computer networking and internet pdf

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CS144 – Introduction to Computer Networking

Homework ∼ 5 lab assignments implemented in C Possibly a problem set or other kind of lab Grading “Max” policy (sort of) Topics Network programming (sockets RPC) Network (esp Internet) architecture Switching Routing Congestion control TCP/IP Wireless networks Using the network

PDF	Introduction to Networking and the Internet  Function calls system calls threads and processes

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Computer Networking and Management Lesson 1 Computer Networks

overview of the Internet and of networking protocols introducing several key terms and concepts We examine the \'edge\' of a computer network looking at the end systems and applications and at the transport service provided to applications running of the end systems

What does a computer network study?
We also examine the 'core' of a computer network, examining the links and switches that transport data. We then take a broader view of networking. From a performance standpoint, we study the causes of packet delay and loss in computer network. We identify key architectural principles in networking, including layering and service models.
What is the purpose of a network?
The basic purpose of the various networks is to share software and other information between two or more computers. Over networks, there is the sharing of files, and in this process, there is the possibility of viruses being shared with the files. In recent times, the common cyber-attacks have been targeted towards big tech companies.

Where are we?

 Function calls, system calls, threads and processes courses.engr.illinois.edu

What’s next?

 Networked communication and distributed applications courses.engr.illinois.edu

Introduction

What is the Internet? Network edge What is a protocol? Protocol layers, service models courses.engr.illinois.edu

What is the Internet?

Communication infrastructure Enables distributed applications Web, VoIP, email, games, e-commerce, file sharing Communication services Provided to applications Reliable data delivery from source to destination “best effort” (unreliable) data delivery Mobile network Global ISP Home network Regional ISP Institutional network courses.engr.illinois.edu

Network Service

Goal Transfer data between end systems Support For Common Services Simplify the role of applications Hide the complexity of the network Semantics and interface depend on applications Example: Sending a Letter courses.engr.illinois.edu

Channels

Channel The abstraction for application-level communication Idea Turn host-to-host connectivity into process-to-process communication courses.engr.illinois.edu

Networked Communication Challenges

Networked communication ≠ IPC Problems typically masked by communication channel abstractions Bit errors (electrical interference) Packet errors (congestion) Link/node failures Message delays Out-of-order delivery Eavesdropping Goal Fill the gap between what applications expect and what the underlying technology provides courses.engr.illinois.edu

Network Architecture

Networks are complex Many “pieces” Hosts Routers Links of various media Applications Protocols Hardware, software Question Is there any hope of organizing structure of network? courses.engr.illinois.edu

Abstraction through Layering

Abstract system into layers: Decompose the problem of building a network into manageable components Each layer provides some functionality Modular design provides flexibility Modify layer independently Allows alternative abstractions Application programs Unconfirmed service Acknowledged service Host-to-host connectivity Hardware courses.engr.illinois.edu

Layering Example: Air Travel

Layers Each layer implements a service Via its own internal-layer actions Relying on services provided by layer below courses.engr.illinois.edu

Why layering?

Complexity Explicit structure allows identification, relationship of complex system’s pieces Modularity Eases maintenance, updating of system Change of implementation of layer’s service transparent to rest of system e.g., change in gate procedure doesn’t affect rest of system courses.engr.illinois.edu

Protocol: Language of communication across hosts

Defines structure of communication between two instances of a layer (on two hosts) Protocols are defined by Specific msgs sent Specific actions taken when msgs received, or other events Protocols define Format Order of msgs sent and received among network entities Actions taken on msg transmission, receipt courses.engr.illinois.edu

Network Protocols

A protocol implements a communication service that higher-layer objects use to exchange messages Service interface To objects on the same computer that want to use its communication services Peer interface To its counterpart on a different machine Peers communicate using the services of lower-level protocols courses.engr.illinois.edu

Peer-to-peer interface

Service interface Peer-to-peer interface Higher-level protocol (TCP) Lower-level Protocol (IP) Lower-level Protocol (IP) courses.engr.illinois.edu

Layering Concepts

Encapsulation Higher layer protocols create messages and send them via the lower layer protocols These messages are treated as data by the lower-level protocol Higher-layer protocol adds its own control information in the form of headers or trailers Multiplexing and Demultiplexing Use protocol keys in the header to determine correct upper-layer pro

Encapsulation

Application Application program DATA program UNC HDR DATA Best effort Reliable Service Service Application Application program DATA program UNC HDR DATA Best effort Reliable Service Service Host-to-Host Host-to-Host HHP HDR UNC HDR DATA HHP HDR UNC HDR DATA courses.engr.illinois.edu

Internet Protocol Stack

Application Transport Network Data Link Physical  Application: courses.engr.illinois.edu

Application specific protocols

 Transport: Process-to-process channel  Network: Host-to-host packet delivery Data Link: Physical: Framing of data bits Transmission of raw bits courses.engr.illinois.edu

Transport Layer

Provide logical communication between application processes running on different hosts Transport protocols run in end systems Send side Break application messages into segments Pass to network layer Receive side Reassemble segments into messages Pass to application layer More than one transport protocol available to applications Internet: TC

Transport vs. Network Layer

Transport layer Logical communication Bob Logical flow of information between Alice processes Relies on, enhances, network layer services Network layer Logical communication between hosts courses.engr.illinois.edu

Internet Architecture

Features No strict layering Application TCP UDP IP Network Internet Architecture – Network courses.engr.illinois.edu

Applications Creating a Network Application

Write programs that Run on (different) end systems Communicate over network e.g., web server software communicates with browser software No need to write software for network-core devices Network-core devices do not run user applications courses.engr.illinois.edu

Client-server Architecture

Server Always-on host Well-known IP address Clients Communicate with server May be intermittently connected May have dynamic IP client/server addresses  Do not communicate directly with each other courses.engr.illinois.edu

P2P Architecture

No always-on server Arbitrary end systems directly communicate peer-peer Peers are intermittently connected and change IP addresses Highly scalable but difficult to manage courses.engr.illinois.edu

Sockets

Process sends/receives messages to/from its socket Analogous to a door host or host or server server Sending process shoves messages out the door courses.engr.illinois.edu

 Transport infrastructure on other side of door brings message to socket at receiving process

process process socket socket TCP with buffers, variables Internet TCP with buffers, variables Sockets API Choice of transport protocol Ability to set a few parameters host or host or server server process socket TCP with buffers, variables Internet process socket TCP with buffers, variables courses.engr.illinois.edu

TCP

Unreliable data transfer Does not provide Connection setup, reliability, flow control, congestion control, timing, throughput guarantee, or security Question Why bother? Why is there a UDP? courses.engr.illinois.edu Unreliable data transfer Does not provide Connection setup, reliability, flow control, congestion control, timing, throughput guarantee, or security Question Why bother? Why is there a UDP? courses.engr.illinois.edu

1.7 History of Computer Networking and Chapter 1 (Introduction to Networking) wrap-up.

Introduction to Networking Network Fundamentals Part 1

How does the internet work? (Full Course)

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