D2C234: What to Do About VMware

Broadcom’s acquisition of VMware has generated a lot of anxiety among VMware customers. In this episode, we closely analyze the situation. First, we look at Broadcom’s past acquisitions in the infrastructure sector. Then we examine the product alignment and possible new product offerings and whether the acquisition will hamper innovation and development. We also cover... Read more »

Implementing ‘Undo’ Functionality in Network Automation

Kurt Wauters sent me an interesting challenge: how do we do rollbacks based on customer requests? Here’s a typical scenario:

You might have deployed a change that works perfectly fine from a network perspective but broke a customer application (for example, due to undocumented usage), so you must be able to return to the previous state even if everything works. Everybody says you need to “roll forward” (improve your change so it works), but you don’t always have that luxury and might need to take a step back. So, change tracking is essential.

He’s right: the undo functionality we take for granted in consumer software (for example, Microsoft Word) has totally spoiled us.

Implementing ‘Undo’ Functionality in Network Automation

Kurt Wauters sent me an interesting challenge: how do we do rollbacks based on customer requests? Here’s a typical scenario:

You might have deployed a change that works perfectly fine from a network perspective but broke a customer application (for example, due to undocumented usage), so you must be able to return to the previous state even if everything works. Everybody says you need to “roll forward” (improve your change so it works), but you don’t always have that luxury and might need to take a step back. So, change tracking is essential.

He’s right: the undo functionality we take for granted in consumer software (for example, Microsoft Word) has totally spoiled us.

OSC Blends Intel HBM CPUs And Nvidia HBM GPUs For “Cardinal” Supercomputer

For a lot of state universities in the United States, and their equivalent political organizations of regions or provinces in other nations across the globe, it is a lot easier to find extremely interested undergraduate and graduate students who want to contribute to the font of knowledge in high performance computing than it is to find the budget to build a top-notch supercomputer of reasonable scale.

OSC Blends Intel HBM CPUs And Nvidia HBM GPUs For “Cardinal” Supercomputer was written by Timothy Prickett Morgan at The Next Platform.

Why Is BFD More Light Weight Than Routing Hellos?

There are many articles on BFD. It is well known that BFD has the following advantages over routing protocol hellos/keepalives:

  • BFD is more light weight than hellos/keepalives.
  • Multiple clients can register to BFD instead of configuring each protocol with aggressive timers.
  • On some platforms, BFD can be offloaded to the hardware instead of the CPU.
  • BFD provides faster timers than routing protocols.
  • BFD is less CPU intensive.

What does light weight mean, though? Does it mean that the packets are smaller? Let’s compare a BFD packet to an OSPF Hello. Starting with the OSPF Hello:

Frame 269: 114 bytes on wire (912 bits), 114 bytes captured (912 bits) on interface ens192, id 1
Ethernet II, Src: 00:50:56:ad:8d:3c, Dst: 01:00:5e:00:00:05
Internet Protocol Version 4, Src: 203.0.113.0, Dst: 224.0.0.5
Open Shortest Path First
    OSPF Header
        Version: 2
        Message Type: Hello Packet (1)
        Packet Length: 48
        Source OSPF Router: 192.168.128.223
        Area ID: 0.0.0.0 (Backbone)
        Checksum: 0x7193 [correct]
        Auth Type: Null (0)
        Auth Data (none): 0000000000000000
    OSPF Hello Packet
    OSPF LLS Data Block

There’s 114 bytes on the wire consisting of:

Applying BGP Policy Templates

I got this question after publishing the BGP Session Templates lab exercise:

Would you apply BGP route maps with a peer/policy template or directly to a BGP neighbor? Of course, it depends; however, I believe in using a template for neighbors with the same general parameters and being more specific per neighbor when it comes to route manipulation.

As my reader already pointed out, the correct answer is It Depends, now let’s dig into the details ;)

Applying BGP Policy Templates

I got this question after publishing the BGP Session Templates lab exercise:

Would you apply BGP route maps with a peer/policy template or directly to a BGP neighbor? Of course, it depends; however, I believe in using a template for neighbors with the same general parameters and being more specific per neighbor when it comes to route manipulation.

As my reader already pointed out, the correct answer is It Depends, now let’s dig into the details ;)

Network Layer: Interface or Node Addresses

The fun question about network layer addresses is: are we addressing nodes or individual node interfaces? On the data link layer, we never had this issue because it was obvious that a data link layer endpoint is an interface, so each interface should have a unique data link layer address.

Interestingly, that’s not the case on transparent bridges. Even though they have multiple interfaces, the whole bridge has a single MAC address, so one could claim we’re addressing nodes connected to a single data link layer. The IEEE standard is unambiguous: in every relevant diagram, the MAC address sits on top of multiple interfaces because the MAC address belongs to the control plane.

Network Layer: Interface or Node Addresses

The fun question about network layer addresses is: are we addressing nodes or individual node interfaces? On the data link layer, we never had this issue because it was obvious that a data link layer endpoint is an interface, so each interface should have a unique data link layer address.

Interestingly, that’s not the case on transparent bridges. Even though they have multiple interfaces, the whole bridge has a single MAC address, so one could claim we’re addressing nodes connected to a single data link layer. The IEEE standard is unambiguous: in every relevant diagram, the MAC address sits on top of multiple interfaces because the MAC address belongs to the control plane.

All you need to know about the Digital Services Act

February 17th, 2024 marked the entry into force of a landmark piece of European Union (EU) legislation, affecting European users who create and disseminate online content as well as tech companies who act as “intermediaries” on the Internet. I am talking of course about the EU Digital Services Act, or DSA for short. The DSA was first proposed in December 2020, and is meant to update a 20-year-old law called the EU e-commerce Directive, which provides important safeguards and legal certainty for all businesses operating online. The principles of that legal framework, most notably the introduction of EU-wide rules on intermediary liability, are still of major importance today. The DSA is a landmark piece of European legislation because it also sets out, for the first time, enhanced regulatory requirements for (large) digital platforms, thus affecting the entire Internet ecosystem.

At Cloudflare, we are supportive of the longstanding legal frameworks both in Europe and other parts of the world that protect Internet companies from liability for the content that is uploaded or sent through their networks by their users, subscribers or customers. These frameworks are indispensable for the growth of online services, and have been essential in the growth Continue reading

Catalyst SD-WAN Enhanced Application Aware Routing

Traditionally, Cisco has leveraged BFD to monitor tunnels and their performance and Application Aware Routing (AAR) to reroute traffic. BFD has been used to measure:

  • Latency.
  • Loss.
  • Jitter.

Additionally, BFD is also used to verify liveliness of the tunnels. This works well, but there are some drawbacks to using a separate protocol for measuring performance:

  • You are adding control plane packets competing for bandwidth with packets in data plane.
  • Sending control plane packets frequently may overload the control plane.
    • This may lead to false positives.
  • It’s not guaranteed that control plane packets and data plane packets are treated equally.
  • AAR did take some time to react to poor transports as it had to collect enough measurements before reacting.
  • AAR didn’t have a built-in dampening mechanism.

With the default BFD settings, BFD packets are sent every second. The default AAR configuration consists of six buckets that hold 10 minutes of data each. This means that with the default settings, AAR will react in 10-60 minutes depending on how poorly the transport is performing. The most aggressive AAR configuration recommended by Cisco was to have 5 buckets holding 2 minutes of data each. AAR would then react in 2-10 minutes which I Continue reading