Edward's CS Journey

Network Layer: Data Plane This week, we had an introduction to the network layer and learned about the data plane. The network layer has the responsibility of routing data from host to host via segments or packets. When sending data, segments are encapsulated into datagrams that hold the data, and the network adds header information to help with the routing process. Routers use the header information to keep the datagrams in order and determine their next hop. Receiving data is sent from the network to the transport layer and then to the appropriate application. In this process, the network is responsible for forwarding packets from one router to another until it reaches its destination and determining the route that needs to be taken to get packets from one place to its intended destination.  In the network layer, there are two planes: the data plane and the control plane. The data plane is local and functions in each router. When datagrams arrive at a router, the next port is determi

 Security In Computer Networks This week, we learned about security in computer networks. There are three principles of network security: confidentiality, authentication, and message integrity. Confidentiality involves ensuring that only the sender and receiver understand the message being sent. Authentication involves confirming the identity of both the sender and receiver. Message integrity involves ensuring that the message has not been altered while being transmitted or after it has been transmitted.  Confidentiality can be obtained by having the user and sender use the same symmetric keys to encrypt and decrypt the messages between them. A symmetric key is a key that both the sender and receiver agree upon. Currently, the Advanced Encryption Standard is used to create symmetric keys. Using this standard, we can process our data and message into 128-bit blocks and use 128, 192, or 256-bit keys to create our symmetric key.  When deciding on a key to use, the sender and receiver can

 Transport Layer This week, we learned about the transport layer of a computer network. When a message is sent on the sender's side, it is broken up into segments and passed through the network layer. On the sender's side, a transport header is added to the segments, and the network sends the data to the receiver via sockets. The receiver then reassembles the message using the transport header information and passes it to the appropriate place in the application layer. This is called demultiplexing. Two transport protocols that can be used to send data through the Internet are the Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP).  In TCP, there is one sender and one receiver. Data can flow in both directions on the same connection. This protocol involves a three-way handshake to start the connection. TCP sockets use four pieces of information to identify a segment: a source IP, a destination IP, a source port number, and a destination port number.  When

 Application Layer This week, we learned about the network application layer. To create a network, programs need to run on different end systems and communicate over a network with network core devices, such as a router. Two possible application architectures are client-server and peer-to-peer (P2P).  In a client-server architecture, the server is always on and has a permanent IP address. Clients communicate with the server but do not directly communicate with each other. The servers may also have data centers to help scale the amount of users using the network. As opposed to servers, clients may have a dynamic IP address.  In a P2P architecture, there is no server that is always one, and end systems directly communicate with each other, which means that applications have both a client and server process. Peers request and provide services for each other, thus creating a self-scaling environment. The more peers contribute, the more services can be provided when a peer requests a servic

Computer Networks and the Internet      This week, we learned about the Internet and how computer networks are connected. The Internet can be viewed in two ways: as billions of connected computing devices or as infrastructure that provides services to applications. Networks consist of clients and servers that send information back and forth to each other.  Two ways that information can be sent is via packet switching or circuit switching. Packet switching is when information is sent as a packet through communication links and routers or link-layered switches. The packet is sent with no resources reserved and between a shared network. If a network is congested, it is possible that a packet can be delayed, or pieces of the packet can be lost if the buffer holding the packet is full. While delivery is not guaranteed, the process is timely. Circuit switching is when packets are sent only on dedicated links. This process can be wasteful as dedicated lines become idle when not in use and can