1. Theory and Practice Dimitrios Kalogeras
IP QoS Principles
Theory and Practice
Dimitrios Kalogeras

2. A Bit of History
The Internet, originally designed for U. S. government use, offered only one service level: Best Effort.
No guarantees of transit time or delivery
Rudimentary prioritization was available, but it was rarely used.
Commercialization began in early 1990’s
Private (intranet) networks using Internet technology appeared.
Commercial users began paying directly for Internet use.
Commerce sites tried to attract customers by using graphics.
Industry used the Internet and intranets for internal, shared communications that combined previously-separate, specialized networks -- each with its own specific technical requirements.
New technologies (voice over the Internet, etc.) appeared, designed to capitalize on inexpensive Internet technologies.

3. The Demands on Modern Networks
Network flexibility is becoming central to enterprise strategy
Rapidly-changing business functions no longer carried out in stable ways, in unchanging locations, or for long time-periods
Network-enabled applications often crucial for meeting new market opportunities, but there’s no time to custom-build a network
Traffic is bursty
Interactive voice, video applications have stringent bandwidth and latency demands
Multiple application networks are being combined into consolidated corporate utility networks
Bandwidth contention as critical transaction traffic is squeezed by web browsing, file transfers, or other low-priority or bulk traffic
Latency problems as interactive voice and video are squeezed by transaction, web browsing, file transfer, and bulk traffic

4. Definitions
Quality of Service (QoS) classifies network traffic and then ensures that some of it receives special handling.
May track each individual dataflow (sender:receiver) separately.
May include attempts to provide better error rates, lower network transit time (latency), and decreased latency variation (jitter).
Differentiated Class of Service (CoS) is a simpler alternative to QoS.
Doesn't try to distinguish among individual dataflows; instead, uses simpler methods to classify packets into one of a few categories.
All packets within a particular category are then handled in the same way, with the same quality parameters.
Policy-Based Networking provides end-to-end control.
The rules for access and for management of network resources are stored as policies and are managed by a policy server.

5. QoS Background
QoS development inspired by new types of applications in IP environment:
Video Streaming Services
Video Conferencing
VoIP
Legacy SNA / DLSw

6. QoS Architecture Models
Best Effort Service
Integrated Service
Differentiated Service

7. Best Effort Service What exactly IP does: All packets treated equally
Unpredictable bandwidth
Unpredictable delay and jitter

8. IntServ (RFC1633)

9. DiffServ (RFC2474/2475)

10. QoS Architecture Components
Classification
Coloring
Admission Control
Traffic Shaping/Policing
Congestion Management
Congestion Avoidance
Signaling

11. Statistical Behavior: Random Arrival
In random arrival, the time that each packet arrives is completely independent of the time that any other packet arrives.
If the true situation is that arrivals tend to be evenly spaced, then random arrival calculations will overestimate the queuing delay.
If the true situation is that arrivals are bunched in groups (typical of data flows, such as packets and acknowledgements), then random arrival calculations will underestimate the queuing delay.
Our intuition is usually misleading when we think of random processes.
We tend to assume that queue size increases linearly as the number of customers increases.
But, with random arrival, there is a drastic increase in queue size as the customer arrival rate approaches 80% of the theoretical server capacity. There’s no way to store the capacity that is unused by late customers, but early customers increase the queue.

12. Random Arrival and Intuition
The surprising increase in queue length is best shown by a graph:

13. Random Arrival vs. Self-Similar
Although random arrival is very convenient mathematically (it’s relatively simple to do random arrival calculations), it has been shown that much data traffic is self-similar.
Ethernet and Internet traffic flows, in particular, are self-similar.
The rate of initial connections is still random, however.
Self-similar traffic shows the same pattern regardless of changes in scale.
Fractal geometry (e.g., a coastline) is an example.
Self-similar traffic has a heavy tail.
The probabilities of extremely large values (e.g., file lengths of a gigabyte or more) don’t decrease as rapidly, as they would with random distributions of file lengths.
This matches real data traffic behaviors.
Long file downloads mixed with short acknowledgements
Compressed video with action scenes mixed with static scenes

