Transcript Bandwidth Assignment Strategy in Label Switch Path for

QoS Strategy in DiffServ aware
MPLS environment
Teerapat Sanguankotchakorn, D.Eng.
Telecommunications Program,
School of Advanced Technologies
Asian Institute of Technology
P.O.Box 4, Klong Luang, Pathumthani, 12120, Thailand
E-mail: [email protected]
Traffic engineering
Service model
• how capacity is shared
• how much capacity
• routing, ...
Quality of service
• transparency
• throughput
• accessibility
Technology
• filtering, scheduling
• queue management
Network business model
•congestion pricing
•volume pricing
Differentiated Services (DiffServ)
• Required Mechanisms for Service Differentiation
−Classification:
To identify the aggregation (class) to which a packet
belongs based on their different QoS requirements.
– Scheduling:
To determine which packet will be transmitted according to its
priority specified by DS Code Point.
– Queue Management:
To decide which packets will be dropped, when
the buffer overflows in the case of network congestions.
Conditioner
classifier
Incoming
Packets
Outgoing
Packets
Marker
Meter
Principle of Service Differentiation
Multi Protocol Label Switching (MPLS)
–
–
–
–
Fast routing
Provide bandwidth management
Less load on core routers
Use of labels in packet headers (short, fixed length and locally
significant)
– Traffic engineering
(classification and identification of IP packets with a
label and forwarding the packets to a switch or router that is modified to operate
with such labels.
– Signaling protocols used in MPLS
(LDP))
– No end-host protocol component
– Quality of Service (QoS)
(Label Distribution Protocol
DiffServ + MPLS
• A scheme which is mutually beneficial for both…
– MPLS provides DiffServ with Path protection
and restoration.
– DiffServ acts as CoS architecture for MPLS
SO, MPLS with DiffServ can give network designers the
flexibility to provide different treatment to certain QoS
classes that need path-protection.
Domain Model
Diffserv aware
MPLS Domain
LSP
LER
LSR
LE
R
LSR
Some kind of mapping
is required to convert
IP header values to label
LE
R
LER: Label Edge Router
LSR: Label Switch Router
LSP: Label Switch Path
LSR
LSR
LE
R
Mapping DiffServ to MPLS
Why:
•Label Switch Routers (LSRs), don’t see the IP header and DSCPs in ToS field of
IPv4 header.
•LSR only reads the Label contents and decides the next hop
How:
•The contents of 6 bits DSCP is mapped into 3 bits EXP field of Label
There are two options to map DSCP value into the Label…
E-LSP
EXP-inferred-PSC LSP
•PHB is determined from EXP bits
•No additional signaling is required
•EXP-PHB mapping is configured
•Shim header is required
•Up to 8 PHBs per LSP
•With Bandwidth reservations,
the bandwidth is shared by set of
transported PSCs
L-LSP
Label-only-inferred-PSC
•PHB is determined from Label or
from label and EXP/CLP bits
•PHB or PSC is signaled at LSP setup
•Label-PHB mapping is signaled.
•EXP/CLP-PHB mapping is well known
•Shim or link layer header may be used
•One PHB per LSP except for AF and
PSC per LSP for AF
•With bandwidth reservation,
the bandwidth is per-PSC
Mapping Traffic to LSPs
Ingress
Node
Incoming
Packets
With both
Diffserv and
MPLS
enable
Premium
Traffic
LSP 1
•
•
High Priority
Traffic
LSP 2
•
A network may have multiple
classes of traffic.
For a same destination, there
might be different classes.
Now, we can map different
classes to different LSPs.
Problem:
Best Effort
Traffic
LSP 3
Again the delay and jitter is
possible as all the premium traffic
is following the same physical
path.
•
We can solve the above mentioned problem by splitting the traffic into
different LSPs, even the destination is the same.
•
We can allocate certain Bandwidth for each service class in a single LSP.
Methodology
• Calculation of:
– Bandwidth Utilization per
traffic flow
where;
N r  Ps  8bits
t  1000
– Throughput
N r  Ps  8bits
(Tstop  Tstart ) 1000
Ps  Packet size
t  Time in second
where;
– Dropped packets
Tstart  Start time of each traffic flow in second
Tstop 
where;
Ng  Nr
Ng
N
D
i 1
Nr
i
where;
Stop time of each traffic flow in second
N g  Number of packets generated at source
Nr 
 100%
– Mean End-to-End Delay
N r  Number of packets received at
destination router in bytes
Number of packets received at source
Di  End-to-End delay of packet ‘i’= Ts  Td
i
i
Tsi  Time of packet ‘i’ en-queue at source router
Td i Time of packet ‘i’ receive at destination
Application Scenario
• DiffServ + MPLS
Ingress Node
Incoming
Packets
Premium Traffic
LSP 1
High Priority
Traffic
LSP 2
Best Effort Traffic
LSP 3
With both DiffServ
and MPLS enable
(Simple)
Overall Packet Loss in %age
For Simple Network
2Mbit/s
c2
SRC 1
5 msec
c3
2Mbit/s
5 msec
2Mbit/s
5 msec
DEST 1
%age Packet Loss
Network Topology:
50
40
30
20
10
0
-10 0
1
2
3
4
5
6
5
6
rate 4 in Mbps
SRC 2
DEST 2
5Mbit/s
5 msec
5 msec
SRC 3
2Mbit/s
5 msec
2Mbit/s
5 msec
3Mbit/s
5 msec
e2
Average End to End Delay
DEST 3
3Mbit/s
DEST 4
5 msec
c4
3Mbit/s
5 msec
c5
0.025
0.02
0.015
0.01
0.005
0
0
Domain
1
2
3
4
rate4 in Mbps
 Traffic sources are CBR sources on UDP agents.
