Transcript CSC 335 Data Communications and Networking I

CSC 581
Communication Networks II
Chapter 9: ISDN and ATM
Dr. Cheer-Sun Yang
Topics
• ISDN
• BISDN
• ATM
2
ISDN
•
•
•
•
ISDN Services
ISDN Architecture
Protocols: SS7 and ISDN Protocols
BISDN
3
ISDN Services
• Integrated voice and data applications
• Example: Teleconferencing
• Computer and telephone can combine.
4
ISDN Architecture
• Basic rate (2B + D): 2 D channels and 1 D
channel
• Prime rate (23B + D): 23 B channels and 1
D channel
5
Signaling System No 7
• SS7 is used for controlling the signaling of voice
data communication.
• X.25 cannot support more advanced telephone
services such as caller ID, 3-way calling, call
forwarding, calling card, etc.
• SS7 provides a common-channel signaling feature
for supporting these advanced telephone services.
Common channel signaling is an out-of band
signaling technique for which signaling
information is transmitted using an extra channel
beyond the voice data channel.
6
SS7 Layers
7
ATM
• Asynchronous Transfer Mode
• NOT the Auto-Teller Machine in a bank
• Cell Switching technique using a fixed-size
cell as the data unit.
8
Benefits of Small Fixed-Size Cells
• Easier to program.
• Faster transmission time for each cell.
• Easier to overlap input and output
operations.
• Smaller outgoing buffer
• Switches can forward multiple packets
concurrently.
9
Protocol Architecture
• Similarities between ATM and packet switching
– Transfer of data in discrete chunks
– Multiple logical connections over single physical
interface
• In ATM flow on each logical connection is in
fixed sized packets called cells
• NNI and UNI
• Minimal error and flow control
– Reduced overhead
• Data rates (physical layer) 25.6Mbps to
622.08Mbps
10
Management plane
Higher layers
Higher layers
Plane management
User plane
Layer management
Control plane
ATM adaptation layer
ATM layer
Physical layer
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Figure 9.2
Protocol Architecture (diag)
12
Reference Model Planes
• User plane
– Provides for user information transfer
• Control plane
– Call and connection control
• Management plane
– Plane management
• whole system functions
– Layer management
• Resources and parameters in protocol entities
13
5 Bytes
Header
48 Bytes
Payload
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Figure 9.1
Voice
A/D
AAL
s1 , s2 …
cells
Digital voice samples
Video
A/D
Compression
…
picture frames
AAL
cells
compressed
frames
AAL
Data
Bursty variable-length
packets
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cells
15
Figure 9.3
User
information
User
information
AAL
AAL
ATM
ATM
ATM
ATM
PHY
PHY
PHY
PHY
…
End system
Network
Copyright 2000 McGraw-Hill LeonGarcia and Widjaja Communication
End system
16
Figure 9.4
Private ATM
network
Private
UNI
X
X
Public ATM
network A
X
X
X
NNI
Public
UNI
X
B-ICI
Public ATM
network B
X
Public
UNI
X
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X
Private
NNI
17
Figure 9.5
ATM layer
Transmission
convergence
sublayer
Physical layer
Physical medium
dependent sublayer
Physical
medium
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Figure 9.6
GFC (4 bits)
VPI (4 bits)
VPI (4 bits)
VCI (4 bits)
ATM cell
header
VCI (8 bits)
VCI (4 bits)
PT (3 bits)
CLP
(1 bit)
HEC (8 bits)
Payload
(48 bytes)
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Figure 9.7
probability density

D0
Peak-to-Peak CDV
Dmax
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Figure 9.8
Service Specific
Convergence
Sublayer
AAL
Layer
Convergence
Sublayer
Common Part
Segmentation
and Reassembly
Sublayer
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Figure 9.9
Higher layer
b1
b2
…
b3
Convergence
sublayer
User data stream
CS PDUs
47
47
47
SAR PDUs
SAR sublayer
ATM layer
H
H
H
1 47
1 47
1 47
H
H
5
48
5
ATM Cells
H
48
5
48
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Figure 9.10
(a) SAR PDU header
CSI
1 bit
SNP
Seq. Count
3 bits
