Exploring the Network

1. Examples of Today‘s Popular Communication Tools

• Instant Messaging(real-time communication)/Texting(Such as QQ, MSN)
• Weblogs (blogs)(individual):easy to update and edit
• Wikis: groups of people can edit and view together.
• Podcasting: an audio-based medium that originally enabled people to record audio and convert it for use.
• Collaboration Tools(work together on shared documents)
• P2P File Sharing: share files with each other.
• Social Media: interactive websites where people create and share user-generated content with friends and family
• TelePresence: provides real-time audio and video conferencing.

2. Networks Supporting the Way We Learn

• Virtual classrooms
• Collaborative learning spaces
• On-demand video
• Mobile learning

3. What is Computer Netwrok?

计算机网络就是指将分布在不同地点具有独立功能的多台计算机及其外部设备用通信线路链接起来，在网络管理设备或管理软件的协调管理下，实现资源共享，信息处理的系统。

4. Components of the Network

• Devices: end devices & intermediary devices
• Media: copper cable & fiber optic cable & radio
• Services: protocols

4.1 End Devices (originate data flow) (host)

• • Computers (work stations, laptops, file servers, web servers)
  • Network printers
  • VoIP phones
  • Security cameras
  • Mobile handheld devices (such as wireless barcode scanners, PDAs)

4.2 Intermediary Devices (ensure data flows across the network)

• • Network Access Devices (Hubs, switches, and wireless access points)
  • Internetworking Devices (routers)
  • Communication Servers and Modems
  • Security Devices (firewalls)

Processes running on the intermediary network devices perform these functions:

• • Regenerate and re-transmit data signals
  • Maintain information about what pathways exist through the network and internetwork
  • Notify other devices of errors and communication failures
  • Direct data along alternate pathways when there is a link failure
  • Classify and direct messages according to QoS priorities
  • Permit or deny the flow of data, based on security settings

4.3 Network Media

• • Metallic wires within cables (copper cable)
  • Glass or plastic fibers (fiber optic cable)
  • Wireless transmission (radio)

Criteria for choosing a network media are:

• • The distance the media can successfully carry a signal.
  • The environment in which the media is to be installed.
  • The amount of data and the speed at which it must be transmitted.
  • The cost of the media and installation

5. The Interaction of Protocols

5.1 Networking protocol suites describe processes such as:

• • The format or structure of the message
  • The method by which networking devices share information about pathways with other networks
  • How and when error and system messages are passed between devices
  • The setup and termination of data transfer sessions

5.2 Technology Independent Protocols

(1) Networking protocols describe the functions that occur during network communications.

(2) Protocols generally do not describe how to accomplish a particular function.

5.3 The Benefits of Using a Layered Model

• Assists
  in protocol design,      because protocols that operate at a specific
  layer have defined      information that they act upon and a defined
  interface to the layers      above and below.
• Fosters competition because      products from different vendors can work together.
• Prevents technology or      capability changes in one layer from affecting other layers above and      below.
• Provides a common language      to describe networking functions and capabilities.

5.4 Protocol and Reference Models

There are two basic types of networking models: protocol models and reference models.

• Protocol model (TCP/IP): provides a model that closely matches the structure of a particular      protocol suite.
• Reference
  model (OSI/RM): provides a common reference for maintaining
  consistency within all types      of network protocols and services.

5.5 Protocol Data Units and Encapsulation

As
application data is passed down the protocol stack on its way to be
transmitted across the network media, various protocols add information
to it at each level. This is         commonly known as the encapsulation
process.

• • Data - The general term for the PDU used at the Application layer
  • Segment - Transport Layer PDU
  • Packet - Internetwork Layer PDU
  • Frame - Network Access Layer PDU
  • Bits - A PDU used when physically transmitting data over the medium

5.6 The TCP/IP Model

• • Application: Represents data to the      user plus encoding and dialog control
  • Transport: Supports communication      between diverse devices across diverse networks.
  • Internet: Determines the best path      through the network.
  • Network      Access:      Controls the hardware devices and media that make up the network.

5.7 The OSI Model

1. Application the means for end-to-end  connectivity between individuals in the human network using data networks
2. Presentation common representation of the data      transferred and to manage data exchange
3. Session this layer create and maintain      dialog between source and destination applications.
4. Transport
   defines serves to segment,      transfer, and reassemble the data for
   individual communications between      the end devices.
5. Network Provides services to exchange the      individual pieces of data over the network between identified end      devices.
6. Data Link describe methods for exchanging      data frames between devices over a common media
7. Physical
   describe the mechanical,  electrical, functional, and produral
   means to activate maintain and      de-activate physical connections for
   bit transmission to and from a      network device.

5.8 Addressing in the Network

6. Providing Network Security

There are two types of network security concerns that must be addressed to prevent serious consequences: network infrastructure security and content security.

• Securing a network infrastructure includes the physical securing of devices that provide network connectivity and preventing unauthorized access to the management software that resides on them.
• Content security refers to protecting the information contained within the packets being transmitted over the network and the information stored on network attached devices.

6.1 Security measures taken in a network should:

• • Prevent unauthorized disclosure or theft of information
  • Prevent unauthorized modification of information
  • Prevent Denial of Service(DoS)

6.2 Network Security:

1. Viruses,      worms, and Trojan horses
2. Spyware and adware
3. Zero-day attacks (zero-hour attacks)
4. Hacker attacks
5. Denial of service attacks      (DoS)
6. Data interception and theft
7. Identity theft

6.3 Means to achieve these goals include:

• • Ensuring confidentiality: Only the intended recipients can access and read the data
  • Maintaining integrity: The assurance that the information has not been altered during transmission.
  • Ensuring availability: The assurance of timely and reliable access to data

7. What is data? What is a data network? What is a converged network?

Data is the pieces of information, such as files, audio, phone calls and video shared across the network.

