3. ethernet and atmbillatnapier.com/cnds2002_03/cnds_unit03_2002_2003.pdftransmitting frames and...
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1
Author: W.Buchanan. Ethernet and ATM (1)
Unit 3
Author: W.Buchanan. Ethernet and ATM (2)
3. Ethernet and ATM
100/1000BaseSwitch
100/1000BaseSwitch
10/100BaseSwitch or Hub10/100Base
Switch or Hub
ServerServer ServerServer
10/100BaseSwitch or Hub10/100Base
Switch or Hub
External connection (uses store-and-forward for external connection)
Segment switch allows direct connectionof any of the connected segments
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Author: W.Buchanan. Ethernet and ATM (3)
Why Ethernet?
• Simplicity. Easy to plan and cheap to install. The introduction of network hubs and twisted-pair cables has made Ethernet networks easy to connect to. It also has cheap and well-supported network components, such as network interface cards (NICs) and connectors (BNC and RJ-45).
• Reliability. Well-proven technology, which is fairly robust and reliable.• Ease-of-use. It is simple to add and remove computers to/from the network.• Upgradeability and compatibility. Ethernet has evolved from 10Mbps, to
100Mbps (Fast Ethernet, in 1985) and now to 1Gbps (Gigabit Ethernet, in 1998). All three Ethernet speeds use the same basic data frame format (IEEE 802.3), have full-duplex operation and have the same flow control methods.
• Popularity. Supported by most software and hardware systems.
Author: W.Buchanan. Ethernet and ATM (4)
3.1 Ethernet (Advantages/Problems)
Advantages:Ethernet networks are easy to plan and cheap to install.Ethernet network components, such as network cards and connectors, are cheap and well supported.Uses coaxial, fibre or twisted-pair cables.It is a well-proven technology, which is fairly robust and reliable.It is simple to add and delete computers on the network.It is supported by most software and hardware systems.Available as 10Mbps (10BASE), 100Mbps (100BASE) and 1Gbps (1000BASE). Dual-speed networks can be used, such as mixed 10Mbps/100Mbps networks. Network hub negotiates the required speed.Easy upgrade for different network speed. A dual-speed network can be run, and gradually upgraded.Standardised as 1EEE 802.3.
Advantages:Ethernet networks are easy to plan and cheap to install.Ethernet network components, such as network cards and connectors, are cheap and well supported.Uses coaxial, fibre or twisted-pair cables.It is a well-proven technology, which is fairly robust and reliable.It is simple to add and delete computers on the network.It is supported by most software and hardware systems.Available as 10Mbps (10BASE), 100Mbps (100BASE) and 1Gbps (1000BASE). Dual-speed networks can be used, such as mixed 10Mbps/100Mbps networks. Network hub negotiates the required speed.Easy upgrade for different network speed. A dual-speed network can be run, and gradually upgraded.Standardised as 1EEE 802.3.
Common bus
All computers have access toa common bus at the same time
Ethernet hub
Problem:A major problem with Ethernet is that, because computers must contend to get access to the network, there is no guarantee that they will get access within a given time. This contention also causes problems when two computers try to communicate at the same time, they must both
back off and no data can be transmitted.
Problem:A major problem with Ethernet is that, because computers must contend to get access to the network, there is no guarantee that they will get access within a given time. This contention also causes problems when two computers try to communicate at the same time, they must both
back off and no data can be transmitted.
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Author: W.Buchanan. Ethernet and ATM (5)
3.2 CSMA/CDCSMA/CDEthernet uses carrier sense, multiple access with collision detection (CSMA/CD). Nodes monitor the bus (or Ether) to determine if it is busy. A node wishing to send data waits for an idle condition then transmits its message. Collisions can occur when two nodes transmit at the same time, thus nodes must monitor the cable when they transmit. When a collision occurs, both nodes stop transmitting frames and transmit a jamming signal. This informs all nodes on the network that a collision has occurred. Each of the nodes involved in the collision then waits a random period of time before attempting a re-transmission. As each node has a random delay time then there
can be a prioritisation of the nodes on the network.
