Category Archives: Five Functional Facts

Five Functional Facts about ….

Five Functional Facts About AWS Service Control Policies

Following on the heels of my previous post, Five Functional Facts about AWS Identity and Access Management, I wanted to dive into a separate, yet related way of enforcing access policies in AWS: Service Control Policies (SCPs).

SCPs and IAM policies look very similar–both being JSON documents with the same sort of syntax–and it would be easy to mistake one for the other. However, they are used in different contexts and for different purposes. In this post, I’ll explain the context where SCPs are used and why they are used (and even why you’d use SCPs and IAM policies together).

Read on, dear reader!

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Five Functional Facts about AWS Identity and Access Management

This post is part of an open-ended series I’m writing where I take a specific protocol, app, or whatever-I-feel-like and focus on five functional aspects of that thing in order to expose some of how that thing really works.

The topic in this post is the AWS Identity and Access Management (IAM) service. The IAM service holds a unique position within AWS: it doesn’t get the attention that the machine learning or AI services get, and doesn’t come to mind when buzzwords like “serverless” or “containers” are brought up, yet it’s used by–or should be used by–every single AWS customer (and if you’re not using it, you’re not following best practice, tsk, tsk) so it’s worthwhile to take the time to really get to know this service.

Let’s begin!

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Five Functional Facts About OSPF

It’s funny, in my experience, OSPF is the most widely used interior gateway protocol because it “just works” and it’s an IETF standard which means it inter-ops between different vendors and platforms. However, if you really start to look at how OSPF works, you realize it’s actually a highly complex protocol. So on the one hand you get a protocol that likely works across your whole environment, regardless of vendor/platform, but on the other you’re implementing a lot of complexity in your control plane which may not be intuitive to troubleshoot.

This post isn’t a judgement about OSPF or link-state protocols in general. Instead it will detail five functional aspects of OSPF in order to reveal–at least in part–how this protocol works, and indirectly, some of the complexity lying under the hood.

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Five Functional Facts about TACACS+ in ISE 2.0

The oft-requested and long awaited arrival of TACACS+ support in Cisco’s Identity Services Engine (ISE) is finally here starting in version 2.0. I’ve been able to play with this feature in the lab and wanted to blog about it so that existing ISE and ACS (Cisco’s Access Control Server, the long-time defacto TACACS+ server) users know what to expect.

Below are five facts about how TACACS+ works in ISE 2.0.

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Five Functional Facts about VXLAN

It seems appropriate to write a FFF post about Virtual Extensible LAN (VXLAN) now since VXLAN is the new hotness in the data center these days. With VMware’s NSX using VLXAN (among other overlays) as a core part of its overall solution and the recent announcement of Cisco’s Application Centric Infrastructure (ACI) and the accompanying Nexus 9000 switch, both of which leverage VXLAN for delivering a network fabric, it seems inevitable that network engineers will have to use and understand VXLAN in the not too distant future.

As usual, this post is not meant to be an introduction to the technology; I assume you have at least a passing familiarity with VXLAN. Instead, I will jump right into 5 operational/technical/functional aspects of the protocol.

For more information on VXLAN, check out the draft at the IETF. Continue reading Five Functional Facts about VXLAN

Five Functional Facts about OTV

Following on from my previous “triple-F” article (Five Functional Facts about FabricPath), I thought I would apply the same concept to the topic of Overlay Transport Virtualization (OTV). This post will not describe much of the foundational concepts of OTV, but will dive right into how it actually functions in practice. A reasonable introduction to OTV can be found in my series on Data Center Interconnects.

So without any more preamble, here are five functional facts about OTV.

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Five Features of Brocade VCS

Virtual Cluster Switching (VCS) is Brocade’s brand of datacenter ethernet switching. VCS allows for the creation of a network fabric that’s capable of converging storage and data traffic via standards-based datacenter bridging. It also solves the “Spanning Tree Protocol (STP) problem” by implementing a standards-based TRILL data plane paired with their own control plane in the form of Fabric Shortest Path First (FSPF). This data + control plane enable the “routing” of MAC addresses through the fabric, negates the need for STP, enables the use of all cabled links, and prevents traffic loops. VCS is only (currently) available on the VDX line of switches from Brocade.

In this post I’m going to outline five aspects of VCS that I found particularly interesting or unique. This is a companion article to an earlier one titled Five Functional Facts about FabricPath where I broke down five features of Cisco’s fabric technology.

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Five Functional Facts about FabricPath

FabricPath is Cisco’s proprietary, TRILL-based technology for encapsulating Ethernet frames across a routed network. Its goal is to combine the best aspects of a Layer 2 network with the best aspects of a Layer 3 network.

  • Layer 2 plug and play characteristics
  • Layer 2 adjacency between devices
  • Layer 3 routing and path selection
  • Layer 3 scalability
  • Layer 3 fast convergence
  • Layer 3 Time To Live field to drop looping packets
  • Layer 3 failure domain isolation

An article on FabricPath could go into a lot of detail and be many pages long but I’m going to concentrate on five facts that I found particularly interesting as I’ve learned more about FabricPath.

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