Category: traffic engineering

You can use SR-MPLS, MPLS-TE, or an SDN controller to build virtual circuits (label-switched paths) across the network core. The controller can push the LSPs into network devices with PCEP, BGP-LU, or some sort of NETCONF/RESTCONF trickery.

Unfortunately, you’re only half done once you have installed the LSPs. You still have to persuade the network devices to use them. Welcome to the confusing world of traffic steering explored in the Loopback as a Service blog post by Dmytro Shypovalov.

Dmytro Shypovalov wrote a great series of detailed posts on Egress Peer Engineering:

• Poor Man’s Traffic Engineering
• Egress Peer Engineering: Basics
• Egress Peer Engineering: Building Blocks

Have fun!

Vendor product managers love discussing mythical use cases to warrant complex functionality in their gear. Long-distance VM mobility was one of those (using it for disaster avoidance was Mission Impossible under any real-world assumptions), and high-volume network-based backups seems to be another. Here’s what someone had to say about that particular unicorn in a LinkedIn comment when discussing whether we need traffic engineering in a data center fabric.

When you’re dealing with a large cluster on a fabric, you will see things like inband backup. The most common one I’ve seen is VEEAM. Those inband backups can flood a single link, and no amount of link scheduling really solves that; depending on the source, they can saturate 100G. There are a couple of solutions; IPv6 or eBGP SID has been used to avoid these links or schedule avoidance for other traffic.

It is true that (A) in-band backups can be bandwidth intensive and that (B) well-written applications can saturate 100G server links. However:

Bruce Davie continues documenting the tradeoffs we had to make in networking, this time with Was MPLS Traffic Engineering Worthwhile? I found this bit particularly familiar:

It wasn’t hard to make a theoretical argument that MPLS-TE could improve network performance and average link utilization, by moving traffic from congested links to uncongested ones. The hard part was proving that it would actually do a better job in practice than the more traditional methods such as using link weights and multipath routing to achieve the same ends.

Last week I published a link to Pete Crocker’s RSVP-TE lab, but there’s more: he created another lab using the same topology that uses SR-MPLS with IS-IS to get the job done.

Jeroen Van Bemmel did something similar for SR Linux: his lab topology has fewer devices (plus SR Linux runs in containers), so it’s easily deployable on machines without humongous amount of memory.

It’s amazing how creative networking engineers become once they have the basic tools to get the job done a bit quicker. Last week Pete Crocker published the largest topology I’ve seen built with netlab so far: a 13-router lab running RSVP TE to transport IP traffic between external autonomous systems¹.

A while ago Russ White (answering a reader question) mentioned some areas where we might find machine learning useful in networking:

If we are talking about the overlay, or traffic engineering, or even quality of service, I think we will see a rising trend towards using machine learning in network environments to help solve those problems. I am not convinced machine learning can solve these problems, in the sense of leaving humans out of the loop, but humans could set the parameters up, let the neural network learn the flows, and then let the machine adjust things over time. I tend to think this kind of work will be pretty narrow for a long time to come.

Guess what: as fancy as it sounds, we don’t need machine learning to solve those problems.

Julien Lucek concluded his PCEP and BGP-LS webinar with a lengthy Q&A session addressing all sorts of questions from the audience (to access all videos in this webinar, register here).

The moment an IETF working group agrees on a protocol someone starts creating extensions. PCEP is no exception; in the last part of the BGP-LS and PCEP webinar Julian Lucek talked about some of them.

After covering the details of PCEP protocol in the BGP-LS and PCEP Deep Dive webinar Julian Lucek focused on how a controller would use PCEP to build MPLS TE paths across a network.

Oh, and don’t forget to explore the rest of the PCEP webinar and other SDN webinars after watching the video ;)

Oliver Steudler from Juniper sent me a link to an interesting Juniper blog post describing zero-bandwidth traffic engineering.

Read the blog post first and then come back for some opinionated rambling ;)

Is the problem real? Yes.

After explaining the basics of BGP-LS and PCEP, and a quick deep dive into BGP-LS, Julian Lucek focused on the second topic of his excellent webinar and described the details of Path Computation Element Protocol (PCEP).

My good friend Tiziano Tofoni (the organizer of wonderful autumn seminars in Rome) sent me these questions after attending the BGP-LS and PCEP Deep Dive webinar, starting with:

Are there real use cases for BGP-LS and PCEP? Are they really useful? Personally I do not think they will ever be used by ISP in their (large) networks.

There are some ISPs that actually care about the network utilization on their expensive long-distance links.

After explaining why you’d want to use BGP-LS and PCEP in your network, Julian Lucek did a quick deep dive into the intricacies of BGP-LS, including printouts relating BGP-LS updates to IS-IS topology database.

This part of the PCEP/BGP-LS webinar is already public, to watch the rest of it fill in a short form on the webinar description page.

I was often asked about two emerging technologies that enable standard controller-based WAN traffic engineering: BGP-LS to extract the network topology and PCEP to establish end-to-end tunnels from a controller.

Unfortunately, I never found time to explore these emerging technologies and develop a webinar. However, after Julian Lucek from Juniper did such a great job on the NorthStar podcast, I asked him whether he would be willing to do a deep dive technology webinar on the two technologies and he graciously agreed to do it.