Video: Kubernetes Architecture

Yesterday I mentioned the giant glob of complexity called Kubernetes (see also more nuanced take on the topic). If you want to slowly unravel it, Kubernetes Architecture video from the excellent Kubernetes Networking Deep Dive webinar by Stuart Charlton is a pretty good starting point.

MTU Settings in Virtual Network Devices

When I finally¹ managed to get SR Linux running with netsim-tools, I wanted to test how it interacts with Cumulus VX and FRR in an OSPF+BGP lab… and failed. Jeroen Van Bemmel quickly identified the culprit: MTU. Yeah, it’s always the MTU (or DNS, or BGP).

I never experienced a similar problem, so of course I had to identify the root cause:

MTU Settings in Virtual Network Devices

When I finally¹ managed to get SR Linux running with netlab, I wanted to test how it interacts with Cumulus VX and FRR in an OSPF+BGP lab… and failed. Jeroen Van Bemmel quickly identified the culprit: MTU. Yeah, it’s always the MTU (or DNS, or BGP).

I never experienced a similar problem, so of course I had to identify the root cause:

Three Dimensions of BGP Address Family Nerd Knobs

Got into an interesting BGP discussion a few days ago, resulting in a wild chase through recent SRv6 and BGP drafts and RFCs. You might find the results mildly interesting ;)

BGP has three dimensions of address family configurability:

• Transport sessions. Most vendors implement BGP over TCP over IPv4 and IPv6. I’m sure there’s someone out there running BGP over CLNS¹, and there are already drafts proposing running BGP over QUIC².
• Address families enabled on individual transport sessions, more precisely a combination of Address Family Identifier (AFI) and Subsequent Address Family Identifier.
• Next hops address family for enabled address families.

Three Dimensions of BGP Address Family Nerd Knobs

Got into an interesting BGP discussion a few days ago, resulting in a wild chase through recent SRv6 and BGP drafts and RFCs. You might find the results mildly interesting ;)

BGP has three dimensions of address family configurability:

• Transport sessions. Most vendors implement BGP over TCP over IPv4 and IPv6. I’m sure there’s someone out there running BGP over CLNS¹, and there are already drafts proposing running BGP over QUIC².
• Address families enabled on individual transport sessions, more precisely a combination of Address Family Identifier (AFI) and Subsequent Address Family Identifier.
• Next hops address family for enabled address families.

More: Hardware Differences between Routers and Switches

Aaron Glenn sent me his thoughts on hardware differences between routers and switches based on the last paragraph of Dmytro Shypovalov’s views on the topic

To conclude, what is the difference between routers and switches in my opinion? I have absolutely no idea.

More: Hardware Differences between Routers and Switches

Aaron Glenn sent me his thoughts on hardware differences between routers and switches based on the last paragraph of Dmytro Shypovalov’s views on the topic

To conclude, what is the difference between routers and switches in my opinion? I have absolutely no idea.

Sample Lab: RSVP TE on Junos

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 netsim-tools so far: a 13-router lab running RSVP TE to transport IP traffic between external autonomous systems¹.

Sample Lab: RSVP TE on Junos

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.

Video: Machine Learning Techniques

After Javier Antich walked us through the AI/ML hype and described the basics of machine learning it was time for a more thorough look at:

• Machine learning techniques, including unsupervised learning (clustering and anomaly detection), supervised learning (regression, classification and generation) and reinforced learning
• Machine learning implementations, including neural networks, deep neural networks and convolutional neural networks.

Video: Machine Learning Techniques

After Javier Antich walked us through the AI/ML hype and described the basics of machine learning it was time for a more thorough look at:

• Machine learning techniques, including unsupervised learning (clustering and anomaly detection), supervised learning (regression, classification and generation) and reinforced learning
• Machine learning implementations, including neural networks, deep neural networks and convolutional neural networks.

Introducing netsim-tools Plugins

Remember the BGP anycast lab I described in December 2021? In that blog post I briefly mentioned a problem of extraneous IBGP sessions and promised to address it at a later date. Let’s see how we can fix that with netsim-tools plugin.

We always knew that it’s impossible to implement every nerd knob someone would like to have when building their labs, and extending the tool with Python plugins seemed like the only sane way to go. We added custom plugins to netsim-tools release 1.0.6, but I didn’t want to write about them because we had to optimize the internal data structures first.

