Video: Kubernetes Principles

After answering the “why should I care about Kubernetes?” question, Stuart Charlton explained the Kubernetes principles you should keep in mind if you want to have a chance of understanding what’s going on.

Local TCP Anycast Is Really Hard

Pete Lumbis and Network Ninja mentioned an interesting Unequal-Cost Multipathing (UCMP) data center use case in their comments to my UCMP-related blog posts: anycast servers.

Here’s a typical scenario they mentioned: a bunch of servers, randomly connected to multiple leaf switches, is offering a service on the same IP address (that’s where anycast comes from).

Local TCP Anycast Is Really Hard

Pete Lumbis and Network Ninja mentioned an interesting Unequal-Cost Multipathing (UCMP) data center use case in their comments to my UCMP-related blog posts: anycast servers.

Here’s a typical scenario they mentioned: a bunch of servers, randomly connected to multiple leaf switches, is offering a service on the same IP address (that’s where anycast comes from).

Packet Forwarding and Routing over Unnumbered Interfaces

In the previous blog posts in this series, we explored whether we need addresses on point-to-point links (TL&DR: no), whether it’s better to have interface or node addresses (TL&DR: it depends), and why we got unnumbered IPv4 interfaces. Now let’s see how IP routing works over unnumbered interfaces.

The Challenge

A cursory look at an IP routing table (or at CCNA-level materials) tells you that the IP routing table contains prefixes and next hops, and that the next hops are IP addresses. How should that work over unnumbered interfaces, and what should we use for the next-hop IP address in that case?

Packet Forwarding and Routing over Unnumbered Interfaces

In the previous blog posts in this series, we explored whether we need addresses on point-to-point links (TL&DR: no), whether it’s better to have interface or node addresses (TL&DR: it depends), and why we got unnumbered IPv4 interfaces. Now let’s see how IP routing works over unnumbered interfaces.

The Challenge

A cursory look at an IP routing table (or at CCNA-level materials) tells you that the IP routing table contains prefixes and next hops, and that the next hops are IP addresses. How should that work over unnumbered interfaces, and what should we use for the next-hop IP address in that case?

Mythbusting: NFV Data Center Fabric Buffering Requirements

Every now and then I stumble upon an article or a comment explaining how Network Function Virtualization (NFV) introduces new data center fabric buffering requirements. Here’s a recent example:

For Telco/carrier Cloud environments, where NFVs (which are much slower than hardware SGW) get used a lot, latency is higher with a lot of jitter due to the nature of software and the varying link speeds, so DC-level near-zero buffer is not applicable.

It seems to me we’re dealing with another myth. Starting with the basics:

Mythbusting: NFV Data Center Fabric Buffering Requirements

Every now and then I stumble upon an article or a comment explaining how Network Function Virtualization (NFV) introduces new data center fabric buffering requirements. Here’s a recent example:

For Telco/carrier Cloud environments, where NFVs (which are much slower than hardware SGW) get used a lot, latency is higher with a lot of jitter due to the nature of software and the varying link speeds, so DC-level near-zero buffer is not applicable.

It seems to me we’re dealing with another myth. Starting with the basics:

Feedback: Kubernetes Networking Deep Dive

Here’s what one of the engineers watching Stuart Charlton’s Kubernetes webinar wrote about it:

Feedback: Kubernetes Networking Deep Dive

Here’s what one of the engineers watching Stuart Charlton’s Kubernetes webinar wrote about it:

Worth Watching: Rethinking BGP in the Data Center

Ever since draft-lapukhov was first published almost a decade ago, we all knew BGP was the only routing protocol suitable for data center networking… or at least Thought Leaders and vendor marketers seem to be of that persuasion.

Worth Watching: Rethinking BGP in the Data Center

Ever since draft-lapukhov was first published almost a decade ago, we all knew BGP was the only routing protocol suitable for data center networking… or at least Thought Leaders and vendor marketers seem to be of that persuasion.

Worth Exploring: Working with Linux VRFs

I remember having an interesting discussion about Linux VRFs (as opposed to namespaces) with Dinesh Dutt years ago, but it looks like I never turned it into a blog post.

Now I won’t have to ? – Jon Langemak published an excellent Working with Linux VRFs deep dive.

Worth Exploring: Working with Linux VRFs

I remember having an interesting discussion about Linux VRFs (as opposed to namespaces) with Dinesh Dutt years ago, but it looks like I never turned it into a blog post.

