Networking Concepts

• Focus is on data communications and computer networks
• Includes discussion of fundamental concepts of computer networks

Data Communication Components

• Message is the information to be communicated
• Sender is the device sending the data
• Receiver is the device receiving the data
• Medium is the physical path the message travels
• Protocol are the rules governing data communication

Data Representation

• Data can be represented through text, numbers, images, audio, and video

Data Flow Types

• Simplex is one-way communication
• Half-duplex is two-way, but only one can send at a time
• Full-duplex is two-way simultaneous communication

Networks Defined

• A network is a set of devices (nodes) connected by communication links
• Topology is the arrangement of these links and nodes
• Nodes include computers, printers, and other devices

Physical Topologies

• Mesh topology: Every device has a dedicated point-to-point link to every other device
  • Link carries traffic only between the two devices it connects
  • A fully connected mesh network has n(n-1)/2 physical duplex links to link n devices
  • Requires n-1 input/output (I/O) ports on each device
  • Advantageous due to less traffic, robustness, security, and ease of maintenance
  • Disadvantageous due to high resource needs (cable and ports), leading to expense
• Star topology: Each device has a dedicated point-to-point link only to a central controller
  • Usually called a hub
  • There is no direct traffic or link between devices
  • Advantages: Less expensive, easy to install and reconfigure, robust
  • Disadvantage: Single point of failure
• Bus topology: Devices connected to a backbone cable via drop lines and taps
  • A multipoint topology
  • Drop line: connects the device and the main cable
  • Tap: A connector that splices into the main cable
  • Advantage: Easy to install
  • Disadvantages: Difficult reconnection and fault isolation; a broken cable halts transmission
• Ring topology: Each device connected to exactly two other devices
  • A signal is passed along the ring until it reaches its destination
  • Each device incorporates a repeater
  • Advantageous due to relative ease of install and reconfiguring, also simplifies fault isolation
  • Disadvantage: Unidirectional traffic
• Tree topology: Integrates multiple topologies together
  • A number of start topologies are connected to a bus
  • Advantages: Point-to-point wiring for individual segments, support from multiple hardware/software vendors
  • Disadvantages: overall length of each segment is limited by the type of cabling, if the backbone cable breaks down

Network Connection Types

• Point-to-point: A dedicated link is provided between two devices
• Multipoint: More than two specific devices share a single link

Network Categories

• Local Area Network (LAN)
• Wireless Local Area Network (WLAN)
• Metropolitan Area Network (MAN)
• Wide Area Network (WAN)

Protocols and Standards

• Protocol is a set of rules for formatting and processing data
  • Rules are synonymous
  • Syntax is the format of the data
  • Semantics is the meaning of each section
  • Timing is when should data should be sent and how fast
• Standards are agreed-upon rules
• Standard Organizations include:
  • International Standers Organization (ISO)
  • International Telecommunication Union - Telecommunication Standards (ITU-T)
  • American National Standards Institute (ANSI)
  • Institute of Electrical and Electronics Engineers (IEEE)
  • Electronic Industries Association (EIA)

Network Models

• Network Model is a layered Architecture
• Tasks are broken into subtasks implemented separately in layers in a stack
• Functions are need in both systemns
• Peer Layers communicate
• Open Systems Interconnection (OSI) model covers all aspects of network communications from ISO
  • Model was introduced in the late 1970s.

OSI Model Layers

• Application (Layer 7): network process to application
• Presentation (Layer 6): data representation and encryption
• Session (Layer 5): inter-host communication
• Transport (Layer 4): end-to-end connections and reliability
• Network (Layer 3): path determination and logical addressing
• Data Link (Layer 2): physical addressing
• Physical (Layer 1): media, signal, and binary transmission
• In the sending device, each layer adds its own information to the message and passes it down.
• At the receiving device, layers are unwrapped, and the relevant data is removed.