Introducing netlab Plugins

Remember the BGP anycast lab I described in December 2021? In that blog post I briefly mentioned a problem of extraneous IBGP sessions and promised to address it at a later date. Let’s see how we can fix that with a netlab plugin.

We always knew that it’s impossible to implement every nerd knob someone would like to have when building their labs, and extending the tool with Python plugins seemed like the only sane way to go. We added custom plugins to netlab in late 2021, but I didn’t want to write about them because we had to optimize the internal data structures first.

Layer-3 Carrier Ethernet

One of ipSpace.net subscribers asked for my opinion about Adaptive IP, a concept promoted by one of the optical connectivity vendors. As he put it:

My interest in Carrier Ethernet moving up to Layer 3 is to see if it would be something to account for in the future.

A quick search resulted in a marketecture using Segment Routing (of course) and an SDN controller (what else could one be using today) using Path Computation Element Protocol (PCEP) to program the network devices… and then I hit a regwall. They wanted to collect my personal details to grace me with their whitepaper, and I couldn’t find even a link to the product documentation.

Layer-3 Carrier Ethernet

One of ipSpace.net subscribers asked for my opinion about Adaptive IP, a concept promoted by one of the optical connectivity vendors. As he put it:

My interest in Carrier Ethernet moving up to Layer 3 is to see if it would be something to account for in the future.

A quick search resulted in a marketecture using Segment Routing (of course) and an SDN controller (what else could one be using today) using Path Computation Element Protocol (PCEP) to program the network devices… and then I hit a regwall. They wanted to collect my personal details to grace me with their whitepaper, and I couldn’t find even a link to the product documentation.

Running IS-IS over Unnumbered Ethernet Interfaces

Last time we figured out that we cannot run OSPF over unnumbered interfaces that are not point-to-point links because OSPF makes assumptions about interface IP addresses. IS-IS makes no such assumptions; IPv4 and IPv6 prefixes are just a bunch of TLVs exchanged between routers over a dedicated layer-3 protocol with ridiculously long network addresses.

Could we thus build a totally unnumbered IP network with IS-IS even when the network contains multi-access segments? It depends:

Running IS-IS over Unnumbered Ethernet Interfaces

Last time we figured out that we cannot run OSPF over unnumbered interfaces that are not point-to-point links because OSPF makes assumptions about interface IP addresses. IS-IS makes no such assumptions; IPv4 and IPv6 prefixes are just a bunch of TLVs exchanged between routers over a dedicated layer-3 protocol with ridiculously long network addresses.

Could we thus build a totally unnumbered IP network with IS-IS even when the network contains multi-access segments? It depends:

Video: Local Area Network Addressing

In the Local Area Network Addressing video (part of How Networks Really Work webinar) I covered numerous obscure LAN addressing details including:

• There’s no layer-2 address in Fibre Channel frames (because FC is routing not bridging);
• Why is the multicast bit lowest bit (0x01) in first byte on Ethernet but highest bit (0x80) on Token Ring or FDDI;
• How some NIC manufacturers never got the memo on what OUI really means.

Video: Local Area Network Addressing

In the Local Area Network Addressing video (part of How Networks Really Work webinar) I covered numerous obscure LAN addressing details including:

• There’s no layer-2 address in Fibre Channel frames (because FC is routing not bridging);
• Why is the multicast bit the lowest bit (0x01) in the first byte on Ethernet but the highest bit (0x80) on Token Ring or FDDI;
• How some NIC manufacturers never got the memo on what OUI really means.

Feedback: Recursive BGP Next Hop Resolution

The Recursive BGP Next Hops: an RFC 4271 Quirk blog post generated tons of feedback (thanks a million to everyone writing a comment on my blog or LinkedIn).

Starting with Robert Razsuk who managed to track down the original email that triggered the (maybe dubious) text in RFC 4271:

The text in section 5.1.3 was not really targeting to prohibit load balancing. Keep in mind that it is FIB layer which constructs actual forwarding paths.

The text has been suggested by Tom Petch in discussion about BGP advertising valid paths or even paths it actually installs in the RIB/FIB. The entire section 5.1.3 is about rules when advertising paths by BGP.