4 bits
(b) CS PDU with pointer in structured data transfer
47 Bytes
AAL 1
Pointer
1 Byte
46 Bytes
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Figure 9.11
AAL
2
ATM cells
Mobile
switching
office
Low bit rate
Short
voice packets
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Figure 9.12
Higher layer
This example assumes
24 byte packets
P3
P2
P1
Service specific
convergence
sublayer
Assume null
Common part
convergence
sublayer
H
H
H
3 24
3 24
3 24
SAR sublayer
PAD
1
ATM layer
Add 3-byte header to
each user packet
H
5
1
47
47
Segment into SAR
PDUs
H
48
5
48
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Figure 9.13
(a) CPS packet structure
CID (8 bits)
CPS packet
header
PPT
(2 bits)
LI (6 bits)
UUI (3 bits)
HEC (5 bits)
Payload
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Figure 9.14 - Part 1
(b) ATM SDU
Cell Header
Start field (STF)
OSF (6 bits)
SN
P
(1 bit) (1 bit)
CPS-PDU
payload
PAD
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Figure 9.14 - Part 2
Higher layer
Information
User message
Service specific
convergence
sublayer
Common part
convergence
sublayer
Assume null
H
2 44
T
4
4
…
SAR sublayer
ATM layer
PAD
Information
Pad message to multiple
of 4 bytes. Add header
and trailer.
2
2 44
2
2 44
2
Each SAR-PDU consists
of 2-byte header, 2-byte
trailer, and 44-byte
payload.
…
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Figure 9.15
(a) CPCS-PDU format
Trailer
Header
CPI Btag BASize
1
1
2
(bytes)
CPCS - PDU Payload
1 - 65,535
(bytes)
Pad AL Etag Length
0-3 1 1
2
(bytes)
(b) SAR PDU format
Trailer (2
bytes)
Header
(2 bytes)
ST SN MID
2 4 10
(bits)
SAR - PDU Payload
44
(bytes)
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LI CRC
6 10
(bits)
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Figure 9.16
Higher layer
Service specific
convergence
sublayer
Common part
convergence and
SAR sublayers
P1
Assume two packets
from different users
P2
MID = a
MID = b
CPCS
SAR
CPCS
SAR


SPDUA2
SPDUB2
SPDUA1
SPDUB1
Each packet is
segmented separately.
SAR PDUs identified by
MID.
Interleaver
ATM layer
Interleaved cells
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Cells from two packets
are interleaved.
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Figure 9.17
Higher layer
Information
Service specific
convergence
sublayer
Assume null
Common part
convergence
sublayer
PAD
Information
T
…
SAR sublayer
48
(0)
48
(0)
48
(1)
…
ATM layer
PTI = 0
PTI = 0
PTI = 1
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Figure 9.18
Information
0 - 65,535
(bytes)
Pad
UU CPI
0-47
1
1
(bytes)
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Length CRC
2
4
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Figure 9.19
Signaling application
Message
Message
SSCF maps SSCOP service to
service required by SSCF user
SSCF
SSCS
SSCOP
CSCP and SAR of
AAL 5
ATM layer
Message
T
As per Figure 9.18
SSCOP identifies gaps in SDU
sequence and requests
retransmissions
AAL 5 provides non-assured
service
…
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Figure 9.20
Information
0 - 65,535
(bytes)
Pad PL RSVD PDU
SN
Type
0-3 2 2
4
24
(bytes)(bits)(bits) (bits) (bits)
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Figure 9.21
(a) DCC ATM format
1
3
13
AFI DCC
HO-DSP
19 20
ESI
IDP
SEL
DSP
IDI
(b) ICD ATM format
1
AFI
3
13
ICD
HO-DSP
19
ESI
IDP
20
SEL
DSP
IDI
(c) E.164 ATM format
1
AFI
9
E.164
IDP
IDI
13
HO-DSP
19
ESI
SEL
DSP
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Figure 9.22
UNI
UNI
Destination
Network
Source
SETUP
CALL PROCEEDING
SETUP
CALL PROCEEDING
CONNECT
CONNECT
CONNECT ACK
CONNECT ACK
RELEASE
RELEASE COMPLETE
RELEASE
RELEASE COMPLETE
Copyright 2000 McGraw-Hill LeonGarcia and Widjaja Communication
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Figure 9.23
Network A
Network B
PNNI
PNNI
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Figure 9.24
Source
Switch
Source A
SETUP
Transit
Switch
SETUP
