.2 of [I-D.sun-v6ops-laft6] Cui, et al. Expires May 2, 2012 [Page 14] Internet-Draft B4-translated ds-lite October 2011 11. Mechanism Analysis Compared with original dual-stack lite, lightweight 4over6 removes the translation burden from the concentrator and distribute the job to initiators on user-side. Also it decreases the state scale on concentrator from per-session level down to per-user level. This would significantly reduce the hardware cost of the concentrator, and relieve the situation that the concentrator becomes the performance bottleneck. Leveraging lightweight 4over6, one concentrator can serve a lot more customers. Besides, since this mechanism reduces the number of simultaneous address mappings of each customer on concentrator to one, it makes concentrator logging much more feasible. Moreover, locating the translation on user side eases the ALG and NAT referral problem since it'll be no different from the situation of local NAT in today's IPv4 network. Solutions like uPnP already exist for quite a long time. Most current CPEs have already implemented NAT44 functionalities, lightweight 4over6 would not bring a lot more complexity to existing CPEs. Lightweight 4over6 allocates port restricted address independent of the IPv6 network in the middle. No specific IPv6 address format is required. IPv4 and IPv6 addressing and routing remain separated. The ISP can provide IPv4 in a flexible, on-demand way, as well as manage the native IPv6 network without the influence of IPv4-over- IPv6 requirements. And it would also be easy to achieve future adjustment of IPv4 address pool. The costs of lightweight 4over6 for achieving all these benefits are lower IPv4 address utilization ratio and extra signaling behavior. The address multiplexing manner of port restricted address is relatively more static than dual-stack lite. And dual-stack lite doesn't require address and port allocation between concentrator and initiators. When compared to stateless solutions, lightweight 4over6 still keeps per-user states rather than becoming purely stateless. Cui, et al. Expires May 2, 2012 [Page 15] Internet-Draft B4-translated ds-lite October 2011 12. Security Consideration Since port randomization algorithm must use ports within the port set, it may cause the port randomization algorithm more predictable. Therefore, non-continuous port set algorithms (e.g. as defined in [I-D.mdt-softwire-mapping-address-and-port]) can be introduced to further improve the security. Cui, et al. Expires May 2, 2012 [Page 16] Internet-Draft B4-translated ds-lite October 2011 13. Acknowledgement The authors would like to thank Alain Durand, Ole Troan, Ralph Droms and Xiaohong Deng for their comments and feedback. Cui, et al. Expires May 2, 2012 [Page 17] Internet-Draft B4-translated ds-lite October 2011 14. References [I-D.bajko-pripaddrassign] Bajko, G., Savolainen, T., Boucadair, M., and P. Levis, "Port Restricted IP Address Assignment", draft-bajko-pripaddrassign-03 (work in progress), September 2010. [I-D.bsd-softwire-stateless-port-index-analysis] Boucadair, M., Skoberne, N., and W. Dec, "Analysis of Port Indexing Algorithms", draft-bsd-softwire-stateless-port-index-analysis-00 (work in progress), September 2011. [I-D.cui-dhc-dhcpv4-over-ipv6] Cui, Y., Wu, P., Wu, J., and T. Lemon, "DHCPv4 over IPv6 transport", draft-cui-dhc-dhcpv4-over-ipv6-00 (work in progress), October 2011. [I-D.cui-softwire-host-4over6] Cui, Y., Wu, J., Wu, P., Metz, C., Vautrin, O., and Y. Lee, "Public IPv4 over Access IPv6 Network", draft-cui-softwire-host-4over6-06 (work in progress), July 2011. [I-D.ietf-pcp-base] Wing, D., Cheshire, S., Boucadair, M., Penno, R., and P. Selkirk, "Port Control Protocol (PCP)", draft-ietf-pcp-base-16 (work in progress), October 2011. [I-D.mdt-softwire-mapping-address-and-port] Troan, O., "Mapping of Address and Port (MAP)", draft-mdt-softwire-mapping-address-and-port-00 (work in progress), October 2011. [I-D.murakami-softwire-4rd] Murakami, T., Troan, O., and S. Matsushima, "IPv4 Residual Deployment on IPv6 infrastructure - protocol specification", draft-murakami-softwire-4rd-01 (work in progress), September 2011. [I-D.sun-v6ops-laft6] Sun, Q. and C. Xie, "LAFT6: Lightweight address family transition for IPv6", draft-sun-v6ops-laft6-01 (work in progress), March 2011. [I-D.tsou-pcp-natcoord] Zhou, C., ZOU), T., Deng, X., Boucadair, M., and Q. Sun, Cui, et al. Expires May 2, 2012 [Page 18] Internet-Draft B4-translated ds-lite October 2011 "Using PCP To Coordinate Between the CGN and Home Gateway Via Port Allocation", draft-tsou-pcp-natcoord-03 (work in progress), July 2011. