switched local area network design switched lan...
TRANSCRIPT
09_Progettazione_L2 - 1 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
Switched Local Area Network Design
-
Switched LAN
Switched Local Area Switched Local Area Network DesignNetwork Design
--
SwitchedSwitched LANLAN
Mario Baldi
Politecnico di Torinohttp://staff.polito.it/mario.baldi
Mario Baldi
Politecnico di Torinohttp://staff.polito.it/mario.baldi
Based on chapter 9 of: M. Baldi, P. Nicoletti, Switched LAN, McGraw-Hill, 2002, ISBN 88-386-3426-2
09_Progettazione_L2 - 2 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
Copyright NoticeThis set of transparencies, hereinafter referred to as slides, is protected by copyright laws and provisions of International Treaties. The title and copyright regarding the slides (including, but not limitedto, each and every image, photography, animation, video, audio, music and text) are property of the authors specified on page 1.
The slides may be reproduced and used freely by research institutes, schools and Universities for non-profit, institutional purposes. In suchcases, no authorization is requested.
Any total or partial use or reproduction (including, but not limited to, reproduction on magnetic media, computer networks, and printedreproduction) is forbidden, unless explicitly authorized by the authorsby means of written license.
Information included in these slides is deemed as accurate at the date of publication. Such information is supplied for merely educational purposes and may not be used in designing systems, products, networks, etc. In any case, these slides are subject to changeswithout any previous notice. The authors do not assume anyresponsibility for the contents of these slides (including, but notlimited to, accuracy, completeness, enforceability, updated-ness of information hereinafter provided).
In any case, accordance with information hereinafter included mustnot be declared.
In any case, this copyright notice must never be removed and must bereported even in partial uses.
09_Progettazione_L2 - 3 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
Topics
Design criteria
Design based on repeaters and switches
Fault tolerance
Design of fibre-basedbackbones
09_Progettazione_L2 - 4 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
Design criteriaDesign criteria
09_Progettazione_L2 - 5 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
Design criteriaDesign criteria
PerformancesPerformances
ReliabilityReliability
SecuritySecurity
Fault toleranceFault tolerance
09_Progettazione_L2 - 6 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
Selection of network devices Selection of network devices
ReliabilityReliability
Observance of standard specifications
Observance of standard specifications
Cabling Cabling
Particular attention is needed forfibre-based backbones
Particular attention is needed forfibre-based backbones
AttenuationAttenuation
09_Progettazione_L2 - 7 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
Transmission bandwidth Transmission bandwidth
Network resourcesNetwork resources
Packet processing capabilities of network devices
Packet processing capabilities of network devices
09_Progettazione_L2 - 8 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
Depends onDepends on
Time Time
Different moments Different moments
Hours Hours
Resource employmentResource employment
Days of the week Days of the week
Special events Special events
Traffic typology Traffic typology
09_Progettazione_L2 - 9 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
Client-server trafficClient-server traffic
Server with high-speed connections(for example 1 Gb/s)
Server with high-speed connections(for example 1 Gb/s)
Clients with lower speed connections
(for example100 Mb/s)
Clients with lower speed connections
(for example100 Mb/s)
Concentratedtraffic flowsConcentratedtraffic flows
09_Progettazione_L2 - 10 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
SwitchSwitch
Crossed traffic flowsCrossed traffic flows
Peer-to-peer trafficPeer-to-peer traffic
09_Progettazione_L2 - 11 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
Network traffic surveyNetwork traffic survey
Time Time
Resourcesemployment
Resourcesemployment
Functionality of network analysys monitors
Functionality of network analysys monitors
0 0
60%
50%
40%
30%
20%
10%
5%
0%
60%
50%
40%
30%
20%
10%
5%
0%
09_Progettazione_L2 - 12 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
Simple to realize Simple to realize
Inexpensive Inexpensive
DimensioningDimensioning
The most common approach is to overdimension the network
The most common approach is to overdimension the network
09_Progettazione_L2 - 13 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
No traffic engineering No traffic engineering
No resource reservation No resource reservation
Simple to manage Simple to manage
DimensioningDimensioning
The most common approach is to overdimension the network
The most common approach is to overdimension the network
09_Progettazione_L2 - 14 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
Design guidelines
Device types and topologies
