Docsity
Log inSign up
Docsity
Prepare for your exams
Prepare for your exams

Study with the several resources on Docsity

Earn points to download
Earn points to download

Earn points by helping other students or get them with a premium plan

Guidelines and tips
Guidelines and tips
Sell on Docsity
Sell on Docsity
Log inSign up

Prepare for your exams

Study with the several resources on Docsity

Find documents

Prepare for your exams with the study notes shared by other students like you on Docsity

Search Store documents

The best documents sold by students who completed their studies

Search through all study resources
Docsity AINEW

Summarize your documents, ask them questions, convert them into quizzes and concept maps

Explore questions

Clear up your doubts by reading the answers to questions asked by your fellow students

Earn points to download

Earn points by helping other students or get them with a premium plan

Share documents
download point icon20 Points

For each uploaded document

Answer questions
download point icon5 Points

For each given answer (max 1 per day)

All the ways to get free points
Get points immediately

Choose a premium plan with all the points you need

Study Opportunities

Choose your next study program

Get in touch with the best universities in the world. Search through thousands of universities and official partners

Community

Ask the community

Ask the community for help and clear up your study doubts

University Rankings

Discover the best universities in your country according to Docsity users

Free resources

Our save-the-student-ebooks!

Download our free guides on studying techniques, anxiety management strategies, and thesis advice from Docsity tutors

From our blog

Exams and Study
Go to the blog

Networking and Internet - Automata, Algorithms and Complexity - Slides | CS A351, Study notes of Computer Science

University of Alaska AnchorageComputer Science
Prof. Kenrick J. Mock

Material Type: Notes; Professor: Mock; Class: Automata, Algorithms, and Complexity; Subject: Computer Science ; University: University of Alaska - Anchorage; Term: Fall 2009;

Typology: Study notes

2009/2010

Uploaded on 03/28/2010

koofers-user-u5g
koofers-user-u5g 🇺🇸

10 documents

1 / 35

Toggle sidebar

This page cannot be seen from the preview

Don't miss anything!

bg1
10/5/2009
1
Networking and the Internet
Introduction: “Everything is Connected
to Everything”
•Seeds of Networking
–1966: ARPA (Advanced Research Projects Agency)
State Defense Department’s research organization.
•Focused major development effort on computer networking.
•ARPA’s Goal: To promote research in advanced future
technologies by funding university and industry research
proposals.
–Distributed communication system
–Enable research communication
–Enable dissimilar computers to share information
–Reroute information automatically
–Act as a network of networks; internetworking
–Result: Thousands of databases became available to
researchers
pf3
pf4
pf5
pf8
pf9
pfa
pfd
pfe
pff
pf12
pf13
pf14
pf15
pf16
pf17
pf18
pf19
pf1a
pf1b
pf1c
pf1d
pf1e
pf1f
pf20
pf21
pf22
pf23

Partial preview of the text

Download Networking and Internet - Automata, Algorithms and Complexity - Slides | CS A351 and more Study notes Computer Science in PDF only on Docsity!

Networking and the Internet

Introduction: “Everything is Connected

to Everything”

• Seeds of Networking

  • 1966: ARPA (Advanced Research Projects Agency)

State Defense Department’s research organization.

  • Focused major development effort on computer networking.
  • ARPA’s Goal: To promote research in advanced future technologies by funding university and industry research proposals. - Distributed communication system - Enable research communication - Enable dissimilar computers to share information - Reroute information automatically - Act as a network of networks; internetworking
  • Result: Thousands of databases became available to

researchers

Original ARPANet Sites

ARPANet 1972

The Internet:

Struggling to Maturity

  • 1983: ARPAnet split.
    • Converted to TCP/IP protocol.
    • Part remained ARPAnet: universities, research institutes.
    • Part became Milnet: non-classified military information.
  • 1989: majority of ARPAnet switched to NSF’s backbone.
    • ARPAnet sites were connected to the NSF backbone through the regional community networks.
  • NSFnet became what is known today as the Internet.

Growth of the Internet

The Physical Organization

of Networks

  • LAN (Local Area Network)
    • A collection of nodes (i.e. computing devices) within a small area.
    • The nodes are linked in a bus, ring, star, tree, or fully connected topology network configuration.
    • Benefits of LANs:
      • Sharing of hardware resources.
      • Sharing of software and data.
      • More efficient person-to-person communication.

The Physical Organization

of Networks

  • The bus network -
    • A continuous coaxial cable to which all the devices are attached.
    • All nodes can detect all messages sent along the bus.
  • The ring network -
    • Nodes linked together to form a circle.
    • A message sent out from one node is passed along to each node in between until the target node receives the message.

Linking nodes:

Both of these topologies are uncommon today

Hardware Architecture

of Networks

• Types of hardware used to create networks:

Hub A device that repeats or broadcasts the network stream of information to individual nodes ( usually personal computers) Switch A device that receives packets from its input link, and then sorts them and transmits them over the proper link that connects to the node addressed. Bridge Transparently links two local networks that have identical rules of communication. Gateway A link between two different networks that have different rules of communication. Router A node that sends network packets in one of many possible directions to get them to their destination.

