Link load balancing using Citrix NetScaler

Introduction

Laymen explanation

Have you thought anytime how ISP increases his customer base. My point is that when ISP likes to increase customer base, he also needs to be prepare about managing these extra traffic. Deployment should scale up progressively otherwise it will either too costly or it will stop scaling affecting business badly. This document tries to explain how to meet this requirement using Citrix NetScaler Load balancer.

Technical explanation

Link load balancing (LLB) balances outbound traffic across multiple Internet connections provided by different service providers. LLB enables the Citrix® NetScaler® appliance to monitor and control traffic so that packets are transmitted seamlessly over the best possible link. Unlike with server load balancing, where a service represents a server, with LLB, a service represents a router or the next hop. A link is a connection between the NetScaler and the router.

Load balancing methods that are applicable to LLB are round robin, destination IP hash, least bandwidth, and least packets. You can optionally configure persistence for connections to be sustained on a specific link.

Use-case

To ensure maximum uptime, many enterprise networks lease two or more ISP links. One of the links connecting the company’s internal network to the ISP acts as a backup. Paying for a link that is rarely used is an inefficient use ofbandwidth, however.

A link load balancer uses traffic managementalgorithms to ensure that all leased ISP links are being used to their best advantage. The network administrator sets policies for the appliance so when it receives a request, it takes into account such things as client and end-user round-trip times and which ISP link has the most available bandwidth before completing the request.

Reference

https://docs.citrix.com/en-us/netscaler/10-5/ns-tmg-wrapper-10-con/ns-llb-gen-wrapper-10-con.html

https://www.youtube.com/watch?v=IvgHNpK0uL0

http://searchnetworking.techtarget.com/definition/link-load-balancer-link-balancer