14. Traffic Classification
Most fundamental QoS building block
The component of a QoS feature that recognizes and distinguishes between different traffic streams
Without classification, all packets are treated the same

15. Traffic Classification/ Admission Control Issues
Always performed at the network perimeter
Makes traffic conform to the internal network policy
Marks packets with special flags (colors)
Colors used afterwards inside the network for QoS management

16. Classification/ Admission Control Scheme
Classifier
Meter
Marker
Shaper/ Policer
Packet
Admitted
Dropped

17. Classification Criteria
IP header fields
TCP/UDP header fields
Routing information
Packet Content (NBAR) i.e. HTTP, HTTPS, FTP, Napster etc.

18. Traffic Coloring Options
IP Precedence
DSCP
QoS Group
802.1p CoS
ATM CLP
Frame Relay DE

19. Type-of-Service (RFC791)
Precedence D T R
Unused
Version
Length
ToS Field
Total Length … 8 15 31 1 D
Normal Delay
Low Delay T
Normal Throughput
High Throughput R
Normal Reliability
High Reliability

20. IP Precedence Values 111 Network Control 110 Internetwork Control 101
Critical
100
Flash Override
011
Flash
010
Immediate
001
Priority
000
Routine

21. DSCP Diffserv Code Point
DSCP (6 bits)
Unused
Class 1
Class 2
Class 3
Class 4
Low Drop Precedence
001010
010010
011010
100010
Medium Drop Precedence
001100
010100
011100
100100
High Drop Precedence
001110
010110
011110
100110

22. Classification mechanisms
MQC ( Modular Qos Command Line Interface)
CAR ( Commited Access Rate)

23. Modular QoS CLI Modular QoS CLI (MQC)
Command syntax introduced in 12.0(5)T
Reduces configuration steps and time
Uniform CLI across all main Cisco IOS-based platforms
Uniform CLI structure for all QoS features

24. Basic MQC Commands
class-map [match-any | match-all] class-name
router(config)#
1. Create Class Map - a traffic class ( match access list, input interface, IP Prec, DSCP, protocol (NBAR) src/dst MAC address, mpls exp).
policy-map policy-map-name
router(config)#
2. Create Policy Map (Service Policy) - Associate a class map with one or more QoS policies (bandwidth, police, queue-limit, random detect, shape, set prec, set DSCP, set mpls exp).
service-policy {input | output} policy-map-name
router(config-if)#
3. Attach Service Policy - Associate the policy map with an input or output interface.

25. Basic MQC Commands
1. Create Class Map – defines traffic selection criteria
Router(config)# class-map class1
Router(config-cmap)# match ip precedence 5
Router(config-cmap)# exit
2. Create Policy Map- associates classes with actions
Router(config)# policy-map policy1
Router(config-pmap)# class class1
Router(config-pmap-c)# set mpls experimental 5
Router(config-pmap-c)# bandwidth 3000
Router(config-pmap-c)# queue-limit 30
Router(config-pmap)# exit
3. Attach Service Policy – enforces policy to interfaces
Router(config)# interface e1/1
Router(config-if)# service-policy output policy1
Router(config-if)# exit

26. Classification Configuring Sample
IOS 12.1(5)T
MQC based
class-map match-all premium
match access-group name premium !
class-map match-any trash
match protocol napster
match protocol fasttrack
policy-map classify
class premium
set ip precedence priority
class trash
police conform-action set-prec-transmit 1 excess-action drop
ip access-list extended premium
permit tcp host any eq telnet
interface serial 2/1
ip unnumbered loopback 0
service-policy input classify
Traffic class definitions
QoS policy definition
ACL definition
QoS Policy attached to interface

