# Presentation: 352918

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

***Jeff Poe, ****NWS Office of Chief Information Officer*
***Bruce Marshak****, NWS Southern Region Headquarters*
*NOAATech 2006*
*November 3, 2005*

## GSLB in NWS Web Farms

***Agenda***
**Problem Overview **
**Global Server Load Balancing (GSLB)**
**Summary**
**Future Plans**

## GSLB in NWS Web Farms

***Problem Overview ***
**NWS currently has six web farms providing Web Services (OCIO, NOAA, SRH, ERH, CRH, WRH)**
**Different circuit capacities from OC-12 to T3 **
**Public’s response to certain severe weather events could use all available circuit capacity at a web farm**
*Hurricane landfall for SR*
*Severe thunderstorm activity in CR or ER*

## GSLB in NWS Web Farms

***National Doppler Radar Sites***

## GSLB in NWS Web Farms

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

## GSLB in NWS Web Farms

***Problem Summary***
**Web farm bandwidth requirement had doubled each year for the past 3 years**
**Web farms did not have capacity to serve projected increase for 2005**
***Strategies to handle increased usage***
**Bigger Faster Circuits**
**Content Delivery Network a.k.a. Web Caching Service**
*Akamai*
*Mirror Image Internet*
**Global Server Load Balancing**

## GSLB in NWS Web Farms

***GSLB Overview***
**GSLB acts as a DNS proxy for selected domain names**
**Local server load balancer (SLB) serving requests to web servers at the web farm for a virtual IP address**
**Multiple virtual IP addresses and multiple domain names**
**Uses algorithm consisting of several configurable policies and metrics in order to select best web farm for a user**
**Automatically redirects users away from failed sites**
**Conceptually aggregates servers and circuit capacity allowing more efficient use of resources**
**Need content mirrored at globally load balanced server farms**

## GSLB in NWS Web Farms

***Domain Name Service (DNS) Operation***
**User requests URL, browser queries local DNS to resolve hostname to IP address**
**Local DNS performs queries iteratively, ultimately reaching the authoritative DNS for requested domain name**
**Authoritative DNS replies with one or more IP addresses for a given domain name**
**Local DNS responds back to user’s browser, which opens TCP connection to given IP address and downloads web pages**
**Local DNS caches authoritative DNS response and provides same address for future requests to domain until time-to-live (TTL) parameter of domain’s IP specified by authoritative DNS expires**

## GSLB in NWS Web Farms

***Drawbacks of DNS***
**Web server farm supporting website is down or at capacity limit, authoritative DNS continues to return that web farms IP address in response to local DNS queries until authoritative DNS is manually updated**
**If application that serves that website is down, users receive error code, timeout, or stale data**

## GSLB in NWS Web Farms

***DNS with GSLB***
**User requests URL, browser queries local DNS to resolve hostname to IP address**
**Local DNS performs queries iteratively, ultimately reaching the GSLB as the authoritative DNS for requested domain name**
**GSLB uses algorithm to select best Virtual IP (VIP) address for a given domain name and responds to local DNS**
**Local DNS responds back to user’s browser, which opens TCP connection to given VIP address and downloads web pages**
**Local DNS caches authoritative DNS response and provides same address for future requests to domain until time-to-live (TTL) parameter of domain’s IP specified by authoritative DNS expires**

## GSLB in NWS Web Farms

***GSLB Policy / Metric processing order***
**Server health check**
**Weight of VIP**
**Remote SI's session capacity threshold**
**Round trip time between remote SI and client**
**Geographic location**
**Remote SI's available session capacity**
**Remote SI's preference value**
**Least response selection**

## GSLB in NWS Web Farms

***Milestones***
**Feb 05: Foundry Training**
**Mar 05: Installation and Configuration**
**Apr 05 – May 05: Testing and Proof of Concept**
**May 05: Serving live data**
**May 05 – Jun 05: Phased Implementation into Production**
**Jul 05: Dennis, Emily**
**Aug 05: Irene, Katrina**
**Sep 05: Ophelia, Rita**
**Oct 05: Stan, Wilma**

## GSLB in NWS Web Farms

***Summary***
**> 100% increase in peak traffic with ample available headroom in bandwidth and server capacity**
**Average response times < 1 sec**
**Improved availability, reliability, and provided a better service to the public**
**Able to take a web farm out of production for maintenance without impacting users**

## GSLB in NWS Web Farms

***Future Plans***
**Additional domains and services**
**NOAA web farms**
**Norman and Boulder**

## GSLB in NWS Web Farms

***Project Team***
**Susan Beckwith – SRH**
**Bill Gery – CRH**
**Alex Hsia – NOAA Boulder**
**Chi Kang – NOAA Silver Spring**
**Paul Kirkwood – SRH**
**Bruce Marshak – SRH**
**Todd Metcalf – ERH**
**Reginald Pace – NOAA Silver Spring**
**Sameka Prather – NWS OCIO**
**Graham Stork - WRH**
**Joe Rizo – Foundry**
**Fortune Vilcko – ERH**
**Eric Williams - NCIRT**

## GSLB in NWS Web Farms

**Thank You!**