Overview 19/9 LAN, MAN, and WAN - I - FTP

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1
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
Overview 19/9
¥ General introduction
¥ High-speed LANs:
- FDDI (& FDDI - II)
- fast ethernet
- isochronous ethernet
- VG-AnyLAN
¥ MANs
- DQDB
¥ WANs:
- Idea and characteristics of ATM
- Physical, ATM, and ATM Adaptation Layers (AALs)
- ATM Signalling
¥ Comparison of High-Speed LANs
¥ Summary
Application Subsystem
Transport Subsystem
Networking System
AP
2
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
LAN, MAN, and WAN - I
¥ Transmission speed in networks increased over the past
decade:
- 5 orders of magnitude, i.e., from Kbit/s to Gbit/s
- advances in VLSI circuits,transmission,switching,protocols,computer tech-
nology
¥ Changes in all types of networks:
- Local Area Networks (LANs)
- Metropolitan Area Networks (MANs)
- Wide Area Networks (WANs)
¥ General characteristics of new networks:
- increased bandwidth
- decreased end-to-end delay
- decreased error probability
- increased number of communication partners available via layer 2 services
3
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
LAN, MAN, and WAN - II
¥ Characteristics of shared LANs:
- integrates multiple workstations to share data within a local organization
- complete ownership by a single organization
- diameter not more than a few kilometers (typically 5)
- total data rate of at least several Mbit/s
- error rates in the range 10
-8
to 10
-11
- all stations receive transmissions of all other stations
- broadcast and multicast support
- only one station may send data at a time
- aggregate of all station is limited to the LAN bit rate
Station
Station
Station
Station
Station
Station
Station
Station
Station
Station
Bus topology Ring topology
4
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
LAN, MAN, and WAN - III
¥ From shared medium LAN to LAN switching:
- reason for shared medium: cables, wiring, and switching were expensive
- idea of simple linear cable turned out to create operational difÞculties
- LANs were organized around cascaded wiring hubs
- resulting topologies: Òlogical bus/physical starÓ or Òlogical ring/physical starÓ
- why not install a switch instead a wiring hub?
=> LAN switch:
ÒStations keep their conventional Ethernet, Token Ring, or FDDI interfaces.
But the shared-medium algorithm is no longer applied site-wide. One or a
few stations are attached to a node located at the wiring hub which may
switch LAN frames. The difÞculty lies in the inter-switch connections which
may act as bottlenecks.Ó
Fluckinger, F.: ÒUnderstanding Networked Multimedia, pp. 407-408
according to: Fluckinger, F.: ÒUnderstanding Networked MultimediaÓ, Prentice Hall, 1995, pp.406
Station
Station
Station
Station
Station
Station
Station
Station
Station
Station
Ethernet wiring hub
Ring wiring hub
5
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
LAN, MAN, and WAN - IV
¥ Characteristics of switched LANs:
- stations are connected to a switch
- shared LAN may be upgraded in small increments by replacing hubs with
switch ports
- switch ports may be shared by stations with low requirements
- stations with high requirements are directly attached to one port
- switches provide isolation
- latency is lower than in shared LANs
- for switch with N ports the maximum aggregate bandwidth is:
Station
Station
Station
Station
Ethernet
switch
Station
Station
Dedicated ethernet segments
BW N media-bit-rate( )×=
6
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
LAN, MAN, and WAN - V
¥ Characteristics of MANs:
- based on LAN technology
- cover an entire city, i.e., ~100 kilometers in diameter
- may connect several private organization
- mainly optical Þber at the physical layer
- bandwidth from 100 Mbit/s to Gbit/s
¥ Characteristics of WANs:
- connecting LANs/WANs
- traditional WAN services: X.25, IP
low bandwidth, e.g., 64 Kbit/s
- error rates in the range 10
-5
to 10
-7
- moving functionality like error correction,ßowcontrol,and congestion control
from intermediate network nodes to the end-systems (and cell switching in
intermediate nodes in hardware):
frame relay - 2 Mbit/s
SMDS - 1.5 Mbit/s to 34 Mbit/s
ATM - up to Gbit/s
7
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
LAN, MAN, and WAN - VI
Bandwidth
(Mbps)
B-ISDN ¥ 155, 622 Mbit/s
¥ ATM
¥ Integrated services (Voice, Data, Video)
MAN (DQDB, SMDS)
¥ 1.5, 45, 155 Mb/s
¥ MAN
¥ CO data
/ CL services
¥ Isochronous service
¥ Compatible with B-ISDN
FDDI
¥ 100 Mbit/s
¥ Data
Ethernet /
Token ring/
Token bus
¥ LANs
¥ Data
Frame relay
¥ ~2 Mbit/s
¥ Data
X.25 ¥ ~56,64 Kbit/s
¥ Data
Campus Metropolitan
National/
International
Distance
1000
100
10
1
according to Lee et al. ÒBroadband Telecommunication TechnologyÓ, Artech House, 1993
8
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
Ethernet
¥ IEEE 802.3
¥ Carrier Sense Multiple Access with Collision Detection
(CSMA/CD)
¥ Bus network
according to Hopper et al. ÒLocal Area Network DesignÓ, Addison Wesley, 1986, pp.43-44
Tap
Ether
Tranciever
Interface
Interface
Controller
Host
computer
cable
Dest.
addr.