Design guidelines
Device types and topologies
09_Progettazione_L2 - 15 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
BridgeBridge
Shared channelShared channel
Once it was also physical structureOnce it was also physical structure
Logical structureLogical structure
09_Progettazione_L2 - 16 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
Based on point to point linksBased on point to point links
HubMultiportrepeater
HubMultiportrepeater
Physical structurePhysical structure
09_Progettazione_L2 - 17 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
Star typologyStar typology
if necessary, it can be hierarchicalif necessary, it
can be hierarchical
09_Progettazione_L2 - 18 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
Suitable linksSuitable links1 Gb/s1 Gb/s
100Mb/s
100Mb/s
10 Mb/s10 Mb/s
09_Progettazione_L2 - 19 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
CoreBackbone
CoreBackbone
DistributionAggregationDistributionAggregation
AccessAccess
Normally on 3 levelsNormally on 3 levels
09_Progettazione_L2 - 20 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
DatacenterBuilding cabinet
DatacenterBuilding cabinet
Horizontal wiringHorizontal wiring
VerticalwiringVerticalwiring
FloorcabinetFloor
cabinet
Normally on 3 levelsNormally on 3 levels
09_Progettazione_L2 - 21 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
In a buildingIn a building
DatacenterDatacenter
Floor cabinetFloor cabinet
HorizontalwiringHorizontalwiring
Vertical wiringVertical wiring
09_Progettazione_L2 - 22 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
Design for faulttoleranceDesign for faulttolerance
09_Progettazione_L2 - 23 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
LinksLinks
Fault toleranceFault tolerance
The network can operate also when facing one or more failures
The network can operate also when facing one or more failures
DevicesDevices
09_Progettazione_L2 - 24 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
Device partsDevice parts
Fault toleranceFault tolerance
InterfaceInterface
Power supplierPower supplier
Thanks toPietro Nicoletti
Thanks toPietro Nicoletti
The network can operate also whenfacing one or more failures
The network can operate also whenfacing one or more failures
09_Progettazione_L2 - 25 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
How to realize itHow to realize it
Adding redundancy on critical elementsAdding redundancy on critical elements
InterfaceInterface
PortPort
ProcessorProcessor
Power supplierPower supplier
LinkLink
Device (for example a switch)Device (for example a switch)
09_Progettazione_L2 - 26 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
Where to introduce redundancy?Where to introduce redundancy?
Processors, power suppliers, NICs Processors, power suppliers, NICs
At device levelAt device level
Parallel interfaces, redundant ports Parallel interfaces, redundant ports
At interface levelAt interface level
Alternative paths Alternative paths
At network levelAt network level Also combining all of these
09_Progettazione_L2 - 27 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
How much redundancy?How much redundancy?
Each element has associateda fault probability and a costEach element has associateda fault probability and a cost
Rendundancy means to addnew elements
Rendundancy means to addnew elements
By increasingBy increasing
The probability of a faultThe probability of a fault
The cost of the networkThe cost of the network
09_Progettazione_L2 - 28 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
Costs Costs
Real tolerance needs Real tolerance needs
The fault tolerant solution is a compromise among
The fault tolerant solution is a compromise among
EssentiallyEssentially
Quality (reliability) of elements Quality (reliability) of elements
09_Progettazione_L2 - 29 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
A golden ruleA golden rule
The fault tolerant solution mustbe as simple as possible and use the lowest number of redundant elements required to guarantee a path that is alternative to
the faulty one
The fault tolerant solution mustbe as simple as possible and use the lowest number of redundant elements required to guarantee a path that is alternative to
the faulty one
09_Progettazione_L2 - 30 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
Uninterruptible Power Supply systems for important devicesUninterruptible Power Supply systems for important devices
Good practicesGood practices
For example star center For example star center
Systems for the management and control of the network for revealing anomalies and faults
Systems for the management and control of the network for revealing anomalies and faults
Redundant devices must have anindependent power supply
Redundant devices must have anindependent power supply
09_Progettazione_L2 - 31 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
Ring: good quality/price ratio
Ring: good quality/price ratio
Redundant linksRedundant links
Physical paths (channels) Physical paths (channels)
Avoid the sharing of critical elementsAvoid the sharing of critical elements
