Technical Drawing: Isometric Projection using Microsoft Visio

The concept of an isometric projection (from the Greek, ísos: “equal” and metrikós: “measure”), or parallel perspective, had existed in a rough empirical form for centuries as a method for visually representing three-dimensional objects in two dimensions. The whole idea consists in keeping the three coordinate axes (x, y and z) equally foreshortened and making the angles between any two of them as 120 degrees.isometric

To project your drawing isometrically, let’s say: a generic computer network topology, all your elements (devices, cabling, surfaces, etc) must obey this rule and as a result you will end up with the following aspect: Continue reading “Technical Drawing: Isometric Projection using Microsoft Visio”

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Technical Drawing: Isometric Projection using Microsoft Visio

Networking: Gateway Load Balancing Protocol (GLBP)

If you came this far you probably have seen acronyms such as VRRP (Virtual Router Redundancy Protocol) and perhaps HSRP (Hot Standby Router Protocol). They all share the same denominator: first hop redundancy. Speaking plainly, first hop redundancy can be achieved by a series of techniques which might include well-known protocols (focus of this discussion), virtual chassis (such as the one implemented by Juniper), clustered hardware (mostly found on firewalls modules and load balancers), and so on. Gateway Load Balancing Protocol is a proprietary alternative – developed by Cisco – for protocol like VRRP, HSRP, and CARP.

The main advantage GLBP offers is (as its name suggests) the traffic load balancing within a pool of GLBP aware devices, where all routers will actively forward traffic. Both VRRP and HSRP provides you with an active-backup architecture, which depending on the set-up might represent a waste of forwarding capacity, making engineers wonder: “Why must I use only one if I could be using both?

Load balancing, or more specifically: load sharing, however, can also be accomplished with VRRP or HSRP by simply using multiple instances of themselves. For example: VLANs 10, 20 and 30 might have the highest HSRP priority set to Router-A, and VLANs 40 and 50 to Router-B. This kind of set-up can easily become complex and difficult to maintain, which makes it an unusual practice, not to mention that the amount of traffic being forwarded per second by each of these VLANs is unpredictable, resulting in a highly discrepant load in each of the routers. Continue reading “Networking: Gateway Load Balancing Protocol (GLBP)”

Networking: Gateway Load Balancing Protocol (GLBP)

Book Review: How We Learn (Benedict Carey)

Not long ago I was paying a visit to an English bookstore somewhere in Amsterdam. I wasn’t looking for anything specific, all I needed was a reading material to help me going through my daily trips to the office, as a time machine of some sort. I must also admit that I am not a eager reader, therefore I cannot measure how serious a review written by me can be taken (if any at all!). How We Learn could be briefly described as a collection of well-tested techniques that help us learn more effectively with less effort. Its author – Benedict Carey – approaches the basics of cognitive science in a down-top manner, starting with the human brain’s anatomy, and progressively walking towards concepts such as interleaving and perceptual learning. I was surprised, considering my former lack of interest in this particular scientific field, how quickly I got hooked up by its contents.

Although the sentence “throw out the rule book and unlock your brain’s potential” is definitely exaggerated for what it really accomplishes, having a scientific insight on how our memory behaves towards learning is meritorious not only for teachers or psychologists. The simplicity in which the book was written, together with a great amount of real life examples, makes it pleasurable even for those who have no previous knowledge in the field (or interest).

As a time machine the book worked just fine, keeping my attention away from the boredom of my daily morning trips, but beyond that, I learnt something new, and so will you if give it a try. I recommend it!

ISBN: 978-1-4472-8634-9

Book Review: How We Learn (Benedict Carey)

Nederlands voor expats: weten en kennen

Since I moved to The Netherlands about one and a half year ago, learning Dutch as a third language became my daily challenge. As a native Portuguese speaker, every Germanic language seem to be full of oddities. Germanic languages can be segmented into three major branches of proto-languages: North Germanic, which is nowadays composed by Danish, Norwegian, Swedish, Icelandic and Faroese. West Germanic, composed by Scots, English, Frisian, Dutch, Low German and German itself. And East Germanic, which for my own good is now extinct. With this in mind, one might think: “Apparently Dutch and English are not that far from one another!”. Well, I am afraid they are. Within these branches you will find entire language families, organized as sub-branches, and so on. These are details that I am certainly not looking forward to entail. What I really want to express is that for those who are not familiar with – perhaps – German, Dutch is an entirely new world. Although knowing English helps, sometimes you have to step away from it whether you wish to truly comprehend ‘het Nederlands‘. As a first example, I would like to share the following Dutch verbs (nlwerkwoorden):

ken.nen [ˈkɛnə(n) ]
we.ten [ˈwetə(n) ]

Both verbs translate to ‘to know‘, but as you can imagine there are specific cases where each of them might be applied. For example:

Weet je waar ik deze winkel kan vinden?
[ Do you know where I can find this store? ]
– Nee, dat weet ik niet.
[ No, I don’t know that ]

Kennen jullie mijn vader?
[ Do you (pl.) know my father? ]
– Ja, we kennen hem!
[ Yes, we know him! ]

Even though this seems confusing at a first glance, the difference between weten and kennen could be described as: kennen [to know (someone, somewhere), acquaintance, cognition] and weten [abstract knowledge]. It becomes even more evident when you bring them into latin based languages such as Portuguese, Spanish or French:

nl: kennen – pt: conhecer – fr: connaître – es: conocer
nl: weten – pt: saber – fr: savoir – es: saber

It is not rocket science. Right?

Nederlands voor expats: weten en kennen