Src.
addr
Checksum
16 Bits8 Bits8 Bits
S
Y
N
Data
~4000 Bits
Accessible to software
9
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
Token Bus
¥ IEEE 802.4
¥ Permission token principle
¥ Physical bus network with speeds of 1, 5, or 10 Mbit/s
P = C
S = D
B
P = C
S = D
A
P = C
S = D
C
P = C
S = D
D
Logical
Ring
Successor
(downstream
neighbour)
of C
P = Predecessor
S = Successor
Predecessor
(upstream neighbour)
of C
according to: Halsall, F.: ÒData Communications, Computer Networks and Open SystemsÓ, AddisonWesley, 3rd Edition, 1992, pp. 289
10
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
Token Ring
¥ IEEE 802.5
¥ Permission token principle
¥ Ring network
according to Hopper et al. ÒLocal Area Network DesignÓ, Addison Wesley, 1986, pp.66-67
Host computer
Adaptor
Ring cable
Distribution
Bidirectional link
panel
To From FCSTC
D
E
L
Frame header
Frame trailer
FCS: Frame Check Sequence
TC: Transport Control
DEL: Delimiter
D
E
L
Data
8 8 832 32 16
11
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
FDDI - I
¥ FDDI: Fiber Distributed Data Interface
¥ FDDI history:
1980 1985 1990 1995
establishing
task group
X3T9.5
1983
Þrst draft
proposal
work on
FDDI
multimedia
application
requirements
-> FDDI-II
FDDI implemented
and applied
FDDI-II
standardized
by ANSI
1993
no FDDI-II
chipset
available
12
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
FDDI - II
¥ Main usage: interconnect LANs
¥ ISO 9314
¥ Double ring topology to increase reliability
¥ Token medium access control
¥ Shared medium with 100 Mbit/s
¥ Max. ring length 100 km with up to 500 Stations
according to: Tannebaum, A.: ÒComputer networksÓ, 3rd Edition, Prentice Hall, 1996, pp. 320
13
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
FDDI - III
¥ Physical Medium Dependent (PMD) layer:
- basic PMD: multimode Þber
- SMF-PMD: single mode Þber
¥ Physical Sublayer (PHY)
- 4B/5B code and NRZI
- maximum frame size 4500 bytes
4B/5B encoder
NRZI encoder
Optical transmitter
125 MHz
local
clock
Clock
synchronizer
TCU
Outgoing Þbre
From MAC unit
4 bits
5 bits
4B/5B decoder
NRZI dencoder
To MAC unit
4 bits
5 bits
Incoming Þbre
according to: Halsall, F.: ÒData Communications, Computer Networks and Open SystemsÓ, AddisonWesley, 3rd Edition, 1992, pp. 314
Optical receiver
14
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
FDDI - IV
¥ Medium Access Control (MAC)
- one token on the ring
- token holder is allowed to transmit data
- 32 bit CRC per frame
- use of three timer:
1. token holding timer: how long a token holding station may continue to
transmit (i.e., transmission quota)
2. token rotation timer: time between two successive token arrivals at a sta-
tion
3. valid transmission timer: time out and recover from certain transient ring
errors
according to: Tannebaum, A.: ÒComputer networksÓ, 3rd Edition, Prentice Hall, 1996, pp. 320
Preamble
Destination
address
Source
address
Data Checksum
Bytes 2 or 6 No limit 41  8 1 12 or 6
Frame control
Start delimiter
Ending delimiter
Frame status
15
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
FDDI - V
¥ ÒSynchronous FDDI is a mode of using the FDDI network
that approaches isochronism, by means of a bandwidth
reservation mechanismÓ
Fluckinger, F.: ÒUnderstanding Networked Multimedia, pp. 413
¥ Synchronous allocation time:
- maximumlength of time that the station can transmit synchronous data each
time it receives the token
¥ Delay to access the ring is strictly bounded
¥ Average bit rate is guaranteed per station
16
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
FDDI-II - I
¥ FDDI-II services:
¥ Basic mode: standard FDDI packet switching
¥ Hybrid mode: additionally support for isochronous data
- if all nodes in a ring are FDDI-II nodes a ring can switch into hybrid mode
- isochronous services by circuit switching
Asynchronous Synchronous Isochronous
Packet Switched Circuit Switched
FDDI-II
also FDDI
services
17
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
FDDI-II - II
¥ A speciÞed station becomes cycle master
- administers isochronous transmission
- assigning channels after receiving band assignments requests from others
- creates every 125  sec a new cycle
¥ Dividing total bandwidth into wideband channels (WBCs)
- 16 WBC each 6.144 Mbit/s
- stations may divide a WBC into 8 Kbit/s units
PA: Preamble
Cycle header (12 bytes)
W
B
C
0
W
B
C
1
W
B
C
2
W
B
C
3
W
B
C
4
W
B
C
5
W
B
C
6
W
B
C
7
W
B
C
8
W
B
C
9
W
B
C
10
W
B
C
11
W
B
C
12
W
B
C
13
W
B
C
14
W
B
C
15
96 rows
16 octets
CG 0 DPG 0
CG 8 DPG 1
CG 88 DPG11
PA
CG: Cyclic Group
DPG: Data Packet
CH: Cyclic Header
PA CH DPG0 CG0 CG7
.........