CSMA/CDEthernet uses carrier sense, multiple access with collision detection (CSMA/CD). Nodes monitor the bus (or Ether) to determine if it is busy. A node wishing to send data waits for an idle condition then transmits its message. Collisions can occur when two nodes transmit at the same time, thus nodes must monitor the cable when they transmit. When a collision occurs, both nodes stop transmitting frames and transmit a jamming signal. This informs all nodes on the network that a collision has occurred. Each of the nodes involved in the collision then waits a random period of time before attempting a re-transmission. As each node has a random delay time then there
can be a prioritisation of the nodes on the network.
Two nodes transmitat the same time
1
Node detect therehas been a collision
2
Nodes transmit ajamming signal
3
Nodes wait a randomperiod before retransmitted
4
Common bus
All computers have access toa common bus at the same time
Author: W.Buchanan. Ethernet and ATM (6)
3.3 CSMA/CD
Common bus
Two nodes transmitat the same time
1 Node detect therehas been a collision
2
Nodes transmit ajamming signal
3 Nodes wait a randomperiod before retransmitting
4
All computers have access toa common bus at the same time
4
Author: W.Buchanan. Ethernet and ATM (7)
3.4 IEEE 802 LANs (802.2/802.3)
PhysicalPhysical
Data linkData link
NetworkNetwork
TransportTransport
SessionSession
PresentationPresentation
ApplicationApplication
PhysicalPhysical
Data linkData link
NetworkNetwork
TransportTransport
SessionSession
PresentationPresentation
ApplicationApplicationA
A
A
A
A
A
P
P
P
P
P
S
S
S
S
T
T
T
N
ND D
Virtualdata flow
Actual data flow
Sender Receiver
PhysicalPhysical
Data linkData link
NetworkNetwork
TransportTransport
SessionSession
PresentationPresentation
ApplicationApplication
PhysicalPhysical
Data linkData link
NetworkNetwork
TransportTransport
SessionSession
PresentationPresentation
ApplicationApplication
PhysicalPhysical
Data linkData link
NetworkNetwork
TransportTransport
SessionSession
PresentationPresentation
ApplicationApplicationA
A
A
A
A
A
P
P
P
P
P
S
S
S
S
T
T
T
N
ND D
Virtualdata flow
Actual data flow
Sender Receiver
PhysicalPhysical
Data linkData link
PhysicalPhysical
Data linkData linkLLC (IEEE 802.2)
Media AccessControl (IEEE 802.3)
Author: W.Buchanan. Ethernet and ATM (8)
3.5 IEEE 802.3 data frameOthers:4 bytes for the CRC (32 bits) and 2 bytes for the LLC length (16 bits). The LLC part may be up to 1500 bytes long. The preamble and delay components define the start and end of the frame. The initial preamble and start delimiter are, in total, 8 bytes long and the delay component is a minimum of 96 bits long.
Others:4 bytes for the CRC (32 bits) and 2 bytes for the LLC length (16 bits). The LLC part may be up to 1500 bytes long. The preamble and delay components define the start and end of the frame. The initial preamble and start delimiter are, in total, 8 bytes long and the delay component is a minimum of 96 bits long.
Preamble (seven bytes) precedes the Ethernet 802.3 frame. Each byte of the preamble has a fixed binary pattern of 10101010 and each node on the network uses it to synchronise their clock and transmission timings. It also informs nodes that a frame is to be sent and for them to check the destination address in the frame.Start delimiter field (SDF) is a single byte (or octet) of 10101011. It follows the preamble and identifies that there is a valid frame being transmitted.
Preamble (seven bytes) precedes the Ethernet 802.3 frame. Each byte of the preamble has a fixed binary pattern of 10101010 and each node on the network uses it to synchronise their clock and transmission timings. It also informs nodes that a frame is to be sent and for them to check the destination address in the frame.Start delimiter field (SDF) is a single byte (or octet) of 10101011. It follows the preamble and identifies that there is a valid frame being transmitted.
Delay. The end of the frame there is a 96-bit delay period, which provides the minimum delay between two frames. This slot time delay allows for the worst-case network propagation delay.
Delay. The end of the frame there is a 96-bit delay period, which provides the minimum delay between two frames. This slot time delay allows for the worst-case network propagation delay.