Layer Specifics

• Application Layer: Responsible for providing services to the user
  • Functions include: Network virtual terminal(remote log-in), file transfer and access, mail services and WWW accessing
• Presentation Layer: Responsible for translation, compression and encryption
  • Includes functions such as translation which is EBCDIC coded text file into ASCII
  • Includes Encryption and Decryption
  • Includes Compression
• Session Layer: Responsible for dialog control and synchronization
  • Functions include dialog control
  • Includes synchronization(checkpoints)
• Transport Layer: Responsible for message delivery from one process to another. (Reliable Process-to- process delivery
  • functions include port addressing
  • Functions include Flow, Error and Connection Control(orientated or connection-less)
  • Includes segmentation and reassembly
• Network Layer: Responsible for delivery of individual packets from original source host to final distention host
  • Includes Logical addressing
  • Includes routing
• Example Situation: To send data from node A with network address and physical 10 to node P with network address and physical address 95 which is another LAN
  • We need to use universal addresses instead of physical addresses that can pass through the LAN boundaries
• Data Link Layer: Moving Frames from one hop(mode) to next
  • Includes framing
  • Included Physical addressing
  • Includes Flow Control
  • Includes Error Control
  • Includes Access Control
• Example Situation: Addressing data between networks
  • Node with physical address 10 sends a frame to a node with physical address 87
  • The two nodes are connected by a link
  • At the data link level, this frame contains physical addresses
• Physical Layer: Movement on indicial bits from on hop(mode) to the next
  • Includes Representation of bits
  • Includes Data Rate
  • Includes synchronization of bits
  • Includes Physical topology
  • Includes Transmission mode

TCP/IP protocol Suite Layers

• Host-to-network Layer
• Internet
• Transport
• Application
• Has 4 defined layers: link, network, transport, and application

Addresses in TCP/IP

• Physical Address(MAC): also known as MAC address
  • It is the address of a node as defined by its LAN
  • is address is also included in the frame used by dta link layer
  • Most local-area networks (Ethernet) use a 48-bit (6-byte) physical address written as 12 hexadecimal digits.
  • ex: 07:01:02:01:2C:4B
• Logical Address(IP): Are necessary for universal communications that are independent of physical network
  • No two host address of the internet can have the same IP
  • IP addresses in the Internet are 32-bit addresses that always define a host. Remain the Same.
• Port address: Is a 16-bit address represented by one decimal number ranged from (0-65535) to choose a process among multiple processes on the destination hots
  • Destination port numbers are needed for delivery
  • Source port numbers are need for receiving a reply as an acknowledgement
  • ex: 753
  • Physical address change from hop to hop while Logical and Port, addresses usually remain the same

Internet Components

• Billions of connected computing devices using a network
• "network of networks" that are Interconnected ISPs
• Hosts = end systems that run network communication links of fiber, copper, radio, satellite with transmission rate
• Protocols that control sending/ receiving of processes as examples of TCP,IP,HTTP and Skype
• RFC is required in comments and Internet Engineering Task Force(IEF) Internet Standards
• Packet is a chunk of Data with routers and switches that forward packets

Network Structure

• Network edge: hosts(servers and patients)
• Access Networks: Physical media, wired, wireless communication links and servers are located in data center
• Network Core: Inter connected routers in network
• Internet services via ISPs that can provide wired/wireless capability through DSL, Cable,WiFi and Cellular

Internet Structure

• End systems connect to the Internet via access ISPs( service providers)
• Connection Types:DSL, Cable,WiFi and Cellular
• Customer and provider ISPs maintain an economic agreement
• Access to ISPS turns in must be inter connected So any two hosts can send data to each other

Key factors in networks

• Link is interconnected from business of which must have a viable agreement
• The Internet exchange point is the meeting point between Internet companies to allow for exchange of data at fast speeds

Packets of Data and Sending functions

• An application message that takes into smaller chunks
• Packets of the length of L bits , transmits packet into access network and transmission rate R transmission delay = time needed to transmit L bit packet into a link

Network Performance

• Packet are in a queue in router buffer to temporarily exceed an output link capacity
• Causes packet to wait for turn transmission of delay
• Limited buffers drop data, which leads to some packet arriving from available buffers being marked *loss *

Four Sources of Packet Delay

• Processing, which is when a packet arrives at its router it examines a packets head and directs he packet to outbound link
• Queuing is the time waiting at output link for transmission which is dependent on congestion
• Dtrans = Transmission is the packet lengths (bits) on rate that determines length ,the equation to calculate

The components within the Internet structure

• Small no of well connected large networks(ISPs)
• Commercial ISPs which are tier 1 has both national an d international coverage also referred to as commercial ISPs
• content provider has centers that connect data to Internet, often by passing tier-1 regional ISPs

Internet Protocol Layers

-Application -supporting network application of applications for example FTP ,SMTP,HTTP -Transports-data- transfers for example TCP UDP -Network - Routing of data for examples IP routing

• Physical bits that exist on the wire

Test your knowledge of data link layer functions, network organization, network types and OSI model layers. Questions cover flow control, physical addressing, and the roles of ISPs in internet structure.