RSTPRSTP
vs
STPSTP
Instructors :
Assoc’ Prof’ Reuven Cohen
Mr. Itay Dabran
Mr. Mordo Shalom
Submitting :
Danny Kalmar 01702821-8
Gilad Wallach 03279719-3
Omer Sharabi 03385662-6
AgendaAgenda Project Definition
Implementation
Test Plan
Results
Main Conclusions
General Observations
AgendaAgenda Project Definition
ImplementationImplementation
Test PlanTest Plan
ResultsResults
Main ConclusionsMain Conclusions
General ObservationsGeneral Observations
IntroductionIntroduction
Why do we need spanning tree bridges?
At the beginning : 802.1d
But : the rules were changed
RSTP as an evolution of STP.
Goals Goals
Implementing STP and RSTP
Comparing between the performances of the protocols
Results’ discussion.
AgendaAgenda Project DefinitionProject Definition
Implementation
Test PlanTest Plan
ResultsResults
Main ConclusionsMain Conclusions
General ObservationsGeneral Observations
S/W ModulesS/W ModulesGeneral:
We implemented a simulation which runs both protocols over a variety of randomized nets
It can run several tests in a single execution and collect statistics about the building and recovery abilities of each protocol
Simulation’s parameters : num’ of bridges and lans , num’ of tests and failures within each test, bridge’s configuration and packet’s lost probability.
The Net Manager Module
Simulation’s main loop
Main features : Creation and initialization of new a randomized net
Running the bridges protocols using the net’s members’ interfaces and the given parameters
Detection of the tree’s : building , failing and recovering
The ability to run multiple tests and failures on a given configuration
Statistics collecting.
The Bridge Module
Supports both protocols due to the mode of operation
Main features for the 802.1W: RSTP’s BPDUs mechanism
Rapid Transition to Forwarding State
Proposal / Agreement mechanism
Sync Mechanism
Uplink Fast
RSTP’s Topology Change Detection and Propagation
Main features for the 802.1D: STP’s BPDUs mechanism
STP’s Topology Change Detection and Propagation
The LAN Module
Main features : Distribution of BPDUs from the previous cycle to their destinations
The LAN receives all messages and prepare them to be sent out the next cycle.
The Testing Module
Main features : Generation of failures on demand : disconnection of a forwarding port or connection of a disabled port while keeping the net with connectivity
Maintenance of failures’ list in order to support running the same tests for both protocols .
System ArchSystem ArchBridge.Tick()
Lan.Tick()
TestCreateFailure()
send_bpdu
rece
ived
_bpd
u
NetManager
Testing
LAN
Bridge
Main Loop (1)Main Loop (1)Case: - Packets’ lost probability != 0
For all tests :
• Set a randomized net
• Run each protocol till its tree become stable
• Collect test’s results.
Print statistics.
Main Loop (2)Main Loop (2)Case: - Packets’ lost probability = 0
For all tests :
• Set a randomized net
• Run each protocol till its tree become stable
• Collect initialization’s results
• For all failures :
Activate the failure
Run each protocol till its tree recover
Collect recovery’s results.
Print statistics.
AgendaAgenda Project DefinitionProject Definition
ImplementationImplementation
Test Plan
ResultsResults
Main ConclusionsMain Conclusions
General ObservationsGeneral Observations
Test’s ParametersTest’s Parameters
All the net’s member possibilities are represented as a pair of (Bridge_Num , LAN_Num ) :
• Dense networks : { (2,6), (5,10) , (8,15) ,(10,17) , (12,25) , (15,30) }
• Sparse networks : { (2,2), (5,5) , (8,8) ,(10,10) , (12,12) , (15,15)}
Bridge’s parameters (following the Cisco configuration) :
• Forward delay = 15000 ticks
• Max age = 20000 ticks
• Hello time = 2000 ticks.
