Lesson 12 (ICND 1 1.9) Describe the components required for network and Internet communications

This is a pretty vague objective and could encompass any number of hardware or software items.  For now we will stick with the basics. A lot of this will be review from Lesson 1 as there is a lot of overlap.  Feel free to visit lesson 1 again for review.

To communicate on a network you first need an originating host.  That host can be a laptop, a desktop, a tablet, a smart phone, an IP phone, a server, or any number of devices with an internet protocol (TCP/IP) address.

Next, you'll need a destination host to communicate with.  That destination host may be a web server in Singapore, the file server in your datacenter, or a laptop in the cubicle next to you.

For that host to communicate on the network to reach this intended destination, you'll need to have a communications medium, that medium can be 802.11 wireless, 3G or 4G cellular networks,  and copper or optical wired ethernet.

Local communications typically will remain on the local area network (LAN) comprised of switches, distant locations will typically require a WAN connection comprised of routers.

If you are looking to get to a destination on the public Internet, you will need to go through a default gateway.  A default gateway is the router closest to you.  It is literally the gateway you must go through to get to the outside.

There may be any number of routers and communications mediums between your local host and the destination.

Here's a video that explains the overall process.Again, this objective has a lot of overlap with Lesson 1, so it's mostly a review.  Many of the blanks will be filled in subsequent videos.

courtesy of http://www.datacenterscanada.com

Lesson 11 (ICND1 1.8) Determine the path between two hosts across a network

When you are asked to determine a path between two hosts in a network, you will most often accomplish this through the traceroute command.

Here's a great video by Cbtnuggets which explains traceroute in detail.

Lesson 10 ICND1(1.7) Interpret network diagrams

This is pretty much already been covered, but I'm going to post a couple interesting tidbits on the subject.

Here's a video on how to create a simple network diagram using Microsoft Visio created by OfficeOnlineVideos.  You can download a trial version of MS Visio.

Go to the below the Networkworld website, and check out the section Interpreting a Network Diagram.
 http://www.networkworld.com/subnets/cisco/053008-ch1-ccna-prep-library.html

The below diagram is referenced:
 http://www.networkworld.com/subnets/cisco/chapters/1587054620/graphics/01fig03.jpg

You should fully understand what is going on in this graphic from previous lessons.  If you have any questions, please post a comment.

Lesson 9 - ICND1(1.6c)Describe the impact of applications such as Voice Over IP on a network

In networking, bandwidth is the amount of data (expressed in bits per second) that can be transmitted within a certain unit of time (i.e. 1000Mbps, 100Mbps, 10Mbps, 28.8Kbps over a physical medium.  

Note: Bandwidth is often confused with throughput.  Throughput is the measurement of of actual network traffic traversing a network. So think of bandwidth as the potential of a connection, and throughput as the reality.  This is often confused by retail internet customers, who buy a 6Mbps DSL link, and complain when they download a file at 100Kbps.  While their bandwidth to the service provider is 6Mbps, the throughput to the destination file server (from end to end over the Internet) is only 100Kbps.

The below graphic is a general idea of bandwidth requirements.  Requirements can vary depending on the application used.

Lesson 9 - ICND1(1.6b)Describe the impact of applications such as Voice Over IP on a network

The second concept I will describe is delay.  Delay (also called latency) is how long a packet takes to get to it's destination.  If you think of a packet as a car driving down the highway, it's latency is how long it takes to get from home to the destination.  

Latency is typically measured in milliseconds.  Ethernet connections are considered low latency (a few milliseconds), while a satellite link is considered high latency (hundreds of milliseconds).  There are many factors which can affect latency.

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The next concept covered is loss.  Loss is the dropping of packets in transit. As you can see below, there is no middle ground for packet loss, it's either very bad or not so bad.  The reason why mission critical data transfers have a low sensitivity to packet loss, is that the upper layers are supposed recognize the loss and request a retransmission.  That being said, a high number of retransmissions will result in data transfers taking a significantly longer amount of time.  In video or audio applications, the audio or video stream will drop off intermittently as packets are loss.

Lesson 8 - ICND1(1.6a)Describe the impact of applications such as Voice Over IP on a network

When we talk about the impact of applications on a network, we are talking about Quality of Service (QoS).  According to TCP/IP Guide:

"The generic term quality of service describe the characteristics of how data is transmitted between devices"

Most people when they think about quality of service, they describe whether the Internet or applications are fast or slow, but it's really much more than this.

Check out the following video by DigitalSocietyOrg on Youtube.