27. Classification Configuring Sample
CAR based
ip cef !
interface serial 2/1
ip unnumbered loopback 0
rate-limit input access-group conform-action set-prec-transmit 1 exceed-action set-prec-transmit 0
access-list 100 permit tcp host any eq http
CAR definition
ACL definition

28. Classification Configuring Sample
Route-map based
route-map classify permit 10
match ip address 100
set ip precedence flash !
route-map classify permit 20
match ip next-hop 1
set ip precedence priority
interface serial 2/1
ip unnumbered loopback 0
ip policy route-map classify
access-list 1 permit
access-list 100 permit tcp host any eq http
Route-map definitions
Route-map attached to interface
ACL definitions

29. Shaping/Policing Used to assign more predictive behavior to traffic
Uses Token Bucket model

30. Token Bucket Model Token Bucket characterizes traffic source tc = Bc/v
Overflow Tokens
Tokens
Incoming
packets
Conform
Exceed Bc v C
Token Bucket main parameters:
Token Arrival Rate - v
Bucket Depth - Bc
Time Interval – tc
Link Capacity - C
tc = Bc/v

31. Token Bucket Model
Bucket is being filled with tokens at a rate v token/sec.
When bucket is full all the excess tokens are discarded.
When packet of size L arrives, bucket is checked for availability of corresponding amount of tokens.
If several packets arrive back-to-back and there are sufficient tokens to serve them all, they are accepted at peak rate (usually physical link speed).
If enough tokens available, packet is optionally colored and accepted to the network and corresponding amount of tokens is subtracted from the bucket.
If not enough tokens, special action on packet is performed.

32. Token Bucket Model Actions performed on nonconforming packets:
Dropped (Policing)
Delayed in queue either FIFO or WFQ (Shaping)
Colored/Recolored

33. Token Bucket Model Bucket depth variation effect:
Bc = 0 Constant Bit Rate (CBR)
Bc No Regulation
Bucket depth is characteristic of traffic burstiness
Maximum number of bytes transmitted over period of time t:
A(t)max = Bc+v·t

34. Excess Burst (Be) Cisco Implementation
GTS ( Generic Traffic Shaping)
If during previous tcn-1 interval bucket Bc was not depleted (there is no congestion), in the next interval tcn Bc+Be bytes are available for burst.
In frame relay implementations packets admitted via Be tokens are marked with DE bit.

35. Excess Burst (Be) Cisco Implementation
CBTS (Class Based Traffic Shaping)
allows higher throughput in uncongested environment up to peak rate calculated as vPeak = vCIR(1+Be/Bc)
Peak rate can be set up manually.

36. Excess Burst (Be) Cisco Implementation
CAR
allows RED like behavior:
traffic fitting into Bc always conforms
traffic fitting into Be conforms with probability proportional to amount of tokens left in the bucket
traffic not fitting into Be always exceeds CAR uses the following parameters:
t – time period since the last packet arrival
Current Debt (Dcur) – Amount of debt during current time interval
Compound Debt (Dcomp) – Sum of all Dcur since the last drop
Actual Debt (Dact) – Amount of tokens currently borrowed

37. Excess Burst (Be) Cisco Implementation
Packet of length L arrived
CAR Algorithm Y
Conform Action
Bccur – L > 0
Bccur = Bccur – L N
Dcur = L - Bccur
Bccur = 0
Dcomp = Dcomp + Dcur
Dact = Dact + Dcur
+v·t Y
Exceed Action
Dact > Be N Y
Dcomp > Be
Dcomp = 0 N

38. Shaping Configuration Sample
GTS Based
interface serial 2/1
ip unnumbered loopback 0
traffic-shape rate !
interface serial 2/2
traffic-shape group
access-list 100 permit tcp host any eq http
Shaper Definitions
ACL definition
Shaper can be only used to control egress traffic flow!