DPG11 CG88 CG95
.........
125  sec
Group
18
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
FDDI-II - III
¥ Physical layer and presence of station management the
same than in FDDI
¥ At MAC level two new components:
- isochronous media access control (I-MAC): rules for sharing channels that
are allocated for circuit switching
- hybrid multiplexer (H-MUX): combines packet switched and circuit switch
trafÞc for transmission onto the medium
LLC: Logical Link Control
CS-MUX: Circuit-Switched Multiplexer
P-MAC: Packet Medium Access Control
I-MAC: Isochronous Medium Acces Control
H-MUX: Hybrid Multiplexer
HRC: Hybrid Ring Control
PHY: Physical Layer
PMD: Physical Medium Dependent
SMT: Station Management
LLC
HRC
SMT
FDDI-II Station
Service data units
P-MAC
I-MAC
CS-MUX
H-MUX
PHY PHY PMD-BPMD-A
19
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
FDDI-II - IV
¥ Normal operation: sequence of cycles on the ring
¥ Initialization:
- ring initializes in basic mode
- afterwards, stations may attempt to move the network to hybrid mode
¥ Programming template maintenance:
- cycle master maintains programming template
- allocation of bandwidth for packet and circuit switched trafÞc may be modi-
Þed dynamically
- SMT requests to cycle master
20
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
Fast Ethernet
¥ Basic idea:
- keep the old packet formats, interfaces, and procedural rules
- reduce the bit time from 100ns to 10ns -> 100 Mbit/s
¥ Cabling [Tannenbaum 96]:
Name Cable Max.Segment Advantages
100Base-T4 Twisted pair 100m Uses category 3 UTP
100Base-TX Twisted pair 100m Full duplex at 100 Mbit/s
100Base-F Fiber optics 2000m Full duplex at 100 Mbit/s; long runs
according to: Fluckinger, F.: ÒUnderstanding Networked MultimediaÓ, Prentice Hall, 1995, pp.412
Multimedia
station
Multimedia
station
Multimedia
station
Multimedia
station
Multimedia
station
Multimedia
server
Fast
Ethernet
switch
100 Mbit/s
10 Mbit/s
21
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
Isochronous Ethernet
¥ Basic idea:
- keep the regular 10 Mbit/s bandwidth unchanged for data
- add channel for isochronous communications
¥ Isochronous channel of 6.144 Mbit/s (96 x 64 Kbit/s)
¥ Hybrid bridging/switching hubs:
- relaying standard ethernet frames
- circuit-switching of isochronous channels
¥ Runs over existing UPT category 5, but requires new net-
work adapters
according to: Fluckinger, F.: ÒUnderstanding Networked MultimediaÓ, Prentice Hall, 1995, pp.415
Multimedia
station
Multimedia
station
Isochronous
Ethernet
hub/switch
16 Mbit/s
10 Mbit/s Ethernet
Multimedia
station
6 Mbit/s ISDN
(96 x 64 Kbit/s)
22
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
VG-AnyLAN - I
¥ 100 Mbit/s LAN under development in IEEE 802.12
¥ Uses frame formats of ethernet and token ring
¥ Also called Demand Priority because of MAC protocol:
- centralized two priority round robin scheme
- controlled by a central hub
¥ Elements of VG-AnyLANs:
- end nodes
- repeaters
- switches, bridges, and router
- network links
Repeater
End node
1
2
2
2
2
3
Root repeater
23
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
VG-AnyLAN - II
¥ Each repeater performs round robin polling:
¥ 2 request pointers to keep track of next port to be serviced
- normal priority
- high priority
¥ All ports are polled at least once per packet transmission
¥ High priority requests are serviced before low priority
requests
¥ Normal priority trafÞc that has been waiting to transmit for
200-300 ms is upgraded to high priority status
Repeater
End node
1
24
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
VG-AnyLAN - II
¥ Signalling for data transmission:
Repeater
End node
1 request_normal
2 polling
1 request_high
Repeater
End node
3 select port and
send grant signal
4 send incoming signal
to all other nodes
5 send data after
reception of grant signal
6 all other nodes stop sending requests after reception of incoming signal
3
5
Repeater
End node
8 sending Idle_Down signal
7 decoding destination address
and deliver packet
to all other nodes
