v6ops J. Brzozowski Internet-Draft Comcast Cable Intended status: Best Current Practice G. Van De Velde Expires: March 18, 2018 Nokia September 14, 2017 Unique IPv6 Prefix Per Host draft-ietf-v6ops-unique-ipv6-prefix-per-host-09 Abstract This document outlines an approach utilising existing IPv6 protocols to allow hosts to be assigned a unique IPv6 prefix (instead of a unique IPv6 address from a shared IPv6 prefix). Benefits of unique IPv6 prefix over a unique service provider IPv6 address include improved host isolation and enhanced subscriber management on shared network segments. 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 https://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 March 18, 2018. Copyright Notice Copyright (c) 2017 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 (https://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 Brzozowski & Van De VeldeExpires March 18, 2018 [Page 1] Internet-Draft Unique IPv6 Prefix Per Host September 2017 the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 2. Motivation and Scope of Applicability . . . . . . . . . . . . 3 3. Design Principles . . . . . . . . . . . . . . . . . . . . . . 4 4. IPv6 Unique Prefix Assignment . . . . . . . . . . . . . . . . 4 5. IPv6 Neighbor Discovery Best Practices . . . . . . . . . . . 6 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 7. Security Considerations . . . . . . . . . . . . . . . . . . . 7 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7 9. Normative References . . . . . . . . . . . . . . . . . . . . 8 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 1. Introduction The concepts in this document are originally developed as part of a large scale, production deployment of IPv6 support for a provider managed shared access network service. A shared network service, is a service offering where a particular L2 access network (e.g. wifi) is shared and used by multiple visiting devices (i.e. subscribers). Many service providers offering shared access network services, have legal requirements, or find it good practice, to provide isolation between the connected visitor devices to control potential abuse of the shared access network. A network implementing a unique IPv6 prefix per host, can simply ensure that devices cannot send packets to each other except through the first-hop router. This will automatically provide robust protection against attacks between devices that rely on link-local ICMPv6 packets, such as DAD reply spoofing, ND cache exhaustion, malicious redirects, and rogue RAs. This form of protection is much more scalable and robust than alternative mechanisms such as DAD proxying, forced forwarding, or ND snooping. In this document IPv6 support does not preclude support for IPv4; however, the primary objectives for this work was to make it so that user equipment (UE) were capable of an IPv6 only experience from a network operators perspective. In the context of this document, UE can be 'regular' end-user-equipment, as well as a server in a datacenter, assuming a shared network (wired or wireless). Brzozowski & Van De VeldeExpires March 18, 2018 [Page 2] Internet-Draft Unique IPv6 Prefix Per Host September 2017 Details of IPv4 support are out of scope for this document. This document will also, in general, outline the requirements that must be satisfied by UE to allow for an IPv6 only experience. In most current deployments, User Equipment (UE) IPv6 address assignment is commonly done using either IPv6 SLAAC RFC4862 [RFC4862] and/or DHCP IA_NA (Identity Association - Non-temporary Address) RFC3315 [RFC3315]. During the time when this approach was developed and subsequently deployed, it has been observed that some operating systems do not support the use of DHCPv6 for the acquisition of IA_NA per RFC7934 [RFC7934]. To not exclude any known IPv6 implementations, IPv6 SLAAC based subscriber and address management is the recommended technology to reach highest percentage of connected IPv6 devices on a provider managed shared network service. In addition an IA_NA-only network is not recommended per RFC 7934 RFC7934 [RFC7934] section 8. This document will detail the mechanics involved for IPv6 SLAAC based address and subscriber management coupled with stateless DHCPv6, where beneficial. This document focuses upon the process for UEs to obtain a unique IPv6 prefix. 1.1. 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 RFC 2119 [RFC2119]. 2. Motivation and Scope of Applicability The motivation for this work falls into the following categories: o Deployment advice for IPv6 that will allow stable and secure IPv6 only experience, even if IPv4 support is present o Ensure support for IPv6 is efficient and does not impact the performance of the underlying network and in turn the customer experience o Allow for the greatest flexibility across host implementation to allow for the widest range of addressing and configuration mechanisms to be employed. The goal here is to ensure that the widest population of UE implementations can leverage the availability of IPv6 o Lay the technological foundation for future work related to the use of IPv6 over shared media requiring optimized subscriber management Brzozowski & Van De VeldeExpires March 18, 2018 [Page 3] Internet-Draft Unique IPv6 Prefix Per Host September 2017 o Two devices (subscriber/hosts), both attached to the same provider managed shared network should only be able to communicate through the provider managed First Hop Router o Provide guidelines regarding best common practices around IPv6 neighborship discovery RFC4861 [RFC4861] and IPv6 address managent settings between the First Hop router and directly connected hosts/subscribers. 