protocols used for communications between entities in a system used for communications between...
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ProtocolsProtocols Used for communications between Used for communications between
entities in a systementities in a system Must speak the same languageMust speak the same language EntitiesEntities
User applicationsUser applications E-mail facilitiesE-mail facilities TerminalsTerminals
SystemsSystems ComputerComputer TerminalTerminal Remote sensorRemote sensor
Protocol ContProtocol Cont Protocol:Protocol:
A set of rules and conventionsA set of rules and conventions Governs how computers exchange information over Governs how computers exchange information over
a shared/network medium. a shared/network medium. Used for communications between entities in a Used for communications between entities in a
systemsystem Defines :Defines :
What is communicatedWhat is communicated How it is communicatedHow it is communicated When it is communicatedWhen it is communicated
Varieties of communication protocols exist.Varieties of communication protocols exist. LAN protocols, WAN protocols, Network LAN protocols, WAN protocols, Network
protocols, Routing protocols etc. protocols, Routing protocols etc.
Key Elements of Protocol Key Elements of Protocol Syntax:Syntax:
Refers to structure or format of the data (the order Refers to structure or format of the data (the order they are presented)they are presented)
Example - data format, codingExample - data format, coding
Semantics:Semantics: Refers to the meaning of each section of the bitsRefers to the meaning of each section of the bits Example - data information, control informationExample - data information, control information
Timing:Timing: Refer to synchronousRefer to synchronous
When data should be sentWhen data should be sent How fast they can be sentHow fast they can be sent
Example sequencing, speed/delay matchingExample sequencing, speed/delay matching
Protocol ArchitectureProtocol Architecture Protocols in networking follows ‘layered’ Protocols in networking follows ‘layered’
architecturearchitecture
Purpose of this layered architecture: Purpose of this layered architecture: functions necessary for transfer of data are functions necessary for transfer of data are
grouped into layers.grouped into layers. a set of/each task(s) is separated from others.a set of/each task(s) is separated from others. several protocols at each layer, each suitable several protocols at each layer, each suitable
for a different situation.for a different situation. work that must be done in networking is work that must be done in networking is
broken down into manageable units. broken down into manageable units.
Protocol ArchitectureProtocol Architecture Task of communication broken up into Task of communication broken up into
modules, for example file transfer could modules, for example file transfer could use three modulesuse three modules File transfer applicationFile transfer application Communication service moduleCommunication service module Network access moduleNetwork access module
A simplified architecture A simplified architecture for file transfer for file transfer
Three-layered ModelThree-layered Model
Network Access LayerNetwork Access Layer Exchange of data between the computer Exchange of data between the computer
and the networkand the network Sending computer provides address of Sending computer provides address of
destination computer.destination computer. May invoke levels of serviceMay invoke levels of service Dependent on type of network used Dependent on type of network used
(LAN, packet switched etc.) (LAN, packet switched etc.)
Cont…Cont…
Transport LayerTransport Layer Reliable data exchangeReliable data exchange Independent of network being usedIndependent of network being used Independent of application Independent of application
Application LayerApplication Layer Support for different user applicationsSupport for different user applications E.g. e-mail, file transfer E.g. e-mail, file transfer
Protocols in simplified Protocols in simplified architecture architecture
Addressing Addressing RequirementsRequirements
Two levels of addressing requiredTwo levels of addressing required Each computer needs unique Each computer needs unique
network addressnetwork address Each application on a (multi-tasking) Each application on a (multi-tasking)
computer needs a unique address computer needs a unique address within the computerwithin the computer The service access point or SAPThe service access point or SAP The port on TCP/IP stacksThe port on TCP/IP stacks
Protocol Data UnitProtocol Data Unit At each layer, protocols are used to At each layer, protocols are used to
communicatecommunicate Control information is added to user data Control information is added to user data
at each layerat each layer Transport layer may fragment user dataTransport layer may fragment user data Each fragment has a transport header Each fragment has a transport header
addedadded Destination SAPDestination SAP Sequence numberSequence number Error detection codeError detection code
This gives a transport protocol data unitThis gives a transport protocol data unit
Protocol Data UnitsProtocol Data Units
Network PDUNetwork PDU
Adds network headerAdds network header Network address for destination computerNetwork address for destination computer Facilities requestsFacilities requests
Standardized Protocol Standardized Protocol ArchitecturesArchitectures
Required for devices to communicateRequired for devices to communicate Vendors have more marketable productsVendors have more marketable products Customers can insist on standards based Customers can insist on standards based
equipmentequipment Two standards:Two standards:
OSI Reference modelOSI Reference model Never lived up to early promisesNever lived up to early promises
TCP/IP protocol suiteTCP/IP protocol suite Most widely usedMost widely used
Also: IBM Systems Network Architecture Also: IBM Systems Network Architecture (SNA)(SNA)
OSI Model OSI Model
The OSI Model The OSI Model A layered framework for network system A layered framework for network system
s design s design allows for communication across all type allows for communication across all type
s of computer systems s of computer systems consists of 7 layers consists of 7 layers each layer defines a segment of process each layer defines a segment of process
of moving information of moving information
Layered Architecture Layered Architecture
Please Do Not Touch Steve’s Pet Alligator
Application
Presentation
Session
Transport
Network
Data Link
Physical
- - Peer to Peer Processes- - Peer to Peer Processes
Application
Presentation
Session
Transport
Network
Data Link
Physical
Application
Presentation
Session
Transport
Network
Data Link
Physical
machineA
machineB
--- - -< peer to pee ---r process >
provides s ervices for
uses se rvices
provide d by
The OSI EnvironmentThe OSI Environment
Functions of the Layers Functions of the Layers
Physical Layer Physical Layer Transmits a bit stream over a physical link Transmits a bit stream over a physical link Deals with the mechanical and electrical spe Deals with the mechanical and electrical spe
cifications of the interface and transmission cifications of the interface and transmissionmediummedium
Specification Responsibilities : defines Specification Responsibilities : defines interface the devices and the transmission mediu interface the devices and the transmission mediu
mm data rates : # of bits sent each second data rates : # of bits sent each second synchronisation of bits : synchronises both side cl synchronisation of bits : synchronises both side cl
ocksocks
Physical Layer (Cont.) Physical Layer (Cont.)