9 after receiving the packet or Idle_Down signal go all stations and repeater into their prior state -> 1
25
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
DQDB - I
¥ IEEE 802.6 & ISO 8802.6 (MAC protocol)
¥ Physical layer, e.g., 34 & 155 Mbit/s (-> ATM)
¥ Stations are connected to 2 unidirectional busses
¥ Head-end stations generating DQDB frames
according toM. de Pryker ÒAsynchronous Transfer ModeÓ, Ellis Horwood, 1993, pp. 273
Frame
Generator
Frame
Generator
26
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
DQDB - II
¥ For each bus one logical queue (physically distributed)
¥ Each node monitors and stores the state of the network
¥ Fixed sized frames, format very similar to ATM cells
¥ 2 control bits in each frame
- busy bit: 0 = empty, 1 = full
- request bit: 0 = no request, 1 = request
Request
Counter
-1 for every empty slot
+1 for every request bit
busy bit
request bit
Node collects status info
no information queued
Bus A
Bus B
27
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
DQDB - III
¥ Information to send (on bus A):
- waiting for Þrst slot on bus B with request bit = 0
- set request bit to 1
- copy request counter to count down counter
- reset request counter to 0
- if count down = 0 put data in next free slot
Request
Counter
-1 for every empty slot
+1 for every request bit
busy bit
request bit
Node collects status information
information queued for bus A
Count
Down
Bus A
Bus B
28
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
DQDB - IV
¥ Good utilization of medium
¥ Enhancements to support fairness
¥ Enhancements support priorities for isochronous services
¥ DQDB standardization in line with ATM standardization
¥ Switched Multimegabit Data Service
- interconnection of MANs (DQDB networks)
- introduced from Bellcore
- high-speed packet switching service
29
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
Idea of Asynchronous Transfer Mode
¥ Starting point Broadband-ISDN (B-ISDN)
- telephony
- low speed data
- audio
- high speed data
- (high quality) video
- yet unknown services
¥ Transfer mode for B-ISDN
- no circuit switching -> waste of resources
- no multirate circuit switching -> inßexible, inefÞcient use of resources,
not able to properly handle bursty sources
- no fast circuit switching -> complexity of controlling and signalling
¥ Fast packet switching, Asynchronous Time Division, ATM
- ßexible and future safe
- efÞcient in use of its resources
- one universal network (according to de Pryker)
30
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
Layered Model of B-ISDN
¥ Horizontal layers:
- physical layer
- ATM layer
- ATM Adaptation layer (AAL)
- higher layers
¥ Vertical structure:
- user plane responsible for transmission of user data
- control plane handles all relevant issues of signalling
- management plane encompasses functions to interact and coordinate
between user plane and control plane activities
Management Plane
Control PlaneUser Plane
Higher Layer Protocols
ATM Adaptation Layer
ATM Layer
Physical Layer
Layer Management
Plane Management
Higher Layer Protocols
31
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
Characteristics of ATM - I
¥ No error protection and ßow control on link-by-link basis
- links have a very low bit error rate
- if error occur no action will take place
- proper resource allocation and queue dimensioning -> no ßow control
- packet loss rates 10
-8
- 10
-12
¥ Connection-oriented mode
- connection set-up phase
- admission control (resource allocation)
- resources are released after information transfer phase
¥ Reduced header functionality
- main function identiÞcation of virtual connections
- Header Error Check (HEC) to prevent error multiplications
¥ Small Þxed sized cells of 53 byte
32
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
Characteristics of ATM - II
¥ ATM protocol structure
¥ User-Network Interface UNI, Network-Node Interface NNI
Physical Layer
ATM Layer
ATM Adaptation
Layer (AAL)
Physical Layer
ATM Layer
ATM Adaptation
Layer (AAL)
Physical Layer
ATM Layer
ATM End System
ATM Switch
Physical Medium
ATM End System
ATM End
System
Private
ATM
Switch
Public
