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Category: QoS

Routing Protocols and SD-WAN: Apples and Furbies

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.

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Overlay-to-Underlay Network Interactions: Document Your Hidden Assumptions

If you listen to the marketing departments of overlay virtual networking vendors, it looks like the world is a simple place: you deploy their solution on top of any IP fabric, and it all works.

You’ll hear a totally different story from the physical hardware vendors: they’ll happily serve you a healthy portion of FUD, hoping you swallow it whole, and describe in gory details all the mishaps you might encounter on your virtualization quest.

The funny thing is they’re all right (not to mention the really fun part when FUDders change sides ;).

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Can We Just Throw More Bandwidth at a Problem?

One of my readers sent me an interesting question:

I have been reading at many places about "throwing more bandwidth at the problem." How far is this statement valid? Should the applications(servers) work with the assumption that there is infinite bandwidth provided at the fabric level?

Moore’s law works in our favor. It’s already cheaper (in some environments) to add bandwidth than to deploy QoS.

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FCoE and Nexus 1000v QoS

One of my readers wanted to deploy FCoE on UCS in combination with Nexus 1000v and wondered how the FCoE traffic impacts QoS on Nexus 1000v. He wrote:

Let's say I want 4Gb for FCoE. Should I add bandwidth shares up to 60% in the nexus 1000v CBWFQ config so that 40% are in the default-class as 1kv is not aware of FCoE traffic? Or add up to 100% with the assumption that the 1kv knows there is only 6Gb left for network? Also, will the Nexus 1000v be able to detect contention on the uplink even if it doesn't see the FCoE traffic?

As always, things aren’t as simple as they look.

You know Nexus 1000v is dead, right? This blog post was left online for historic reasons ;)
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Queuing Mechanisms in Modern Switches

A long while ago there was an interesting discussion started by Brad Hedlund (then at Dell Force10) comparing leaf-and-spine (Clos) fabrics built from fixed-configuration pizza box switches with high-end chassis switches. The comments made by other readers were all over the place (addressing pricing, wiring, power consumption) but surprisingly nobody addressed the queuing issues.

This blog post focuses on queuing mechanisms available within a switch; the next one will address end-to-end queuing issues in leaf-and-spine fabrics.

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RSVP over DMVPN

A while ago Tomasz Kacprzynski asked me whether I'd ever run RSVP over DMVPN. I hadn't - after all, you'd only need that in VoIP environments and I try to stay as far away from voice as possible.

In the meantime, Tomasz solved the problem (short summary: you have to turn Phase 3 DMVPN into Phase 2 DMVPN) and wrote a lengthy blog post describing the problem (RSVP split horizon rule) and his solution (including numerous debugging printouts). Definitely worth reading if there's a non-zero chance you'll have to get the two working together.

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Juniper MX Routers – all you ever wanted to know

During a recent ExpertExpress engagement I got an interesting question: “could we do per-customer policing and shaping on an MX-80 if we want to offer VPLS services and have Q-in-Q encapsulation on customer-facing links?” As I have preciously little Junos/MX knowledge, it was time for the classic “I’ll get back to you” reply and some heavy research.

You probably know how hard it is to find in-depth information on an unknown platform running unfamiliar software. Fortunately, Doug Hanks (@douglashanksjr) sent me a review copy of his new Juniper MX Series book a while ago. It was time for some serious reading.

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