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Introduction of Computer Networking
Professor Wei Chen
Tennessee State University
Computer Network and Internet
• Internet/Intranet
Regional ISP
• LAN (10/100 Mbps, 1/10 Gbps )
• host (end system)
• Communication link
Local ISP
Sever
• transmitting rate
• router (packet switch)
• ISP
• Connection-oriented
reliable/connectionless unreliable
service
• multiplexing in circuit-switched
networks (frequency-division
multiplexing/time-division
multiplexing)
Company Network
Public Internet
• bandwidth (width of frequency
spectrum)
• delay and packet loss
Computer Network Protocols
Application
Protocol
Application Layer
Source
Application
Presentation Layer
Transport
Network
Session Layer
Link
Physical
Link
#
Transport Protocol
Physical
Transport Layer
(end-to-end transfer of message)
Network Layer
(Transfer of packets across network)
Data Link Layer
(Transfer of blocks across a link)
Physical Layer
Application
Transport
Network
Link
Physical
Destination
ISO/OSI Reference Model
Router
Network
Link
Physical
Link-layer
Switch
Application Layer
Popular Network Applications
Communicating Process and Socket
• Email
• Process and Socket: A process
(analogous to a house) sends messages
into, and receives messages from, the
underlying network through its socket
(analogous to a door).
• Web
• Remote login (Telnet)
• File transfer (FTP)
• Multi-user networked game
• Internet phone
• Real-time video conferencing
• IP address and Port Number: IP address
is a 32-bit quantity that uniquely identifies
the host. Port number identifies the type of
process.
Application-Layer Protocols
Network Application Architectures
• Type of messages (request, response)
• Client-server architecture (with fixed
always-on sever)
• Syntax of message type, semantics of the
fields
• P2P architecture (decentralized)
• Rules for determining when and how a
process sends and responds to messages.
• Hybrids of client-server and P2P
Important Issues: Reliable data transfer, Band
width, Timing
Transport Layer
Provides for logical communication between application
processes running on different hosts: (1) break the
application messages into smaller chunks, (2) adding a
transport-layer header to each chunk to create the transportlayer segment, and (3) then pass the segment to the network
layer.
Transport Layer in the Internet (TCP/IP)
• UDP (User Datagram Protocol) provides an unreliable, connectionless service, where
the transport layer packet is called as segment.
• TCP (Transmission Control Protocol) provides a reliable, connection-oriented service,
where the transport layer packet is called as datagram. TCP provides congestion control.
• Transport-layer multiplexing (gather data chunks at the source host from different
sockets and pass to network layer) and demultiplexing (delivering the data in transportlayer to the correct socket) extend host-to-host services between two end systems to a
delivery service between two processes running on the end system.
Important Issues: Reliable data transfer, Congestion control
Example 1: TCP Segment Structure
32 bits
Source port #
Dest port #
Sequence number
Acknowledgement number
Header Length
……
Receive window
Urgent data pointer
Internet checksum
Options
Data
Example 2: UDP Segment Structure
32 bits
Source port #
Length
Dest port #
Checksum
Data
Network Layer
Two important network layer functions
• Forwarding: transfers a packet from an incoming link to an outgoing link within
a single router.
• Routing: involves all of a network’s routers, whose collective interaction via
routing protocols (algorithms) determine the paths that packets take on their trips
from source to destination node.
Routing algorithms
Local forwarding table
IPv4 datagram format
32 bits
Version
Header
Length
Type of service
Datagram length (bytes)
Versio16-bit Identifier
Time to live
Flags
13-bit Fragmentation offset
Upper-layer protocol
Header checksum
32-bit Source IP address
32-bit Destination IP address
Options (if any)
Data
IPv6 datagram format
Version
32 bits
Flow label
Traffic class
Pay-load length
Next hdr
128-bit Source IP address
128-bit Destination IP address
Data
Hop limit
Link Layer
A link-layer protocol (Ethernet, 802.11 wireless LAN, token ring, PPP) is used
to move a datagram over an individual link. It defines the format of the packets
exchanged between nodes at the ends of the link, as well as the actions taken by
these nodes when the packets are sent and received.