ATM
Switch
ATM End
System
ATM End
System
Public
ATM
Switch
Public
ATM
Switch
Public
ATM
Switch
ATM End
System
private UNI
public
UNI public
UNI
NNI
33
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
Physical Layer - I
¥ 2 sublayers
¥ Physical Medium (PM) sublayer:
- responsible for transmission and reception of bits on the physical medium
- bit timing reconstruction at the receiver
¥ Transmission Convergence (TC) sublayer:
- adaptation to the transmission systemincluding:frame generation,recovery,
and mapping of cells into lower layer containers
- 8 bit header error control to correct single bit errors and detect multiple bit
errors
- cell delineation (~ framing)
- cell payload scrambling
Detection
mode
Correction
mode
Multiple-bit error detected
(Cell discarded)
No error detected
(No action)
Single-bit error detected
(Correction)
No error detected
(No action)
Error detected
(Cell discarded)
according to M. de Pryker ÒAsynchronous Transfer ModeÓ, Ellis Horwood, 1993, pp. 123
34
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
Physical Layer - II
¥ 4 standards for transmission frame adaptation:
- Synchronous Digital Hierarchy (SDH) by CCITT
- Plesiochronous Digital Hierarchy (PDH) by CCITT
- cell based by CCITT
- FDDI option by ATM forum
¥ SDH PM characteristics:
- optical Þber and coaxial cable as physical medium
- several bit rates supported
Data Rate Mbit/s SONET STS/OC CCITT STM
51.84 1 -
155.52 3 1
622.08 12 4
1,244.16 24 8
2,488.32 48 16
35
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
Physical Layer - III
¥ SDH TC characteristics:
- clock extraction and recovery
- frame generation and recovery
¥ Cell based interface:
- physical medium characteristics to SDH based interface
- cells are transported continuously without regular framing
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


270 x n Columns (bytes)
9 x n
261 x 9
STM - payload
9 Rows
125  s
Section
overhead
Section
overhead
AU Pointer
according to Lee et al. ÒBroadband Telecommunication TechnologyÓ, Artech House, 1993
36
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
Physical Layer - IV
¥ PDH PM layer:
- currently the standard digital hierarchy
- various bit rates
North American PDH European PDH
DS-1 1.544 Mbit/s DS-1E 2.048 Mbit/s
DS-1C 3.152 Mbit/s DS-2E 8.448 Mbit/s
DS-2 6.312 Mbit/s DS-3E 34. 368 Mbit/s
DS-3 44.736 Mbit/s DS-4E 139.264 Mbit/s
DS-4E 139.264 Mbit/s DS-5E 564.992 Mbit/s
37
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
Physical Layer - V
¥ PDH TC layer:
- mapping ATM cells into PDH frames
¥ FDDI based interface:
- physical medium sublayer based on FDDI physical layer
- cell delineation in TC sublayer by special line codes not by using the header
error control bits
according to M. de Pryker ÒAsynchronous Transfer ModeÓ, Ellis Horwood, 1993, pp. 121
59 Columns
9 Rows
FA1FA 2
EM
TR
MA
NR
GC
FA : Frame Alignment
EM: Bit Interleaved Parity
TR: Trail Trace
MA: Far End Receive Failure etc.
NR: Network Operator byte
GC: General purpose Communication
channel
38
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
ATM Cell Structure - I
¥ Fixed cell size of 53 byte:
¥ ATM header structure at NNI:
- Virtual Path IdentiÞer (VPI) 12 bits
- Virtual Channel IdentiÞer (VCI) 16 bits
- Payload Type IdentiÞer (PTI) 3 bits
- Cell Loss Priority (CLP) 1 bit
- Header Error Control (HEC) 8 bits
Header
5 Bytes
Payload
48 Bytes
VPI
VPI
VCI
VCI PTI CLP
HEC
1
2
3
4
5
8 7 6 5 4 3 2 1
VCI
39
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
ATM Cell Structure - II
¥ ATM header at UNI:
- Generic Flow Control (GFC) 4 bits
- Virtual Path IdentiÞer (VPI) 8 bits
- Virtual Channel IdentiÞer (VCI) 16 bits
- Payload Type IdentiÞer (PTI) 3 bits
- Cell Loss Priority (CLP) 1 bit
- Header Error Control (HEC) 8 bits
GFC VPI
VPI
VCI
VCI PTI CLP
HEC
1
2
3
4
5
8 7 6 5 4 3 2 1
VCI
40
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
VCs and VPs - I
¥ Virtual Channel (VC):
- unidirectional logical ATM connection which has some reserved resources
¥ Virtual Path (VP):
- number of virtual channels as unit of observation for unidirectional trafÞc
