Network Working Group P. Wu Internet-Draft Q. Sun Intended status: Informational Tsinghua University Expires: January 10, 2013 July 9, 2012 Deployment Considerations for Public 4over6 draft-wu-softwire-public4over6-deployment-00 Abstract Public 4over6 is a stateful transition mechanism which assigns public IPv4 address to CPE/host and uses IPv4-in-IPv6 tunnel. It doesn't involve CGN as in DS-lite and reduces the mapping scale on the Concentrator to per-subscriber level. This document describers deployment models for Public 4over6, and the deployment considerations of the Public 4over6 architecture. 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/. 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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 Wu & Sun Expires January 10, 2013 [Page 1] Internet-Draft public-4over6-deployment July 2012 described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Requirements Language . . . . . . . . . . . . . . . . . . . . . 3 3. Concentrator Deployment Considerations . . . . . . . . . . . . 3 3.1. Interface Consideration . . . . . . . . . . . . . . . . . . 3 3.2. MTU Consideration . . . . . . . . . . . . . . . . . . . . . 3 3.3. Fragmentation . . . . . . . . . . . . . . . . . . . . . . . 3 3.4. Logging at Concentrator . . . . . . . . . . . . . . . . . . 3 3.5. Reliability Considerations of Concentrator . . . . . . . . 4 3.6. Placement of Concentrator . . . . . . . . . . . . . . . . . 4 3.7. Considerations for Geographically Aware Services . . . . . 4 4. Initiator Deployment Considerations . . . . . . . . . . . . . . 4 4.1. Concentrator Discovery Considerations . . . . . . . . . . . 4 4.2. DNS Deployment Considerations . . . . . . . . . . . . . . . 4 4.3. Optional NAT44 Functionality on Initiator . . . . . . . . . 5 5. Deployment Experience . . . . . . . . . . . . . . . . . . . . . 5 6. IDC Transition Usage . . . . . . . . . . . . . . . . . . . . . 5 7. Security Consideration . . . . . . . . . . . . . . . . . . . . 5 8. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . . 5 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5 9.1. Normative References . . . . . . . . . . . . . . . . . . . 5 9.2. Informative References . . . . . . . . . . . . . . . . . . 6 Wu & Sun Expires January 10, 2013 [Page 2] Internet-Draft public-4over6-deployment July 2012 1. Introduction Public 4over6 [I-D.ietf-softwire-public-4over6] is a transition mechanism that enables operators to assign public IPv4 addresses to end users over IPv6. Public 4over6 uses IPv4-in-IPv6 softwire to provide IPv4 connectivity between users in IPv6 access networks and IPv4 Internet.This document discuss various Public 4over6 deployment considerations for operators. Terminology of this document follows the definitions and abbreviations of [I-D.ietf-softwire-public-4over6] . 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]. 3. Concentrator Deployment Considerations Public 4over6 and DS-Lite [RFC6333] shares some deployment considerations, while Concentrator and Initiator of Public 4over6 play a similar role to AFTR and B4 of DS-Lite. 3.1. Interface Consideration Tunnel Concentrator is deployed at the IPv4-IPv6 network border where the tunnel interface is IPv6 and the external interface is IPv4. It shares the same deployment considerations with [I-D.ietf-softwire-dslite-deployment]. 3.2. MTU Consideration Same with [I-D.ietf-softwire-dslite-deployment]. 3.3. Fragmentation Same with [I-D.ietf-softwire-dslite-deployment]. 3.4. Logging at Concentrator Timestamped logging is essential for back tracking specific users when a problem is identified with one of the assigned public IPv4 address. Operators only log one entry per subscriber. The log should include the subscriber's IPv6 address and the public IPv4 address. 3.5. Reliability Considerations of Concentrator Wu & Sun Expires January 10, 2013 [Page 3] Internet-Draft public-4over6-deployment July 2012 For redundancy, the backup Concentrator should apply either of the following types. One is that a dedicated DHCP server synchronizes mapping entries with all Concentrators considering that the DHCP server is responsible for IPv4 address allocation. Each Concentrator maintain per-subscriber mapping table accordingly. Once the working Concentrator is down, subscribers will switch to the backup Concentrator using technologies like anycast etc. The other method is that Initiators PING the Concentrator periodically to check the status of the Concentrator. If the PING test fails for a specific number of times, Initiators should release the current public IPv4 address and require for another public IPv4 address from the backup Concentrator. 