Category: MPLS

Here’s a question I got from someone attending the Building Next-Generation Data Center online course:

Cisco NCS5000 is positioned as a building block for a data center MPLS fabric – a leaf-and-spine fabric with MPLS and EVPN control plane. This raised a question regarding MPLS vs VXLAN: why would one choose to build an MPLS-based fabric instead of a VXLAN-based one assuming hardware costs are similar?

There’s a fundamental difference between MPLS- and VXLAN-based transport: the amount of coupling between edge and core devices.

Mr. Anonymous (my most loyal reader and commentator) sent me this question as a comment to one of my blog posts:

Is there any use case of running EVPN (or PBB EVPN) in DC with MPLS Data Plane, most vendors seems to be only implementing NVO to my understanding.

Sure there is: you already have MPLS control plane and want to leverage the investment.

Rich sent me a question about temporary traffic blackholing in networks where every router is running IGP (OSPF or IS-IS) and iBGP.

He started with a very simple network diagram:

Continuing the Do Enterprises Need VRFs discussion, let’s see which enterprise networks might need MPLS.

Do you need VRFs?

Read the previous blog post. If the answer is NO, you can stop reading. Otherwise, carry on.

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.

Julian Lucek did a fantastic job describing how NorthStar controller uses BGP-LS and PCEP, so I asked him whether he’d be willing to do a deep dive on these two topics. He gracefully agreed, and the results are already online.

Content providers were using centralized traffic flow optimization together with MPLS TE for at least 15 years (some of them immediately after Cisco launched the early MPLS-TE implementation in their 12.0(5)T release), but it was always hard to push the results into the network devices.

PCEP and BGP-LS all changed that – they give you a standard mechanism to extract network topology and install end-to-end paths across the network, as Julian Lucek of Juniper Networks explained in Episode 43 of Software Gone Wild.

One of my readers was having an LDP argument with his colleague:

Yesterday I was arguing with someone who works for a large MPLS provider about LDP label allocation. He kept saying that LDP assigns a label to each next-hop, not to each prefix. Reading your blog, I believe this is the default behavior on Juniper but on Cisco LDP assigns a unique label for each IGP (non-BGP) prefix.

He’s absolutely right; Cisco and Juniper use different rules when allocating MPLS labels.

In the final part of our MPLS-focused discussion (now part of MPLS Essentials webinar), Seamus wanted to know how one could combine MPLS/VPN, MPLS-TE and QoS (for example, sending VoIP traffic for one customer over a different path).

Short answer: don’t even think about doing that. The added complexity is not worth whatever extra money you’ll be charging the customer (or not).

Load sharing in MPLS networks is always an interesting topic, and we couldn’t possibly avoid it during our MPLS-focused Tech Talks – watch the video.

After discussing the load sharing intricacies we briefly dabbled with the concept of entropy labels.