39. Policing Configuration Sample
IOS 12.0(5)T
CAR Based
ip cef
interface serial 2/1
ip unnumbered loopback 0
rate-limit output access-group conform-action transmit excess-action drop !
interface serial 2/2
rate-limit input conform-action transmit excess-action drop
access-list 100 permit tcp host any eq http
CAR Definitions
ACL definition
Policer can be used to control ingress traffic flow!

40. Shaping/Policing Configuration Sample
IOS 12.1(5)T
MQI Based
class-map match-all policed
match protocol http
class-map match-all shaped
match access-group name ftp-downloads !
policy-map bad-boy
class policed
police conform-action transmit exceed-action drop
class shaped
shape average
interface serial 2/1
ip unnumbered loopback 0
service-policy output bad-boy
ip access-list extended ftp-downloads
permit tcp any eq ftp-data any
Class definitions
QoS policy definition
QoS Policy attached to interface
ACL definition

41. CAR Policing Problem Why cannot my traffic reach CIR value?
Cause: Improper setting of Bc and Be values
CAR is aggressive, as drops excessive packets and the lost data needs to be retransmitted by upper layers (mainly TCP) after timeout. This also causes TCP to shrink its window reducing flow throughput.
Cisco Systems recommends the following settings:
Bc = 1.5xCIR/8
Be = 2xBc

42. Congestion Management

43. Queuing Traffic burst may temporarily exceed interface capacity
Without queuing this excess traffic will be lost
Queuing allows bursty traffic to be transmitted without drops
Queuing strategy defines order in which packets are transmitted through egress interface
Queuing introduced additional delay which signals to adaptive flows (like TCP) to back off their throughput

44. Queuing Algorithms FIFO Priority (Absolute) Weighted Round Robin (WRR)
Fair

45. FIFO Simplest queuing method with the least CPU overhead
No congestion control
Transmits packets in the order of arrival
High volume traffic can suppress interactive flows
Default queuing for interfaces > 2Mbps (i.e. Ethernet)

46. FIFO average queue depth dependence on load

47. Absolute Priority Queuing
Generic Priority Queuing
Custom Queuing
RTP Priority Queuing
Low Latency Queuing (LLQ)

48. Simplest QoS Algorithm: Priority Queuing
Stated requirement:
“If <application> has traffic waiting, send it next”
Commonly implemented
Defined behavior of IP precedence 11

49. Priority Queuing Implementation Approach
Identify interesting traffic
Access lists
Place traffic in various queues
Dequeue in order of queue precedence 12

50. Q Length Defined by Q Limit Interface Buffer Resources
Priority Queuing (PQ)
Interface Hardware
Ethernet
Frame Relay
ATM
Serial Link
Etc.
High
Traffic Destined for Interface
Medium
Classify
Normal
Transmit Queue
Output Line
Low
Q Length Defined by Q Limit
Absolute Priority Scheduling
Interface Buffer Resources
Classification by:
Protocol (IP, IPX, AppleTalk, SNA, DecNet, Bridge, etc.)
Incoming Interface (EO, SO, S1, etc.) 13

51. Priority Queuing Scheme
High Empty?
Medium Empty?
Normal Empty?
Low Empty? N N N N
Send packet from High
Send Packet from Medium
Send Packet from Normal
Send Packet from Low

52. Generic PQ Drawbacks Needs thorough admission control
No upper limit for each priority level
High risk of low priority queues` starvation effect

53. Generic PQ Configuration Sample
priority-list 1 protocol ip high tcp telnet
priority-list 1 protocol ip high list 100
priority-list 1 protocol ip medium lt 1000
priority-list 1 interface ethernet 0/0 medium
priority-list 1 default low !
interface serial 2/1
ip unnumbered loopback 0
priority-group 1
access-list 100 permit tcp host any eq http
PQ Definition
PQ Attached to Interface
ACL definition

