MMUSIC T. Reddy Internet-Draft P. Patil Intended status: Standards Track P. Martinsen Expires: August 1, 2014 Cisco January 28, 2014 Happy Eyeballs Extension for ICE draft-reddy-mmusic-ice-happy-eyeballs-05 Abstract This document provides guidelines on how to make ICE [RFC5245] conclude faster in IPv4/IPv6 dual-stack scenarios where broken paths exist. This will lead to more sustained IPv6 deployment as users will no longer have an incentive to disable IPv6. 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." This Internet-Draft will expire on August 1, 2014. 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 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. Reddy, et al. Expires August 1, 2014 [Page 1] Internet-Draft Happy Eyeballs for ICE January 2014 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Notational Conventions . . . . . . . . . . . . . . . . . . . 2 3. Improving ICE Dual-stack Fairness . . . . . . . . . . . . . . 2 4. Compatibility . . . . . . . . . . . . . . . . . . . . . . . . 3 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 6. Security Considerations . . . . . . . . . . . . . . . . . . . 4 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4 8. Normative References . . . . . . . . . . . . . . . . . . . . 4 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5 1. Introduction There is a need to introduce more fairness in the handling of connectivity checks for different IP address families in dual-stack IPv4/IPv6 ICE scenarios. Section 4.1.2.1 of ICE [RFC5245] points to [RFC3484] for prioritizing among the different IP families. [RFC3484] is obsoleted by [RFC6724] but following the recommendations from the updated RFC will lead to prioritization of IPv6 over IPv4 for the same candidate type. Due to this, connectivity checks for candidates of the same type (HOST, RFLX, RELAY) are sent such that an IP address family is completely depleted before checks on the other address family are started. This results in user noticeable setup delays if the path for the prioritized address family is broken. To avoid such user noticeable delays when either IPv6 or IPv4 path is broken, this specification encourages intermingling the different address families when connectivity checks are conducted. Introducing IP address family fairness into ICE connectivity checks will lead to more sustained dual-stack IPv4/IPv6 deployment as users will no longer have an incentive to disable IPv6. The cost is a small penalty to the address type that otherwise would have been prioritized. 2. Notational Conventions 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]. This document uses terminology defined in [RFC5245]. 3. Improving ICE Dual-stack Fairness Candidates SHOULD be prioritized such that a long sequence of candidates belonging to the same address family will be intermingled with candidates from an alternate IP family. For example, promoting Reddy, et al. Expires August 1, 2014 [Page 2] Internet-Draft Happy Eyeballs for ICE January 2014 IPv4 candidates in the presence of many IPv6 candidates such that an IPv4 address candidate is always present after a small sequence of IPv6 candidates, i.e., reordering candidates such that both IPv6 and IPv4 candidates get a fair chance during the connectivity check phase. This makes ICE connectivity checks more responsive to broken path failures of an address family. An ICE agent can choose an algorithm or a technique of its choice to ensure that the resulting check lists have a fair intermingled mix of IPv4 and IPv6 address families. Modifying the check list directly can lead to uncoordinated local and remote check lists that result in ICE taking longer to complete. The best approach is to modify the formula for calculating the candidate priority value described in ICE [RFC5245] section 4.1.2.1. 4. Compatibility ICE [RFC5245] section 4.1.2 states that the formula in section 4.1.2.1 SHOULD be used to calculate the candidate priority. The formula is as follows: priority = (2^24)*(type preference) + (2^8)*(local preference) + (2^0)*(256 - component ID) ICE [RFC5245] section 4.1.2.2 has guidelines for how the type preference value should be chosen. Instead of having a static value for IPv4 and a static value for IPv6 type of addresses, it is possible to choose this value dynamically in such a way that IPv4 and IPv6 address candidate priorities ends up intermingled. The local and remote agent can have different algorithms for choosing the type preference value without any impact on coordination between the local and remote check list. The check list is made up by candidate pairs. A candidate pair is two candidates paired up and given a candidate pair priority as described in [RFC5245] section 5.7.2. Using the pair priority formula: pair priority = 2^32*MIN(G,D) + 2*MAX(G,D) + (G>D?1:0) Where G is the candidate provided by the controlling agent and D the priority provided by the controlled agent. This ensures that the local and remote check lists are coordinated. Even if the two agents have different algorithms for choosing the candidate priority value to get an intermingled set of IPv4 and IPv6 Reddy, et al. Expires August 1, 2014 [Page 3] Internet-Draft Happy Eyeballs for ICE January 2014 candidates, the resulting checklist, that is a list sorted by the pair priority value, will be identical on the two agents. The agent that has promoted IPv4 cautiously i.e. lower IPv4 candidate priority values compared to the other agent, will influence the check list the most due to (2^32*MIN(G,D)) in the formula. These recommendations are backward compatible with a standard ICE implementation. If the other agent have IPv4 candidates with higher priorities due to intermingling, the effect is canceled when the checklist is formed and the pair priority formula is used to calculate the pair priority. 5. IANA Considerations None. 6. Security Considerations STUN connectivity check using MAC computed during key exchanged in the signaling channel provides message integrity and data origin authentication as described in section 2.5 of [RFC5245] apply to this use. 7. Acknowledgements Authors would like to thank Dan Wing, Ari Keranen, Bernard Aboba, Martin Thomson and Jonathan Lennox for their comments and review. 8. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3484] Draves, R., "Default Address Selection for Internet Protocol version 6 (IPv6)", RFC 3484, February 2003. [RFC5245] Rosenberg, J., "Interactive Connectivity Establishment (ICE): A Protocol for Network Address Translator (NAT) Traversal for Offer/Answer Protocols", RFC 5245, April 2010. [RFC6724] Thaler, D., Draves, R., Matsumoto, A., and T. Chown, "Default Address Selection for Internet Protocol Version 6 (IPv6)", RFC 6724, September 2012. Reddy, et al. Expires August 1, 2014 [Page 4] Internet-Draft Happy Eyeballs for ICE January 2014 Authors' Addresses Tirumaleswar Reddy Cisco Systems, Inc. Cessna Business Park, Varthur Hobli Sarjapur Marathalli Outer Ring Road Bangalore, Karnataka 560103 India Email: tireddy@cisco.com Prashanth Patil Cisco Systems, Inc. Bangalore India Email: praspati@cisco.com Paal-Erik Martinsen Cisco Systems, Inc. Philip Pedersens Vei 22 Lysaker, Akershus 1325 Norway Email: palmarti@cisco.com Reddy, et al. Expires August 1, 2014 [Page 5]