1.3.10 Packet tracer: packet switching simulation
Packet Tracer is a fun, take-home, flexible software program that allows you to experiment with network behavior, build network models, and ask 'what if' questions. In this activity, you will explore how Packet Tracer serves as a modeling tool for network representations. While doing so, you will explore a simulation of how packets are created and sent across the network traveling from source device to destination device.
Watch this demonstration of the Packet Tracer – Packet Switching Simulation activity.
Download this video clip.Video player: ioe_1_video_1_3_10_packet_tracer_packet_switching_simulation.mp4
Transcript
INSTRUCTOR
This Packet Tracer file is a great demonstration of the internet of everything. In this file, we have our user down here June, and she has her internet-enabled personal device. She's got a smartphone, and she also has a tablet. And they're wirelessly connected to her Cisco access point, and from there, to her internet service provider.
We have redundant links from her internet service provider to an internet exchange. And from an internet exchange, we have the core of the internet and all of the connections that take place from router to router in the internet core.
And then from there, across, let's say, continents and oceans over to the Facebook data centre over here, and Facebook web servers, Facebook 1 here and Facebook 2, let's say the Facebook web server here is located in Ireland and this other Facebook web server may be located somewhere else in Europe.
Now, in this activity, June is going to upload information from her phone to her Facebook account to share information with her friends. We can watch this information and the various paths that it can take to travel from her and her internet service provider across the internet to reach these Facebook web servers and back.
So let's try it out. We'll follow the instructions. We'll go down here to June, click on her smartphone, open up her web browser, and type in www.facebook.com, and press Go. You can see we're met with a web page, internet of everything, IoE. And we're just waiting for this graphic to load.
And there it is. So we have here our Facebook website where we've posted information about some restaurants that we visited or that we've rated, and we're recommending them to our friends, let's say.
So we'll close that. Now, our experience was instantaneous. We open up our smartphone. We open up a web browser. We put in Facebook.com, and we're greeted with a web page, and information is uploaded and downloaded in the flash of an eye, in an instant.
It all seems really simple and instantaneous, but in reality the path that the information has travelled from June to Facebook is fairly complex. Let's take a look.
We can click on this cloud representing the internet exchange and look inside. And inside, we find in internet exchange point, which is a physical infrastructure through which internet service providers exchange internet traffic between their networks. I'll click Back.
We can click on this cloud representing the internet core and look inside it. The internet backbone or core refers to the principal data routes between large strategically interconnected networks and core routers on the internet.
These data routes are hosted by commercial, government, academic, and other high-capacity network centres, the internet exchange points and network access points that interchange internet traffic between the countries, continents, and across the oceans of the world.
Internet service providers, often Tier 1 networks, participate in internet backbone exchange traffic by privately negotiated interconnection agreements primarily governed by the principle of settlement-free peering. And we can see these core internet backbone routers here. I'll click Back.
And then finally, the Facebook data centre itself, which we can click on it and see the servers that make it up-- Facebook 1, Facebook 2. I'll click Back.
Let's open up another Packet Tracer file where we can see all of the interconnected devices, and we can trace the information and watch packets travel as they go from June's smartphone all the way over to the Facebook web servers.
To do this, I'll open up another Packet Tracer file. And in this Packet Tracer file, the clouds that contain the core backbone have all been opened up, and so we can see inside them. So here's the smartphone and the tablet. Here's the internet service provider, the gateway, the router. This is June's gateway, her internet service provider.
And connected to the core routers of, let's say, the service provider over to the internet exchange core between service providers. And then the core of the internet right here, these are all of the strategic locations representing states, cities, travelling across continents even, countries all the way over to the Facebook gateway over here. And here is the Facebook data centre.
Now, the Facebook data centre, we have Facebook 1 here located in Ireland. Facebook 2, let's say, located in Europe. This is all hypothetical but worth examining. And data is travelling from Facebook 2 all the way over there. Let's watch the whole process in action as we simulate it right here in packet tracer.
So to do that, what I'm going to do is I'm going to click on Simulation Mode. I am going to click on Edit Philtres. And I'm going to turn off all these protocols. We're interested in the ICMP protocol and the HTTP protocol because we're going to send a ping, and maybe we'll get a web page from a web browser.
And then before I close this, I'm going to speed up this slider here which will move the packets a little bit faster as they jump from location to location. I'll close the Simulation panel. I'm ready to go, and I'm in simulation mode. You can see I have the Simulation tab here selected.
So now I'll jump over to June's phone. I'll click on June's phone, open up the command prompt, and we'll start with a ping. So what I'll do is I'll type ping www.facebook.com. I'll hit Enter. And you can see it's paused here because it's waiting for me, since we're in simulation mode, to play so we can watch the traffic happen visually.
So I'll minimise this. And all I have to do is go down here to Packet Tracer and click this Auto Capture Play button, and we can watch the packets travel and see the paths that they take to get from her smartphone all the way over to the Facebook web server.
So let's do that. So I'll click Auto Capture Play. Here's her first ping, her first ICMP packet. You can see it hits the Cisco access point, travels across the switch to her gateway, over to the internet service provider router, over to this core router here, 3, core router 4, to an edge router.
It's going from her service provider over to the internet exchange, which exchange traffic between service provider networks. Here's the internet exchange edge 2, and here are a bunch of ISP core routers as the data travels from, let's say, state to state, city to city, continent to continent, country to country, even across oceans as it reaches finally the Facebook gateway router, over to the Facebook data centre, into their switches.
And we'll see which web server replies. In fact, it is the Facebook 2 web server. And now that it's reached, an echo reply is generated, and the reply is sent back.
Let's see if the data takes the same path on the way back. Over to the Facebook gateway, ISP core 6-- you can see it's already taking a different path on the way back as it heads back to June's smartphone. And there it is. Hits her ISP routers, ISP gateway, LAN switch. And finally, from her wireless Cisco access point, back to her network, and onto her smartphone, and that's it.
Interactive feature not available in single page view (see it in standard view).
The video demonstration is the primary source for how to navigate the activity. However, after viewing the video, you can download the following files to investigate the activity on your own.
- Packet Tracer – Packet Switching Simulation.pdf [Tip: hold Ctrl and click a link to open it in a new tab. (Hide tip)]
- Packet Tracer – Packet Switching Simulation A.pkz
- Packet Tracer – Packet Switching Simulation B.pkz
Essential note: If you are new to Packet Tracer, you can watch a tutorial. You must install Packet Tracer before you can open .pkz files. To install Packet Tracer, return to the course progress page where a copy is available to download and install .
Packet Tracer is available for both Microsoft Windows and Linux systems. The Open University Cisco Academy team support a moderated Facebook Community helping Mac users port this application onto all versions of the Apple Mac OSX. For more information, you will need to join the community.
Cisco also offer a free course on how to use Packet Tracer and how to obtain a free copy.