How important is encrypting traffic that never leaves a data center?

To me, it seems both important and (thanks to IPsec) easy to achieve. However, it seems to rarely be done; Google does not do it, for example.

How important is encryption traffic within a data center, and why is it so rarely done, even when the needed infrastructure is already in place?

  • 1
    There are lots of variables here. A data centre might refer to a few servers in one rack owned by one company. Or it might mean thousands of servers shared between multiple customers. We could be talking one small network, a medium size routed network or multiple networks peering by BGP. Some clarification would help. – David Oct 7 '18 at 21:54
  • @David I was mostly thinking of the cloud provider case (thousands of servers owned by the same company), but am also interested in the other cases you mentioned. – Demi Oct 7 '18 at 21:57

Encrypting internal data is important when there are multiple trust zones in the data centre.

The most common trust zones can come about from having multiple companies sharing a data centre. Having a network encryption ensures that in the event that packets going to one machine ends up arriving at the wrong one, they'll be in a form that's unreadable to tenants from different trust zones.

However even if a single company owns the entire data centre, usually a large companies are composed of multiple departments and it's often necessary for a security conscious company to enforce internal boundaries. For example, Accounting systems may be segregated from HR systems except through a number of predefined exchange points that can be monitored.

Another common reason why you want internal encryption is to protect from physical attacks, from interception of cables between machines. In a large data centre, you will have cables going from many different directions. You may not want the cleaning service staffs to have access to the locked server racks, but you may have cables that need to cross racks. When a data centre gets sufficiently complicated, it can be difficult to keep track of which cable needs to go where and which needs to be encrypted, so having a global must-encrypt policy can actually reduce the load on decision making process. In another scenario, you may want to enforce a two man rule where nobody can have physical access to a machine alone. Encrypting the local traffic can reduce the amount of zones that would be considered a two-man zones.


I think it depends upon your company's security goals and risk assessment. Are you happy to own the risk? In a worst case scenario where your data gets snooped upon or stolen, what will be the impact on your business? How important is your data?

Take these factors into consideration during planning.


Think about why we encrypt network (or what threats does encryption address?). The answer is to avoid someone in the middle to capture/modify the data. Encryption ensures even if the packets are captured, they are of no use to the attacker.

If you trust your data center network (trusted zone) and you have assurance no one will sniff within your data center network, you may not need to encrypt the traffic.

The traffic leaves your data center is entering the non-trusted zone, hence we are encrypting it with help of IPSEC, etc.

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