Computer Networks: Peer-to-Peer

• A network is a group of computers and devices connected by transmission media.
• Stand-alone computers are not connected to other computers and use local software and data.
• Networks facilitate device sharing, save money and time, and enable central network management.
• Network models include peer-to-peer and client/server.

Peer-to-Peer Networks

• Involve direct computer communication with equal authority among devices.
• Enable individual resource sharing, with the option to prevent access to certain resources.
• Consist of two or more general purpose computers capable of sending/receiving data to/from every other computer.
• Simple to configure and less expensive than other network models.
• Can be inflexible and not necessarily secure and are not practical for large installations.
• Environments for peer-to-peer include small home or office networks.
• Newer peer-to-peer networks over the Internet are known as P2P networks.
  • Examples: Gnutella, Bitcoin, original Napster, and BitTorrent software.

Client/Server Networks

• Clients are personal computers, also know as workstations.
• Centralized resource sharing is controlled by a server.
  • It shares data, storage space and devices.
  • There is no direct sharing of client resources.
• Server roles include running local applications and storing data locally and using a server as intermediary.
• Client/server communication occurs through switches or routers.
• Servers require a network operating system to:
  • Manage client data and resources
  • Ensure authorized user access
  • Control and restrict user file/network access
  • Dictate computer communication rules
  • Supply applications to clients
  • Server examples: UNIX, Linux, Microsoft Server 2008 R2, MAC OS X Server
• Servers have more memory, processing, and storage capacity.
  • They are equipped with special hardware and provides network management functions
• Client/server networks involve more complex design and maintenance relative to peer-to-peer networks.
• Client/server networks share advantages relative to peer-to-peer networks:
  • User credentials can be assigned from one place
  • Multiple shared resources access is centrally controlled.
  • Central problem monitoring, diagnostics, and correction capabilities exist.
  • Optimized to handle heavy processing loads.
  • The ability to connect many computers on a network.
  • Increased scalability.

Network Geography

• LAN: a network confined to a relatively small space (classroom, school, or single building).
  • LANs are inexpensive and provide higher speeds.
  • In the 1980s, LANs became popular as peer-to-peer based networks.
  • Today they are larger and more complex client/server networks.
• MAN: connects clients and servers from multiple buildings.
  • It uses different transmission media and technology than LANs.
  • Spans the distance of a typical metropolitan city
  • Have higher installation and operation costs.
  • Uses high-speed connections such as fiber optics
• WAN: connects two or more geographically distinct LANs or MANs.
  • Employs different transmission methods and media than LAN.
  • Spans a larger area than a single city.
  • Uses long distance telecommunication networks, thereby increasing the cost.
  • The Internet is a good example of a WAN.
  • WANs provide a network connection for: - Separate offices in the same organization. - Separate offices in different organizations.

Elements Common to Client/Server Networks

• Client: requests resources or services from another network computer.
• Client workstation human user.
• Client software is installed on the workstation.
• Server: manages shared resources and it runs network operating software.
• Workstation: personal computer that might or might not be connected to a network.
• NIC (network interface card): device inside computer that connects it to network media and allows communication with other computers.
• NOS (network operating system): server software that enables the server to manage data, users, groups, security, applications and other networking functions.
• Host: a computer enables network resource sharing by other computers.
• Node: a client, server, or other device that communicates over a network and is identified by a unique network address.
• Connectivity device: allows multiple networks or multiple parts of one network to connect and exchange data.
• Segment: A group of nodes using the same communications channel for traffic.
• Backbone: Connects segments and significant shared devices which creates "a network of networks."
• Topology: Computer network physical layout (ring, bus, star or hybrid formation)
• Protocol: Standard method/format for communication between networked devices.
• Packet: Distinct data units exchanged between nodes.
• Addressing: Scheme for assigning a unique identifying number to every node.
• Transmission media: Means through which data is transmitted and received.

How Networks Are Used:

• Network services: functions provided by a network

  • E-mail
  • Printer sharing
  • File sharing
  • Internet access and Web site delivery
  • Remote access capabilities
  • Voice and video services
  • Network management

• File and Print Services: file services provide a foundation of networking.

  • The capability of server to share data files, applications and disk storage space is useful.
  • Provides file services.
  • It shares printers across network and saves time and money.

• Access Services: allow remote user network connection.

• Allows network users to connect to machines outside the network

• The Remote Access Server, known as Access Server.

• Communications Services

  • Convergence: Offering multiple types of communications services on the same network.
  • Unified communications: Centralized management of multiple network-based communications.
  • Mail server: Computer responsible for e-mail storage and transfer.

• Internet Services

  • Web server: Computer installed with appropriate software to supply Web pages to different clients upon demand.
    • File transfer capabilities.
    • Internet addressing schemes.
    • Security filters.
    • Means for directly logging on other Internet computers.

• Management services:

  • Small network management: Single network administrator
  • Today’s larger network management: Centrally administered network management tasks

• Important Network Management Services :

• Traffic monitoring and control: Determines how much traffic is taking place on a network and notifying administrator when network becomes over loaded.

• Load balancing: Distributes the data transfers activity evenly.

• Hardware diagnosis and failure alert: Determines when a network component fails and automatically notifies the network administrator through a text message or email.

• Asset management: Collects and stores the data on number and types of software and hardware assets in an organization’s environment.

• License tracking: Determines how many copies of single application are currently in use in network and ensure that the number of copies does not exceed.

• Security auditing: Evaluates what security measures are currently in force and notify net work administrator if security breach occurs,

• Address management: Centrally manage a finite number of network addresses for the whole network.

• Software distribution: Automatically transfers a file or installs an application from the server to the client on the network.

• Backup and restoration of data: Backs up critical data files to a secure storage area and then restores data if the original files are last or deleted.