Source/destination addresses (2 or 6 bytes, Most Ethernet systems use a 48-bit MAC address for the sending and receiving node. Each Ethernet node has a unique MAC address, which is normally defined as hexadecimal digits, such as:
4C-31-22-10-F1-32 (4C31 : 2210: F132)
A 48-bit address field allows 248
different addresses (or approximately 281474976710000 different addresses).
Source/destination addresses (2 or 6 bytes, Most Ethernet systems use a 48-bit MAC address for the sending and receiving node. Each Ethernet node has a unique MAC address, which is normally defined as hexadecimal digits, such as:
4C-31-22-10-F1-32 (4C31 : 2210: F132)
A 48-bit address field allows 248
different addresses (or approximately 281474976710000 different addresses).
IP TCP HTTP DataE.g.
Preamble(7B)
Startdelimiter (1B)
Dest.address (6B)
Src.Address (6B)
Len(2B)
FCS(4 B)
Delay(92bits)
Data field(Logical link control)
52 to 1500 bytes
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Author: W.Buchanan. Ethernet and ATM (9)
3.6 Ethernet Limitations
Parameter 10BASE5 10BASE2 10BASE-T Common name
Standard or thick-wire Ethernet
Thinnet or thin-wire Ethernet
Twisted-pair Ethernet
Data rate
10 Mbps 10 Mbps 10 Mbps
Maximum segment length
500 m 200 m 100 m
Maximum nodes on a segment
100 30 3
Maximum number of repeaters
2 4 4
Maximum nodes per network
1024 1024
Minimum node spac-ing
2.5 m 0.5 m No limit
Location of trans-ceiver electronics
located at the cable connection
integrated within the node
in a hub
Typical cable type
RG-50 (0.5” diameter)
RG-6 (0.25” diameter)
UTP cables
Connectors
N-type BNC RJ-45/ Telco
Cable impedance
50 Ω 50 Ω 100 Ω
10BASE510BASE5
RG-50 backbonecable
N-typeT-connector
9-pin D-typeconnector (AUI)
9-pin D-typeconnector (AUI)
Vampire(or bee-sting)tap
BNCT-connector
BNC connector
10BASE2
10BASE-T
Hub
RG-50 backbonecable
Twisted-paircable
RJ-45connector
10BASE5 10BASE2
10BASE210BASE-T
Author: W.Buchanan. Ethernet and ATM (10)
3.7 Ethernet types
• Standard, or thick-wire, Ethernet (10BASE5).• Thinnet, or thin-wire Ethernet, or Cheapernet (10BASE2).• Twisted-pair Ethernet (10BASE-T).• Optical fibre Ethernet (10BASE-FL).• Fast Ethernet (100BASE-TX and 100VG-Any LAN).• Gigabit Ethernet (1000BASE-SX, 1000BASE-T, 1000BASE-LX and 1000BASE-
CX).
New standards relating to 100Mbps Ethernet are now becoming popular:
• 100BASE-TX (twisted-pair) – which uses 100Mbps over two pairs of Cat-5 UTP cable or two pairs of Type 1 STP cable.
• 100BASE-T4 (twisted-pair) – which is the physical layer standard for 100Mbps over Cat-3, Cat-4 or Cat-5 UTP.
• 100VG-AnyLAN (twisted-pair) – which uses 100Mbps over two pairs of Cat-5 UTP cable or two pairs of Type 1 STP cable.
• 100BASE-FX (fibre-optic cable) – which is the physical layer standard for 100Mbps over fibre-optic cables.
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Author: W.Buchanan. Ethernet and ATM (11)
HubHubConnects to thehub to give a startopology
Internal connectioninside the hub isstill a bus network
3.8 Ethernet hubs
Author: W.Buchanan. Ethernet and ATM (12)
BridgeBridge
BridgeBridge
Port1
Port2
A1 A2 A3 A4
B1 B2 B3 B4
C1 C2 C3
A1A2A3A4
B1B2B3B4
Port1 Port2A1A2A3A4
C1C2C3
Port1 Port2
Address tables whichassign MAC addresseswith ports
3.13 Transparent bridges with address tables
7
Author: W.Buchanan. Ethernet and ATM (13)
146.176.151.100 146.176.151.130
Destination SourceFF-FF-FF-FF-FF-FF 65-F1-21-10-05-01
Destination Source146.176.151.130 146.176.151.100
ARP Request
Frame headerIP header
Destination Source65-F1-21-10-05-01 21-10-11-AA-42-FF
Destination Source146.176.151.100 146.176.151.130
ARP Reply
Frame headerIP header
3.14 ARP request and reply
Author: W.Buchanan. Ethernet and ATM (14)
Destination Source21-10-11-AA-42-FF 65-F1-21-10-05-01
Destination Source146.176.151.255 ????????
