CS 6250 INTERNET ARCHITECTURE AND SECURITY REVIEW QUESTIONS WITH COMPLETE SOLUTION GUIDE

CS 6250 INTERNET ARCHITECTURE AND
SECURITY REVIEW QUESTIONS WITH
COMPLETE SOLUTION GUIDE

●● Layered Architecture Advantages
Answer: - Scalability,
- Flexibility
- Ease of adding / removing components making it easier for cost-
effective implementations.


●● Layered Architecture Disadvantages
Answer: - 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
- Overhead in message headers caused by abstraction barriers between
layers.


●● OSI and Five-Layered Internet model Similarities
Answer: Many of the layers are the same


●● OSI and Five-Layered Internet model Differences

,Answer: - Three of the layers are combined in the 5-layered model.
- Specifically the five-layer model combines the
- Application
- Presentation
- Session layers
from the OSI model into a single Application layer.


●● What are sockets?
Answer: - 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.
- ."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.
Answer: - Application layer: Service, Interface, Protocol.

,- Presentation layer: Plays intermediate role of formatting the
information received from the layer below and delivering it to the
application layer.


- Session layer: Responsible for the mechanism that manages the
different transport streams that belong to the same session between end-
user and application process.


- Transport layer: Responsible for the end-to-end communication
between end hosts.


Network layer: This layer is responsible for moving the packet of
information, called a datagram, from one host to another.


- Data Link layer: Responsible for moving the frames from one node
(host or router) to the next node.


- Physical layer: This layer is the actual hardware responsible to transfer
bits within a frame between two nodes c


●● Provide examples of popular protocols at each layer of the five-
layered Internet model.
Answer: Application: NFS, DNS, SNMP, ftp, rcp, telnet, HTTP

, Transport: TCP, UDP


Internet: IP, ARP, ICMP


Data Link: PPP, IEEE 802.2, Ethernet


Physical Network: Token Ring, RS-232


●● What is encapsulation, and how is it used in a layered model?
Answer: Encapsulation is when data (called 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?
Answer: A design choice that shaped the current internet architecture.


It states the network core should be simple and minimal, while the end
systems should carry the intelligence.


Network functions should be simple and essential commonly used
functions so any host can utilize the service and higher form functions
should be built into the application itself.