Optical fibre is preferableOptical fibre is preferable
BackboneBackbone
Link ends (panels) Link ends (panels)
09_Progettazione_L2 - 32 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
Redundancy of the star centerRedundancy of the star center
09_Progettazione_L2 - 33 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
Redundancy and ProtocolsRedundancy and Protocols
Alternative paths areDifficult for switches
Alternative paths areDifficult for switches
Spanning tree protocolIEEE 802.1d
Spanning tree protocolIEEE 802.1d
09_Progettazione_L2 - 34 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
Spanning tree protocolSpanning tree protocol
Choice of the root bridgeChoice of the root bridge
Bridge Protocol Data Unit (BPDU)Bridge Protocol Data Unit (BPDU)
Selection of the root portsSelection of the root ports
Selection of the designated portsSelection of the designated ports
09_Progettazione_L2 - 35 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
Spanning tree reconfigurationSpanning tree reconfiguration
Fault reactionFault reaction
Needed time: 50 secNeeded time: 50 sec
09_Progettazione_L2 - 36 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
It can be managed by modifyingthe time-out
It can be managed by modifyingthe time-out
Maximum 7 cascading bridgesMaximum 7 cascading bridges
Underused resources Underused resources
Single routing treeSingle routing tree
Slow reconfigurationSlow reconfiguration
Drawbacks of the spanning tree protocolDrawbacks of the spanning tree protocol
09_Progettazione_L2 - 37 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
Reconfiguration time: less than 1 s Reconfiguration time: less than 1 s
Rapid spanning tree protocol IEEE 802.1wRapid spanning tree protocol IEEE 802.1w
Managing the limits of the spanning tree protocolManaging the limits of the spanning tree protocol
Overcoming dimension limits Overcoming dimension limits
Multiple spanning tree protocol IEEE 802.1sMultiple spanning tree protocol IEEE 802.1s
Hierarchy of trees Hierarchy of trees
09_Progettazione_L2 - 38 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
Blocked ports Blocked ports
Designing the details of the treeDesigning the details of the tree
Spanning tree protocol designSpanning tree protocol design
It replaces the root bridge facing a failure
It replaces the root bridge facing a failure
Chose the backup root bridgeChose the backup root bridge
Chose the root bridgeChose the root bridge
09_Progettazione_L2 - 39 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
In the case: time-out tuningIn the case: time-out tuning
Study of the optimal tree in normal conditions
Study of the optimal tree in normal conditions
At leastAt least
Study of the tree during failures
Study of the tree during failures
Maximum diameter: 7 switches Maximum diameter: 7 switches
Spanning tree protocol designSpanning tree protocol design
09_Progettazione_L2 - 40 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
Network and spanning treeNetwork and spanning treeRoot bridgeRoot bridge
Root portRoot port
Designated portDesignated port
Blocking portBlocking port
LEGENDALEGENDA
S1S1--PP
2457624576S1S1--SS
2867228672
S2S2
3276832768
S3S3
3276832768
S4S4
3276832768
S5S5
3276832768
S6S6
3276832768
S7S7
3276832768
BridgepriorityBridgepriority
09_Progettazione_L2 - 41 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
Active topology without faultsActive topology without faults
S1S1--SS
2867228672
S2S2
3276832768
S3S3
3276832768
S4S4
3276832768
S5S5
3276832768
S6S6
3276832768
S1S1--PP
2457624576
S7S7
3276832768
09_Progettazione_L2 - 42 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
Reaction to faultsReaction to faults
S1S1--PP
2457624576S1S1--SS
2867228672
S2S2
3276832768
S3S3
3276832768
S4S4
3276832768
S5S5
3276832768
S6S6
3276832768
S7S7
3276832768Root portRoot port
Designated portDesignated port
Blocking portBlocking port
LEGENDALEGENDA
FaultFault
09_Progettazione_L2 - 43 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
Reaction to faultsReaction to faults
S1S1--PP
2457624576S1S1--SS
2867228672
S2S2
3276832768
S3S3
3276832768
S4S4
3276832768
S5S5
3276832768
S6S6
3276832768
Fault
Fault
S7S7
3276832768Root portRoot port
Designated portDesignated port
Blocking portBlocking port
LEGENDALEGENDA
09_Progettazione_L2 - 44 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
Reaction to faultsReaction to faults
S1S1--PP
2457624576S1S1--SS
2867228672
S2S2
3276832768
S3S3
3276832768
S4S4
3276832768
S5S5
3276832768
S6S6
3276832768
S7S7
3276832768
Root bridgeRoot bridge
FaultFault
Root portRoot port
Designated portDesignated port
Blocking portBlocking port
LEGENDALEGENDA
09_Progettazione_L2 - 45 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
S1S1--PP
3276832768S1S1--SS
3276832768
S3S3
3276832768
S2S2
3276832768S5S5
3276832768S6S6
3276832768S4S4
3276832768S7S7
3276832768
Active topology with a bad configurationActive topology with a bad configuration
Root bridgeRoot bridge
09_Progettazione_L2 - 46 Copyright 2002 - M. Baldi - P. Nicoletti: see page 2
SW-1 SW-2
1 2 3
4
3 2 1
4
A
B
C
D
E
F
B. Priority
24576B. Priority
286726 6
Multiple floor switches