Now I won’t have to 😉 – Jon Langemak published an excellent Working with Linux VRFs deep dive.

Video: We Still Need Networking in Public Clouds

Whenever someone starts mansplaining that you we need no networking when we move the workloads into a public cloud, please walk away – he has just proved how clueless he is.

He might be a tiny bit correct when talking about software-as-a-service (after all, it’s just someone else’s web site), but when it comes to complex infrastructure virtual networks, there’s plenty of networking involved, from packet filters and subnets to NAT, load balancers, firewalls, BGP and IPsec.

For more details, watch the We Still Need Networking in Public Clouds video (part of Introduction to Cloud Computing webinar).

Video: We Still Need Networking in Public Clouds

Whenever someone starts mansplaining that we need no networking when we move the workloads into a public cloud, please walk away – he has just proved how clueless he is.

He might be a tiny bit correct when talking about software-as-a-service (after all, it’s just someone else’s web site), but when it comes to complex infrastructure virtual networks, there’s plenty of networking involved, from packet filters and subnets to NAT, load balancers, firewalls, BGP and IPsec.

For more details, watch the We Still Need Networking in Public Clouds video (part of Introduction to Cloud Computing webinar).

Automation: Dealing with Vendor-Specific Configuration Keywords

One of the students in our Building Network Automation Solutions online course asked an interesting question:

I’m building an IPsec multi-vendor automation solution and am now facing the challenge of vendor-specific parameter names. For example, to select the AES-128 algorithm, Juniper uses ‌aes-128-cbc, Arista aes128, and Checkpoint AES-128.

I guess I need a kind of Rosetta stone to convert the IKE/IPSEC parameters from a standard parameter to a vendor-specific one. Should I do that directly in the Jinja2 template, or in the Ansible playbook calling the template?

Both options are awkward. It would be best to have a lookup table mapping parameter values from the data model into vendor-specific keywords, for example:

Automation: Dealing with Vendor-Specific Configuration Keywords

One of the students in our Building Network Automation Solutions online course asked an interesting question:

I’m building an IPsec multi-vendor automation solution and am now facing the challenge of vendor-specific parameter names. For example, to select the AES-128 algorithm, Juniper uses ‌aes-128-cbc, Arista aes128, and Checkpoint AES-128.

I guess I need a kind of Rosetta stone to convert the IKE/IPSEC parameters from a standard parameter to a vendor-specific one. Should I do that directly in the Jinja2 template, or in the Ansible playbook calling the template?

Both options are awkward. It would be best to have a lookup table mapping parameter values from the data model into vendor-specific keywords, for example:

Back to Basics: Unnumbered IPv4 Interfaces

In the previous blog post in this series, we explored some of the reasons IP uses per-interface (and not per-node) IP addresses. That model worked well when routers had few interfaces and mostly routed between a few LAN segments (often large subnets of a Class A network assigned to an academic institution) and a few WAN uplinks. In those days, the WAN networks were often implemented with non-IP technologies like Frame Relay or ATM (with an occasional pinch of X.25).

The first sign of troubles in paradise probably occurred when someone wanted to use a dial-up modem to connect to a LAN segment. What subnet (and IP address) do you assign to the dial-up connection, and how do you tell the other end what to use? Also, what do you do when you want to have a bank of modems and dozens of people dialing in?

Back to Basics: Unnumbered IPv4 Interfaces

In the previous blog post in this series, we explored some of the reasons IP uses per-interface (and not per-node) IP addresses. That model worked well when routers had few interfaces and mostly routed between a few LAN segments (often large subnets of a Class A network assigned to an academic institution) and a few WAN uplinks. In those days, the WAN networks were frequently implemented with non-IP technologies like Frame Relay or ATM (with an occasional pinch of X.25).

The first sign of troubles in paradise probably occurred when someone wanted to use a dial-up modem to connect to a LAN segment. What subnet (and IP address) do you assign to the dial-up connection, and how do you tell the other end what to use? Also, what do you do when you want to have a bank of modems and dozens of people dialing in?

Packet Bursts in Data Center Fabrics

When I wrote about the (non)impact of switching latency, I was (also) thinking about packet bursts jamming core data center fabric links when I mentioned the elephants in the room… but when I started writing about them, I realized they might be yet another red herring (together with the supposed need for large buffers in data center switches).

Here’s how it looks like from my ignorant perspective when considering a simple leaf-and-spine network like the one in the following diagram. Please feel free to set me straight, I honestly can’t figure out where I went astray.