A data network consists of:

Devices that communicate with each other

A means of connecting these devices together—a medium that can transport messages from one device to another

The digital messages or units of information that will travel from one device to another

Rules or agreements to govern how the messages are sent, directed, and received

Converged networks:

One network now carries multiple types of messages and information. Separate networks are no longer required to support voice, video, and data traffic.

Network Architectures:

• Cisco Borderless Networks architecture

The Cisco Borderless Network Architecture is a network solution that allows organizations and individuals to connect securely, reliably, and seamlessly to the corporate network in a BYOD environment.

• Collaboration architecture (meet expanding collaboration needs)
  • Tele-Presence
  • Collaboration Applications
  • Customer Collaboration
  • Unified Communications

• Data center and virtualization architecture
  • Cisco Unified Computing:       Modular Stateless Computing Elements
  • Cisco Unified Fabric:       Highly Scalable, Secure Network Traffic
  • Cisco Unified Management:       Automated Resource Management (Physical and Virtual)

Communicating the Messages

Segmenting messages has two primary benefits. Multiplexing & reliability

(1) Multiplexing: The process used to interleave the pieces of separate conversations together on the network

(2) Segmentation can increase the reliability of network communications.

Disadvantages:

The downside to using segmentation and multiplexing to transmit messages across a network is the level of complexity that is added to the process.

All networks have four basic elements in common (Sender, Receiver, and channel)

• Rules
• Medium
• Messages
• Devices

Connecting to the Internet:

• Cable: a high bandwidth, always      on , uses coaxial cable as a medium
• DSL: a high bandwidth, always      on, telephone cable, split into three channels:
  • One channel: voice       telephone calls
  • Second channel: faster       download channel
  • Third channel: for sending       or uploading information.
• Cellular: use a cell phone      network to connect.
• Satellite: for homes or      offices don’t need DSL or cable. Not suited Heavily wooded areas
• Dial-up Telephone: an      inexpensive option that uses any phone line and a modem.  Low BW

Many homes and small offices are more commonly being connected directly with fiber optic cables. This enables an Internet service provider to provide higher bandwidth speeds and support more services such as Internet, phone, and TV.  Satellite

Connecting Businesses to the Internet：Higher bandwidth, dedicated bandwidth, managed service

• Dedicated Leased Line:  T1 (1.544MB/s) and T3 (44.7MB/s)   E1 (2MB/s) E3 (34MB/s)
• Metro Ethernet: providing      bandwidth speeds of 10Mb/s to 10Gb/s
• DSL: Business DSL is      available in various formats. Symmetric Digital Subscriber      Lines.(upload=download)
• Satellite: provide a      connection when a wired solution is not available.  geographical location and service      provider availability.

Appendx Protocol Suites and Industry Standards

ISOC: The Internet Society

Responsible for promoting open development, evolution, and Internet use throughout the world.

IAB: The Internet Architecture Board

Responsible for the overall management and development of Internet standards.

IEEE: Institute of Electrical and Electronics Engineers

A professional organization for those in the electrical engineering and electronics fields who are dedicated to advancing technological innovation and creating standards.

Standards are developed using a six stage lifecycle diagram

Offers online tools and resources for standards and developers.

• • 802.1 Higher Layer LAN      Protocols Working Group
  • 802.3 Ethernet Working Group
  • 802.11 Wireless LAN Working      Group
  • 802.15 Wireless Personal      Area Network (WPAN) Working Group
  • 802.16 Broadband Wireless      Access Working Group
  • 802.18 Radio Regulatory TAG
  • 802.19 Wireless Coexistence      Working Group
  • 802.21 Media Independent      Handover Services Working Group
  • 802.22 Wireless Regional      Area Networks
  • 802.24 Smart Grid TAG

IETF: Internet Engineering Task Force

Develop, update, and maintain Internet and TCP/IP technologies.  Produce RFC documents.

Makes the Internet work better, using and engineering approach

RFC are official documents which are used to describe a standard or protocol that is related to the Internet.

These protocols are open standards &not vendor proprietary.   The RFC process includes significant review and comment by the community.

Once an RFC is published, it means that the standard is completed

ISO: The International Organization for Standardization

ICANN: The Internet Corporation for Assigned Names and Numbers

Coordinates IP address allocation, the management of domain names used by DNS, and the protocol identifiers or port numbers used by TCP and UDP protocols

IANA: The Internet Assigned Numbers Authority

Overseeing and managing IP address allocation, domain name management, and protocol identifiers for ICANN.

TIA: The Telecommunications Industry Association

Responsible for developing communication standards in variety of areas including radio equipment, cellular towers, voice over IP (VoIP) devices, satellite communications.

Creates standards for worldwide cabling infrastructure

Develops standards/protocols affecting cloud computing

Develops standards for homeland security/emergency response teams.

ITU-T: The International Telecommunications Union-Telecommunication Standardization Sector

Video compression, IPTV, broadband communications, DSL Uses communications standards to predict famines and global climate changes   Supports “bridge the digital     divide” initiatives

Supports navigation and online maps via radio/satellite transmissions