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Mario Gerla and Gianluca Reali
Computer Science Department
University of California, Los Angeles (UCLA)
www.cs.ucla.edu/NRL/
IP DiffServ Architecture for Providing Voice/Video QoS Guarantees:
CAC, QoS Routing and Forwarding
Multiple constraints QoS RoutingGiven:
- a (real time) connection request with specified QoS requirements (e.g., Bdw, Delay, Jitter, packet loss, path reliability etc)
Find:
- a min cost (typically min hop) path which satisfies such constraints
- if no feasible path found, reject the connection
Example of QoS Routing
A
B
D = 30, BW = 20D = 25, BW = 55
D = 5, BW = 90
D = 3, BW = 105
D =
5, B
W =
90
D = 1, BW = 90
D = 5, B
W = 90
D =
2, B
W =
90
D = 5, BW = 90D = 14, BW = 90
Constraints: Delay (D) <= 25, Available Bandwidth (BW) >= 30
2 Hop Path --------------> Fails (Total delay = 55 > 25 and Min. BW = 20 < 30)3 Hop Path ----------> Succeeds!! (Total delay = 24 < 25, and Min. BW = 90 > 30)5 Hop Path ----------> Do not consider, although (Total Delay = 16 < 25, Min. BW = 90 > 30)
A
B
D = 30, BW = 20D = 25, BW = 55
D = 5, BW = 90
D = 3, BW = 105
D =
5, B
W =
90
D = 1, BW = 90
D = 5, B
W = 90
D =
2, B
W =
90
D = 5, BW = 90D = 14, BW = 90
Constraints: Delay (D) <= 25, Available Bandwidth (BW) >= 30
We look for feasible path with least number of hops
Benefits of QoS Routing
• Without QoS routing: • must probe path & backtrack; non optimal path, control
traffic and processing OH, latency
With QoS routing:• optimal route; “focused congestion” avoidance• more efficient Call Admission Control (at the source)• more efficient bandwidth allocation (per traffic class)• resource renegotiation possible
The components of QoS Routing• Q-OSPF: link state based protocol; it disseminates
link state updates (including QoS parameters) to all nodes; it creates/maintains global topology map at each node
• Bellman-Ford constrained path computation algorithm: it computes constrained min hop paths to all destinations at each node based on topology map
• Call Acceptance Control • Packet Forwarding: source route or MPLS
OSPF Overview
5 Message Types
1) “Hello” - lets a node know who the neighbors are
2) Link State Update - describes sender’s cost to it’s neighbors
3) Link State Ack. - acknowledges Link State Update
4) Database description - lets nodes determine who has the most recent link state information
5) Link State Request - requests link state information
OSPF Overview
A
B
C
D
E
1
1
2
2
2
3
3
“Link State Update Flooding”
OSPF Overview
“Hello” message is sent every 10 seconds and only between neighboring routers
Link State Update is sent every 30 minutes or upon a change in a cost of a path
Link State Update is the only OSPF message which is acknowledged
Routers on the same LAN use “Designated Router” scheme
Implementation of OSPF in the QoS Simulator
Link State Update is sent every 2 seconds
No acknowledgement is generated for Link State Updates
Link State Update may include (for example):
- Queue size of each outgoing queue (averaged over 10s sliding window)
- Throughput on each outgoing link (averaged over 10s sliding window)
- Total bandwidth (capacity of the link)
Source router can use above information to calculate
- end-to-end delay
- available buffer size
- available bandwidth
Bellman-Ford Algorithm
110
1 2 4 2
3 2
1
2 4
3 5
Bellman Equation : jDih+1
Dh=min[ d(i ,j) + ]
1
3
1
2 4
3 5
D11=0
D21=1
D31=3
D41=00
D51=00
one hop
1