VPI = 7
, VCI = 1, 2, 3
VPI = 5
, VCI = 1, 2, 3
VPI = 7
, VCI = 1, 2, 3
VPI = 9,
VPI = 7
, VCI = 3, 4
VPI = 3
, VCI = 3, 4
VCI = 3, 4
VPI
in
VPI
out
5 7
7
9
7
7
3
VPI
in
VPI
out
VPI
in
VPI
out
5
A
B
C
according to M. de Pryker ÒAsynchronous Transfer ModeÓ, Ellis Horwood, 1993, pp.86
ATM node
1
ATM node
2
ATM node
3
physical link
VC
41
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
VCs and VPs - II
¥ Virtual Channel Link (VCL)
¥ Virtual Path Link (VPL)
¥ Virtual Channel Connection (VCC)
¥ Virtual Path Connection (VPC)
according to B. Stiller: ÒA Survey of UNI Signalling Systems and Protocols for ATM NetworksÓ
VCC 1
VPC 1
VCI 1
VPI 1
ATM
Crossconnect
ATM
End-System
ATM
Switch
ATM
End-System
ATM
Switch
VPL 1
VPL 2 VPL 3 VPL 4
VPI 2 VPI 3 VPI 41
VCI 2 VCI 3
VPC 2 VPC 3
Links
Connections
IdentiÞers
Equipp-
ment
physical
logical
42
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
ATM Switches
¥ Switching Fabric [de Pryker 93]:
A switching fabric is composed of identical basic switching building blocks,
interconnected in a speciÞc topology.Thus,a switching fabric is deÞned when
its topology is determined and when the basic switching building blocks are
deÞned.
¥ Basic Switching Building Block [de Pryker 93]:
A basic switching building block is a generic building block to construct an
ATMswitching fabric.Another name used for basic switching building block is
switching element. Identical switching elements will compose a switching fab-
ric.
¥ Switching System [de Pryker 93]:
Any means to switch ATM cells, either by an ATM switching element, or an
ATM switching fabric. Also often called an ATM switch.
43
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
Switching Fabrics
¥ Input, output, and central buffering
¥ Examples for switching fabrics:Athena,St.Louis,Starlite,
Moonshine
¥ Combining basic building blocks in complex networks,
e.g., Delta networks (a subclass of Banyan networks)
according to M. de Pryker ÒAsynchronous Transfer ModeÓ, Ellis Horwood, 1993, pp.193
1011
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
1011
1
0
1
1
1
0
1
incoming cell
incoming cell
44
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
Service Classes of B-ISDN
¥ ClassiÞcation of possible services over ATM
- time relation between source and destination: required or not
- bit rate: constant and variable
- connection mode: connectionless and connection oriented
Class A Class B Class C Class D
Timing between
Bit rate
Connection mode
Required
Not Required
Constant Variable
Connection oriented
Connection-
source and
destination
less
45
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
ATM Adaptation Layer (AAL)
¥ Enhancing the service of the ATM layer to the require-
ments of a speciÞc service
¥ Mapping user/control/management PDUs into ATM cell
payloads and vice versa
¥ Adaptation layers are divided in 2 sublayer
- segmentation and reassembly sublayer (SAR)
- convergence sublayer (CS), service dependent
¥ CCITT recommended 4 types of AAL protocols
- AAL 1
- AAL 2
- AAL 3/4
- AAL 5
46
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
AAL 1
¥ Transfer of SDUs with constant source bit rate and deliv-
ery in the same bit rate
¥ Transfer of timing information
¥ Transfer of data structure information
¥ Indication of lost or errored information which is not recov-
ered by the AAL (optional)
¥ Constant bit rate services like audio and video
¥ SAR structure:
CSI SN SNP SAR-SDU
1 bit 3 bits 4 bits
48 bytes
CSI = CS Indication
SN = Sequence Number
SNP = Sequence Number Protection
SDU = Service Data Unit
according to M. de Pryker ÒAsynchronous Transfer ModeÓ, Ellis Horwood, 1993, pp.131
47
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
AAL 2
¥ Adaptation of variable bit rate services
¥ Forward error correction for audio and video services
¥ SAR and CS still in discussion
¥ Possible SAR structure:
SN IT SAR-SDU
1 bit 3 bits 4 bits
48 bytes
SN = Sequence Number
IT = Information Type
LI = Length Indicator
according to M. de Pryker ÒAsynchronous Transfer ModeÓ, Ellis Horwood, 1993, pp.133
LI CRC
CRC = Cyclic Redundancy Code
