My Path to Success, and First Day

Time is a companion that goes with us on a journey. it reminds us to cherish every moment, because it will never come again. ~ Jean Luc Picard (Star Trek Generations) 

Such a great quote from a great movie, I can feel eyes glaring now. Honestly, it's how I paved my way of life. Pushed myself through hard times, with God' help of course. It says you'll never obtain this moment in time ever again, so why waste it? Well, I'm here to help myself and others throughout their Cisco Journey. 

Day 1 - OSI Model, Networking Fundamentals

Before we leap into creating a VLAN, setting up WAN connections, we need to begin with the fundamentals. Personally I dread this part, I want my first day to be creating fancy things that make us look cool. Well, without fundamentals for almost everything, we wouldn't be able to troubleshoot or dig deeper into an issue during that troubleshooting phase. Our coolness would drop if we're asked a simple question we're unsure of. 

If I could direct your attention to a Wiki page for the OSI model. As stated in the first paragraph:

The OSI model is a conceptual model that characterizes and standardizes the communication functions of a telecommunication or computing system without regard to their underlying internal structure and technology. (OSI Model (n.d). In Wikipedia. Retrieved December 12, 2015,

from https://en.wikipedia.org/wiki/OSI_model).

This website offers a plethora of information not only on the OSI model, but for other topics throughout our Cisco/CCNA journey. Let's start off and name these models and a short description of each, and possibly some examples:

OSI Model (From Bottom up):

1. Physical Layer- The physical medium between nodes(computers, switches/hubs to computers, phone lines to headset). These connections can range from RJ11, RJ45, even a serial RS232 between a console port in a switch to a USB to serial adapter on a laptop. Before switches became popular, Hubs allows multiple devices to communicate over a network, those devices are part of the Data Link Layer. 
2. Data Link Layer - While bit level communication is traversed over our cable. We need a way to convert this data into something readable by hardware or software. At this layer, these bits are converted into Frames. Two major topics to remember here, the MAC(Media Access Control) and LLC(Logical Link Control). Layer 2 switches operate at this level, VLANs can be created and workstations or switches use ARP to identify IP address to MAC address of a device. 
• MAC addresses are hard coded into a Network interface card, or NIC. Not one device as the same MAC address in the entire world
• LLC is responsible for identifying the network protocols and encapsulation. 
3. Network Layer - Those Frames are now Packets. Now we're getting into IP addresses and Layer 3 Routing. As stated before, MAC addresses are baked into NIC cards. The network layer allows us to use 32-bit (IPv4) or 128-bit(IPv6) addresses, easier for us humans to communicate those values.
4. Transport Layer - responsible for TCP/UDP traffic. Here's you'll be introduced to the 3 Way handshake which initiates a reliable TCP connection between nodes. UDP uses best effort to initiate a connection. Further description of this topic can be found here.
5. Session Layer - After communication has started, there need to be a method to organize this right? Session layer takes care of this. It allows us to create multiple SSL or FTP sessions at one time, without data going to the wrong location.
6. Presentation Layer - Handles character encoding, different file types like GIF translation also encryption and decryption. It's responsible for transforming data into a format an application recognizes. HTML and CSS are also part of this layer. 
7. Application Layer - here's were ports and application specific traffic comes into play. Such as FTP, HTTP, SMTP and others. 

Granted, this information doesn't completely cover the OSI Model, this honestly why my Cisco Journey didn't happen years ago. Memorizing layers 2-4 really put a burden on remembering this stuff, for me at least.

Since taking my Network + in 2010, I've actually retained move of this information, and it's helped me greatly throughout my career. Next time we encounter each-other, I'll digging deeper into TCP/UDP. 

Thanks for joining!