Destination
Switch
SETUP
Destination B
SETUP
CALL PROCEEDING
CALL PROCEEDING
CALL PROCEEDING
CALL PROCEEDING
CONNECT
CONNECT
CONNECT
CONNECT
CONNECT ACK
CONNECT ACK
CONNECT ACK
CONNECT ACK
RELEASE
RELEASE
RELEASE
RELEASE COMPLETE
RELEASE
RELEASE COMPLETE
RELEASE COMPLETE
RELEASE COMPLETE
Copyright 2000 McGraw-Hill LeonGarcia and Widjaja Communication
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Figure 9.25
Logical Link
A
B
Logical Group Node
Peer Group Leader
PG(A)
A.2
A.1
PG(A.1)
PG(B)
PG(A.2)
B.1
A.2.2
A.1.2
B.3
A.1.1
A.1.3
A.2.1
A.2.3
A.2.4
B.2
B.4
Physical Link
Copyright 2000 McGraw-Hill LeonGarcia and Widjaja Communication
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Figure 9.26
A.2
B
A.1.2
A.1.1
A.1.3
Copyright 2000 McGraw-Hill LeonGarcia and Widjaja Communication
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Figure 9.27
ATM Logical Connections
•
•
•
•
•
•
•
Virtual channel connections (VCC)
Analogous to virtual circuit in X.25
Basic unit of switching
Between two end users
Full duplex
Fixed size cells
Data, user-network exchange (control) and
network-network exchange (network management
and routing)
• Virtual path connection (VPC)
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– Bundle of VCC with same end points
ATM Connection Relationships
42
Advantages of Virtual Paths
• Simplified network architecture
• Increased network performance and
reliability
• Reduced processing
• Short connection setup time
• Enhanced network services
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Virtual Channel Connection Uses
• Between end users
– End to end user data
– Control signals
– VPC provides overall capacity
• VCC organization done by users
• Between end user and network
– Control signaling
• Between network entities
– Network traffic management
– Routing
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VP/VC Characteristics
• Quality of service
• Switched and semi-permanent channel
connections
• Call sequence integrity
• Traffic parameter negotiation and usage
monitoring
• VPC only
– Virtual channel identifier restriction within VPC
45
Control Signaling - VCC
• Done on separate connection
• Semi-permanent VCC
• Meta-signaling channel
– Used as permanent control signal channel
• User to network signaling virtual channel
– For control signaling
– Used to set up VCCs to carry user data
• User to user signaling virtual channel
– Within pre-established VPC
– Used by two end users without network intervention to
46
establish and release user to user VCC
Control Signaling - VPC
• Semi-permanent
• Customer controlled
• Network controlled
47
ATM Cells
•
•
•
•
Fixed size
5 octet header
48 octet information field
Small cells reduce queuing delay for high
priority cells
• Small cells can be switched more efficiently
• Easier to implement switching of small cells
in hardware
48
ATM Cell Format
49
Header Format
• Generic flow control
– Only at user to network interface
– Controls flow only at this point
• Virtual path identifier
• Virtual channel identifier
• Payload type
– e.g. user info or network management
• Cell loss priority
• Header error control
50
Generic Flow Control (GFC)
• Control traffic flow at user to network interface
(UNI) to alleviate short term overload
• Two sets of procedures
– Uncontrolled transmission
– Controlled transmission
• Every connection either subject to flow control or not
• Subject to flow control
– May be one group (A) default
– May be two groups (A and B)
• Flow control is from subscriber to network
– Controlled by network side
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Single Group of Connections (1)
• Terminal equipment (TE) initializes two variables
– TRANSMIT flag to 1
– GO_CNTR (credit counter) to 0
• If TRANSMIT=1 cells on uncontrolled connection
may be sent any time
• If TRANSMIT=0 no cells may be sent (on
controlled or uncontrolled connections)
• If HALT received, TRANSMIT set to 0 and
