Load Balancing Presentation 13a4r

Load Balancing

Contents 

What is Load Balancing



Load Balancer and Back-End



Layer-2 Load Balancing



Layer-4 Load Balancing



Layer-7 Load Balancing



Persistence



DNS Load Balancing



Database Load Balancing



Load-Balancing Clusters



More Software Solutions

What is Load Balancing? 

Load balancing is a computer networking methodology to distribute workload across multiple resources to achieve 

optimal resource utilization



maximize throughput



minimize response time



avoid overload

Load Balancer and Back-End 





A Load Balancer (Front-End Server) is usually used Receives computed outputs from several BackEnd Servers In Multitier architecture, terminology of designs may include 

Stovepipes



Bowties

Load Balancer and Back-End 

Redirects traffic according to algorithm/availability/traffic but stays as a mediator between the and the back-end servers 



Server Health Checking through Ping/T Connect/HTTP Get Header/HTTP Get Content Custom checks can be designed too

Layer-2 Load Balancing ● ●

Bonding Bond two or more links into a single, higherbandwidth logical link ●

NIC Teaming

●

Link Aggregation Control Protocol (LA)

Layer 4 Load Balancer/Router 

MultiLayer Switch 



Modern load balancing routers can use rules 

least load



fastest response times



balancing requests out





Practically a NAT with port and transaction awareness

if one machine is not up, the router will not send traffic to it

IPVS in the Linux Virtual Server (LVS)

Layer-7 Load Balancing  



Reverse Proxy Parse requests in application layer and distribute requests to servers based on different types of request contents LoadBalancing.org recommends HAProxy for open-source 



Citrix netscaler and F5 are also said to dominate this market

Also KTVS

Layer-7 Load Switching

Persistence 

When a is directed to one server



The is kept redirected to that server



Source IP Persistence 



Not good for multiple access behind one IP

Cookie Based 

Good for HTTP but there are famous vendors that also do RDP Cookies (HAProxy)

DNS Load Balancing 

Using the Zone File



When the Server is down... 

Its DNS will not respond



Quickest DNS responder will be the closest

@ in a 192.0.2.1 one.example.org A 192.0.2.1 two.example.org A 203.0.113.2 www.example.org NS one.example.org www.example.org NS two.example.org

Database Load Balancing 

Oracle RAC



MySQL Cluster



or through middle-ware like MySQL Load Balancing Proxy

Load-Balancing Clusters 





Usually a group of computers connected in a LAN to make a ”Virtual Server” More cost-effective than single computers with similar performance Some software used is  

MPI Library Beowulf, distcc, and MPICH. Linux Virtual Server, Linux-HA

More Software Solutions 

Apache web server's mod_proxy_balancer extension



Varnish (HTTP Accelerator/Reverse Proxy)



Pound (Reverse Proxy/Load Balancer)



 

Gearman (application framework designed to distribute appropriate computer tasks to multiple computers) Redundant Firewalls with OpenBSD F5 uses FreeBSD, RedHat Cluster, Linux-HA, Ultra Monkey, Linux Virtual Server