54. Custom Queuing (CQ) (Weighted Round Robin)
Interface Hardware
Ethernet
Frame Relay
ATM
Serial Link
Etc.
1/10
2/10
Traffic Destined for Interface
3/10
Transmit Queue
Output Line
2/10
Classify
3/10
Up to 16
Link Utilization Ratio
Weighted Round Robin Scheduling
(byte count)
Q Length Deferred by Queue Limit
Classification by:
Protocol (IP, IPX, AppleTalk, SNA, DecNet, Bridge, etc.)
Incoming interface (EO, SO, S1, etc.)
Interface Buffer Resources
Allocate Proportion of Link Bandwidth)

55. WRR Drawbacks Unpredictable jitter
Fairness significantly depends on MTU and TCP window size
Complex calculations to achieve desired traffic proportions

56. CQ Byte-count Calculus
Distribute bandwidth to 3 queues with proportion x:y:z and packet sizes qx, qy, qz.
Calculate ax=x/qx, ay=y/qy, az=z/qz.
Normalize and round ax, ay, az. ax’= round(ax/min(ax, ay, az)); ay’= round(ay/min(ax, ay, az)); az’= round(az/min(ax, ay, az)).
Convert obtained packet proportion into byte count bcx = ax’·qx; bcy = ay’·qy; bcz = az’·qz.
Actual bandwidth share of i-th queue can be calculated with the following formula:
For better approximation obtained byte-counts can be multiplied by some positive whole number.
Starting with IOS 12.1 CQ employs Deficit Round Robin algorithm and there is no need in such byte-count tuning.

57. CQ Configuration Sample
queue-list 1 protocol ip 1 tcp telnet
queue-list 1 protocol ip 2 list 100
queue-list 1 protocol ip 3 udp 53
queue-list 1 interface ethernet 0/0 4
queue-list 1 queue 1 byte-count 3000
queue-list 1 queue 2 byte-count 4500
queue-list 1 queue 3 byte-count 3000
queue-list 1 queue 4 byte-count 1500
queue-list 1 default 4 !
interface serial 2/1
ip unnumbered loopback 0
custom-queue-list 1
access-list 100 permit tcp host any eq http
CQ List Definition
CQ Attached to Interface
ACL Definition

58. “Bitwise Round Robin” Fair Queuing
TDM Model
Time Division Multiplexer
Keshav, Demers, Shenker, and Zhang
Simulates a TDM
One flow per channel 22

59. TDM Message Arrival Sequence6 4 1 5 2
Time Division Multiplexer 3 23

60. TDM Message Delivery Sequence5 4 1 6 3
Time Division Multiplexer 2 24

61. Fair Queuing Algorithm
Employs virtual bit-by-bit round robin model (BRR)
BRR dynamics are described by the equation:
i-th packet from flow a arriving at time t0 is services at time t :
Servicing of i-th packet from flow a will start at Sia and finish at Fia :
Additional  parameter is added for priority assignment to inactive flows :
Packets are ordered for transmission according to Bia values.

62. Fair Queuing Approach
Enqueue traffic in the sequence the TDM would deliver it
As a result, be as fair as the TDM 25

63. Effects of Fair Queuing
Low-bandwidth flows get
As much bandwidth as they can use
Timely service
High-bandwidth flows
Interleave traffic
Cooperatively share bandwidth
Absorb latency 26

64. What Weighting Does In TDM In WFQ Result:
Channel speed determines message “duration”
In WFQ
Multiplier on message length changes simulated message “duration”
Result:
Flow’s “fair” share predictably unfair 27

65. Weighted Fair Queuing (WFQ)
Traffic Destined for Interface
Transmit Queue
Output Line
Classify
Weighted Fair Scheduling
Configurable Number of Queues
Flow-Based Classification by:
Source and destination address
Protocol
Session identifier (port/socket)
Interface Buffer Resources
Weight Determined by:
Requested QoS (IP Procedure, RSVP)
Frame Relay FECN, BECN, DE (For FR Traffic)
Flow throughput (weighted-fair)

