Download Introduction & Course overview

Introduction & Course Overview
Lesson 1
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Teacher
Martin Hjorth Stender
Room: 426
[email protected]
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Course Overview
• Generel communication in Protocol stacks
• Peer-to-peer communication
• Upper and lower layer
• Syntaxes for describing PDU (messages exchanged
between peer layers)
• Protocol Design (Patterns)
• Testing protocols
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Outline for today
• Fundamentals of Computer Networks (Rep.)
• Circuit Switching vs. Packet Switching
• Connection-Oriented vs. Connectionless
• Communication Protocol Stacks in Action
• Standard Organizations
•
•
•
•
3GPP
IETF
BlueTooth
Zigbee
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Outline for today
• Fundamentals of protocols in a multi-service network
• Layers of Communication
• Horizontal Communication
• Vertical Communication
• Protocols in Real
•
•
•
•
3GPP Long Term Evolution
ZigBee
ETSI Digital Enhanced Cordless Telecommunications
TCP
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Fundamentals of Computer Networks
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Fundamentals of Computer Networks
Two fundamental types of Network Switching:
Circuit Switching
Packet Switching
*Time-Division Multiplexing
Frequency-Division Multiplexing
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Network core – Circuit switching
Circuit Switching
•Requires a Setup/release phase
• for ressource reservation
•Quaranteed end-to-end connection
•Quaranteed constant rate (bandwidth)
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Fundamentals of Computer Networks
10 Mb/s
Ethernet
statistical multiplexing
A
B
C
1.5 Mb/s
queue of packets
waiting for output
link
Packet Switching
D
E
• data stream divided into packets
• packets share network resources
• packets uses full link bandwidth and as needed
• packets are stored & forwarded and queued.
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Packet- and Circuit switched
Packet switching allows more users to use network!
•1 Mb/s link
•each user:
•100 kb/s when “active”
•active 10% of time
•circuit-switching:
N users
1 Mbps link
•10 users
•packet switching:
•with 35 users, probability >
10 active less than .0004 =
0.04%
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Connection-Oriented Service
• Before two computers can communicate, they:
• Establish a ’connection’ through the network, by
• One computer requests a connection
• Second computer accepts the connection
• Data is transferred (full duplex…)
• Connection is terminated
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Connectionless Service
• When computer wants to send data, it:
• Place data in an appropriate frame format
• Attach the address of the destination computer
• Pass the frame to the network for delivery
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Communication Protocol Stacks in Action
GSM
GPRS
HTTP
TCP/IP
EDGE
SIP
RTP/RTCP
HSPA
UMTS
FTP
UDP/IP
LTE
DECT
LTE-A
SDP
TETRA
BlueTooth
Zigbee
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Standard Organizations
• 3GPP
• Specifies mobile communication protocols
•
GSM, GPRS, EDGE, UMTS, HSPA, LTE, LTE-A
The 3rd Generation Partnership Project (3GPP) is a collaboration
between groups of telecommunications associations, to make a
globally applicable third generation (3G) mobile phone system
specification within the scope of the International Mobile
Telecommunications-2000 project of the International
Telecommunication Union (ITU).
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Standard Organizations
• IETF
• Specifies all Internet related protocols
• TCP, UDP, IP, HTTP, FTP, SIP, SDP……
The Internet Engineering Task Force (IETF) develops and promotes
Internet standards, cooperating closely with the W3C and ISO/IEC
standard bodies and dealing in particular with standards of the TCP/IP
and Internet protocol suite
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Standard Organizations
• BlueTooth
• Specifies (surprise surprise) BlueTooth (core + profiles)
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Standard Organizations
• Zigbee Alliance
• Specifies (surprise) Zigbee (core + profiles)
ZigBee is a specification for a suite of high level communication
protocols using small, low-power digital radios based on the IEEE
802.15.4-2003 standard for wireless personal area networks
(WPANs), such as wireless headphones connecting with cell phones
via short-range radio.
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Fundamentals of protocols in a multi-service network
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Layered Communication
Computer Networks & Communication Systems
Ressource
Management
Integrity protection
- a need for structure?
