• Georgia Institute Of Technology

• CS 6250

Lesson 1: Introduction, History, and Internet Architecture ● What are advantages and disadvantages of a layered architecture? Each protocol layer offers different services. Some advantages are scalability, flexibility, and ease of adding / removing components making it easier for cost-effective implementations. Disadvantages include: some layers functionality depends on the information from the other layer and violates the goal of layer separation; one layer may duplicate lower layer functionalities; overhead both in computation and in message headers caused by abstraction barriers between layers. ● What are the differences and similarities of the OSI model and five-layered Internet model? The OSI model and the 5-layered Internet Model have many of the same layers, with the difference being three of the layers are combined in the 5-layered model. Specifically the five-layer model combines the application, presentation, and session layers from the OSI model into a single application layer.` ● What are sockets? A network socket is a software structure within a network node of a computer network that serves as an endpoint for sending and receiving data across the network. The structure and properties of a socket are defined by an application programming interface (API) for the networking architecture. Sockets are created only during the lifetime of a process of an application running in the node. https://en.wikipedia.org/wiki/Network_socket “A process sends messages into, and receives messages from, the network through a software interface called a socket. Let’s consider an analogy to help us understand processes and sockets. A process is analogous to a house and its socket is analogous to its door….a socket is the interface between the application layer and the transport layer within a host.” - Kurose and Ross, 2.1 ● Describe each layer of the OSI model. Application layer: Service, Interface, Protocol. Ex: Turn on your smartphone and look at the list of apps. (HTTP, SMTP, FTP, DNS) Presentation layer: Plays intermediate role of formatting the information received from the layer below and delivering it to the application layer. Ex: converting big endian to little endian. Session layer: Responsible for the mechanism that manages the different transport streams that belong to the same session between end-user and application process. Ex: teleconference app, it is responsible for tying together audio and video streaming.