Exam 1 Study Guide Lesson 1 Introduction History and Internet Architecture What are advantages and disadvantages of a layered architecture The functionality in a network architecture is implemented by dividing the architectural model into layers Each layer offers different services An example of a network layer is an airline system ticket baggage gates plan takeoff airplane routing Advantages Scalability Modularity Flexibility Disadvantages Some layers functionality depend on the information from other layers One layer may duplicate lower layer functionality Overhead What are the differences and similarities of the OSI model and five layer Internet model The Internet Architecture model has 5 layers The application presentation and session are combined into a single layer known as the Sockets are the interface between the application and the transport layer application layer What are sockets Describe each layer of the OSI model Application Message Presentation Presentation layer plays the intermediate role of formatting the information it receives from the layer below and delivering it to the application layer Functionality Formatting a video stream Translating integers from big endian to little endian Session Session layer is responsible for the mechanism that manages the different transport streams that belong to the same session between end user application processes It ties audio and video stream together for example Transport Segment Transport layer is responsible for end to end communication between end hosts The network layer is responsible for moving datagrams from one Internet host to another A source Internet host sends the segment along with the destination address from the transport layer to the network layer The data link layer is responsible to move the frames from one node to the next The physical layer facilitates the interaction with the actual hardware It is responsible to transfer bits within a frame between two nodes that are connected through a physical link Application Message Provide examples of popular protocols at each layer of the five layer Internet model Network Datagram Data Link Frame Physical HTTP SMTP FTP DNS TCP UDP IP Transport Segment Network Datagram Data Link Frame Ethernet PPP WiFi Physical Twisted pair copper wire Coaxial cable Single mode fiber What is encapsulation and how is it used in a layered model Encapsulation is when data a header is appended to the packet through each layer to signify its on the correct path to the destination host What is the end to end e2e principle The e2e principle suggests that application level functions cannot be built into the lower levels of the system at the core of the network To summarize The network core should be simple The end systems should carry the intelligence What are the examples of a violation of e2e principle Violations of the e2e principle are when it is not possible to implement a functionality entirely at the ends hosts such as NAT Network Address Translation firewalls and traffic filters NAT takes care of the communication between the hosts on the private network and the hosts on the public network NAT violates the e2e because the hosts that are behind NAT boxes are not globally addressable or routable What is the EvoArch model The Evolutionary Architecture model is an hourglass shaped model of the Internet where the outer bands are more frequently modified or replaced The further in you go the harder it is for that layer to be altered or modified It considers an abstract model of the Internets protocol stack that has the following components Layers Nodes Edges Node incoming edges Node substrates Node outgoing edges Layer generality Node evolutionary value Node competitors Node death rate Node basic birth process Explain a round in the EvoArch model EvoArch is a discrete time model that is executed over rounds At each round Introduce new nodes and place them randomly at layers Examine all layers from top to bottom Stop the execution of the model when the network reaches a given number of nodes What are the ramifications of the hourglass shape of the internet Many technologies that were not originally designed for the internet have been modified so that they have versions that can communicate over the Internet It has been difficult and slow process to transition to IPv6 Repeaters hubs bridges routers operate on which layers Repeats and Hubs Layer 1 Physical Bridges and Layer2 switches Layer 2 Data link Routers and Layer3 switches Layer 3 Network What is a bridge and how does it learn A bridge is a device with multiple inputs and outputs It transfers frames from an input to one or more outputs It populates and maintains a forwarding table It learns when the bridge receives any frame that is a learning opportunity to know which hosts are reachable through which ports What is a distributed algorithm interconnected processors Explain the Spanning Tree Algorithm A distributed algorithm is an algorithm designed to run on computer hardware constructed from Every node has an ID The node with the smallest ID is selected as the root At each node it excludes the link if not on the shortest path to the root Tiebreakers go to the node with the smallest ID Messages are passed with a message origin claimed root distance Each node adds 1 to the distance received in the message and checks to see if the message claimed root is the claimed root What is the purpose of the Spanning Tree Algorithm The spanning tree algorithm avoids looping packets forever The goal is to have the bridges select which links ports to use for forwarding eliminating loops It also prevents broadcast The transport layer provides an end to end connection between two applications that are running Lesson 2 Transport and application layers What does the transport layer provide on different hosts What is a packet for the transport layer called Segment for a TCP connection storms What are the two main protocols within the transport layer TCP and UDP What is multiplexing and why is it necessary Multiplexing is the ability for a host to run multiple applications to use the network simultaneously It ensures the incoming packets are delivered to the correct application we need an addressing mechanism to distinguish the many processes sharing the same IP address on the same host Describe the two types of multiplexing demultiplexing Connectionless Connection oriented Uses the UDP socket that consists of a two tuple made up of a destination IP