3
1
2 4
3 5
D12=0
D22=1
D32=2
D42=11
D52=5
10
1
2
two hops
iDh
h
D
h*three hops1
1
2 4
3 5
D13=0
D23=1
D33=2
D43=7
D53=4
1
2
2
3
B/F Algorithm properties
• B/F slightly less efficient than Dijkstra ( O(N) instead of O (NlgN) )
• However, B/F generates solutions by increasing hop distance; thus, the first found feasible solution is “hop” optimal (ie, min hop)
• polynomial performance for most common sets of multiple constraints (e.g., bandwidth and delay )
CAC and packet forwarding
• CAC: if feasible path not found, call is rejected; alternatively, source is notified of constraint violation, and can resubmit with relaxed constraint (call renegotiation)
• Packet forwarding: (a) source routing (per flow), and (b) MPLS (per class)
Application I: IP Telephony
• CAC at source; no bandwidth reservation along path• 36 node, highly connected network• Trunk capacity = 15Mbps• Voice calls generated at fixed intervals• Non uniform traffic requirement• Two routing strategies are compared:
Minhop routing (no CAC)
QoS routing • Simulation platform: PARSEC wired network simulation
QoS simulator: priority queues
PRIORITY 1
PRIORITY 2
PRIORITY 3
SIGNALLING (OSPF)
QoS Sources (Voice)
Non-QoS Sources (TCP)
RESERVED
QoS Simulator: buffer allocations
CBQ
1 MB
1 MB
1 MB
1 MB
1 MB
1 MB
QoS Simulator: Voice Source Modeling
TALK SILENCE
1/ = 352 ms
1/ = 650 ms
1 voice packet every 20ms during talk state
0
12
18
5421 3
6
30
24
14
87
13 1716
10 11
15
9
19
26 27
34
28
2220 21 23
33 35
2925
31 32
50 Km
15 Mbit/sec
Simulation Parameters
10 Minute Simulation Runs
Each voice connection lasts of 3 minutes
OSPF updates are generated every 2 seconds (30 minute OSPF update interval in Minhop scheme)
New voice connections generated with fixed interarrival
Measurements are in STEADY-STATE (after 3 minutes)
100 msec delay threshold
• 3Mbit/sec bandwidth margin on each trunk
NON-UNIFORM TRAFFIC GENERATION
Light Load Experiment
Voice Call interarrival T = 375ms; No TCP traffic
MC Bellman Ford Minhop
#calls generated: 1120 1120
#calls accepted: 1120 1120
% packet lost: 0% 0%
% packet above Delay Thresh: 0% 0%
% packet below Delay Thresh: 100% 100%
DELAY THRESHOLD = 100ms
MC Bellman Ford Minhop
#calls generated: 2800 2800
#calls accepted: 2800 2800
% packet lost: 0.0% 22.61%
% packet above Delay Thresh: 0.0% 48.83%
% packet below Delay Thresh: 100.0% 28.56%
DELAY THRESHOLD = 100ms
Heavy Load Experiment
Voice Call interarrival T = 150ms; No TCP traffic
0
12
18
5421 3
6
30
24
14
87
13 1716
10 11
15
9
19
26 27
34
28
2220 21 23
33 35
2925
31 32
50 Km
15 Mbit/sec
MINHOP ROUTING
0
12
18
5421 3
6
30
24
14
87
13 1716
10 11
15
9
19
26 27
34
28
2220 21 23
33 35
2925
31 32
50 Km
15 Mbit/sec
MINHOP ROUTING
0
12
18
5421 3
6
30
24
14
87
13 1716
10 11
15
9
19
26 27
34
28
2220 21 23
33 35
2925
31 32
50 Km
15 Mbit/sec
QoS ROUTING
0
12
18
5421 3
6
30
24
14
87
13 1716
10 11
15
9
19
26 27
34
28
2220 21 23
33 35
2925
31 32
50 Km
15 Mbit/sec
QoS ROUTING
(src, dst) Throughput
(3, 32) 471353bps = 471Kbps
(4, 32) 578806bps = 579Kbps
(5, 32) 729800bps = 730Kbps
(10, 32) 796863bps = 797Kbps
(16, 32) 404768bps = 405Kbps
Sum 2981590bps = 3.0Mbps
- TCP source/destination pairs same as for voice
- FTP infinite backlog
- TCP Reno
Heavy Load Experiment with TCP
Voice Call interarrival T = 150ms
TCP steady state performance with QoS Routing
Throughput of FTP traffic running concurrently with Minhop routed voice traffic
0
5000000
10000000
15000000
200000000.