Specification Responsibilities : defines ( Specification Responsibilities : defines (cont.)cont.) Line configuaration : Line configuaration :
concerns with the connection of devices to the m concerns with the connection of devices to the mediumedium
- - point to point configuration- - point to point configuration 2 devices are connected together through a link 2 devices are connected together through a link
multipoint configuaration multipoint configuaration a aaaa aa aaaaaa aaaaaaa aaaaaaa aaaaaaaa aaaa aa aaaaaa aaaaaaa aaaaaaa aaaaaaa
physical topology, defines physical topology, defines how devices are connected (mesh, star, etc.) how devices are connected (mesh, star, etc.)
Physical Layer (Cont.) Physical Layer (Cont.)
Specification Responsibilities : define Specification Responsibilities : define s (cont.) s (cont.)
Transmission mode, defines Transmission mode, defines 2direction of transmission between devices 2direction of transmission between devices
- -simplex, halfdupl ex, f ul l dupl ex - -simplex, halfdupl ex, f ul l dupl ex
Data Link Layer Data Link Layer - - node to node delivery- - node to node delivery fix the errors for the next layer fix the errors for the next layer Specification Responsibility Specification Responsibility
framing framing devides the stream of bits into frames devides the stream of bits into frames
physical addressing physical addressing add headers (souce address, destination address) add headers (souce address, destination address)
aaaa aaaaaaaaaaa aaaaaaa prevent overflow transmission prevent overflow transmission
aaaaa aaaaaaaaaaaa aaaaaaa add mechanism for detecting damages add mechanism for detecting damages
Data Link Layer Data Link Layer
Specification Responsibility (cont.) Specification Responsibility (cont.) access control access control
aaa a aaaaaaaaa aaaaaaaaaaaaaaaaa a aaaaaaaaa aaaaaaaaaaaaaa determines which device has control over the link determines which device has control over the link
at any given time at any given time
Responsible the delivery of packets b Responsible the delivery of packets b etween 2 systems on the same netwo etween 2 systems on the same netwo
rk link rk link
Network Layer Network Layer
- -Responsi bl e f or t he source t o dest - -Responsi bl e f or t he source t o dest i nat i on del i very of packet across i nat i on del i very of packet across
mul i t pl e net work l i nks mul i t pl e net work l i nks ensures t hat a packet get s f romi t ensures t hat a packet get s f romi t
ori gi n t o dest i nat i on ori gi n t o dest i nat i on Specification Responsibilities Specification Responsibilities
logicall addressing logicall addressing add source/destination addresses add source/destination addresses
routingrouting
Network Layer (cont.) Network Layer (cont.)
- - Responsible for end to end delivery of - - Responsible for end to end delivery of individual packet individual packet
each packet is treated independently each packet is treated independently gets the packet to the correct comput gets the packet to the correct comput
erer
Transport Layer Transport Layer
- - Responsible for source to destination ( - - Responsible for source to destination (- - end to end) delivery of- - end to end) delivery of entire message entire message
ensure that the whole message arrives int ensure that the whole message arrives int act and in order act and in order
Specification Responsibilities Specification Responsibilities - service point addressing- service point addressing
port address port address gets the entire message to the correct progra gets the entire message to the correct progra
m on the computer m on the computer
Transport Layer (cont.) Transport Layer (cont.)