Actions in Link layer
• sending and receiving frames including error detection
• retransmission
• flow control
• random access
Multiple Access Protocols
• Channel partitioning protocols (Time division multiplexing,
frequency-division multiplexing)
• Random access protocols
• Taking-turns protocols
Communication Unit in A Sensor Node
for Sensor Network
Overall Communication Process
Application
Protocol
Application Layer
Presentation Layer
Session Layer
Transport Protocol
Application Layer
Correlation-based
Communication Layer
Transport Layer
(end-to-end transfer of message)
Network Layer
(Transfer of packets across network)
Data Link Layer
(Transfer of blocks across a link)
Physical Layer
ISO/OSI Reference Model
Physical Layer
Wireless Ad-Hoc Model
Correlation-based Communication Layer
Fusion-Oriented Application Layer
Communication Tasks
Broadcasting
System Maintenance Tasks
Global Synchronization
Multicasting
Network Reconfiguration
Hierarchical Communication/routing protocols
Highest Level
Lowest Level
Structured (Hierarchical) Communication Network
Static/Dynamic Grained-Clustering
Physical Layer (Flat Communication Network)
Architecture of Sensor Nodes
RF Transceiver
Power tracking unit
Communication System
Power System
Micro controller
System timers
Control and computing
System
Data
path
Sensor array
Sensor System
Data memory
• Tradeoffs between power consumption, bandwidth, and latency
• Interrelationship between transmission rates, processor speed and power
consumption.
• Interface between an application and its communication protocols
Types of Nodes in Sensor Networks
(1) Homogeneous Sensor Network
•
Uniform sensor nodes & sink nodes
•
No base station
(2) Heterogeneous Sensor Network
•
Sensing nodes, processing nodes, mobile nodes, sink nodes
•
Mixed with base station
Wireless Stands
• IEEE 802.11 (Wi-Fi): Mainly used for the access between wireless devices
and base stations. Possible for the access between wireless devices.
• IEEE 802.15 (based on Bluetooth): Used for Ad-hoc network without base
station.
Comparison between standards
standard
Frequency
(unlicensed)
Data rate
MAC Protocol
802.11b
2.3-2.485 GHz
Up to 11 Mbps
Random access
CSMA/CA
802.11a
5.1-5.8 GHz
Up to 54 Mbps
Same as above
802.11g
2.4-2.485 GHz
Up to 54 Mbps
Same as above
802.15(based on
Bluetooth)
2.4 GHz
Up to 1 Mbps
TDM access
CAMA/CA: carrier sense multiple access with collision avoidance
TDM: time division multiplexing
54 Mbps
5-11 Mbps
I Mbps
802.11(a,g)
802.11b
802.15
UMTS/WCDMA,CDMA2000
IS-95 CDMA, GSM
384 Kbps
56 Kbps
Indoor
Outdoor
Mid range
Long range
10-30 m
50-200 m
200m-4km
5Km-20Km
IEEE802.11 Frame
Bytes:
16
2
6
Frame
Control
Duration
Address
1
MAC address of
the station that
transmits the
frame
6
Address
2
6
2
6
Address
3
Seq
Control
Address
4
MAC address of
the destination
station
MAC address of
the router
interface
0-2312
Payload
Using for
Ad-Hoc network
2
CRC
Cyclic
redundancy
check
Communication Unit
Application control
MAC
(Media access control )
protocol
Protocol processing
Synchronizer
Channel coding
Transmission
power control
RF transceiver
Communication Unit (Based on 802.11b)
• Radio transceiver
• Synchronizer (Global clock)
• No collision detection
• Each node has a distinguish ID.
• TDM access/Random access.
Software Sensor Nodes
• node ID
• node mode: sleeping, waking, charging
• communication range
• channel mode
• power level
• frame type: data, management, control
• memory size
• local clock
• physical location?
• global clock?
• QoS