Category: MPLS

Using MPLS+EVPN in Data Center Fabrics

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.

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Why Would You Need BGP-LS and 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.

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Optimizing Traffic Engineering with NorthStar Controller on Software Gone Wild

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.

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LDP Label Allocation Revisited

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.

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Combining MPLS/VPN, MPLS-TE and QoS on MPLS Talks

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).

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