CDNI M. Stiemerling Internet-Draft NEC Europe Ltd. Intended status: Informational July 4, 2011 Expires: January 5, 2012 Considerations on Request Routing for CDNI draft-stiemerling-cdni-routing-cons-00 Abstract Request routing in CDNs and also in the case of interconnecting multiple CDNs requires to match against a set functional requirements but also operational requirements. This memo discusses a few operational requirements and the impact to the current request routing proposals. 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 January 5, 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. Stiemerling Expires January 5, 2012 [Page 1] Internet-Draft Request Routing Cons. July 2011 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Speed Matters . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Failure Detection and Recovery . . . . . . . . . . . . . . . . 6 4. Security Considerations . . . . . . . . . . . . . . . . . . . 7 5. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . 8 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 6.1. Normative References . . . . . . . . . . . . . . . . . . . 9 6.2. Informative References . . . . . . . . . . . . . . . . . . 9 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 10 Stiemerling Expires January 5, 2012 [Page 2] Internet-Draft Request Routing Cons. July 2011 1. Introduction Request routing in CDNs and also in the case of interconnecting multiple CDNs requires to match against a set functional requirements (see [I-D.lefaucheur-cdni-requirements]) but also operational requirements. This memo discusses a few operational requirements and the impact to the current request routing proposals [I-D.peterson-cdni-strawman] and [I-D.xiaoyan-cdni-requestrouting]. This draft presents some initial considerations about request routing in CDN interconnect scenarios. Comments and discussions about this memo should be directed to the CDNI WG: cdni@ietf.org. Stiemerling Expires January 5, 2012 [Page 3] Internet-Draft Request Routing Cons. July 2011 2. Speed Matters The speed of content delivery matters a lot in CDNs for the actual content consumer, but also for the content provider. The content consumer does not like to wait for too long until the content is being displayed on its device. The content provider wants to achieve a fast and reliable content delivery. However, the current request routing proposals suggest that the time from the first content request to the actual start of delivery does not matter much. For instance, method 1 of [I-D.peterson-cdni-strawman], shown in Figure 1, requires 4 "transactions", as seen from the End-User to start the delivery of content. The total time from the first request to the actual data delivery is: t_start = t_I + t_II + t_III + t_IV. End-User Operator B Operator A |DNS cdn.cp.com | | +--|-------------------------------------------------->| (I)| | | | | |IPaddr of A's Request Router | +--|<--------------------------------------------------| |HTTP cdn.cp.com | | +--|-------------------------------------------------->| (II)| | | | | |302 peer.op-b.net/cdn.cp.com | +--|<--------------------------------------------------| |DNS peer.op-b.net | | +--|------------------------>| | (III)| | |(3) | | |IPaddr of B's Delivery Node | +--|<------------------------| | |HTTP peer.op-b.net/cdn.cp.com | +--|------------------------>| | (IV)| | |(4) | | | |DNS dca.cdn.cp.com | | | |------------------------>| | | | | | | |IPaddr of A's Delivery Node | | |<------------------------| | | |HTTP dca.cdn.cp.com | | | |------------------------>| | | | | | | |Data | | | |<------------------------| | |Data | | +--|<------------------------| | Stiemerling Expires January 5, 2012 [Page 4] Internet-Draft Request Routing Cons. July 2011 Figure 1: Method 1 of CDNI Strawman proposal To give an impression about the times to expect for t_total here are some values for a DNS resolution process and also round trip times (RTT). NB: These numbers are measured from Germany via an ADSL access, German research network (DFN) access, and via a 3G network operator in Germany (Eplus). NB: Those numbers are not representative as they are out of single runs and not multiple runs spread over a larger time windows. They are rather given to illustrate the challenge. +------------------+--------------------------------+---------------+ | Access-Type | DNS resolution (gmx.de,cached) | RTT (Germany) | +------------------+--------------------------------+---------------+ | ADSL (11 MBit/s) | 26 ms | 30 ms | | | | | | DFN (32 MBit/s) | 12 ms | 10 to 20 ms | | | | | | 3G (EPlus) | 200 to 300 ms | 200 to 300 ms | +------------------+--------------------------------+---------------+ Table 1: Some time measurements As compared to a popular video site (e.g., youtube.com) where the video is delivered after roughly 2 seconds (19 ms to resolve FQDN of cache in charge, 2 ms for TCP 3-way handshake, and yet 2 seconds until the content is actually requested). This has been test from the DFN network connection. The 2 seconds time seem to come from the usage of the Flash player, as the network connection is up,running, and already being used for yet another request to the cache. Here are the times, assuming that steps I, II, and III are consuming the RTT, but neglect the processing times: o ADSL: t_total = 3*30ms + t_IV = 90ms + t_IV o DFN: t_total = 3*20ms + t_IV = 60ms + t_IV o 3G: t_total = 3*300ms + t_IV = 900ms + t_IV The numbers for step I to III may look reasonable low (except for the 3G case), but t_IV isn't know yet, leaving still potential to prolong the long process anyhow. Stiemerling Expires January 5, 2012 [Page 5] Internet-Draft Request Routing Cons. July 2011 3. Failure Detection and Recovery It is hard to foresee from the current request routing specifications how a failure in the downstream CDN is detected by the upstream CDN and such a failure case can be corrected. Stiemerling Expires January 5, 2012 [Page 6] Internet-Draft Request Routing Cons. July 2011 4. Security Considerations TBD Stiemerling Expires January 5, 2012 [Page 7] Internet-Draft Request Routing Cons. July 2011 5. Conclusion This draft lists some operational challenges for the request routing for the interconnection of CDNs and is more than incomplete. The current proposals ( [I-D.peterson-cdni-strawman] and [I-D.xiaoyan-cdni-requestrouting]) for request routing seem not to consider the overall time from the first service request to the start of the content delivery. Stiemerling Expires January 5, 2012 [Page 8] Internet-Draft Request Routing Cons. July 2011 6. References 6.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. 6.2. Informative References [I-D.lefaucheur-cdni-requirements] Faucheur, F., Viveganandhan, M., Watson, G., and Y. Lee, "Content Distribution Network Interconnection (CDNI) Requirements", draft-lefaucheur-cdni-requirements-01 (work in progress), March 2011. [I-D.peterson-cdni-strawman] Peterson, L. and J. Hartman, "A Simple Approach to CDN Interconnection", draft-peterson-cdni-strawman-01 (work in progress), May 2011. [I-D.xiaoyan-cdni-requestrouting] He, X., Li, J., Dawkins, S., and G. Chen, "Request Routing for CDN Interconnection", draft-xiaoyan-cdni-requestrouting-01 (work in progress), June 2011. Stiemerling Expires January 5, 2012 [Page 9] Internet-Draft Request Routing Cons. July 2011 Author's Address Martin Stiemerling NEC Laboratories Europe Kurfuerstenanlage 36 Heidelberg 69115 Germany Phone: +49 6221 4342 113 Fax: +49 6221 4342 155 Email: martin.stiemerling@neclab.eu URI: http://ietf.stiemerling.org Stiemerling Expires January 5, 2012 [Page 10]