NWS Experiences in Outsourcing Web Content Delivery Robert Bunge NWS OCIO 11/2/05

Dealing with Flash Crowds National Hurricane Center Website hits, Hurricane Rita, Cat 5 announcement

The Problem ● Much NOAA web data is subject to flash crowds ● Options – NOAA can build out infrastructure in-house for peak traffic – Out source hosting to commercial vendor – Out source content delivery to vendor

CDN Solution ● Out source to content delivery vendor – Content Delivery Network (CDN) – Not hosting – CDNs cache your content – store and forward – Used by NWS for National Hurricane Center since 2003 – Used for other NWS websites in 2005

NWS use of CDNs ● First use: 2003; National Hurricane Center for hurricane Isabel ● Month long experiment with weather.gov, 2004 ● Continued use with NHC through current ● Week long test with weather.gov, summer, 2005; different vendor ● Switch of weather.gov during hurricane Rita

How a CDN works Internet CDN Origin Server

Moving Weather.gov to a CDN Transfer of weather.gov traffic from origin servers to a CDN (Mirror Image Internet) during hurricane Rita.

Controlling Content on the CDN ● CDNs cache your content on their system ● They expire the content based on: – A generic rule that you provide – Obeying cache headers that your web server provides ● Good idea to use cache headers anyway – AOL – Browsers – Corporate proxies

A Normal Cache Control Headers

Summary ● NWS has found CDNs to be effective – Allow NWS to focus on mission and content – No sweat or worry over flash crowds – Rapid capacity increase for a single web server based website ● Don't have to engage in a technology “war” with users, increased broadband, more graphically oriented NOAA content ● Still control content production, php scripts, cgi's and the core server environment ● Down side: up front $$$ ● Down side: unpredictable spending of $$$ during flash crowds