1
48.7
97.3
146
195
243
292
340
389
438
486
535
583
Time (sec)
Thro
ughp
ut (b
its/s
ec) (8, 20)
(3, 32)
(4, 32)
(5, 32)
(10, 32)
(16, 32)
(0, 34)
Throughput of FTP traffic running concurrently with MC Bellman-Ford routed voice traffic
0
5000000
10000000
15000000
200000000.
1
48.7
97.3
146
195
243
292
340
389
438
486
535
583
Time (sec)
Thro
ughp
ut (b
its/s
ec) (8,20)
(3, 32)
(4, 32)
(5, 32)
(10, 32)
(16, 32)
(0, 34)
Scalability of OSPF with QoS enhancements
0
20
40
60
80
100
120
140
0 50 100 150
number of nodes
Kbi
t/sec Maximum OSPF control
traffic on a link
• OSPF packet size was 350 bytes
• OSPF (LSA) updates were generated every 2 seconds
• Measurements were performed on a “perfect square grid” topology
75ms voice call generation rate
Effect of OSPF update interval on call acceptance control of IP Telephony traffic
0
1000
2000
3000
4000
5000
6000
0.1 0.5 2 10 60
OSPF (LSA) update interval (sec)
# of
voi
ce c
alls
Accepted
Rejected
Offered Load
Application II: MPEG video
• Measurement based CAC (which worked well for IP telephony) is now replaced by reservation based CAC
• RSVP type signaling required• Effective bandwidth & buffer reservations• 36 node grid-type topology• Trunk capacity = 5.5 Mbps• Inputs = Measured MPEG traces• QoS guarantees: no-loss; delay < Tmax• Simulation platform: PARSEC wired network simulation
DLB #1
DLB #2
DLB #n
C
B
S1
S2
Sn
EDGE ROUTER
MPEGSOURCES
NETWORK ACCESS SECTION
DLB1
DUAL LEAKY-BUCKET REGULATOR
rs Ps
DLB2
BTS
bBrP
cPTS
ss
s
maxDc
b
bBrP
cPTS
ss
s
BTS
b
cPsrs c0
b0
LOSSLESS ALLOCATION
maxDc
b
SCHEDULING
Token buffer
Sustainable rate Peak rate
Input rate Output rate
NETWORK CORE SECTION
• Each router keeps a resource bookkeeping table:
OUGOING LINK; AB;AC ;NS1 ,NS2 ,...NSn ;
AB: Available Buffers; AC: Available Capacity
NSk , k=1,…,n: the number additional flows belonging to
class Sk that the router can accept within QoS constraints
• Each router loads the AB, AC and NS information in the
OSPF Link State Update packet
. Link State Parameters updated at each reservation
APPLICATION ORDER
SOURCE NODE DESTINATION NODE
PATH CACY/N
REJECTION
NODE
1 0 35 1 18 19 20 21 22 28 29 35 Y
2 24 13 25 19 20 14 13 Y
3 19 20 25 31 32 26 20 Y
4 1 18 18 Y
5 34 35 28 29 35 Y
6
18 21
19 20 21 N 19
1 7 8 14 20 21 Y
7 29 35 NO PATH FOUND
8 9 18 8 7 1 18 N 1
8 14 20 19 18 Y
9 27 21 26 20 21 N 20
26 20 14 8 9 15 21 Y
10 22 28 28 Y
11 22 28 21 20 19 25 24 34 28 Y
SIMULATION RESULTS Bandwidth/link: 5.5 Mbps unidirectionalTmax: 0.1 s Effective bandwidth: 2.6 MbpsEffective buffer: 260 KB (no buffer saturation)
0
12
18
5421 3
6
30
24
14
87
13 1716
10 11
15
9
19
26 27
34
28
2220 21 23
33 35
2925
31 32
1
2
3
4
5
6
6
7
8
8
9
9
10
11
0
12
18
5421 3
6
30
24
14
87
13 1716
10 11
15
9
19
26 27
34
28
2220 21 23
33 35
2925
31 32
1
2
3
4
5
6
6
7
8
8
9
9
10
11
SIMULATION RESULTSno reservations; measurement based CAC
Bandwidth/link: 5.5 Mbps unidirectionalTmax: 0.1 s
CONNECTIONORDER
SOURCE NODE
DESTINATIONNODE
PATH CACY/N
REJECTION
1 0 35 1 18 19 20 21 22 28 29 35 Y
