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Category Archives for "Networking"

The DNS Negative Cache

Considering the DNS query chain—

  • A host queries a local recursive server to find out about banana.example
  • The server queries the root server, then recursively the authoritative server, looking for this domain name
  • banana.example does not exist

There are two possible responses in this chain of queries, actually. .example might not exist at all. In this case, the root server will return a server not found error. On the other hand, .example might exist, but banana.example might not exist; in this case, the authoritative server is going to return an NXDOMAIN record indicating the subdomain does not exist.

Assume another hosts, a few moments later, also queries for banana.example. Should the recursive server request the same information all over again for this second query? It will unless it caches the failure of the first query—this is the negative cache. This negative cache reduces load on the overall system, but it can also be considered a bug.

Take, for instance, the case where you set up a new server, assign it banana.example, jump to a host and try to connect to the new server before the new DNS information has been propagated through the system. On Continue reading

Demand for managed SD-WAN services skyrockets

Demand for SD-WAN delivered as a managed service is exploding as customers see the benefits that SD-WAN can bring to their distributed organizations.For example, communications service providers (CSPs) such as Verizon, NTT, and BT all report strong demand for SD-WAN services. Plus, hundreds of other CSPs, cable providers (e.g. Comcast), managed service providers (MSPs), and system integrators have recently deployed new SD-WAN services.Also on Network World: SD-WAN: What is it and why you’ll use it one day | How to make the transition to SD-WAN We also see that managed SD-WAN revenues are growing rapidly as they displace traditional managed WAN services (e.g. private lines and MPLS) — an addressable market of over $40 billion in business services.To read this article in full, please click here

Demand for managed SD-WAN services skyrockets

Demand for SD-WAN delivered as a managed service is exploding as customers see the benefits that SD-WAN can bring to their distributed organizations.For example, communications service providers (CSPs) such as Verizon, NTT, and BT all report strong demand for SD-WAN services. Plus, hundreds of other CSPs, cable providers (e.g. Comcast), managed service providers (MSPs), and system integrators have recently deployed new SD-WAN services.Also on Network World: SD-WAN: What is it and why you’ll use it one day | How to make the transition to SD-WAN We also see that managed SD-WAN revenues are growing rapidly as they displace traditional managed WAN services (e.g. private lines and MPLS) — an addressable market of over $40 billion in business services.To read this article in full, please click here

BrandPost: The New SD-WAN Edge Enables Improved Security Architectures

With the beginning of the new year, it’s popular to opine on what the new year might bring in terms of technology advances. My predictions for the WAN in 2018 have been covered in several publications here, here and here. In this blog, I’m going to expand on one of my predictions: how the new WAN edge enables improved security architectures. I believe there are three primary ways the new WAN edge will enable improved security architectures for enterprises building an SD-WAN.To read this article in full, please click here

EVPN Is More than VPLS on Steroids

Tiziano Tofoni wrote a lengthy comment on my EVPN in small data center fabrics blog post continuing the excellent discussion we started over a beer last October. Today I’ll address the first part:

I think that EVPN is an excellent standard for those who love Layer 2 (L2) services, we may say that it is an evolution of the implementation of the VPLS service, which addresses some limits in the original standard (RFCs 4761 and 4762).

I might be missing something, but in my opinion there’s no similarity between EVPN and VPLS (apart from the fact that they’re trying to solve the same problem).

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