3.6. Placement of Concentrator Concentrator maintains a per-subscriber mapping table, smaller than the per-session binding table on DS-Lite AFTR. As a result, Concentrator can be deployed closer to core of the network to cover a larger region. And the amount of subscribers and the capability of devices should be taken into account. 3.7. Considerations for Geographically Aware Services Even though Public 4over6 supports the assignment of public IPv4 address, identification by IP address is no easier than that in DS- Lite. Thus applications that assume such geographic information may not work as intended. In Public 4over6, each address represents a single machine, a single household, or a single small office, but it's hard to identify geographic information over IPv6 access networks. The considerations are similar to section 2.11 of [I-D.ietf-softwire-dslite-deployment] 4. Initiator Deployment Considerations 4.1. Concentrator Discovery Considerations A public 4over6 Initiator must discover the Concentrator's IPv6 address before starting IPv4 connections. The IPv6 address can be learned through out-of-band mechanism, manual configuration or DHCPv6 option. If an operator uses DHCPv6 for provision the Initiator, DHCPv6 option defined in [RFC6334] must be implemented in the Initiator. 4.2. DNS Deployment Considerations The Initiator can implement a proxy resolver that will proxy DNS query from IPv4 transport to the DNS server in the IPv6 network. Wu & Sun Expires January 10, 2013 [Page 4] Internet-Draft public-4over6-deployment July 2012 Alternatively, the Initiator can tunnel IPv4 DNS query to an external DNS server over IPv6 network. 4.3. Optional NAT44 Functionality on Initiator The Initiator can be a host or a CPE device. If it's a host, the host can get Public IPv4 address and does not need NAT44 function. If it's a CPE, NAT44 function must be enabled for local private IPv4 Network. 5. Deployment Experience Tsinghua University has deployed a Tunnel Concentrator in CERNET lab. The DHCP server collocates on the same device with Tunnel Concentrator. Public4over6 client software has also been released, with Win7 version and Linux version. The system has provided IPv4 service over IPv6 access networks of universities from China. The IPv4-over-IPv6 services Public 4over6 provided is transparent to the upper layer applications. Even though in IPv6 networks, users can also get access to IPv4 websites with no difference to native IPv4. Because of assignment of public IPv4 address to Initiators, users can experience P2P services. Public 4over6 is able to provide qualified IPv4 services with no side impact on native IPv6. 6. IDC Transition Usage IDC is responsible for steady service for users. And as a server, a public IPv4 address does good to guarantee the IDC's QoS. Public 4over6 is able to provide service for IDC locating in an IPv6-only network. As an Initiator, an IDC will get a public IPv4 address and achieve "dual-stack" environment, which is essential for better service. 7. Security Consideration This specification raises no new security issues. [I-D.ietf-softwire-public-4over6] discusses public 4over6 related security issues. 8. Acknowledgement TBD 9. References 9.1. Normative References Wu & Sun Expires January 10, 2013 [Page 5] Internet-Draft public-4over6-deployment July 2012 [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. 9.2. Informative References [I-D.ietf-softwire-dslite-deployment] Lee, Y., Maglione, R., Williams, C., Jacquenet, C., and M. Boucadair, "Deployment Considerations for Dual-Stack Lite", draft-ietf-softwire- dslite-deployment-03 (work in progress), March 2012. [I-D.ietf-softwire-public-4over6] Cui, Y., Wu, J., Wu, P., Metz, C., Vautrin, O., and Y. Lee, "Public IPv4 over IPv6 Access Network", draft-ietf-softwire- public-4over6-01 (work in progress), March 2012. Authors' Addresses Peng Wu Tsinghua University Department of Computer Science, Tsinghua University Beijing 100084 P.R.China Phone: +86-10-6278-5822 EMail: peng-wu@foxmail.com Qi Sun Wu & Sun Expires January 10, 2013 [Page 6] Internet-Draft public-4over6-deployment July 2012 Tsinghua University Department of Computer Science, Tsinghua University Beijing 100084 P.R.China Phone: +86-10-6278-5822 EMail: sunqi@csnet1.cs.tsinghua.edu.cn Wu & Sun Expires January 10, 2013 [Page 7]