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC6333] Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual- Stack Lite Broadband Deployments Following IPv4 Exhaustion", RFC 6333, August 2011. [RFC6334] Hankins, D. and T. Mrugalski, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6) Option for Dual-Stack Lite", RFC 6334, August 2011. Cui, et al. Expires May 2, 2012 [Page 19] Internet-Draft B4-translated ds-lite October 2011 1. Appendix:Experimental Result We have deployed lightweight 4over6 in our operational network of HuNan province, China. It is designed for broadband access network, and different versions of initiator have been implemented including a linksys box, a software client for windows XP, vista and Windows 7. It can be integrated with existing dial-up mechanisms such as PPPoE, etc. The major objectives listed below aimed to verify the functionality and performance of lightweight 4over6: o Verify how to deploy lightweight 4over6 in a practical network. o Verify the impact of applications with lightweight 4over6. o Verify the performance of lightweight 4over6. o Verify the coexistence between lightweight 4over6 and DS-Lite. 1.1. Experimental environment The network topology for this experiment is depicted in Figure 2. +--------+ +-----+ +---------+ | Syslog | |Host1+--+Initiator|--+ | Server | -------- +-----+ +---------+ | +---+----+ /// \\\ | /------\ | // \\ | // \\ +---+----+ | | +-----+ +---------+ +-+--+ | IPv6 | | | | IPv4 Internet | |Host2+--|Initiator|--+BRAS+--| Network |---| Concen-+-+ | +-----+ +---------+ +-+--+ \\ // | trator | \\ // | \---+--/ +--------+ \\\ /// | | --------- +-----+ +---------+ | | |Host3+--+Initiator+---+ | +-----+ +---------+ | -------- | // \\ | / \ +---------------------+IPv6 Internet + | | \ / \\ // ------- Figure 2 Lightweight 4over6 experiment topology In this deployment model, concentrator is co-located with a extended PCP server to assign restricted IPv4 address and port set for Cui, et al. Expires May 2, 2012 [Page 20] Internet-Draft B4-translated ds-lite October 2011 initiator. It also triggers subscriber-based logging event to a centrilized syslog server. IPv6 address pools for subscribers have been distributed to BRASs for configuration, while the public available IPv4 address pools are configured by the centralized concentrator with a default address sharing ratio. It is rather flexible for IPv6 addressing and routing, and there is little impact on existing IPv6 architecture. In our experiment, initiator will firstly get its IPv6 address and delegated prefix through PPPoE, and then initiate a PCP-extended request to get public IPv4 address and its valid port set. The concentrator will thus create a subscriber-based state accordingly, and notify syslog server with {IPv6 address, IPv4 address, port set, timestamp}. 1.2. Experimental results In our trial, we mainly focused on application test and performance test. The applications have widely include web, email, Instant Message, ftp, telnet, SSH, video, Video Camera, P2P, online game, voip and so on. For performance test, we have measured the parameters of concurrent session numbers and throughput performance. The experimental results are listed as follows: +--------------------+----------------------+-----------------------+ | Application Type | Test Result |Port Number Occupation | +--------------------+----------------------+-----------------------+ | Web | ok | normal websites: 10~20| | | IE, Firefox, Chrome | Ajex Flash