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OPINION
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By Pavelas Sokolovas , Head of Infrastructure , Custodian Data Centres
www . custodiandc . com
The QoS evolution : take a greater amount of control of your network by cost-effectively managing traffic
some transits available that are much cheaper due to its geographical location . PoP B has a more convenient location , just outside the M25 , with an abundance of power available . Consequently , we want to take a transit from where it ’ s cheap , to where it ’ s needed . This is achieved by taking two diverse links from one location to another , with each of them capable of taking your entire normal traffic down to PoP B . If your ‘ normal ’ traffic is 4-5Gbit / s , you will need two diverse 10G links from PoP A to PoP B to carry it . The theory behind having two links is because one of them can fail and you need a contingency plan for this .
Please note : In PoP A , you would have to have at least three transits to facilitate your inter-PoP capacity at 20G . You have to allow for at least one transit to fail or to do maintenance work . Normally , you would have four or even more , just to allow for the maintenance failure and to minimise the disruptions .
We live in a world where money dominates , whether we like it or not . Importantly , even if your primary goal isn ’ t to save money , if a solution is designed and implemented correctly , it will do just that .
The importance of having proper Quality of Service ( QoS ) enabled on your network usually becomes apparent during two different scenarios : the first being when an actual problem arises and the second , which is something all network engineers should be striving towards , is during the planning of a QoS strategy .
Planning is the key Don ’ t wait for things to happen – it ’ s already too late when you have a situation you didn ’ t think of occur . Part of planning a comprehensive QoS strategy is to continually discuss and theorise about all the variables that can go wrong . Imagine a simple network consisting of two PoPs . PoP A has
Overcoming attacks Unfortunately , we live in a world of antagonists who thrive on attacking you and / or your client . This may be down to a specific reason , but they could just be having fun , which is saddening . Attacks are one of the reasons you will no longer have your normal level of traffic . For the sake of the QoS , the attack we are concerned with is your transit uplink or intersite link saturation .
First of all , an attacker can succeed or fail . For the purpose of this illustration , we will say that success is when they have managed to saturate the transit uplink .
In this situation , we would have to black hole the target IP to save everyone from being affected by a packet loss . Please bear in mind , we will not discuss DDoS mitigation options , as this out of QoS scope .
If the attack fails , it can still cause issues . Why ? If the attack managed to create inbound traffic of 7-8Gbps on each of 4x10Gbps transit providers , despite the actual transit ports not being saturated , we still have 28-32Gpbs of traffic inbound to PoP A . This simply won ’ t fit via 10Gbps ( 2x10Gbps accounted for a failure of one ) link down to PoP B . So , what are the options ?
Upgrade links Option 1 :
A lazy approach would be to upgrade our links between PoPs from 10Gbps to 40Gbps . Engineers don ’ t tend to focus on money however , so when management calculates the cost of upgrades , the answer is often no . Simultaneously , they need to solve the problem of one client being affected by an attack on another client . Unfortunately , a lot of colocation facilities won ’ t do this ,
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