Performance's CriteriaPerformance's CriteriaCase: - Packets’ lost probability = 0 :
• Average Initialization time
• Average number of BPDUs’ that were sent during initialization
• Average recovery time
• Average number of BPDUs’ that were sent during recovery
Case: - Packets’ lost probability =! 0 :
The same without the recovery information
AgendaAgenda Project DefinitionProject Definition
ImplementationImplementation
Test PlanTest Plan
Results
Main ConclusionsMain Conclusions
General ObservationsGeneral Observations
Recover Time In Sparse Networks
0
5000
10000
15000
20000
25000
0 2 4 6 8 10 12 14 16
Num Bridges=Num Lans
Tic
ks
un
till
sta
bili
tyW Recover TimeD recover time
Recover Time in Sparse NetworksRecover Time in Sparse Networks
Immediate conclusions:Immediate conclusions:
RSTP recovers much faster than STPRSTP recovers much faster than STP
Recover Time In Dense Networks
0
5000
10000
15000
20000
25000
30000
35000
0 2 4 6 8 10 12 14 16
Num Of Bridges
Tic
ks
un
till
sta
bili
ty
W recover time
D recover time
NumBridges NumLans 2 6 5 10 8 15 10 17 12 25 15 30
Recover Time in Dense NetworksRecover Time in Dense Networks
Immediate conclusions:Immediate conclusions:
RSTP recovers much faster than STPRSTP recovers much faster than STP
Recover time is similar to that in sparse networks.Recover time is similar to that in sparse networks.
Num of BPDU In recover In Sparse Networks
0
50
100
150
200
250
0 2 4 6 8 10 12 14 16
Num Bridges=Num Lans
Nu
m B
PD
UW Num of BPDU
W Num of BPDU
BPDUs Num sent during Recovery Time in BPDUs Num sent during Recovery Time in Sparse NetworksSparse Networks
Immediate conclusions:Immediate conclusions:
RSTP requires less BPDU to achieve stabilityRSTP requires less BPDU to achieve stability
This is caused mainly because the recovery time is This is caused mainly because the recovery time is much faster .much faster .
Num of BPDU In recover In Dense Networks
0
50
100
150
200
250
300
350
400
450
0 2 4 6 8 10 12 14 16
Num Bridges
Nu
m B
PD
U
W Num of BPDU
D Num of BPDU
NumBridges NumLans 2 6 5 10 8 15 10 17 12 25 15 30
BPDUs Num sent during Recovery Time in BPDUs Num sent during Recovery Time in Dense NetworksDense Networks
Graph Explanation:Graph Explanation:
RSTP requires less BPDU to achieve stabilityRSTP requires less BPDU to achieve stability
Dense network requires much more BPDUs to Dense network requires much more BPDUs to stabilize. stabilize.
AgendaAgenda Project DefinitionProject Definition
ImplementationImplementation
Test PlanTest Plan
ResultsResults
Main Conclusions
General ObservationsGeneral Observations
ConclusionsConclusions Recovery – RSTP recovers significantly faster than STP , less significantly better in BPDUs count
Dense and Sparse networks – We did not find any critical differences except the expected gap between BPDUs count
Packet Lost Probability – both protocols act as usual as long as the the probability is less than 10%. Both protocols stability is not guaranteed over ~60%.
AgendaAgenda Project DefinitionProject Definition
ImplementationImplementation
Test PlanTest Plan
ResultsResults
Main ConclusionsMain Conclusions
General Observations
ObservationsObservations The uplink fast feature in the RSTP can improve if it will use the “Back Up” port feature in addition to the “Alternate” port feature
RSTP’s initialization’s performances can be increased significantly through appropriate configuration (“slow” transition avoidance)
Attention to the fact that RSTP recovers faster than STP which is a very important thing in today networks. RSTP “pays” in increased BPDUs count which is less important due to today possible band width.
Additional tests could explore more deeply the affects and the exact legal range of values of Packet Lost Probability for each protocol .
Old FoilsOld Foils
INITIALIZATION TIME IN NOT BUSY NETWORKS
0
5
10
15
20
25
30
35
40
45
50
0246810121416
Num Bridges=Num Lans
cycl
es
un
till
stab
ility
in in
itia
lizat
ion
D Initilalization time with fd 3
W initialization with fd 3
D Initilalization time with fd 10
W initialization with fd 10
D initialization with fd 20
W Initilalization time with fd20
Initialization Time in not busy NetworksInitialization Time in not busy Networks
Graph Explanation:Graph Explanation:
Similar initialization times in medium and large size Similar initialization times in medium and large size Networks,with slight advantage to the RSTP protocolNetworks,with slight advantage to the RSTP protocol
In small Networks RSTP builds the tree much fasterIn small Networks RSTP builds the tree much faster
As expected, a long Forward Delay lengthens the As expected, a long Forward Delay lengthens the initialization time.initialization time.