Specification Responsibilities (cont.) Specification Responsibilities (cont.) segmentation and reassembly segmentation and reassembly
devides message into segment (packet) devides message into segment (packet) addes a sequence number to each segment addes a sequence number to each segment
flow control flow control similar to the data link flow control similar to the data link flow control
perform end to end (machine) rather than across a link perform end to end (machine) rather than across a link
error control error control makes sure that the entire message arrives at the r makes sure that the entire message arrives at the r
eceiver without error (damage, loss, etc.) eceiver without error (damage, loss, etc.) retransmission mechanism retransmission mechanism
Session Layer Session Layer
The network dialog controller The network dialog controller Establishes, maintains, synchronise the int Establishes, maintains, synchronise the int
eraction between communication systems eraction between communication systems Specification Responsibilities Specification Responsibilities
dialog control dialog control - - agree to take either simplex, half duplex, full duplex - - agree to take either simplex, half duplex, full duplex
modemode synchronisationsynchronisation
allows a process to add checkpoints (synchronisatio allows a process to add checkpoints (synchronisatio n points in to a data stream) n points in to a data stream)
Session Layer (Cont.) Session Layer (Cont.)
a message of 1320 bytes
100
100
100
100
…...
checkpoint
synchronisation
Presentation Layer Presentation Layer
Concernswi t h t he synt ax and semant i cs of i Concernswi t h t he synt ax and semant i cs of i nformation exchanged between 2 sys nformation exchanged between 2 sys
t emst ems Specification Responsibilities Specification Responsibilities
translationtranslation character string character string numbers, etc. numbers, etc.
different computers use different encodi different computers use different encodi ng systems ng systems
Presentation Layer (Cont. Presentation Layer (Cont.))
Specification Responsibilities (cont.) Specification Responsibilities (cont.) responsible for interoperability between responsible for interoperability between
these different encoding methods these different encoding methods encryption encryption
aaa aaaaaaaaa aaaaaa aaaaaaaa aaaaaaaaa aaaaaa aaaaa aaaaaa aaaaa/ aaaaaa aaaaa/
compressioncompression reduce the number of bits to be transmitted reduce the number of bits to be transmitted
Application Layer Application Layer
Enables the user (human/software) t Enables the user (human/software) t o access the network o access the network
Specification Responsibilities Specification Responsibilities Applications : examples Applications : examples
aaaa aaa aaaaaaa aaaa aaaaaaaa aaa aaaaaaa aaaa aaaa to remote login to a remote machine to remote login to a remote machine
aaaa aaaaaaaaaaaa aaaaaaaa a aaa aaaaaaaaa aaa aaaaaaaa
TCP/IP Protocol Suite TCP/IP Protocol Suite
Used in the Internet Used in the Internet Developed before the OSI Model Developed before the OSI Model
do not match exactly with OSI Model do not match exactly with OSI Model 5 layers 5 layers
ApplicationApplication TransportTransport InternetworkingInternetworking NetworkNetwork PhysicalPhysical
TCP/IP Protocol Suite (Co TCP/IP Protocol Suite (Cont.)nt.)
Two main protocols Two main protocols Transmission Control Protocol Transmission Control Protocol aaaaaaaaa aaaaaa aaaaaaaaaaaaaaaaa aaaaaa aaaaaaaa
Many other protocols Many other protocols Hierarchical protocol Hierarchical protocol archi t ect ure archi t ect ure
made up f or i nt eract i ve modul es made up f or i nt eract i ve modul es - each upper level protocol is supported b - each upper level protocol is supported b
- y one or more lower level protocols - y one or more lower level protocols
TCP/IP Protocol Suite (Co TCP/IP Protocol Suite (Cont.)nt.)
AttheTransport l ayer, TCP/I P defi nes t w AttheTransport l ayer, TCP/I P defi nes t w o prot ocol s o prot ocol s
TCP TCP aaa aaaaa aaaaaaaa aaaaaaaaaaaa aaaaa aaaaaaaa aaaaaaaaa
At the Network layer At the Network layer IP IP
OSI vs TCP/IPOSI vs TCP/IP
TCP/IP and the OSI Model TCP/IP and the OSI Model
Physical
DataLink
Protocols defined b y the underlying ne
tworks
Network
ICMP IP
RARP
IGMP AR
P
Transport UDP TCP
ApplicationPresen
tationSession
ApplicationSMTP TELNET NFSFTP DNS SNMP
Addressing levelAddressing level Level in architecture at which entity is Level in architecture at which entity is
namednamed Unique address for each end system Unique address for each end system
(computer) and router(computer) and router Network level address Network level address
IP or internet address (TCP/IP)IP or internet address (TCP/IP) Network service access point or NSAP (OSI)Network service access point or NSAP (OSI)
Process within the systemProcess within the system Port number (TCP/IP)Port number (TCP/IP) Service access point or SAP (OSI)Service access point or SAP (OSI)
Trace of Simple Trace of Simple OperationOperation
Process associated with port 1 in host Process associated with port 1 in host A sends message to port 2 in host BA sends message to port 2 in host B
Process at A hands down message to Process at A hands down message to TCP to send to port 2TCP to send to port 2
TCP hands down to IP to send to host TCP hands down to IP to send to host BB
IP hands down to network layer (e.g. IP hands down to network layer (e.g. Ethernet) to send to router JEthernet) to send to router J
Generates a set of encapsulated PDUsGenerates a set of encapsulated PDUs
PDUs in TCP/IPPDUs in TCP/IP
Standard OrganizationsStandard Organizations
ISO ITU
IEEE
ANSI
EIA
State Department
Carriers Other org.