Hub

• A hub looks like a star configuration but really

implements a bus

Bridge LAN / Backbone Design

Switch

• A switch is a true star configuration

• Consumer devices today are switches, not

hubs

The Physical Organization

of Networks

• MAN (Metropolitan Area Network)

  • Consists of many local area networks linked together.
  • Span the distance of several few miles.

• WAN (Wide Area Network)

  • Consists of a number of computer networks including LANs.
  • Connected by many types of links.

Connecting Independent Networks

• Router: fundamental building block of the

Internet

  • Has a processor, memory, and network interface, its own specialized software
  • Connects LANs to backbone WANs
  • Forwards data from one network to another
  • Determines best routes for data to travel

Routers Enable Different Paths

between Networks

Path 1 Router

Path 6 Path 5

Path 3

Path 4

Path 2 Network A

Network B

Network C

Routers – Connect Networks

CSMA/CD

Operation

Frames must be long enough to detect collision during transmission!

Wireless LANs

  • IEEE 802.
  • Basic service set (cell)
    • One or more stations using same protocol, together with an access point or base station
    • Typically some radius (~200 ft) from the access point
    • Competing to access shared medium
    • May connect to backbone via access point (bridge)
  • Extended service set
    • Two or more BSS connected by distributed system
    • Appears as single logic LAN to Data Link layer

Wireless – 802.

• CSMA/CD approach doesn’t work because of

the Hidden Terminal Problem

802.11 Media Access

  • If media is idle for some time then it is allowed to transmit
  • If media is busy
    • Wait until media is free
    • Then wait an additional random time (less greedy than 802.3)
  • Data is sent with a checksum
    • A checksum is a simple check to see if the data was received properly
    • E.g. if sending the numbers 10, 20, and 30 then the checksum might be the sum of all numbers (60), so 10,20,30 and 60 are sent. The receiver verifies that all numbers received add up to 60.
  • If the checksum matches, the receiver sends an ACK to the sender
  • Receiver might get a collision, but no detection for one – instead the checksum will (hopefully) fail - If sender doesn’t receive ACK in some time period, resends

4-

The client/server model compared to the peer-

to-peer model

4-

Internet Architecture

• Internet Service Provider (ISP)

  • Tier-
    • Major communication companies
  • Tier-

• Access ISP: Provides connectivity to the

Internet

  • Traditional telephone (dial up connection)
  • Cable connections
  • DSL
  • Wireless

4-

Internet Composition

4-

Internet Addressing

  • IP address: pattern of 32 or 128 bits often represented in dotted decimal notation - IP 4: 32 bits - Four groups of 8 bits; each 8 bit group can be represented by a value from 0 to 255 - 0.0.0.0 to 255.255.255. - 232 or about 4.3 billion addresses theoretically possible, but not divided equally; exhaustion predicted 2010- - IP 6: 128 bits - Addresses often assigned to clients via DHCP – Dynamic Host Configuration Protocol
  • Domain name system (DNS)
    • Provides a way to assign a more meaningful name to the IP address
    • Name servers
    • DNS lookup

Hierarchy of Names - DNS

  • Routers are based on IP address (e.g.

134.114.140.34), not the English-like domain name!

  • DNS = Domain Name Server system
    • Way to translate from domain name to IP address
  • Tree-based hierarchy, with .org, .com, .edu, and .gov

at the top of the tree

math.uaa.alaska.edu engr.uaa.alaska.edu ...

uaa.alaska.edu

alaska.edu ucdavis.edu ...

.edu

DNS Client-

Server

  • DNS names are managed by a hierarchy of DNS servers
  • Hierarchy is related to DNS domain hierarchy
  • Root server at top of tree knows about next level servers
    • Next level servers, in turn, know about lower level servers

DNS Servers

  • Each DNS server is the authoritative server for the names it manages
  • If request contains name managed by receiving server, that server replies directly
  • Otherwise, request must be forwarded to the appropriate authoritative server
  • Process:
    • Client contacts local DNS server, L
    • – If L knows the requested IP or is the authority, return the IPOtherwise, contact the root server
      • • Root server returns to L the authoritative server for the domainL contacts this server
      • Process may repeat until we find the authoritative server

DNS Lookup Example

  1. Computer requests IP for comp.walnut.candy.foobar.com from local DNS
  2. Not found in local DNS, local DNS becomes a client and contacts root server
  3. Root server returns server below, for foobar.com
  4. Local DNS contacts server at foobar.com
  5. Foobar.com server returns server below, for walnut.foobar.com
  6. Local DNS contacts server at walnut.foobar.com
  7. This is the authority, returns IP
  8. Local DNS returns IP to Computer

2,

4,

6,

Iterative Resolution