RARP Request
Frame headerIP header
Destination Source65-F1-21-10-05-01 21-10-11-AA-42-FF
Destination Source146.176.151.100 146.176.151.130
RARP Reply
Frame headerIP header
RARPserver
Disklessworkstation
65-F1-21-10-05-01 146.176.151.100
Physical address IP address
65-F1-21-34-CD-A1 146.176.151.10165-F1-21-FF-1D-EF 146.176.151.102
RARP table
3.15 RARP
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Author: W.Buchanan. Ethernet and ATM (15)
Router_2Router_2
Router_1Router_1
Dest MAC address = 00-80-55-43-FE-FF
Port_1 IP address = 146.176.151.1MAC address = 00-80-55-43-FE-FF
Dest IP address = 146.176.120.2
Port_2 IP address = 146.176.130.1MAC address = 00-60-DD-E0-12-34
Dest MAC address = 00-90-10-33-DE-EE
Dest IP address = 146.176.120.2
Port_1 IP address = 146.176.120.1MAC address = 00-10-32-11-BC-B1
Port_2 IP address = 146.176.130.2MAC address = 00-65-21-44-33-A1
Node_A
Node_B
3.16 Example ARP
Author: W.Buchanan. Ethernet and ATM (16)
ATM
44
66
77
11
22
55
33
User 1
User 3
User 2
VCI=12
VCI=06
VCI=22
VCI=10VCI=15
IN OUT12 06
Routing tableIN OUT06 22
Routing table
9
Author: W.Buchanan. Ethernet and ATM (17)
3.17 ATM overview
00.10.20.30.40.50.60.70.80.9
1
Example traffic profile for speech signal
00.10.20.30.40.50.60.70.80.9
1
Example traffic profile for computer-type data
ATM copes with real-time traffic with:Analysing the type of connection to be made. The type of data dictates the type of connection; for example, computer data requires a reliable connection, whereas real-time sampled data requires a connection with a low propagation time. Analysing the type of data to be transmitted and knowing its traffic profile. Computer data tends to create bursts of trafficwhereas real-time data will be constant traffic.Reserving a virtual path for the data to allow the data profile to be transmitted within the required quality of service.Splitting the data into small packets which have the minimum overhead in the number of extra bits. These ‘fast-packets' traverse
the network using channels which have been reserved for them.
ATM copes with real-time traffic with:Analysing the type of connection to be made. The type of data dictates the type of connection; for example, computer data requires a reliable connection, whereas real-time sampled data requires a connection with a low propagation time. Analysing the type of data to be transmitted and knowing its traffic profile. Computer data tends to create bursts of trafficwhereas real-time data will be constant traffic.Reserving a virtual path for the data to allow the data profile to be transmitted within the required quality of service.Splitting the data into small packets which have the minimum overhead in the number of extra bits. These ‘fast-packets' traverse
the network using channels which have been reserved for them.
Ethernet/FDDI/Token Ring are not suited to real-time traffic as:There is no guarantee that the connection can support a given Quality of Service (for errors, time delay, and so on).There is no guarantee that they can transmit the data within a given time limit.They allow nodes to burst data onto the network which can swamp other network traffic.
Ethernet/FDDI/Token Ring are not suited to real-time traffic as:There is no guarantee that the connection can support a given Quality of Service (for errors, time delay, and so on).There is no guarantee that they can transmit the data within a given time limit.They allow nodes to burst data onto the network which can swamp other network traffic.