Modulation
Channel coding
Flow control
Interleaving
Authentication
Error concealment
Encryption
Connection
Management
Addressing
Error correction
Re-transmission
Identification
Assembly
Link adaptation
Segmentation
File transfer
Error detection
Web browsing
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Location
Tracking
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Layered Communication
Conclusion:
- Computer Networks & Communication Systems are complicated processes.
- To cope with this complexity we organize the systems into:
LAYERS
- A layer performs some of the functions necessary to achive communication
between systems
-Each layer built upon the layer below (except for the lowest layer)
- The layers provide levels of abstraction
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Layered Communication
The OSI Reference Model
End System A
End System A
Application
Application
Intermediate Systems
Application Layer
Application Layer
Presentation Layer
Presentation Layer
Session Layer
Session Layer
Transport Layer
Transport Layer
Network Layer
Network
Layer
Network
Layer
Network Layer
Data Link Layer
Data Link
Layer
Data Link
Layer
Data Link
Layer
Data Link
Layer
Data Link
Layer
Data Link
Layer
Data Link Layer
Physical Layer
Physical
Layer
Physical
Layer
Physical
Layer
Physical
Layer
Physical
Layer
Physical
Layer
Physical Layer
Physical medium
Physical medium
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Physical medium
Physical medium
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Layered Communication
OSI Reference Model – Lower layers
The physical layer
Provides the mechanical, electrical and procedural means for transmitting bits over a communication
medium.
The data link layer
Provides services for the transmission of data between directly connected systems in a
communication network.
The network layer
Handles the routing of data through communication networks.
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Layered Communication
OSI Reference Model – Upper layers
The transport layer
Provides reliable end-to-end services without being concerned about the route
through communication networks.
The Session layer
provides facilities to organise and synchronise dialogues, i.e. communications that consist of several
strands such as audio and video components.
The Presentation layer
deals with issues about how data is represented and ensures that the systems agree on how the
information is transferred.
The Application layer
provides the means for application programs to access the communication system represented by the
OSI reference model. For instance, the application layer can provide services for supporting file
transfer and email.
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Layered Communication
OSI Reference Model – Reflections
1.
There should not be more layers than is necessary.
2.
Boundaries should be located where they have proved successful in the past.
3.
Boundaries should be located to minimise the interactions between layers.
4.
Boundaries should be located where a standardised interface may be useful.
5.
Separate layers should be created to perform functions that are associated with
different technologies or levels of abstraction.
6.
Functions associated with similar technology should be collected together in the same
layers.
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Layered Communication
Example – 4 layered protocol stack
System A
Application
Layer 4
Layer 3-4 interface
Layer 3
Layer 2-3 interface
Layer 2
Layer 1-2 interface
Layer 1
System B
peer-to-peer communication
Layer 4 protocol between peer layers
Layer 3 protocol between peer layers
Layer 2 protocol between peer layers
Layer 1 protocol between peer layers
Application
Layer 4
Layer 3
Layer 2
Layer 1
Physical media
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Layered Communication
Definition:
- The rules for sending blocks of data (each known as a Protocol
Data Unit (PDU)) from one node in a network to another node.
A protocol specification defines the operation of the protocol and
may also suggest how the protocol should be implemented. It
consists of three parts:
• Definition of Protocol Control Information (PCI) format which
forms the PDU header
• Definition of procedures for transmitting and receiving PDUs
• Definition of services provided by the protocol layers
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Layered Communication
Protocol Data Unit
• Header (PCI - Protocol Control Information
• Payload (SDU - Service Data Unit)
• The protocol does not define or constrain the
data carried in the payload part.