INITIALIZATION TIME IN BUSY NETWORKS
0
5
10
15
20
25
30
35
40
45
50
0246810121416
Bridge Num
cycl
es
un
till
stab
ility
in in
itia
lizat
ion
D initialization with fd 3
W initialization with fd 3
D initialization with fd 10
W initialization with fd 10
D initialization with fd 20
W initialization with fd 20
# Bridges # Lans
2 6 5 10 8 15 10 17 12 25 15 30
Initialization Time in busy NetworksInitialization Time in busy Networks
Graph Explanation:Graph Explanation:
Similar initialization times in medium and large size Similar initialization times in medium and large size Networks,with slight advantage to the RSTP protocolNetworks,with slight advantage to the RSTP protocol
In small Networks RSTP builds the tree much fasterIn small Networks RSTP builds the tree much faster
As expected, a long Forward Delay lengthens the As expected, a long Forward Delay lengthens the initialization time.initialization time.
Initialization time is similar to that in not busy Initialization time is similar to that in not busy networks.networks.
RECOVER TIME IN NOT BUSY NETWORKS
0
5
10
15
20
25
30
35
40
45
0246810121416
num bridges=num lans
cycl
es u
nti
ll st
abili
ty in
rec
ove
r
D recover with fd 3
W recover with fd 3
D recover with fd 10
W recover with fd 10
D recover with fd 20
W recover with fd 20
RECOVER TIME IN BUSY NETWORKS
0
5
10
15
20
25
30
35
40
45
0246810121416
Bridge num
cycl
es
un
till
stab
ility
in r
eco
ve
r
D recover with fd 3
W recover with fd 3
D recover with fd 10
W recover with fd 10
D recover with fd 20
W recover with fd 20
# Bridges # Lans
2 6 5 10 8 15 10 17 12 25 15 30
BPDU NUM IN INITIALIZATION IN NOT BUSY NETWORKS
0
100
200
300
400
500
600
700
0246810121416
Num Bridges=Num Lans
Nu
m O
f B
PD
U m
es
sag
es
D in initialization with fd 3
W in initialization with fd 3
D in initialization with fd 10
W in initialization with fd 10
D in initialization with fd 20
W in initialization with fd 20
BPDUs Num sent during Initialization Time BPDUs Num sent during Initialization Time in not busy Networksin not busy Networks
Graph Explanation:Graph Explanation:
Linear growth in bpdu sent during initialization in Linear growth in bpdu sent during initialization in relation to the network size in both protocolsrelation to the network size in both protocols
RSTP sends much more BPDUs because of levels RSTP sends much more BPDUs because of levels of distribution.of distribution.
BPDU NUM IN INITIALIZATION IN BUSY NETWORKS
0
100
200
300
400
500
600
700
800
900
0246810121416
Bridges Num
Nu
m O
f B
PD
U m
ess
age
s
D in initialization with fd 3
W in initialization with fd 3
D in initialization with fd 10
W in initialization with fd 10
D in initialization with fd 20
W in initialization with fd 20
#Bridges #Lans 2 6 5 10 8 15 10 17 12 25 15 30
Bpdus Num sent during Initialization Time in Bpdus Num sent during Initialization Time in busy Networksbusy Networks
Graph Explanation:Graph Explanation:
Linear growth in bpdu sent during initialization in Linear growth in bpdu sent during initialization in relation to the network size in both protocolsrelation to the network size in both protocols
the gap between the number of BPDUs in RSTP and the gap between the number of BPDUs in RSTP and STP is not as big in busy networks.STP is not as big in busy networks.
BPDU NUM IN RECOVER IN NOT BUSY NETWORKS
0
20
40
60
80
100
120
140
160
180
0246810121416
Bridge Num=Lan Num
Nu
m O
f B
PD
U m
ess
age
s
D in recover with fd 3
W in recover with fd 3
D in recover with fd 10
W in recover with fd 10
D in recover with fd 20
W in recover with fd 20
BPDU NUM IN RECOVER IN BUSY NETWORKS
0
50
100
150
200
250
300
350
400
0246810121416
Bridge Num
Nu
m O
f B
PD
U m
essag
es
D in recover with fd 3
W in recover with fd 3
D in recover with fd 10
W in recover with fd 10
D in recover with fd 20
W in recover with fd 20
#Bridges #Lans 2 6 5 10 8 15 10 17 12 25 15 30
BPDU NUM IN RECOVER IN BUSY NETWORKS
0
50
100
150
200
250
300
350
400
0246810121416
Bridge Num
Nu
m O
f B
PD
U m
essag
es
D in recover with fd 3
W in recover with fd 3
D in recover with fd 10
W in recover with fd 10
D in recover with fd 20
W in recover with fd 20
#Bridges #Lans 2 6 5 10 8 15 10 17 12 25 15 30
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