Category: WAN

You might remember the great idea David Barroso had last autumn – turn an Arista switch into an Internet edge router (SDN Internet Router – SIR). In the meantime, he implemented that solution in production environment serving high-speed links at multiple Internet exchange points. It was obviously time for another podcast on the same topic.

Another week, another ExpertExpress session, as is often the case focusing on two data centers with stretched VLANs spanning both of them. However, this one was particularly irksome, as the customer ran a firewall cluster stretched across two locations.

I gave the customer engineers my usual recommendations:

When I wrote my stretched VSAN post, I thought VSAN uses asynchronous replication across WAN. Duncan Epping quickly pointed out that it uses synchronous replication, and I fixed the blog post.

The “What about latency?” question immediately arose somewhere in my subconscious, but before I could add that thought to the blog post, Anders Henke wrote a lengthy comment that totally captured what I was thinking, so I’m including it in its entirety:

When I asked “Are there any truly QoS-aware routing protocols out there?” in one of my SD-WAN posts, Marcelo Spohn from ADARA Networks quickly pointed out that they have one – Dynamic Link-State Routing Protocol.

He also claimed that DLSP has no scalability concerns – more than enough reasons to schedule an online chat, resulting in Episode 40 of Software Gone Wild. We didn’t go too deep this time, but you should get a nice overview of what DLSP is and how it works.

One of my readers recently pointed me to a blog post written by Andrew Lerner from Gartner describing the drawbacks of stretched VLANs.

TL&DR: He’s saying more-or-less the same things I’ve been preaching for years. Now I can put Blessed by Gartner logo on my blog posts ;), and you can use the report to sway your CIO.

My Business Case for SD-WAN blog post received numerous comments pointing out the potential pitfalls of hybrid WAN, including reduced security, unreliable Internet services and denial-of-service attacks.

While all those comments are perfectly valid, I still think hybrid WAN (whether implemented with traditional technologies or SD-WAN products) makes perfect sense.

One of my readers sent me an interesting reliability design question. It all started with a catastrophic WAN failure:

Once a particular volume of encrypted traffic was reached the data center WAN edge router crashed, and then the backup router took over, which also crashed. The traffic then failed over to the second DC, and you can guess what happened then...

Obviously they’re now trying to redesign the network to avoid such failures.

Ethan Banks recently wrote a nice blog post detailing the benefits and drawbacks of traditional routing protocols and comparing them with their SD-WAN counterparts.

While I agree with everything he wrote, the comparison between the two isn’t exactly fair – it’s a bit like trying to cut the cheese with a chainsaw and complaining about the resulting waste.

An anonymous commenter wrote this comment to my initial SD-WAN post:

I can still hardly imagine the business case behind SD-WAN. Any thoughts?

This question is really easy to answer. There’s a huge business case that SD-WAN products are aiming to solve: replacing traditional MPLS/VPN networks with encrypted transport over public Internet. However…

One of the Software Defined Evangelists has declared 2015 as the Year of SD-WAN, and my podcast feeds are full of startups explaining how wonderful their product is compared to the mess made by legacy routers, so one has to wonder: is SD-WAN really something fundamentally new, or is it just another old idea in new clothes?