1. Advanced Computer Networks cs538, Fall 2014 @ UIUC
Klara Nahrstedt
Lecture 8, September 18, 2014
Based on
Zheng Wang and Jon Crowcroft, “QoS Routing for Supporting Multimedia Applications”, IEEE JSAC 1996

2. Announcements
Next Reading for Thursday, September 26:
X. Yang, D. Clark, A. Berger, “NIRA: A New Inter-Domain Routing Architecture”, IEEE/ACM Transactions on Networking, Vol. 15, No. 4, August 2007
Proposals for Final Projects
Prepare project proposal
At most 1 page describing
Problem description
Steps you plan to take to address the problem
Related work (at least 3 full academic papers citations) and why your proposed problem is different than those or why your proposed solution is better.
Deadline for proposal: 11:59pm Tuesday, September 23, 2014
No CLASS on Tuesday, September 23, 2014
Submit project proposal via to instructor: (with subject: cs538 – Final Project Proposal)

3. Outline QoS Concept Single Mixed Metric Multiple Metrics
Bandwidth and Delay QoS Routing Problem
Path Computation Algorithms
Source Routing Algorithms
Hob-by-Hop Routing Algorithms

4. Window of Resources 1980 1990 2000 2010 2020 Requirements Interactive
Network
File access
High-quality
Audio
HDTV
Interactive
HDTV-quality
multi-view video
abundant
Sufficient
Sufficient but
Scarce to
Insufficient -
But scarce
1980
1990
2000
insufficient
2010
2020 To
sufficient
insufficient
abundant
Hardware
support
CS Spring 2011

5. Quality of Service (How to parameterize services?)
To manage resources, we need services over resources
to schedule AV data, to shape access for AV data, to process AV data, to move AV data, etc.
Multimedia systems consist of set of AV-specific services
Processing (media-related) services: retrieve audio/video, record video/audio, compress audio/video, fast forward video, rewind video
Transport (network) services: Stream video, fast forward video, rewind video
To provide multimedia services, services get parameterized with quality levels called Quality of Service
CS Spring 2011

6. Layered Model for QoS Quality of Experience Quality of Service
CS Spring 2011

7. Application AV QoS Parameters
QoS for Audio service:
Sample rate – 8000 samples/second (8KHz), 44.1 KHz
Sample resolution – 8 bits per sample, 16 bits per sample
QoS for Video service:
Video frame rate – 25 frames per second, 30 frames per second
Frame Period – 40 ms, 30 ms, 25 ms, …
Frame resolution – 320x240 pixels, 640x480 pixels, 1920x1080 pixels, …
Pixel resolution – 24 bits per pixel, 8 bits per pixel
Frame size – 64KB
Compression rate – 8:1
CS Spring 2014

8. Network QoS Bandwidth – Rate of data transfer, Bit Rate
e.g., 1 Gbps (Ethernet throughput) – level 1
e.g., 100 Mbps (WiFi throughput) – level 2
e.g., 128 kbps (ISDN throughput) – level 3
measured in bits per second
Throughput – rate of successful message delivery over communication channel
Measured in packets per second, data packets per time slot, or bits per second
30 packets per second; 128 kbps, 10 packets per time slot
CS Spring 2014

9. Network QoS Connection setup time Error Rate
time how long it take to connect the sender and receiver
e.g., 50 ms, 10 ms, …
Error Rate
Measures the total number of bits (packets) that were corrupted or incorrectly received compared with the total number of transmitted bits (packets)
Bit Error Rate (BER) – at physical/MAC layer
In fiber optics, bit error rate (BER) is of the order of 10-8 to
In satellite networks, BER is of the order 10-7
Packet Error Rate (PER) – at IP/transport/application layer – also called Packet Loss Rate
CS Spring 2014

10. Network QoS Delay End-to-End Delay Latency Response time
End-to-end delay in telecommunication
Response time
Round-trip delay in telecommunication
End-to-End Delay
time interval from the time packet is sent from the sender until the time it is received at the receiver (Treceive – Tsend)
e.g., 80 ms, 100 ms, 160 ms
CS Spring 2014