3. Design Principles The First Hop router discussed in this document is the L3-Edge router responsible for the communication with the devices (hosts and subscribers) directly connected to a provider managed shared network, and to transport traffic between the directly connected devices and between directly connected devices and remote devices. The work detailed in this document is focused on providing details regarding best common practices of the IPv6 neighbor discovery and related IPv6 address management settings between the First Hop router and directly connected hosts/subscribers. The documented Best Current Practice helps a service provider to better manage the shared provider managed network on behalf of the connected devices. This document recommends providing a unique IPv6 prefix to devices connected to the managed shared network. Each unique IPv6 prefix can function as control-plane anchor point to make sure that each device receives expected subscriber policy and service levels (throughput, QoS, security, parental-control, subscriber mobility management, etc.). 4. IPv6 Unique Prefix Assignment When a UE connects to the shared provider managed network and is attached, it will initiate IP configuration phase. During this phase the UE will, from an IPv6 perspective, attempt to learn the default IPv6 gateway, the IPv6 prefix information, the DNS information RFC8106 [RFC8106], and the remaining information required to establish globally routable IPv6 connectivity. For that purpose, the the subscriber sends a RS (Router Solicitation) message. The First Hop Router receives this subscriber RS message and starts the process to compose the response to the subscriber originated RS message. The First Hop Provider Router will answer using a solicited RA (Router Advertisement) to the subscriber. When the First Hop Provider Router sends the solicited RA response, or a periodic unsolicited RA, the RA MUST be sent only to the UE/ Brzozowski & Van De VeldeExpires March 18, 2018 [Page 4] Internet-Draft Unique IPv6 Prefix Per Host September 2017 subscriber that has been assigned the Unique IPv6 prefix contained in the RA. This is achieved by sending a unicast RA response, as detailed in [RFC4861] section 6.2.6, or by sending a multicast RA response or unsolicited RA to the all-nodes group, as detailed in [RFC4861] section 6.2.4 and 6.2.6, but instead of using the link- layer multicast address associated with the all-nodes group, the link-layer unicast address of the UE/subscriber that has been assigned the Unique IPv6 prefix contained in the RA MUST be used as the link-layer destination RFC6085 [RFC6085]. This solicited RA contains two important parameters for the EU/ subscriber to consume: a Unique IPv6 prefix (currently a /64 prefix) and some flags. The Unique IPv6 prefix can be derived from a locally managed pool or aggregate IPv6 block assigned to the First Hop Provider Router or from a centrally allocated pool. The flags indicate to the subscriber to use SLAAC and/or DHCPv6 for address assignment; it may indicate if the autoconfigured address is on/off- link and if 'Other' information (e.g. DNS server address) needs to be requested. The IPv6 RA flags used for best common practice in IPv6 SLAAC based Provider managed shared networks are: o M-flag = 0 (subscriber address is not managed through DHCPv6), this flag may be set to 1 in the future if/when DHCPv6 prefix delegation support is desired) o O-flag = 1 (DHCPv6 is used to request configuration information i.e. DNS, NTP information, not for IPv6 addressing) o A-flag = 1 (The subscriber can configure itself using SLAAC) o L-flag = 0 (the prefix is not an on-link prefix, which means that the subscriber will never assume destination addresses that match the prefix are on-link and will always send packets to those addresses to the appropriate gateway according to route selection rules.) The use of a unique IPv6 prefix per subscriber adds an additional level of protection and efficiency as it relates to how IPv6 Neighbor Discovery and Router Discovery processing. Since the UE has a unique IPv6 prefix all traffic by default will be directed to the First Hop router. Further, the flag combinations documented above maximise the IPv6 configurations that are available by hosts including the use of privacy IPv6 addressing. The architected result of designing the RA as documented above is that each subscriber gets its own unique IPv6 prefix. Each host can Brzozowski & Van De VeldeExpires March 18, 2018 [Page 5] Internet-Draft Unique IPv6 Prefix Per Host September 2017 consequently use SLAAC or any other method of choice to select its /128 unique address. Either stateless DHCPv6 RFC3736 [RFC3736] or IPv6 Router Advertisement Options for DNS Configuration RFC8106 [RFC8106] can be used to get the IPv6 address of the DNS server. If the subscriber desires to send anything external including other subscriber devices (assuming device to device communications is enabled and supported), then, due to the L-bit being unset, it SHOULD send this traffic to the First Hop Router. After the subscriber received the RA, and the associated flags, it will assign itself a 128 bit IPv6 address using SLAAC. Since the address is composed by the subscriber device itself, it will need to verify that the address is unique on the shared network. The subscriber will for that purpose, perform Duplicate Address Detection algorithm. This will occur for each address the UE attempts to utilize on the shared provider managed network. 