2 24 13 25 19 20 14 13 Y
3 19 20 20 Y
4 1 18 18 Y
5 34 35 28 29 35 Y
6 18 21 19 20 21 Y
7 29 35 35 Y
8 9 18 8 7 1 18 Y
9 27 21 26 20 21 Y
10 22 28 28 Y
11 22 28 28 Y
Video Only Result Comparisons Class based QoS routing with reservation
vs. Measurement based QoS routing without reservation
Bandwidth/link: 5.5 Mbps unidirectionalTmax: 0.1 s, Duration 10 min
Class Based QoS routing withreservation
Measurement based QoS routingw/o reservation
Number of packets sent 551820 607002
Percentage of packets lost 0% 0%
Percentage of packets received: 100% 100%
Max delay for video packets: 0.0806 s 0.3725 s
Percentage of Packets exceedingdelay threshold
0% 0.8%
Number of connection requests 11 11
Number of rejections 1 0
Number of routing retries 3 N/A
Effects of Reservation Algorithms on TCPScenario: 5 ftp (TCP) applications run between
Node 0 (server) and Node 35(client) over 1 min period. Case 1: TCP only
Case 2: TCP & video using class based algorithms with reservationCase 3: TCP & video using measurement based algorithms w/o reservation
TCP
SESSION
SOURCE
NODE
DEST.
NODE
TIME
(s)
RECEIV.
DATA
case 1 (bytes)
RECEIV.
DATA
case 2 (bytes)
RECEIV.
DATA
case 3 (bytes)
1 0 35 60 7639208 5870767 4251468
2 0 35 60 7604068 5853718 4035787
3 0 35 60 7604068 5808244 3968244
4 0 35 60 7604068 6220530 4360450
5 0 35 60 7604068 5817280 4053859
Effects of Reservation Algorithms on TCPContinued
Number ofbottleneck
videoconnections
Availablethroughput
for TCPGood put Utilization
TCP only 0 330Mb 304.44Mb 92.2%
TCP &Video no
reservation4 185.32Mb 165.35Mb 89.2%
TCP &Video withreservation
2 257.66Mb 236.56Mb 91.8%
Conclusions• QoS routing beneficial for CAC, enhanced routing,
resource allocation and resource renegotiation• Can efficiently handle flow aggregation (Diff Serv)• Q-OSPF traffic overhead manageable up to
hundreds of nodes• Can be scaled to thousands of nodes using
hierarchical OSPF• Major improvements observed in handling of IP
telephony and MPEG video• MPEG video best served via reservations
Future Work
• Use of MPLS instead of source routing• extension to hierarchical OSPF• extension to Interdomain Routing• extension to multiple classes of traffic • Statistical allocation of MPEG sources
Throughput of FTP traffic running concurrently with Minhop router voice traffic
(detail)
01000000200000030000004000000500000060000007000000
0.1
47.6
95.1 143
190
238
285
333
380
428
475
523
570
Time (sec)
Thro
ughp
ut
(bits
/sec
)
(16, 32)
(3, 32)
(4, 32)
(5, 32)
(10, 32)
Throughput of FTP traffic running concurrently with QoS routed voice traffic
( detail )
0
1000000
2000000
3000000
4000000
5000000
6000000
70000000.1
47.4
94.7
142
189
237
284
331
379
426
473
520
568
Time (sec)
Th
rou
gh
pu
t (b
its/s
ec)
(16, 32)
(3, 32)
(4, 32)
(5, 32)
(10, 32)
75ms voice call generation rate
Effect of OSPF update interval on voice packet delivery rate
0
20
40
60
80
100
120
0.1 0.5 2 10 60
OSPF (LSA) update interval (sec)
deliv
ery
rate
(%)
% packets below100ms delaythreshhold