Real-timetraffic profile
Computer-typetraffic profile
Author: W.Buchanan. Ethernet and ATM (18)
3.18 Data types
Data type Error or loss sensitive Delay sensitiveReal-time control system yes yesTelephone/hi-fi music no yesFile transfer/application progs. yes noTeletex information no no
Real-timecontrol system
Telephone/hi-fimusic
File transfer/application programsTeletex information
Error sensitive
Delay sensitive
SensitiveNot sensitive
Sensitive
Not sensitiveATMATM
10
Author: W.Buchanan. Ethernet and ATM (19)
3.19 ATM cells (small ‘fast packets’)
VCI Label(24 bits)
VCI Label(24 bits)
Control(8 bits)
Control(8 bits)
Checksum(8 bits)
Checksum(8 bits)
Optional(32 bits)
Optional(32 bits)
Data(44 or 48 bytes)
Data(44 or 48 bytes)
The control field also contains bits which specify whether this is a flow control cell or an ordinary data cell, a bit to indicate whether this packet can be deleted in a congested network, and so on.
The control field also contains bits which specify whether this is a flow control cell or an ordinary data cell, a bit to indicate whether this packet can be deleted in a congested network, and so on.
The ETSI definition of an ATM cell also contains 53 bytes with a 5-byte header and 48 bytes of data. The main differences between ETSI and ANSI T1S! are the number of bits in the VCI field, the number of bits in the header checksum, and the definitions and position of the control bits.
The ETSI definition of an ATM cell also contains 53 bytes with a 5-byte header and 48 bytes of data. The main differences between ETSI and ANSI T1S! are the number of bits in the VCI field, the number of bits in the header checksum, and the definitions and position of the control bits.
The VCI label identifies the route for the data.
The VCI label identifies the route for the data.
Simple checksum for error detection. It is the 2’s complement of the sum of all the bytes in the cell.
Simple checksum for error detection. It is the 2’s complement of the sum of all the bytes in the cell.
Cell header (with every little overhead)
Author: W.Buchanan. Ethernet and ATM (20)
3.20 ATM cell routing
44
66
77
11
22
55
33
User 1
User 3
User 2
VCI=12
VCI=06
VCI=22
VCI=10VCI=15
IN OUT
12 06
Routing tableIN OUT
06 22
Routing table
11
Author: W.Buchanan. Ethernet and ATM (21)
3.21 ATM call setup
44
66
77
11
22
55
33
End system A
End system B
Connect to B
Connect to B
Connect to B
OkayOkay
Okay
Signaling request
Connection routed
Connect accept/reject
Dataflow
Connectiontear-down
Signaling packet:VCI=5; VPI=0
As the path is set up, two VCI/VPI labels are assigned for each of
the flows of traffic on the virtual circuit.
44
66
77
11
22
55
33
End system A
End system B
Connect to B
Connect to B
Connect to B
OkayOkay
Okay
Signaling request
Connection routed
Connect accept/reject
Dataflow
Connectiontear-down
Signaling packet:VCI=5; VPI=0
As the path is set up, two VCI/VPI labels are assigned for each of
the flows of traffic on the virtual circuit.
Author: W.Buchanan. Ethernet and ATM (22)
3.22 Virtual Channels and Virtual Paths
VC1VC2
VC3VC4
VC5
VC7VC8
VC6
VC9
VC1
VC3VC2
Transmissionchannel
Virtual path VP
Virtual path
Virtual path
VP
VP
Virtual pathsNetwork user groups or interconnected networks can be mapped to virtual paths and are thus easily administered.Simpler network architecture which consists of groups (virtual paths) with individual connections (virtual circuits).Less network administration and shorter connection times arise from fewer set-up connections.
Virtual pathsNetwork user groups or interconnected networks can be mapped to virtual paths and are thus easily administered.Simpler network architecture which consists of groups (virtual paths) with individual connections (virtual circuits).Less network administration and shorter connection times arise from fewer set-up connections.