webs: 30~40| +--------------------+----------------------+-----------------------+ | Video | ok, web based or | 30~40 | | | client based | | +--------------------+----------------------+-----------------------+ | Instant Message | ok | | | | QQ, MSN, gtalk, skype| 8~20 | +--------------------+----------------------+-----------------------+ | P2P | ok | lower speed: 20~600 | | |utorrent,emule,xunlei | (per seed) | | | | higher speed: 150~300 | +--------------------+----------------------+-----------------------+ | FTP | need ALG for active | 2 | | | mode, flashxp | | +--------------------+----------------------+-----------------------+ | SSH, TELNET | ok |1 for SSH, 3 for telnet| +--------------------+----------------------+-----------------------+ | online game | ok for QQ, flash game| 20~40 | +--------------------+----------------------+-----------------------+ Cui, et al. Expires May 2, 2012 [Page 21] Internet-Draft B4-translated ds-lite October 2011 Figure 3 Lightweight 4over6 experimental result The performance test for concentrator is taken on a normal PC. Due to limitations of the PC hardware, the overall throughput is limited to around 800 Mbps. However, it can still support more than one hundred million concurrent sessions. 1.3. Coexistent test with DS-Lite In our coexistent test for lightweight 4over6 and DS-Lite, both lightweight concentrator and DS-Lite AFTR have run in the same PC. Two different virtual interfaces are configured with 4over6 concentrator IPv6 addresses and DS-lite AFTR IPv6 address, which will be notified to the initiators and B4s seperately. Besides, seperated public IPv4 address pools have been configured for these two approaches. Each CPE would only run one mechanism, either lightweight 4over6 or DS-Lite. For outbound traffic arriving at the concentrator, it will be routed either to 4over6 concentrator or DS-Lite AFTR interface according to different destination addresses. While for inbound IPv4 traffic, it will also be destinated to different interfaces based on seperated destination IPv4 address pools. 1.4. Conclusions From the experiment, we can have the following conclusions: o Lightweight 4over6 has good scalability. As it is a lightweight solution which only maintains per-subscriber state information, it can easily support a large amount of concurrent subscribers. o Lightweight 4over6 can be deployed rapidly. There is no modification to existing addressing and routing system in our operational network. And it is simple to achieve traffic logging. o Lightweight 4over6 can support a majority of current IPv4 applications. o Lightweight 4over6 can be coexistent with DS-Lite easily. Cui, et al. Expires May 2, 2012 [Page 22] Internet-Draft B4-translated ds-lite October 2011 Authors' Addresses Yong Cui Tsinghua University Department of Computer Science, Tsinghua University Beijing 100084 P.R.China Phone: +86-10-62603059 Email: yong@csnet1.cs.tsinghua.edu.cn Jianping Wu Tsinghua University Department of Computer Science, Tsinghua University Beijing 100084 P.R.China Phone: +86-10-62785983 Email: jianping@cernet.edu.cn Peng Wu Tsinghua University Department of Computer Science, Tsinghua University Beijing 100084 P.R.China Phone: +86-10-62785822 Email: weapon@csnet1.cs.tsinghua.edu.cn Qiong Sun China Telecom Room 708, No.118, Xizhimennei Street Beijing 100035 P.R.China Phone: +86-10-58552936> Email: sunqiong@ctbri.com.cn Chongfeng Xie China Telecom Room 708, No.118, Xizhimennei Street Beijing 100035 P.R.China Cui, et al. Expires May 2, 2012 [Page 23] Internet-Draft B4-translated ds-lite October 2011 Phone: +86-10-58552116> Email: xiechf@ctbri.com.cn Cathy Zhou Huawei Technologies Section B, Huawei Industrial Base, Bantian Longgang Shenzhen 518129 P.R.China Phone: +86-10-58552116 Email: cathyzhou@huawei.com Yiu L. Lee Comcast One Comcast Center Philadelphia, PA 19103 USA Email: yiu_lee@cable.comcast.com Tina Tsou Huawei Technologies (USA) 2330 Central Expressway Santa Clara, CA 95050 USA Phone: +1 408 330 4424 Email: tena@huawei.com Cui, et al. Expires May 2, 2012 [Page 24]