11. Network QoS Response Time
Measured as round-trip delay and is the total time required for sender to send a packet and receive an acknowledgement from the receiver. It can be described as sum of network delay and interface delay.
Network delay – composed of transit delay and transmission delay
Transit delay is caused by time needed to send data on a physical connection between sender and receiver
Transmission delay is time needed to transmit packet through network as result of processing delays (e.g., look up routing tables)
Interface delay – incurred between the time a sender is ready to begin sending and the time a network is ready to accept and transmit the data (due to traffic policing and shaping)
CS Spring 2014

12. Other QoS Parameters Jitter
Undesired deviation from true periodicity in telecommunication
Also called packet delay variation – important QoS factor in assessment of network performance
Packet jitter – variation in latency as measured in the variability over time of the packet latency across network.
CS Spring 2014

13. QoS Classes Guaranteed Service Class Predictive Service Class
QoS guarantees are provided based on deterministic and statistical QoS parameters
Predictive Service Class
QoS parameter values are estimated and based on the past behavior of the service
Best Effort Service Class
There are no guarantees or only partial guarantees are provided
CS Spring 2011

14. QoS Classes (cont.)
QoS Class determines: (a) reliability of offered QoS, (b) utilization of resources
CS Spring 2011

15. Deterministic QoS Parameters
Single Value: QoS1 – average (QoSave), contractual value, threshold value, target value
Throughput – 10 Mbps
Pair Value: <QoS1, QoS2> with
QoS1 – required value; QoS2 – desired value
<QoSavg,QoSpeak>; <QoSmin, QoSmax>
Throughput - <8,12> Mbps
CS Spring 2011

16. Deterministic QoS Parameter Values
Triple of Values <QoS1, QoS2, QoS3>
QoS1 – best value
QoS2 – average value
QoS3 – worst value
Example:
<QoSpeak, QoSavg, QoSmin>, where QoS is network bandwidth
Throughput <12, 10, 8> Mbps
CS Spring 2011

17. Guaranteed QoS
We need to provide 100% guarantees for QoS values (hard guarantees) or very close to 100% (soft guarantees)
Current QoS calculation and resource allocation are based on:
Hard upper bounds for imposed workloads
Worst case assumptions about system behavior
Advantages: QoS guarantees are satisfied even in the worst case case (high reliability in guarantees)
Disadvantage: Over-reservation of resources, hence needless rejection of requests
CS Spring 2011

18. Predictive QoS Parameters
We utilize QoS values (QoS1, ..QoSi) and compute average
QoSbound step at K>i is QoSK = 1/i*∑jQoSj
We utilize QoS values (QoS1, , QoSi) and compute maximum value
QoSK = max j=1,…i (QoSj)
We utilize QoS values (QoS1, , QoSi) and compute minimum value
QoSK = min j=1,…i (QoSj)
CS Spring 2011

19. Best Effort QoS No QoS bounds or possible very weak QoS bounds
Advantages: resource capacities can be statistically multiplexed, hence more processing requests can be granted
Disadvantages: QoS may be temporally violated
CS Spring 2011

20. Quality-of-Service Routing
Audio/Video Multimedia Applications
Real-time requirement
Throughput requirement
Sustainable performance
Routing: A Key Network Function to Support QoS
Diverse QoS constraints (NP-complete problems)
Best-effort traffic and QoS traffic
Dynamic network state

21. QoS Routing – Single Metric Bandwidth
50Mbps
30Mbps
40 Mbps
100 Mbps
50 Mbps
60 Mbps
120 Mbps S D
Minimum Metric
b(S,D) = min(b1, b2, b3, …, bn)

22. QoS Routing – Single Metric Delay
30 ms
40 ms
50 ms
15 ms
60 ms
120 ms S D
100 ms
Additive Metric
d (S,D) = d1 + d2 + …. dn

23. QoS Routing with Single Mixed Metric
(50 Mbps, 30 ms, 0.02)
(30 Mbps, 35 ms, 0.5)
(40 Mbps, 40 ms, 0.4)
(100 Mbps, 20 ms, 0.01)
(50 Mbps, 35 ms, 0.1)
(30 Mbps, 40 ms, 0.2)
(120 Mbp, 15 ms, 0.01)
(50 Mbps, 30 ms, 0.2)
(60 Mbps, 25 ms, 01) S D
F(p) = B(P)/ (D(p) x L(p), where B is bandwidth, D is delay, L is loss probability for path p;
path with large value is