Several virtual channels grouped together to create a virtual path
Several virtual channels grouped together to create a virtual path
12
Author: W.Buchanan. Ethernet and ATM (23)
3.23 Example ATM network (EaStMAN)
FDDI
router
FDDI
router
FDDI
router
FDDIrouter
FDDI
router
FDDI
router
FDDI
router
FDDI
router
FDDI
router
FDDI
router
FDDI
routerNapier(Merchiston) UoE
(New College)
Moray House(Holyrood)
UoE(Old College)
UoE(Pollock Halls)
ECA(Grassmarket)
ECA(Lauriston)
Napier(Sighthill)
QMC(Corstorphine)
Moray House(Cramond)
Heriot Watt(Riccarton)
ATMswitch
ATM
switch
ATMswitch
FDDI
router
UoE(King’s Buildings)ATM
switch
ATM
switch
ATMswitch
ATM
switch
ATM
switch
UoE (Western General Hospital)
University ofStirling
SuperJANET
AbMAN, FatMAN, ClydeNET
QMC(Leith Links)
ATM
switch Napier(Craighouse)
ATM
switchNapier(Craig lockhart)
Heriot Watt(Riccarton Campus)
Napier(Sighthill)
QMC
Crammond
WesternGeneralHospital
QMC (Leith)
Napier(Merchiston )
Napier(Craighouse)Napier
(Craiglockhart)
UoE (King’s Buildings)
UoE (Pollock Halls)
UoE (New College)
City of Edinburgh
College ofArt UoE
(Old College)
Moray House ( Holyrood )
Connection toUniversity of Stirling
Author: W.Buchanan. Ethernet and ATM (24)
Napier (Merchiston)
UoE(New College)
Moray House (Holyrood)
UoE(Old College)
UoE(Pollock Halls)
ECA(Grassmarket)
ECA(Lauriston)
Napier(Sighthill)
QMC (Corstorphine)
Moray House(Cramond)
Heriot-Watt(Riccarton)
UoE(King’s Buildings)
UoE (WesternGeneral Hospital)
University ofStirling
SuperJANET
AbMAN, FatMAN, ClydeNET
QMC (Leith Links)
Napier (Craighouse)
Napier (Craiglockhart)
3.24 EaStMAN network
ATMswitchATM
switchATM
switchATM
switchATM
switchATM
switch
ATMswitchATM
switchATM
switchATM
switch
ATMswitchATM
switch
ATMswitchATM
switch
ATMswitchATM
switch
ATMswitchATM
switch
ATMswitchATM
switch
FDDIrouter
FDDIrouter
FDDIrouter
FDDIrouter
FDDIrouter
FDDIrouter
FDDIrouter
FDDIrouter
FDDIrouter
FDDIrouterFDDI
router
FDDIrouter
FDDIrouter
FDDIrouter
FDDIrouter
FDDIrouter
FDDIrouter
FDDIrouter
FDDIrouter
FDDIrouter
FDDIrouter
FDDIrouter
FDDIrouter
FDDIrouter
13
Author: W.Buchanan. Ethernet and ATM (25)
3.25 SuperJanet Network
London
Bristol
Manchester
Leeds
London MAN(ATM 155Mbps)
ULCC(UoL ComputerCentre)
ULC(University College London)
Telehouse
University ofGreenwich
South BankUniversity
UoL,ImperialCollege
Bristol
Birmingham
Exeter
Cardiff
Belfast
Edinburgh
Nottingham
Newcastle
SuperJANET
III
UoE (King’sBuildings)
Napier
University
(Craighouse)
Napier
University
(Craiglockhart)
EaSt MAN(ATM 155Mbps)
Heriot-Watt(Riccarton)
Napier University(Sighthill)
Napier University(Merchiston)
UoE(Old College) QMC
34
155
155
34
2x155TEN-155
Europeantraffic
TeleglobeUS ISP traffic
LINX(London Internet Exchange)
UK ISP traffic
London
Interconnect toClydeNETFatMANAbMAN
G-MANMAN
South WalesMAN
BWE
155
Author: W.Buchanan. Ethernet and ATM (26)
So to conclude?
• For organisational connections: Ethernet 10/100Mbps.• For organisational backbones: Ethernet 100Mbps/1Gbps.• For remote connections: ADSL (10Mbps), IEEE
802.11b (11Mbps), GPRS (10Mbps), Modem (56kbps).
• For wide area connections: ATM (155Mbps upwards),Gigabit Ethernet (for short distances), Frame relay.