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The QoS concept I will discuss first is jitter. Jitter is simply packets arriving at their destination at unpredictable rates, also defined as a variation in packet delay.  This can cause issues with real-time streaming applications such as voice or video.  It is often experienced as a skip or a chirp in the audio or video.  

Lesson 7 - ICND1(1.5b) Describe the purpose and basic operation of the protocols in the OSI and TCP models

Session Layer 5
Maps to TCP/IP Model Application Layer 

Examples: NetBIOS, RPC

Communication using Sessions.
Definition from TCP/IP Guide:

"As its name suggests, it is the layer intended to provide functions for establishing and managing sessions between software processes. Session layer technologies are often implemented as sets of software tools called application program interfaces (APIs), which provide a consistent set of services that allow programmers to develop networking applications without needing to worry about lower-level details of transport, addressing and delivery."

Presentation Layer 6
Maps to TCP/IP Model Application Layer 

Examples: Encryption, Compression, Translation

Communication using Data Formatting.
Definition from TCP/IP Guide: 

"Protocols at this layer take care of manipulation tasks that transform data from one representation to another, such as translation, compression and encryption. In many cases, no such functions are required in a particular networking stack; if so, there may not be any protocol active at layer six."

Application Layer 7
Maps to TCP/IP Model Application Layer 

Examples:Telnet, FTP, HTTP

Communication using User Input.

Lesson 6 - ICND1(1.5a) Describe the purpose and basic operation of the protocols in the OSI and TCP models

Physical Layer 1
Maps to TCP/IP Model Network Interface Layer 

Examples: Physical wiring and equipment

Communication using bits.

Data-Link Layer 2
Maps to TCP/IP Model Network Interface Layer

Examples: Ethernet / Token-Ring / PPP

Communication using frames.

 Be familiar with the sublayers of Layer 2.

Network Layer 3
Maps to TCP/IP Model Internet Layer  

Examples: IP / IPv6

Communication using packets.

Transport Layer 4
Maps to TCP/IP Model Transport Layer 

Examples: TCP / UDP

Communication using Segments.

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Coming up in part B


Session
Presentation
Application

Lesson 5 - ICND1(1.4) Describe common networking applications including web applications

Here are some common networking applications:

Application | Port  (TCP / UDP  / Both) |  Description / Use

HTTP            80                                         Unsecure Web Browsing

HTTPS         443                                        Secure Web Browsing (SSL)

DHCP           67 (Server), 68 (Client)       Dynamic Host Configuration Protocol

FTP               20 (Data),21 (Control)        File Transfer Protocol

TFTP            69                                         Trivial File Transfer Protocol

Telnet           23                                         Telnet

SSH              22                                         Secure Shell

SNMP          161 (Query), 162 (Trap)      Simple Network Management Protocol

SMTP          25                                          Simple Mail Transfer Protocol

POP3            110                                         Post Office Protocol 3

ICMP           NA                                         Internet Message Control Protocol

DNS             53                                          Domain Name System

NTP             123                                         Network Time Protocol

There are many other applications as well, these can be viewed at:

http://en.wikipedia.org/wiki/List_of_TCP_and_UDP_port_numbers (Exit to Wikipedia)

You should have a basic understanding of what the common applications do.  You should also be familiar with their port numbers.  We will cover many of these applications again at a later time.

If you'd like any of these applications explained in the meantime, let me know in the comments.

Lesson 4 - ICND1(1.3b) Use the TCP/IP model and their associated protocols to explain how data flows in a network

The TCP/IP model was brought to you by the folks at DARPA specifically for TCP/IP.  Other than that, it has exactly the same function as the OSI model.

You can see from this image borrowed from TCP/IP Guide (http://www.tcpipguide.com/free/t_TCPIPArchitectureandtheTCPIPModel-2.htm), that the TCP/IP Model maps directly to the OSI model.  More importantly, layers 1,2, 3, and 4  have the same function in both models, they are just named differently.  For a description of each layer, click the above link.

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At this point, you should be able to reproduce the above graphic from memory.  You should also be able to supply a short description for each layer. 

Lesson 3 - ICND1(1.3a) Use the OSI model and their associated protocols to explain how data flows in a network

The OSI Model has no functional application; it is simply a way we can talk about networks, and helps explain a process called Encapsulation.  Refer to the image below, which shows the different layers of the OSI.  Note that user data flows down from the application layer to the physical layer before it is transmitted to the destination.  When it arrives at the destination, it travels back up from the physical layer to the application layer.  The corresponding layers on both the transmitter and receiver believe they are communicating directly.  Layers below it are transparent.  This process is called encapsulation, which will be explained later.

