Using Global Server Load Balancing to Improve Web Site Performance Jeff Poe, NWS Office of Chief Information Officer Bruce Marshak, NWS Southern Region

Using Global Server Load Using Global Server Load Balancing to Improve Web Balancing to Improve Web Site PerformanceSite Performance

Jeff Poe, Jeff Poe, NWS Office of Chief Information OfficerNWS Office of Chief Information Officer

Bruce MarshakBruce Marshak, NWS Southern Region Headquarters, NWS Southern Region Headquarters

NOAATech 2006NOAATech 2006

November 3, 2005November 3, 2005


GSLB in NWS Web FarmsGSLB in NWS Web Farms

AgendaAgenda• Problem Overview Problem Overview

• Global Server Load Balancing (GSLB)Global Server Load Balancing (GSLB)

• SummarySummary

• Future PlansFuture Plans



Problem Overview Problem Overview • NWS currently has six web farms providing Web NWS currently has six web farms providing Web

Services (OCIO, NOAA, SRH, ERH, CRH, WRH)Services (OCIO, NOAA, SRH, ERH, CRH, WRH)

• Different circuit capacities from OC-12 to T3 Different circuit capacities from OC-12 to T3

• Public’s response to certain severe weather events Public’s response to certain severe weather events could use all available circuit capacity at a web farmcould use all available circuit capacity at a web farm– Hurricane landfall for SRHurricane landfall for SR

– Severe thunderstorm activity in CR or ERSevere thunderstorm activity in CR or ER



National Doppler Radar SitesNational Doppler Radar Sites



Maximum Bandwidth per day in Mbits/sec for 2004Maximum Bandwidth per day in Mbits/sec for 2004

Charley

GastonFrancis

Ivan

Jeanne



Problem SummaryProblem Summary• Web farm bandwidth requirement had doubled each Web farm bandwidth requirement had doubled each

year for the past 3 yearsyear for the past 3 years• Web farms did not have capacity to serve projected Web farms did not have capacity to serve projected

increase for 2005increase for 2005

Strategies to handle increased usageStrategies to handle increased usage• Bigger Faster CircuitsBigger Faster Circuits• Content Delivery Network a.k.a. Web Caching ServiceContent Delivery Network a.k.a. Web Caching Service– AkamaiAkamai– Mirror Image InternetMirror Image Internet

• Global Server Load BalancingGlobal Server Load Balancing



GSLB OverviewGSLB Overview• GSLB acts as a DNS proxy for selected domain namesGSLB acts as a DNS proxy for selected domain names

• Local server load balancer (SLB) serving requests to web Local server load balancer (SLB) serving requests to web servers at the web farm for a virtual IP addressservers at the web farm for a virtual IP address

• Multiple virtual IP addresses and multiple domain namesMultiple virtual IP addresses and multiple domain names

• Uses algorithm consisting of several configurable policies and Uses algorithm consisting of several configurable policies and metrics in order to select best web farm for a usermetrics in order to select best web farm for a user

• Automatically redirects users away from failed sitesAutomatically redirects users away from failed sites

• Conceptually aggregates servers and circuit capacity allowing Conceptually aggregates servers and circuit capacity allowing more efficient use of resourcesmore efficient use of resources

• Need content mirrored at globally load balanced server farmsNeed content mirrored at globally load balanced server farms



Domain Name Service (DNS) OperationDomain Name Service (DNS) Operation• User requests URL, browser queries local DNS to resolve User requests URL, browser queries local DNS to resolve

hostname to IP addresshostname to IP address

• Local DNS performs queries iteratively, ultimately reaching the Local DNS performs queries iteratively, ultimately reaching the authoritative DNS for requested domain nameauthoritative DNS for requested domain name

• Authoritative DNS replies with one or more IP addresses for a Authoritative DNS replies with one or more IP addresses for a given domain namegiven domain name

• Local DNS responds back to user’s browser, which opens TCP Local DNS responds back to user’s browser, which opens TCP connection to given IP address and downloads web pagesconnection to given IP address and downloads web pages

• Local DNS caches authoritative DNS response and provides Local DNS caches authoritative DNS response and provides same address for future requests to domain until time-to-live same address for future requests to domain until time-to-live (TTL) parameter of domain’s IP specified by authoritative DNS (TTL) parameter of domain’s IP specified by authoritative DNS expiresexpires