48
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
AAL 3/4 - I
¥ Transfer of data that is sensitive to loss, but not to delay
¥ 2 modes: message and streaming
¥ Variable length PDUs
¥ Error detection (10 bit CRC) and handling
¥ Thought for class C and class D
¥ SAR structure:
SAR-SDU
48 bytes
according to M. de Pryker ÒAsynchronous Transfer ModeÓ, Ellis Horwood, 1993, pp.136
ST SN
RES/MID LI
CRC
2 bits 4 bits
10 bits 6 bits
10 bits
ST = Segement Type
SN = Sequence Number
RES = Reserved (Type 3)
MID = Multiplexing IdentiÞer (Type 4)
LI = Length Indicator
CRC = Cyclic Redundancy Check
49
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
AAL 3/4 - II
¥ Common Part Convergence Sublayer (CPCS)-PDU
format
according to M. de Pryker ÒAsynchronous Transfer ModeÓ, Ellis Horwood, 1993, pp.137
CPCS-PDU
Header
CPCS-PDU Payload
PAD
CPCS-PDU
Trailer
CPI Btag BASize
CPCS-PDU Header
AL Etag Length
CPCS-PDU
CPCS-PDU Trailer
CPI: Common Part Indicator (1 byte)
Btag: Beginning Tag (1 byte)
BASize: Buffer Allocation Size (2 bytes)
PAD: Padding (0 .. 3 bytes)
AL: Alignment (1 byte)
Etag: End Tag (1 byte)
Length: Length of Payload (2 bytes)
50
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
AAL 5 - I
¥ Objective: service with less overhead and better error
detection
¥ Variable length PDUs
¥ 32 bit CRC
¥ SAR structure:
SAR-SDU
48 bytes
51
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
AAL 5 - II
¥ CPCS-PDU format
according to M. de Pryker ÒAsynchronous Transfer ModeÓ, Ellis Horwood, 1993, pp.139
CPCS-PDU
Header
CPCS-PDU Payload PAD
CPCS-PDU
Trailer
CPCS-PDU Header
Note 2
CRCLength
CPCS-PDU
CPCS-PDU Trailer
PAD: Padding (0 .. 47 bytes)
Note 1
Note 1: The need and the function of a CPCS-PDU Header are for further study
Note 2: Additional functions besides a 32-bit alignment are for further study
Length: Length of CPCS-PDU Payload
CRC: Cyclic Redundancy Check
52
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
Comparison of AALs
Ò... The overall impression that AAL gives is of too many variants with too
many minor differences and a job half done. The original four service
classes,A,B,C,D,have been effectively abandoned.AAL 1 is probably not
really necessary; AAL 2 is broken; AAL3 and AAL4 never saw the light of
day;and AAL 3/4 is inefÞcient and has too short a checksum.The future lies
in AAL 5, but even there is room for improvement. ....Ó
A. S. Tanenbaum: ÒComputer NetworksÓ 3rd Edition, Prentice Hall 1996, pp. 554-555
Item AAL 1 AAL 2 AAL 3/4 AAL 5
Service Class A B C/D C/D
Multiplexing No No Yes No
Message delimiting None None BTAG/ETAG Bit in PTI
Advanced buffer allocation No No Yes No
User bytes available 0 0 0 1
CS padding 0 0 32-Bit word 0-47 bytes
CS protocol overhead 0 0 8 Bytes 8 Bytes
CS checksum None None None 32 Bits
SAR payload bytes 46-47 45 44 48
SAR protocol overhead 1-2 Bytes 3 Bytes 4 Bytes 0
SAR checksum None None 10 Bits None
53
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
Signalling - I
¥ B. Stiller: ÒA Survey of UNI Signaling Systems and ....Ó
¥ Signalling in ATM in 3 layers:
- layer 1: signalling between physical hardware devices
- layer 2: interconnection of interworking units
- layer 3: establishment of calls and connections
¥ UNI signalling in B-ISDN is located in layer 3
- Q.2931 from ITU-T
- UNI 3.0, 3.1 from ATM-Forum
- SPANS from Fore Systems
¥ Two distinct control areas:
- Connection (Bearer) Control: procedures to set-up or initialize features of
user data connection, e.g., the ATM connection, process of connecting
- Call Control: procedures for maintaining the connection itself, e.g., associat-
ing speciÞc VPIs and VCIs with a calling user, clearing VPI/VCI tables
54
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
Signalling - II
¥ Two important tasks exist in any signalling scenario:
- network-dependent
- service-dependent
¥ Network-dependent tasks:
- set-up, maintenance, and clear of VCCs and VPCs
- negotiation of trafÞc characteristics
¥ Service-dependent tasks:
- independent of any speciÞc network feature
- not compulsory, may be integrated