Diagram of the OSI Model from University of Washington (http://www.washington.edu/lst/help/computing_fundamentals/networking/osi/). A short description of each layer is also available here.

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The following is a very high level explaination of the OSI Reference Model (Exit to Cisco Website):

https://learningnetwork.cisco.com/videos/1125

Part 1 Lesson 1 - Story Time-Analogy for The OSI Ref Model & Review 

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The following explains the levels of the OSI Reference Model in more detail(Exit to Cisco Website): 

https://learningnetwork.cisco.com/videos/1126

 Part 1 Lesson 2 - Framework & Function of the OSI Ref Model & Review 

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The following is a review (Exit to Cisco Website):

https://learningnetwork.cisco.com/videos/1127 

Part 1 Lesson 3 - Review Games - OSI Ref Model 

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Great video on OSI Model from elithecomputerguy via Youtube.
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For a great explanation of encapsulation in regard to the OSI model, refer to the following page (From TCP/Guide)

http://www.tcpipguide.com/free/t_DataEncapsulationProtocolDataUnitsPDUsandServiceDa.htm
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At this point you should have a good understanding of the OSI model.

Lesson 2 - ICND1(1.2) Select the components required to meet a given network specification

The following video is a good introduction to understanding the elements of a network design.  It also describes the various basic topology icons you might run into.

Register for an account at https://learningnetwork.cisco.com. It's the same thing as a CCO account, so you'll need it anyways, and it's free!
Log in and watch the following videos:

The following video goes over a basic network diagram and functions.  Download and take a look at the associated diagram and make sure you understand what is going on.
https://learningnetwork.cisco.com/videos/1144

Lesson 1 - Identify Network Devices in a Topology (Exit to Cisco Website)

https://learningnetwork.cisco.com/docs/DOC-15266

Accompanying Diagram (Exit to Cisco Website)

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 Continuation of the discussion in lesson 1
https://learningnetwork.cisco.com/videos/1168/

Lesson 2 - Characteristics of a Network Review(Exit to Cisco Website)

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The last video reviews the content using a game (Optional). 
https://learningnetwork.cisco.com/videos/1169 

Lesson 3 - Review Game - Who Am I (Exit to Cisco Website)

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Go to the following page http://www.cisco.com/web/about/ac50/ac47/2.html (Exit to Cisco.com). It contains icons for JPEG,Visio and, Powerpoint for creating your network diagrams. If you don't download these Icons now, be aware that this page exists and of its location.

Download the following PDF on the same page and add it to your reference collection. It contains all available Cisco network diagram icons and will help you decode network diagrams provided by Cisco
http://www.cisco.com/web/about/ac50/ac47/PDF_icons.zip (Exit to Cisco.com).

By this point you should have a basic understanding of how to read a network diagram.

Next up, the OSI model.

 

Lesson 1 - ICND1(1.1) Describe the purpose and functions of various network devices

Welcome to the first lesson (Estimated time for completion: 20 Minutes).  This lesson is an introduction to get your feet wet, and the topic will be further explored in subsequent lessons.   I will go through the whole blueprint for the CCNA ICND1.  You can view it yourself here (https://learningnetwork.cisco.com/community/certifications/ccna/icnd1 (Exit to Cisco.com, Registration required))

Every Aspiring Network Engineer Must Watch This Video! It's cheesy and a bit outdated, but it gets the job done.  It's a rite of passage (Via YouTube).

Routers/Switches

 This video from Cisco explains routers versus switches (very basic,Via YouTube)

Firewalls

 This video from Cisco explains firewalls  (very basic,Via YouTube)

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These videos are adequate to get us into subsequent items, which will explain network devices in more detail.  Heading into the next lesson, you should know the following network diagram components:

Switch

Router

Follow the Packet

What is a packet, and why would we want to follow one?  

Packets are the medium through which data is exchanged over the internet end to end. If you can follow a packet from source to destination, you can gain an understanding of the various enabling technologies which power the Internet. 

The purpose of this blog is two-fold, to provide a condensed source of information to aid in passing Cisco certifications exams, and to give would-be engineers an understanding of networking.  In order to accomplish this, I will start with the the entry-level Cisco certification CCENT, which is also half the requirement to achieve CCNA.

There is a lot of very good information out there already.  My goal is not to reinvent the wheel, it is simply to aggregate the best sources of information, and fill in any blanks.  I encourage you to make comments and ask questions.  If you find a better source of information, please add it.

Everything linked here is free to access, unless otherwise stated.  Nothing here is plagiarized or pirated, links to this information will not be permitted.  Links to external content will be labeled as such.  There are also braindumps here, nor will they be permitted.