24. Multiple Metrics Problem: Find path subject to multiple constraints
This is NP-complete problem
Simple problem with two constraints is called
“shortest weight-constrained path”
Definition:
d(i,j) be a metric for link (i,j). For any path p = (i,j,….l,m), we say
metric d is additive if d(p) = d(i,j) + d(j,k) +…+ d(l,m).
Metric d is multiplicative if d(p) = d(i,j) x d(j,k) x … x d(l,m)
Metric d is concave if d(p) = min[d(i,j), d(j,k), …, d(l,m)

25. Path Computation Algorithms – Source Routing – Bandwidth-Delay Routing
Consider directed graph G=(N, A) with N number of nodes (vertices) and A arcs (edges).
(i,j) is arc (edge)
bij be available bandwidth
dij be propagation delay
p = (i,j,k,…, l,m)
Bottleneck bandwidth of path is width (p) = min(bij, bjk,…., blm)
Length of path is length (p) = dij + djk + … + dlm
Given any two nodes i and m of the graph and two constraints W and D, the QoS routing problem is then to find a path p* between i and m so that
width (p*) ≥𝐵 and length(p*) ≤𝐷.
Bandwidth-delay constrained paths

26. Routing Algorithm S D Constraints: B = 50 Mbps, D = 55ms
(50 Mbps, 30 ms)
(60 Mbps, 35 ms)
(40 Mbps, 40 ms)
(100 Mbps, 20 ms)
(50 Mbps, 35 ms)
(50 Mbps, 40 ms)
(120 Mbp, 15 ms)
(50 Mbps, 30 ms)
(60 Mbps, 25 ms) S D
Constraints: B = 50 Mbps, D = 55ms
Step1: find all paths that satisfy B
Step 2: find the final path that satisfies D

27. Hop-by-Hop Routing
(50 Mbps, 30 ms)
(60 Mbps, 35 ms)
(40 Mbps, 40 ms)
(100 Mbps, 20 ms)
(50 Mbps, 35 ms)
(50 Mbps, 40 ms)
(120 Mbp, 15 ms)
(50 Mbps, 30 ms)
(60 Mbps, 25 ms) S D
With multiple metrics the best path with all parameters at their optimal values
may not exist at all!!!!

28. Hop-by-Hop Algorithm (1)
(50 Mbps, 30 ms)
(60 Mbps, 35 ms)
(40 Mbps, 40 ms)
(100 Mbps, 20 ms)
(50 Mbps, 35 ms)
(50 Mbps, 40 ms)
(120 Mbp, 15 ms)
(50 Mbps, 30 ms)
(60 Mbps, 25 ms) S D
Shortest-widest algorithm with distance vector approach
Step 1: find all widest path from node 1 to each node ‘i’. If there are more than one widest path found,
Step 2 chooses one with minimum length
Step 3 updates the width and length for the shortest-widest path from node 1 to node i (using distance vector approach)

29. Hop-by-Hop Algorithm (2)
(50 Mbps, 30 ms)
(60 Mbps, 35 ms)
(40 Mbps, 40 ms)
(100 Mbps, 20 ms)
(50 Mbps, 35 ms)
(50 Mbps, 40 ms)
(120 Mbp, 15 ms)
(50 Mbps, 30 ms)
(60 Mbps, 25 ms) S D
Shortest-widest algorithm based on link state
Step 1: find the nodes with maximum width among the tentatively labeled nodes if there are more than one node found
Step 2 chooses one with minimum length and permanently labels
Step 3 updates the tentatively labeled nodes around the new permanently labeled node

30. Conclusion QoS Routing is integral part of resource management
QoS routing might be integrated with path reservation
Status
QoS has been explored in routers, but not much used
QoS has been used in ATM networks (backbone)
QoS service class concept is now being explored by broadband providers for multimedia services
QoS in wireless challenging and statistical over unlicensed spectrum