5. IPv6 Neighbor Discovery Best Practices An operational consideration when using IPv6 address assignment using IPv6 SLAAC is that after the onboarding procedure, the subscriber will have a prefix with certain preferred and valid lifetimes. The First Hop Provider Router extends these lifetimes by sending an unsolicited RA, the applicable MaxRtrAdvInterval on the first hop router MUST therefore be lower than the preferred lifetime. One consequence of this process is that the First Hop Router never knows when a subscriber stops using addresses from a prefix and additional procedures are required to help the First Hop Router to gain this information. When using stateful DHCPv6 IA_NA for IPv6 subscriber address assignment, this uncertainty on the First Hop Router is not of impact due to the stateful nature of DHCPv6 IA_NA address assignment. Following is a reference table of the key IPv6 router discovery and neighbor discovery timers for provider managed shared networks: o Maximum IPv6 Router Advertisement Interval = 300s (or 600s when battery consumption is a concern according RFC7772 [RFC7772]). o IPv6 Router LifeTime = 3600s o Reachable time = 30s o IPv6 Valid Lifetime = 3600s o IPv6 Preferred Lifetime = 1800s o Retransmit timer = 0s Brzozowski & Van De VeldeExpires March 18, 2018 [Page 6] Internet-Draft Unique IPv6 Prefix Per Host September 2017 The stateless nature of the subscriber IPv6 SLAAC connectivity model introduces non-optimal resource consumption (i.e. memory, neighbor state) on the First Hop Router. To reduce undesired resource consumption, such as in the case of WiFi hotspots, is to remove subscriber context as quickly as possible when a device or subscriber becomes non-active. A possible solution is to use a subscriber or device inactivity timer, that after tracking a pre-defined (currently unspecified) number of minutes, deletes the subscriber context on the First Hop Router. When employing stateless IPv6 address assignment, a number of widely deployed operating systems will attempt to utilise RFC 4941 RFC4941 [RFC4941] temporary 'private' addresses. Similarly, when using this technology in a datacenter, the UE server may need to use several addresses from the same Unique IPv6 Prefix, for example because is using multiple virtual hosts, containers, etc. in the bridged virtual switch. This can lead to the consequence that a UE has multiple /128 addresses from the same IPv6 prefix. The First Hop Provider Router MUST be able to handle the presence and use of multiple globally routable IPv6 addresses. For accounting purposes, the First Hop Provider Router must be able to send usage statistics per subscriber using Radius attributes. 6. IANA Considerations No IANA considerations are defined at this time. 7. Security Considerations The mechanics of IPv6 privacy extensions RFC4941 [RFC4941] is compatible with assignment of a unique IPv6 Prefix per Host. However, when combining both IPv6 privacy extensions and a unique IPv6 Prefix per Host a reduced privacy experience for the subscriber is introduced, because a prefix may be associated with a subscriber, even when the subscriber implemented IPv6 privacy extensions RFC4941 [RFC4941]. No other additional security considerations are made in this document. 8. Acknowledgements The authors would like to thank the following, in alphabetical order, for their contributions: Brzozowski & Van De VeldeExpires March 18, 2018 [Page 7] Internet-Draft Unique IPv6 Prefix Per Host September 2017 Ben Campbell, Brian Carpenter, Tim Chown, Lorenzo Colitti, Killian Desmedt, David Farmer, Brad Hilgenfeld, Wim Henderickx, Erik Kline, Suresh Krishnan, Warren Kumari, Thomas Lynn, Jordi Palet, Phil Sanderson, Colleen Szymanik, Jinmei Tatuya, Eric Vyncke, Sanjay Wadhwa 9. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC3315] Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins, C., and M. Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July 2003, . [RFC3736] Droms, R., "Stateless Dynamic Host Configuration Protocol (DHCP) Service for IPv6", RFC 3736, DOI 10.17487/RFC3736, April 2004, . [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, DOI 10.17487/RFC4861, September 2007, . [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless Address Autoconfiguration", RFC 4862, DOI 10.17487/RFC4862, September 2007, . [RFC4941] Narten, T., Draves, R., and S. Krishnan, "Privacy Extensions for Stateless Address Autoconfiguration in IPv6", RFC 4941, DOI 10.17487/RFC4941, September 2007, . [RFC6085] Gundavelli, S., Townsley, M., Troan, O., and W. Dec, "Address Mapping of IPv6 Multicast Packets on Ethernet", RFC 6085, DOI 10.17487/RFC6085, January 2011, . [RFC7772] Yourtchenko, A. and L. Colitti, "Reducing Energy Consumption of Router Advertisements", BCP 202, RFC 7772, DOI 10.17487/RFC7772, February 2016, . Brzozowski & Van De VeldeExpires March 18, 2018 [Page 8] Internet-Draft Unique IPv6 Prefix Per Host September 2017 [RFC7934] Colitti, L., Cerf, V., Cheshire, S., and D. Schinazi, "Host Address Availability Recommendations", BCP 204, RFC 7934, DOI 10.17487/RFC7934, July 2016, . [RFC8106] Jeong, J., Park, S., Beloeil, L., and S. Madanapalli, "IPv6 Router Advertisement Options for DNS Configuration", RFC 8106, DOI 10.17487/RFC8106, March 2017, . Authors' Addresses John Jason Brzozowski Comcast Cable 1701 John F. Kennedy Blvd. Philadelphia, PA USA Email: john_brzozowski@cable.comcast.com Gunter Van De Velde Nokia Antwerp Belgium Email: gunter.van_de_velde@nokia.com Brzozowski & Van De VeldeExpires March 18, 2018 [Page 9]