{"id":37,"date":"2019-06-29T18:31:49","date_gmt":"2019-06-29T10:31:49","guid":{"rendered":"http:\/\/mayanknauni.com\/?p=37"},"modified":"2019-06-29T18:31:49","modified_gmt":"2019-06-29T10:31:49","slug":"active-active-data-centers-network-architects-perspective","status":"publish","type":"post","link":"https:\/\/mayanknauni.com\/?p=37","title":{"rendered":"Active-Active Data Centers \u2013 Network Architect\u2019s Perspective"},"content":{"rendered":"

Disclaimer:- This note was written by me ( Mayank Nauni)\u00a0in my personal capacity. The opinions expressed in this article are solely my own and do not reflect the view of my employer or my preference towards any of the OEMs.<\/em><\/strong><\/p>\n

The first thing I hear from a lot of network architects after we talk about active\/active Data Centers is \u201cGlobal Traffic Load Balancers\u201d … and that is it! I believe it is one of the component of an active\/active DC, quite important component though, but we seem to be not noticing the elephant in the room and setting the wrong expectations with the design at the same time.<\/p>\n

Let us understand a bit about active\/active DCs. There are two kind of active\/active DCs:-<\/p>\n

1.\u00a0\u00a0\u00a0\u00a0\u00a0Active\/Active DC Infrastructure<\/p>\n

2.\u00a0\u00a0\u00a0\u00a0\u00a0Active\/Active application infrastructure<\/p>\n

In order to have an active\/active application setup, we must first have active\/active data center infrastructure (network is just one key component of active\/active DC).\u00a0An active\/active DC can be divided into two halves from purely network\u2019s perspective:-<\/p>\n

\u00b7\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Ingress Traffic<\/p>\n

\u00b7\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Egress Traffic<\/p>\n

Ingress Traffic:-<\/strong> Global Traffic Managers (Intelligent DNS) to your rescue, wouldn\u2019t go into the details but most common configuration used here is priority based ( yet to see a round-robin deployment as calling DC active\/active is a jargon rather and one DC still tends to be more \u201cactive\u201d than other owing to infra sizing and hence attracting more ingress traffic).<\/p>\n

Egress Traffic: –<\/strong> Here is the tricky part though IGPs in the internal network and BGP on the core helps to some extent but still not considered to be a viable solution. Quite often we experience \u201cTraffic Tromboning Effect\u201d for the traffic but modern day network infra has been addressing this from quite some time, different names by OEM but it is anycast IP gateway with LISP<\/strong> if I had simplify it, not to mention overlays like VxLAN have been simplifying it for us.\u00a0I did consider \u201cFirewall Clustering\u201d between DCs once, but it seems to be a complex deployment and prone to run into a race condition if DCI goes down, firewall cluster was more to address the issue caused by VMs flying around the DCs due to Vmotion and outbound traffic getting dropped by the firewalls as this session is maintained by the other firewall (when not operating in cluster).<\/p>\n

So active\/active network ( GTM+ stretched L2\/L3 with anycast gateway+BGP outbound load sharing) achieves high availability and a true active\/active DC?\u00a0The answer is \u201cNo\u201d.\u00a0Then from the business perspective why would I even invest a hefty sum on it? The answer is, \u201cit is one of the indispensable and core component of active\/active DC and serves as the first building block or rather as the foundation itself”.<\/p>\n

What are the core components of Active\/Active DC:-<\/p>\n