Lesson 1 - A History and Internet Architecture Flashcards
What is an EvoArch model?
An abstract model for studying protocol stacks and their evolution.
The EvoArch model can help to study layered architectures and their evolution in a quantitative manner. Through this model researchers were able to explain how the hierarchical structure of the layer architecture eventually led to the hourglass shape.
Protocols in the Data Link Layer
Ethernet
PPP
WiFi
Which layer includes the Internet Protocol (IP) & routing protocols?
Network layer
OSI model layers proposed by the International Organization for Standardization (ISO)
- Application
- Presentation
- Session
- Transport
- Network
- Data Link
- Physical Layer
What is the purpose of the Spanning Tree Algorithm?
The goal of the spanning tree algorithm is to have the nodes (bridges) select which links (ports) to use for forwarding eliminating loops.
Internet Protocol Stack layers are:
- Application
- Transport
- Network
- Data Link
- Physical
In which layer do the TCP and UDP protocols reside
Transport Layer
Data Link layer packets of information
Frames
What is encapsulation? And how is it used in the layered model?
Each layer adds header information to the payload (message from layer above) -> message to segment to datagram to frame and then reverse at the end host (de-encapsulation).
What is the interface between the application and transport layer?
Sockets
What responsibility does the data link layer have?
Data link layer is responsible to move the frames from one node (host or router) to the next node.
Transport layer packet of information
Segments
End-to-end principle
Complexity and intelligence at the edges of the network while core kept simple to essential/commonly shared functions. Benefit = flexibility and autonomy provided to an application designer
What is OSI model
A 7-layer internet architecture model proposed by ISO
What are the advantages of internet layered architecture
- Scalability
- Modularity
- Flexibility
Transport layer is responsible for
End-to-end communication between end hosts.
The Session Layer is responsible for
The session layer is responsible for the mechanism that manages the different transport streams that belong to the same session between end-user application processes
On which layers to repeaters, hubs, bridges, routers operate?
repeaters/hubs - physical layer - receive and forward digital signals to connect different Ethernet segments.
Bridges - Data Link layer (layer 2) Receive packets and forward them to the appropriate destination.
Routers - Network Layer (Layer 3)
What are the ramifications of the hourglass shape of the internet?
A. Many technologies that were not originally designed for the internet have been modified so that they have versions that can communicate over the internet (such as Radio over IP).
B. It has been a difficult and slow process to transition to IPv6, despite the shortage of public IPv4 addresses.
Describe the Physical Layer
The physical layer facilitates the interaction with the actual hardware
It is responsible for transferring bits within a frame between two nodes that are connected through a physical link.
Describe the steps of the Spanning Tree Algorithm.
Runs in rounds. Each node first thinks it is the root. Each node sends a configuration message with the sending node’s id, root as perceived by this node, and number of hops from this node to its root. When a node receives a message, it updates its root if it finds a lower id root, better path to the root, or equal path to equal id if the sender of the message has a lower id.
What does the Presentation Layer do?
formats the information that it receives from the layer below and delivering it to the application layer.
What is the Network Layer is responsible for?
Moving datagrams from one Internet host to another.
Network layer packet of information
Datagram
Describe the Application Layer
includes multiple protocols (web, email, ftp, DNS) and multiple services.
What are 3 disadvantages of layered protocol stack model
- Some layers’ functionality depends on the information from the other layers.
- One layer may duplicate lower layer functionalities.
- Overhead that is caused by the abstraction between layers.
What are examples of a violation of the end-to-end principle?
firewalls, traffic filters, Network address translation box (sometimes home router),
Name each of the 5 internet layer’s packet of information
Application - Message Transport - Segment, Network - Datagram Data-Link - Frame Physical -Payload
What are some examples of application layer protocols?
HTTP (web)
SMTP (email)
FTP (file transfer)
DNS (domain name)
What does the TCP protocol offer?
- Connection oriented service
- Guaranteed delivery of the application layer messages
- Flow control
- Congestion control
What does the UDP protocol offer?
- Connectionless “best effort” service
- No Reliability
- No Flow Control
Explain a round in EvoArch model.
Introduce new nodes and place them randomly at layers
Examine all layers from top to bottom and perform:
Connect new nodes at each layer by choosing substrates (lower layer node) based on the generality probabilities of the layer below and choosing products (higher layer) based on the generality probability of the current layer
Update the value of each node at this layer
Examine all nodes in order of decreasing value in the layer and remove nodes that should die
Stop when we reach a given number of nodes
What is a bridge and how does it learn?
A device with multiple inputs/outputs that transfers frames from an input to one or multiple outputs. It learns from each frame it receives by populating a forwarding table so that it forwards frames on specific ports instead of broadcasting everywhere.
