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The Floating Point Fix

15 July 2019 | Comments Off on The Floating Point Fix

Floating point is not something many network engineers think about. In fact, when I first started digging into routing protocol implementations in the mid-1990’s, I discovered one of the tricks you needed to remember when trying to replicate the router’s metric calculation was always round down. When EIGRP was first written, like most of the rest of Cisco’s IOS, was written for processors that did not perform floating point operations. The silicon and processing time costs were just too high.

What brings all this to mind is a recent article on the problems with floating point performance over at The Next Platform by Michael Feldman. According to the article:

While most programmers use floating point indiscriminately anytime they want to do math with real numbers, because of certain limitations in how these numbers are represented, performance and accuracy often leave something to be desired.

History of ATM

25 June 2019 | Comments Off on History of ATM

In these two episodes of the History of Networking, Dan Grossman joins Donald and I to discuss the history of Asynchronous Transfer Mode (ATM). While this is a technology that is no longer widely used, it had a major influence on the networking world.

https://historyofnetworking.s3.amazonaws.com/Dan+Grossman+-+ATM+01.mp3

https://historyofnetworking.s3.amazonaws.com/Dan+Grossman+-+ATM+02.mp3

For future History of Networking episodes, please subscribe to https://rule11.tech/category/hon/feed/ in your podcast application or RSS reader.

The next episode, OSI and IP with Dave Piscatello, will be released on the 9th of July.

These recordings are non-commercial and can be syndicated so long as they are not modified or advertising added—if you would like to distribute these recordings on your podcast channel, please get in touch with me.

It’s not a CLOS, it’s a Clos

17 June 2019 | Comments Off on It’s not a CLOS, it’s a Clos

Way back in the day, when telephone lines were first being installed, running the physical infrastructure was quite expensive. The first attempt to maximize the infrastructure was the party line. In modern terms, the party line is just an Ethernet segment for the telephone. Anyone can pick up and talk to anyone else who happens to be listening. In order to schedule things, a user could contact an operator, who could then “ring” the appropriate phone to signal another user to “pick up.” CSMA/CA, in essence, with a human scheduler.

This proved to be somewhat unacceptable to everyone other than various intelligence agencies, so the operator’s position was “upgraded.” A line was run to each structure (house or business) and terminated at a switchboard. Each line terminated into a jack, and patch cables were supplied to the operator, who could then connect two telephone lines by inserting a jumper cable between the appropriate jacks.

An important concept: this kind of operator driven system is nonblocking. If Joe calls Susan, then Joe and Susan cannot also talk to someone other than one another for the duration of their call. If Joe’s line is tied up, when someone tries to call him, they will receive a busy signal. The network is not blocking in this case, the edge is—because the node the caller is trying to reach is already using 100% of its available bandwidth for an existing call. Blocking networks did exist in the form of trunk connections, or connections between these switch panels. Trunk connections not only consume ports on the switchboard, they are expensive to build, and they require a lot of power to run. Hence, making a “long distance call” costs money because it consumes a blocking resource. It is only when we get to packet switched digital networks that the cost of a “long distance call” drops to the rough equivalent of a “normal” call, and we see “long distance” charges fade into memory (many of my younger readers have never been charged for “long distance calls,” in fact, and may not even know what I’m talking about).

Service Fabrics

28 May 2019 | Comments Off on Service Fabrics

NTP Best Practices

7 May 2019 | Comments Off on NTP Best Practices

DNS Challenge and Response

10 April 2019 | Comments Off on DNS Challenge and Response

Implications of 5G

26 February 2019 | Comments Off on Implications of 5G

My friends from ECI join the Network Collective to discuss 5G—well worth listening to for an understanding of 5G from a wired network perspective. Outro Music: Danger Storm Kevin MacLeod (incompetech.com) Licensed under Creative Commons: By Attribution 3.0 License http://creativecommons.org/licenses/by/3.0/

History of Networking: ILNP with Saleem Bhatti

5 February 2019 | Comments Off on History of Networking: ILNP with Saleem Bhatti

Using a single IP address to provide both identity and location information can create challenges and inefficiencies in network design. In this History of Networking episode, we sit down with Saleem Bhatti to talk about the history of ILNP and IP mobility to see how this tech aims to resolve this challenge. Outro Music: Danger…

CAA Records and Site Security

19 November 2018 | Comments Off on CAA Records and Site Security

The little green lock—now being deprecated by some browsers—provides some level of comfort for many users when entering personal information on a web site. You probably know the little green lock means the traffic between the host and the site is encrypted, but you might not stop to ask the fundamental question of all cryptography:…

Short Take: DNSSEC Deployment

6 November 2018 | Comments Off on Short Take: DNSSEC Deployment
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