remains until NO_HALT
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Header Error Control
• 8 bit error control field
• Calculated on remaining 32 bits of header
• Allows some error correction
53
Cell Based Physical Layer
• No framing imposed
• Continuous stream of 53 octet cells
• Cell delineation based on header error
control field
54
Cell Delineation State Diagram
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SDH Based Physical Layer
•
•
•
•
•
Imposes structure on ATM stream
e.g. for 155.52Mbps
Use STM-1 (STS-3) frame
Can carry ATM and STM payloads
Specific connections can be circuit switched
using SDH channel
• SDH multiplexing techniques can combine
several ATM streams
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STM-1 Payload for SDH-Based
ATM Cell Transmission
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ATM Service Categories
• Real time
– Constant bit rate (CBR)
– Real time variable bit rate (rt-VBR)
• Non-real time
– Non-real time variable bit rate (nrt-VBR)
– Available bit rate (ABR)
– Unspecified bit rate (UBR)
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Real Time Services
• Amount of delay
• Variation of delay (jitter)
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CBR
• Fixed data rate continuously available
• Tight upper bound on delay
• Uncompressed audio and video
– Video conferencing
– Interactive audio
– A/V distribution and retrieval
60
rt-VBR
• Time sensitive application
– Tightly constrained delay and delay variation
• rt-VBR applications transmit at a rate that varies
with time
• e.g. compressed video
– Produces varying sized image frames
– Original (uncompressed) frame rate constant
– So compressed data rate varies
• Can statistically multiplex connections
61
nrt-VBR
• May be able to characterize expected traffic flow
• Improve QoS in loss and delay
• End system specifies:
– Peak cell rate
– Sustainable or average rate
– Measure of how bursty traffic is
• e.g. Airline reservations, banking transactions
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UBR
• May be additional capacity over and above that
used by CBR and VBR traffic
– Not all resources dedicated
– Bursty nature of VBR
• For application that can tolerate some cell loss or
variable delays
– e.g. TCP based traffic
• Cells forwarded on FIFO basis
• Best efforts service
63
ABR
• Application specifies peak cell rate (PCR)
and minimum cell rate (MCR)
• Resources allocated to give at least MCR
• Spare capacity shared among all ARB
sources
• e.g. LAN interconnection
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ATM Adaptation Layer
• Support for information transfer protocol not
based on ATM
• PCM (voice)
– Assemble bits into cells
– Re-assemble into constant flow
• IP
– Map IP packets onto ATM cells
– Fragment IP packets
– Use LAPF over ATM to retain all IP infrastructure
65
ATM Bit Rate Services
66
Adaptation Layer Services
•
•
•
•
Handle transmission errors
Segmentation and re-assembly
Handle lost and misinserted cells
Flow control and timing
67
Supported Application types
•
•
•
•
•
Circuit emulation
VBR voice and video
General data service
IP over ATM
Multiprotocol encapsulation over ATM
(MPOA)
– IPX, AppleTalk, DECNET)
• LAN emulation
68
AAL Protocols
• Convergence sublayer (CS)
– Support for specific applications
– AAL user attaches at SAP
• Segmentation and re-assembly sublayer (SAR)
– Packages and unpacks info received from CS into cells
• Four types
–
–
–
–
Type 1
Type 2
Type 3/4
Type 5
69
AAL Protocols
70
Segmentation and Reassembly
PDU
71
AAL Type 1
• CBR source
• SAR packs and unpacks bits
• Block accompanied by sequence number
72
AAL Type 2
• VBR
• Analog applications
73
AAL Type 3/4
• Connectionless or connected
• Message mode or stream mode
74
AAL Type 5
• Streamlined transport for connection
oriented higher layer protocols
75
Reading
• Chapter 9
• ATM Forum Web site
• Frame Relay forum
76