 All packets follows the same smallest path e1-c1-e2 for simple case.
 For each case we will keep constant all the above 3 sources and will vary only last source
from 500kbps to 5000kbps.
 Other constant rates are:
 Rate1: 1.9 Mbps (Real Time 1---RT1)
 Rate2: 1.1 Mbps (Real Time 2---RT2)
 Rate3: 1.0 Mbps (High Priority Best Effort---HPBE)
 Rate4: 500kbps 5Mbps (Simple Best Effort—SBE)
 Simulation time is 30.0 seconds
Overall Link Utilization of Network
Link Utilization in
%age
SRC 4
c1
5Mbit/s
delay in msec
e1
25
20
15
10
5
0
0
2
4
rate4 in Mbps
6
(DiffServ)
Overall Packet Loss in %age
%age Packet Loss
Network Topology:
For Diffserv Network
2Mbit/s
C2
SRC 1
5 msec
C3
2Mbit/s
5 msec
2Mbit/s
5 msec
SRC 2
1
C1
5 msec
SRC 3
2Mbit/s
5 msec
5Mbit/s
5 msec
2Mbit/s
5 msec
3Mbit/s
5 msec
DEST 3
3Mbit/s
DEST 4
5 msec
C4
3Mbit/s
5 msec
C5
3
4
5
6
5
6
Average End to End Delay
E2
delay in msec
5Mbit/s
2
rate 4 in Mbps
DEST 2
E1
0.02
0.015
0.01
0.005
0
0
1
2
DiffServ Domain
3
4
rate4 in Mbps
Overall Link Utilization of Network
 Traffic sources are CBR sources on UDP agents
 For each case we will keep constant all the above 3 sources and will vary only last source
from 500kbps to 5000kbps.
 Other constant rates are:
 Rate1: 1.9 Mbps (Real Time 1---RT1)
 Rate2: 1.1 Mbps (Real Time 2---RT2)
 Rate3: 1.0 Mbps (High Priority Best Effort---HPBE)
 Rate4: 500kbps 5Mbps (Simple Best Effort—SBE)
Simulation time is 30.0 seconds
Link Utilization in
%age
SRC 4
DEST 1
50
40
30
20
10
0
-10 0
25
20
15
10
5
0
0
2
4
rate4 in Mbps
6
(MPLS)
Overall Packet Loss in %age
For MPLS Network
2Mbit/s
LSR7
SRC 0
5 msec
LSR8
2Mbit/s
5 msec
2Mbit/s
5 msec
SRC 1
4
3
2
1
0
-1 0
1
2
DEST 12
5Mbit/s
LSR5
5 msec
SRC 2
2Mbit/s
5 msec
5Mbit/s
5 msec
2Mbit/s
5 msec
3Mbit/s
5 msec
3Mbit/s
5 msec
4
5
6
5
6
rate 4 in Mbps
DEST 13
3Mbit/s
Average End to End Delay
DEST 14
5 msec
LSR9
3
LSR6
LSR10
MPLS Domain
delay in msec
LSR4
0.02
0.015
0.01
0.005
0
0
 If no ER-LSP is defined, all packets follow the same smallest path LSR4-LSR5-LSR6. In our case,
we establish ER-LSP as soon as simulation starts.
 Traffic sources are CBR sources on UDP agents
 For each case we will keep constant all the above 3 sources and will vary only last source from
500kbps to 5000kbps.
 Other constant rates are:
 Rate1: 1.9 Mbps (Real Time 1---RT1)
 Rate2: 1.1 Mbps (Real Time 2---RT2)
 Rate3: 1.0 Mbps (High Priority Best Effort---HPBE)
 Rate4: 500kbps 5Mbps (Simple Best Effort—SBE)
Simulation time is 30.0 sec
1
2
3
4
rate4 in Mbps
Overall Link Utilization of Network
Link Utilization in
%age
SRC 3
DEST 11
%age Packet Loss
Network Topology:
80
60
40
20
0
0
5
10
rate4 in Mbps
15
Conclusions
From our “Dumbbell” network topology,
• The overall performance (packet Loss, End-to-End elay, Link
utilization) of DiffServ is quite similar to the Simple scheme, but
MPLS is superior than DiffServ.
• In Simple case, there is no mechanism to classify the packets, so
packets are randomly dropped from all 4 sources.
• In DiffServ, the low priority packets (Best effort packets) are
discarded. Since RED queue has been used, some early dropping of
high priority traffic can also be predicted in the network.
• If we simply assign the priority in descending order to RT1,RT2 then
HPBE and SBE in case of MPLS, Link utilization can be increased by
mapping different traffic through different routers.
Thank You!