• It does specify the format of the PCI, defining
the fields which are present and the way in
which the patterns of bits are to be interpreted
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PDU
PCI
Packet
Header
SDU
Packet
Payload
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Layered Communication
A protocol also defines the procedures which determine how the
PDU will be processed at the transmit and receive nodes. The
procedures specify the valid values for the PCI fields, and the
action be taken upon reception of each PCI value (usually based
on stored control information). Examples of procedures which are
implemented in protocols include :
•error recovery (e.g. the go-back-n procedure)
•flow control
•segmentation
•service access point selection
•connection management
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Horizontal Communication
End System A
End System A
Application
Application
PDU
Data
PCI
AH
Data
Application Layer
PH
Data
Presentation Layer
SH
Data
Session Layer
TH
Data
Transport Layer
NH
Data
Network Layer
DH
Data
Data Link Layer
PH
Data
Physical Layer
Virtual connection
Virtual connection
Virtual connection
Virtual connection
Virtual connection
Virtual connection
Virtual connection
Application Layer
Presentation Layer
Session Layer
Transport Layer
Network Layer
Data Link Layer
Physical Layer
Physical medium
AH
Application layer header
TH
Transport layer header
PH
Presentation layer header
NH
Network layer header
SH
Session layer header
DH
Data link layer header
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PH
Physical layer header
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Vertical Communication
Protocol Header Processing for Transmission by Layer N
N+1 Protocol
Layer
PDU
PCI
+
Layer N+1
Protocol Data Unit
becomes a Layer N
Service Data Unit
SDU
N Protocol
Layer
PCI
SDU
Layer N PDU
N-1 Protocol
Layer
PCI
+
SDU
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Vertical Communication
Protocol Header Processing on Reception by Layer N
N+1 Protocol
Layer
PDU
PCI
+
Layer N+1
Protocol Data Unit
is formed from
the Layer N
Service Data Unit
SDU
N Protocol
Layer
PCI
SDU
Layer N PDU
N-1 Protocol
Layer
PCI
+
SDU
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Vertical Communication
Summary:
- A layer encapsulates the SDU by adding a protocol header (PCI)
- The combined PCI and SDU are known as a PDU
- The PDU of Layer N forms the SDU of the layer below (N-1)
Reflections:
- Layer N does NOT know anything about the content of the PDU received
How do we cope with a layer below that is providing multi-services?
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Vertical Communication
How do communication takes place between two adjacent
layers in the same system?
(N+1)-layer
(N+1)-entity
OSI view of adjacent layer communication
• Service Access Points (SAP)
• Processes that communicates across the
interface are called entities
(N)service
access
point
(N)-entity
(N)-layer
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Vertical Communication
The interaction between adjacent layers is expressed in
terms of issuing and receiving primitives
For each primitive up to four basic types are available
• request – an entity invokes a service
• indication – an entity is informed of an event
• response – an entity reacts to an event
• confirm – an entity is infromed of the result of an earlier request
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Vertical Communication
Sending system
(N+1)-layer
Receiving system
(N+1)-layer
Vertical communication
(N+1)-entity
(N+1)-entity
(N)response
primitive
(N)-service access point
(N)confirm
primitive
(N)request
primitive
(N)-entity
Horizontal communication over virtual connections
(N)-layer protocol
(N)-layer
(N)indication
primitive
(N)-entity
(N)-layer
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Vertical Communication
Example: DECT Call Control (NWK Layer) services:
• Setup
• Setup a phone call to remote (called party)
• Alert service
• Alert to the caller that the call is received (but not answered)
• Connect
•Connect to an incoming call
• Release
• Release (terminate) a call
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Vertical Communication
Example: DECT Call Control (NWK Layer) services:
• Setup service
•Setup.req, Setup.ind, Setup.res, Setup.cfm primitives
• Alerting service
•Alert.req, Alert.ind
• Connect service
•Connect.req, Connect.ind, Connect.res, Connect.cfm
• Release service
• Release.req, Release.ind, Release.res, Release.cfm
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Vertical Communication
Example: DECT Call Control (NWK Layer) services:
Sending system
(N+1)-layer
Receiving system
(N+1)-layer
Vertical communication
Application
Application
4.
Setup.res
6.
Setup.cfm
PDUs
1.
Setup.req
3.
Setup.ind
2. {SETUP REQUEST}
NWK Layer
5. {SETUP COMPLETE}
(N)-layer
NWK Layer
(N)-layer
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Vertical Communication
Most primitives carries data
Example DECT Setup.req:
• Called party number
• Calling party number
• Transaction Identifier
• Presentation Indication (may my number be displayed?)
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Vertical Communication
Most primitives carries data
Example DECT Setup.req:
• Called party number
• Calling party number
• Transaction Identifier
• Presentation Indication (may my number be displayed?)
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3G – Access Stratum Example
control
L3
control
control
control
control
RRC
PDCP
PDCP
L2/PDCP
BMC
L2/BMC
RLC
RLC
RLC
RLC
RLC
RLC
RLC
L2/RLC
RLC
Logical
Channels
MAC
L2/MAC
Transport
Channels
PHY
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L1
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