Reading Journal Week 8 Networks - echadbourne/ChadbourneSYS-140 GitHub Wiki

Homework

How would you classify Champlain's network (for example, is it a PAN, LAN, or WAN)? Justify your answer.

It is too small to be a PAN, which is just the connection between a computer and various directly connected devices like keyboard and mouse. A LAN would be a collection of devices in classrooms connected to a common area’s router, like Juniper or another area router. Therefore, I think that Champlain’s network is a MAN or Metropolitan Area Network, because it is connecting various different LANs across the campus.

Between the OSI and TCP/IP Model, which one seems more useful for describing networks? Justify your answer.

I think the OSI model is more useful for describing networks because it gives a name for each theoretical layer that data has to go through. In addition, certain devices only operate at a certain layer of the model, and different types of information are used or added to a header at each layer. The TCP/IP model is good too, but it relies on the extra context of TCP/IP protocols, while the OSI model can stand by itself.

Suppose a colleague came to you and said that they could not connect to a website. How might you use some or all of the network tools from this chapter to diagnose the problem?

I would use the ping command on the colleague’s computer to ping the website IP address and website name. If the ping to the IP address worked and the name didn't, I would know that the problem is with the DNS server and work from there. If neither worked, then it is likely a problem with the network. From there I can ping something else in the same LAN as the DNS server. If that was successful, I know that the problem is with the connection to the DNS server and will have isolated it. If it is not, I can ping another device in the same LAN as the original computer. If that works then the problem is with the connection between the LANs or with the other LAN, and I can work from there. If it doesn't work then I can use the ping command with other devices in the same LAN as the colleague’s computer to isolate the problem. Instead, I could also use the tracert command to find where the problem is occuring and work from there. Essentially, I would use some combination of the ping and tracert commands to determine where the problem is occurring in the network (Assuming the problem is even with the network - it could be just the computer, which I would check first before doing all of that).

Reading Notes

Networking Overview

Summary:

A computer network is a collection of computers that are connected to each other and can share resources and communication. Networks can be PAN, LAN, MAN, WAN, WLAN, and WWAN. What these mean and how they work are outlined in the graphic below.

My Response:

This isn’t new to me because I am currently in a networking class, but I liked the analogy of all of the different networks that we have around us, like our family network and road networks. I had never thought of it that way before and it was helpful.

Network Topologies

Summary:

Networks are organized in physical topologies, which is how the network is wired in. The most common topology is the Star topology, where computers are connected to a central hub or switch that facilitates communication between the connected devices. Switches are smarter than hubs because they keep a table of MAC addresses and what port they are connected to for faster communication later, while a hub simply broadcasts any communication to all ports except the source. An image of the various network topologies can be seen below.

My Response:

Once again, most of this I already knew, but I had not seen the Extended Star topology or the Hierarchical topology before. Knowing how networks in general work, those two extra ones make sense to me, they just had not been given a specific name before. I would love to know in what situations those two topologies are used.

OSI Model

Summary:

The OSI (Open Systems Interconnect) Model is a standard used for connecting devices and transferring information on a network. It is composed of 7 layers, which from the bottom up are physical, data link, network, transmission, session, presentation, application (Which can be remembered with the mnemonic Active People Seldom Take Naps During Parties). Each layer adds a header of information to the data as it enters the network, and when a computer receives this data it strips away these headers as the data comes up out of the network again. The attached table further explains each of the layers

My Response:

I am very familiar with the OSI model, but I still have some issues completely grasping it. As such, I really liked the mnemonic that this chapter introduced. I had heard others before, but I am going to try and really remember this one because I think it will help me. In addition, I liked how the table explained each of the layers, because hearing many different explanations helps me understand the concept better.

TCP/IP Model

Summary:

Similar to the OSI model, the TCP/IP model shows how information travels on a network with respect to TCP/IP protocols, which are the most common protocols used in a network today. This model only has 4 layers, which are from the bottom up network access, internet, transport, and application. The attached table explains each of the layers

My Response:

To me it seems that this model is like a modified version of the OSI model that we already know and love, with the network access layer being like the physical, data link, and network layer of the OSI model. This model just adds in the bonus of the internet protocols that are used at each later instead of it just being how the information travels through each layer, which is actually really useful and helps to put things into perspective.

Network Addressing

Summary:

There are two types of addressing utilized on a network, MAC addresses and IP addresses. MAC addresses are physically assigned to a computer’s Network Interface Card (NIC) and are 48 bits, typically represented by a hexadecimal number. IP addresses can be either IPv4 (IP version 4) or IPv6 (IP version 6). IPv4 is more common at the moment, and is 32 bits, usually shown in dotted decimal notation (like 192.168.10.1). Each portion of the IPv4 address is an 8-bit binary number called an octet. IPv6 is 128 bits in length and is shown in hexadecimal, like the MAC address (ex. fe80::13e:4586:5807:95f7). IP addresses are also grouped into 5 classes, A, B, C, D, and E. These classes will be elaborated on more in the next section.

My Response:

I knew all of the information on the MAC addresses and IPv4 addresses, but it was interesting to learn more about IPv6 since that has not been discussed much in my networking class. I don’t totally understand the link-local address thing that was mentioned, but everything else seems to make sense to me.

More IPv4 Addressing

Summary:

IP address classes A, B, and C are the most commonly used in the common network. The image below shows what portions of each class of IP address are the network ID (The address of the overall network) and which portion of the address is the host ID (specific to each device; is essentially what is leftover from the network ID). The subnet mask indicates what portion of the IP address is the network ID. For example, the default subnet mask of a class A address would be 255.0.0.0, indicating that the first octet of the address is the net ID. Similarly, the default subnet mask for a class B address is 255.255.0.0, indicating that the first 2 octets are the net ID, and the rest is the host ID. Subnet masks can be different from the defaults, and can look like 255.255.254.0, indicating that those bits in any address with this mask are the network ID, and the rest are the host ID.

My Response:

It was interesting to see the IP address classes outlined like this, and very helpful. I’m sure we went over the different classes of IPv4 addresses, but I don’t remember it, so this was really useful and felt new to me. I included the graphic because it was a simple way of looking at the different classes of addressing.

Network Troubleshooting

Summary:

You can use the ping command to check the connectivity of various devices on a network, such as two devices in the same LAN, two devices on different but connected LANs, and the DNS server of a website (if the IP address for the website works, but the website name doesn’t then you have a problem with the DNS server). Using the ping command this way helps to isolate problems in a network. The command ipconfig for windows and ifconfig for linux is used to view the ip configuration of a device. ipconfig /all is used for also viewing MAC addresses. The command tracert is used to view the path of a data packet through a network, and can be used to find problems that occur in a larger network (where does it stop?) along with the network latency. nslookup is used for viewing the IP addresses of domain names. The net command is used for managing various network things, and can be followed by any of the things in the table below.

My Response:

Most of these commands I have used before, however the net command and the stuff that follows it was new to me, which is why I included the table for future reference. We have not had to set up a network with a command line interface yet, as we have been building the topologies of the networks virtually instead. It is also nice to have all of these commands in one place for future reference.