Chapter 4: Networking and the Internet
Security
Attacks Malware (viruses, worms, Trojan horses, spyware, phishing software) Denial of service (DoS) Spam Protection Firewalls Spam filters Proxy Servers Antivirus software
Protocols
CSMA/CD Used in Ethernet Silent bus provides right to introduce new message CSMA/CA Used in WiFi Hidden terminal problem
Inter-process Communication
Client-server Peer-to-peer (P2P)
Client Side Versus Server Side
Client-side activities Javascript Macromedia Flash Server-side activities Common Gateway Interface (CGI) Servlets JavaServer Pages (JSP) / Active Server Pages (ASP) PHP
Switch
Connects several compatible networks
Bridge
Connects two compatible networks
Router
Connects two incompatible networks resulting in a network of networks called an internet
Hypertext Markup Language (HTML)
Encoded as text file Contains tags to communicate with browser Appearance <h1> to start a level one heading <p> to start a new paragraph Links to other documents and content <a href = . . . > Insert images <img src = . . . >
Repeater
Extends a network
Encryption
HTTPS and SSL Public-key Encryption Public key: Used to encrypt messages Private key: Used to decrypt messages Certificates and Digital Signatures Certificate authorities
World Wide Web
Hypertext combines internet technology with concept of linked-documents Embeds hyperlinks to other documents Browsers present materials to the user Webservers provide access to documents Documents are identified by URLs and transferred using HTTP
Internet Addressing
IP address: pattern of 32 or 128 bits often represented in dotted decimal notation Mnemonic address: Domain names Top-Level Domains Domain name system (DNS) Name servers DNS lookup
Internet Architecture
Internet Service Provider (ISP) Tier-1 Tier-2 Access or tier-3 ISP: Provides connectivity to the Internet Hot spot (wireless) Telephone lines Cable/Satellite systems DSL Fiber optics
Network Classifications
Scope Personal area network (PAN) Local area network (LAN) Metropolitan area (MAN) Wide area network (WAN) Ownership Closed versus open Topology (configuration) Bus (Ethernet) Star (Wireless networks with central Access Point)
TCP/IP Protocol Suite
Transport Layer Transmission Control Protocol (TCP) User Datagram Protocol (UDP) Network Layer Internet Protocol (IP) IPv4 IPv6
Peer-to-peer (P2P)
Two processes communicating as equals Peer processes can be short-lived
More Recent Applications
Voice Over IP (VoIP) Internet Multimedia Streaming N-unicast Multicast On-demand streaming Content delivery networks (CDNs)
Extensible Markup Language (XML)
XML: A language for constructing markup languages similar to HTML A descendant of SGML Opens door to a World Wide Semantic Web
Connecting Networks
Repeater Bridge Switch Router
Internet Corporation for Assigned Names & Numbers (ICANN)
Allocates IP addresses to ISPs who then assign those addresses within their regions. Oversees the registration of domains and domain names.
The Internet
An internet that spans the world Original goal was to develop a means of connecting networks that would not be disrupted by local disasters Today a commercial undertaking that links a worldwide combination of PANs, LANs, MANs, and WANs involving millions of computers
Internet Software Layers
Application: Constructs message with address Transport: Chops message into packets Network: Handles routing through the Internet Link: Handles actual transmission of packets
Early Internet Applications
Network News Transfer Protocol (NNTP) File Transfer Protocol (FTP) Telnet and SSH Hypertext Transfer Protocol (HTTP) Electronic Mail (email) Domain mail server collects incoming mail and transmits outing mail Mail server delivers collected incoming mail to clients via POP3 or IMAP
Client-server
One server, many clients Server must execute continuously Client initiates communication
Distributed Systems
Systems with parts that run on different computers Cluster computing Grid computing Cloud computing Amazon's Elastic Compute Cloud Google Drive