- deÞnition and support of multicast and multipeer
- symmetric or asymmetric behaviour of connections
- QoS parameter negotiation
55
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
Signalling - III
¥ => QoS is related to network and service
- Peak Cell Rate (PCR),MinimumCell Rate (MCR),Sustained Cell Rate SCR
- Cell Loss Ration (CLR)
- Cell Transfer Delay (CTD) and Cell Delay Variation (CDV)
- Burst Tolerance (BT)
¥ Out-of-Band Virtual Signalling Channels (VSC)
- Meta Virtual Signalling Channel
- Broadcast Virtual Signalling Channel
- Point-to-Point Virtual Signalling Channel
¥ Comparison of ATM and X.25 signalling:
- reliable Òtransport serviceÓ required in both
- X.25 signalling between end-user, ATM signalling between end-user and
switch and between switch and switch
- similar abstractions:
X.25 Data Terminal Equipment Data Circuit-Terminating Equipment
ATM ATM end-user ATM switch
# Lost Cells
# Transmitted Cells
-----------------------------------------------=
MBS 1Ð( )
1
SRC
-----------
1
PCR
-----------Ð
 
 
=
56
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
Signalling - IV
ATM
End-System
ATM
Switch
ATM
End-System
ATM
Switch
Originator Network Responder
Set-up
Call processing
Alerting
Connect
Connect
acknowledge
Set-up
Alerting
Connect
Connect
acknowledge
according to B. Stiller: ÒA Survey of UNI Signalling Systems and Protocols for ATM NetworksÓ
57
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
Comparison of Signalling Protocols
¥ UNI 3.0 vs. UNI 3.1:
- UNI 3.0 is based on Q.93B plus extensions for multicast
- UNI 3.1 is update of UNI 3.0 to become compatible with Q.2931
- UNI 3.1 is incompatible with UNI 3.0
¥ Q.2931 vs. UNI 3.1:
- UNI 3.1 does not support ÒAlertingÓ and ÒNotifyÓ
- Differences in information elements
- Set-up message differs in terms of mandatory/optional information elements
¥ Standards vs. Non-Standards:
- no real commonalities, except for abstract design issues
- non-standards tend to focus on speciÞc project or hardware requirements
- currently no interworking between non-standards known
58
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
Comparison of High-Speed LANs - I
¥ Cronin et al.: ÒA Comparison of High-Speed LANsÓ
¥ Summary of protocol attributes
FDDI 100BASE-T VG-AnyLAN ATM
# Stations 500 1024 (unspeciÞed) implementa-
tion limits
Access
Method
Token Passing CSMA/CD Round Robin Full Duplex
Packet size 4500 bytes 1500 bytes 1500 or 4500
bytes
48 bytes
Extent 100 km 210 ,2.5 km unlimited
Complexity medium low medium high
59
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
Comparison of High-Speed LANs - II
¥ Summary of topology attributes
FDDI 100BASE-T VG-AnyLAN ATM
Topology Star Wired Hierarchical
star
Dual Ring of
Trees
Mesh of
Switches
Category 3
UTP
100 m 100 m
Category 5
UTP
100 m 100 m 100 m 100 m
150 Ohm STP 100 m 100 m 100 m 100 m
Multimode
Fiber
2 km 2 km 2 km
Singlemode
Fiber
60 km 40 km
60
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
Comparison of High-Speed LANs - III
¥ EfÞciency of protocol
¥ Latency control:
- VG-AnyLAN has Demand Priority
- FDDI has synchronous priority
- ATM provides multiple service classes and bandwidth reservation during
connection establishment
Packet
Size
(bytes)
VG-AnyLAN
1 hub, 200 m
VG-AnyLAN
3 hubs, 2.2 km
100-BaseT
210 m
FDDI
3 hubs, 2.2 km
ATM
1 Link
64 46 % 19 % 65 % 84 % 58 %
128 63 % 32 % 74 % 91 % 78 %
256 77 % 49 % 80 % 96 % 78 %
512 87 % 66 % 83 % 98 % 85 %
1024 93 % 79 % 86 % 99 % 85 %
1518 95 % 85 % 87 % 99 % 86 %
61
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
Summary - I
¥ General introduction into LAN, MAN, and WAN
- shared medium LAN
- switched LAN
¥ Traditional LAN
¥ High-speed LAN
- FDDI (& FDDI-II)
- fast ethernet
- isochronous ethernet
- VG-AnyLAN
¥ MAN
- DQDB
62
UNIK
UNIKI 305, Protocols for Multimedia Communication, Fall 2000 © 2000 THOMAS PLAGEMANN
Summary - II
¥ General idea of ATM
¥ Layers of B-ISDN
- physical layer
- ATM layer
- ATM adaptation layer
¥ Horizontal plane in B-ISDN: signalling
¥ Comparison of high-speed LANs
¥ Next week: resource reservation in end-systems