Drawbacks of DNSDrawbacks of DNS• Web server farm supporting website is down or at Web server farm supporting website is down or at

capacity limit, authoritative DNS continues to return capacity limit, authoritative DNS continues to return that web farms IP address in response to local DNS that web farms IP address in response to local DNS queries until authoritative DNS is manually updatedqueries until authoritative DNS is manually updated

• If application that serves that website is down, users If application that serves that website is down, users receive error code, timeout, or stale datareceive error code, timeout, or stale data



DNS with GSLBDNS with GSLB• User requests URL, browser queries local DNS to resolve User requests URL, browser queries local DNS to resolve

hostname to IP addresshostname to IP address

• Local DNS performs queries iteratively, ultimately reaching the Local DNS performs queries iteratively, ultimately reaching the GSLB as the authoritative DNS for requested domain nameGSLB as the authoritative DNS for requested domain name

• GSLB uses algorithm to select best Virtual IP (VIP) address for a GSLB uses algorithm to select best Virtual IP (VIP) address for a given domain name and responds to local DNSgiven domain name and responds to local DNS

• Local DNS responds back to user’s browser, which opens TCP Local DNS responds back to user’s browser, which opens TCP connection to given VIP address and downloads web pagesconnection to given VIP address and downloads web pages

• Local DNS caches authoritative DNS response and provides Local DNS caches authoritative DNS response and provides same address for future requests to domain until time-to-live same address for future requests to domain until time-to-live (TTL) parameter of domain’s IP specified by authoritative DNS (TTL) parameter of domain’s IP specified by authoritative DNS expiresexpires



GSLB Policy / Metric processing orderGSLB Policy / Metric processing order• Server health checkServer health check

• Weight of VIPWeight of VIP

• Remote SI's session capacity thresholdRemote SI's session capacity threshold

• Round trip time between remote SI and clientRound trip time between remote SI and client

• Geographic locationGeographic location

• Remote SI's available session capacityRemote SI's available session capacity

• Remote SI's preference valueRemote SI's preference value

• Least response selectionLeast response selection



MilestonesMilestones• Feb 05: Foundry TrainingFeb 05: Foundry Training

• Mar 05: Installation and ConfigurationMar 05: Installation and Configuration

• Apr 05 – May 05: Testing and Proof of ConceptApr 05 – May 05: Testing and Proof of Concept

• May 05: Serving live dataMay 05: Serving live data

• May 05 – Jun 05: Phased Implementation into ProductionMay 05 – Jun 05: Phased Implementation into Production

• Jul 05: Dennis, EmilyJul 05: Dennis, Emily

• Aug 05: Irene, KatrinaAug 05: Irene, Katrina

• Sep 05: Ophelia, RitaSep 05: Ophelia, Rita

• Oct 05: Stan, WilmaOct 05: Stan, Wilma



SummarySummary• > 100% increase in peak traffic with ample available > 100% increase in peak traffic with ample available

headroom in bandwidth and server capacityheadroom in bandwidth and server capacity

• Average response times < 1 secAverage response times < 1 sec

• Improved availability, reliability, and provided a Improved availability, reliability, and provided a better service to the publicbetter service to the public

• Able to take a web farm out of production for Able to take a web farm out of production for maintenance without impacting usersmaintenance without impacting users



Future PlansFuture Plans• Additional domains and servicesAdditional domains and services

• NOAA web farmsNOAA web farms

• Norman and BoulderNorman and Boulder



Project TeamProject Team• Susan Beckwith – SRHSusan Beckwith – SRH• Bill Gery – CRHBill Gery – CRH• Alex Hsia – NOAA BoulderAlex Hsia – NOAA Boulder• Chi Kang – NOAA Silver SpringChi Kang – NOAA Silver Spring• Paul Kirkwood – SRHPaul Kirkwood – SRH• Bruce Marshak – SRHBruce Marshak – SRH• Todd Metcalf – ERHTodd Metcalf – ERH• Reginald Pace – NOAA Silver SpringReginald Pace – NOAA Silver Spring• Sameka Prather – NWS OCIOSameka Prather – NWS OCIO• Graham Stork - WRHGraham Stork - WRH• Joe Rizo – FoundryJoe Rizo – Foundry• Fortune Vilcko – ERHFortune Vilcko – ERH• Eric Williams - NCIRTEric Williams - NCIRT



Thank You!Thank You!

Documents

Using Global Server Load Balancing to Improve Web Site Performance Jeff Poe, NWS Office of Chief Information Officer Bruce Marshak, NWS Southern Region