66. Weighted Fair Queuing (WFQ)
Fair bandwidth per flow allocation
Low delay for interactive applications
Protection from ill-behaved sources

67. Weighted Fair Queuing (WFQ)
Flow classified by the following fields:
Source address
Source port
Destination address
Destination port
ToS
Weight of each flow (queue) depends on ToS:
weight = 1/(precedence+1)
Bandwidth distributed in 1/weight proportions

68. Weighted Fair Queuing (WFQ)
Packets are ordered according to the expected virtual departure time of their last bit.
Low volume flows have preference over high volume transfers.
Low volume flow is identified as using less than its share of bandwidth.
The special queue length threshold value is established, after which only low volume flows can enqueue. All the packets, that belong to high volume flows are dropped.

69. Drawbacks of Weighted Fair Queuing
Requires more sorting than other approaches 31

70. Weighted Fair Queuing (WFQ)
FTP
Telnet t
Delay

71. Weighted Fair Queuing (WFQ)
FTP
Telnet t
Delay

72. WFQ Configuration Sample
interface serial 2/1
ip unnumbered loopback 0
fair-queue
Queue Threshold
(packets)
Number of reservable queues
Maximal number of queues

73. RTP Priority Queuing Classifies only by UDP port range
Only even ports from the range are classified
Establishes upper limit via integrated policer
Excess traffic dropped during congestion periods
RTP PQ has priority over LLQ

74. RTP PQ Configuration Sample
interface serial 2/1
ip unnumbered loopback 0
ip rtp priority
Starting UDP port
Bandwidth Limit (kbps)
Range length

75. Low Latency Queuing (LLQ)
Implemented using MQI
Very rich classification criteria (class-map)
Establishes upper limit via integrated policer
Excess traffic dropped during congestion periods

76. LLQ Configuration Sample
IOS 12.0(5)T
class-map match-all voice
match access-group name voip !
policy-map llq
class voip
priority 30
class class-default
fair-queue 64
interface serial 2/1
ip unnumbered loopback 0
service-policy output llq
ip access-list extended voip
permit ip host any
Class definitions
LLQ policy definition
LLQ Policy attached to interface
ACL definition

77. Class Based WFQ (CBWFQ)
Based on the same algorithm as WFQ
Weights can be manually configured
Allows to easily specify guaranteed bandwidth for a class
Configuration based on Cisco MQI

78. CBWFQ Configuration Sample
IOS 12.0(5)T
class-map match-all premium
match access-group name premium-cust
class-map match-all low-priority
match protocol napster !
policy-map cbwfq-sample
class premium
bandwidth 512
class low-priority
shape average 128
shape peak 512
class class-default
fair-queue 64
interface serial 2/1
ip unnumbered loopback 0
max-reserved-bandwidth 85
service-policy output cbwfq-sample
ip access-list extended premium-cust
permit ip host any
Class definitions
Qos policy definition
QoS Policy attached to interface
ACL definition

79. CBWFQ Configuration Sample
IOS 12.1(5)T
Hierarchical Design
class-map match-all premium
match access-group name premium-cust
class-map match-all voice
match ip precedence flash !
policy-map total-shaper
class class-default
shape average 1536
service-policy class-policy
policy-map class-policy
class premium
bandwidth 512
class voice
priority 64
fair-queue 128
interface fastethernet 1/0
ip unnumbered loopback 0
max-reserved-bandwidth 85
service-policy output total-shaper !
ip access-list extended premium-cust
permit ip host any

80. Hierarchical CBWFQ Limitations
Only two levels of hierarchy are supported
set command not supported in child policy
Shaping allows only in parent policy
LLQ can be configured only either in child or parent policies but not in both
FQ allowed only in child policy

81. Congestion Avoidance

82. Global Synchronization Effect
Load t
Link Capacity
Avg. Throughput

83. Tail Drop and TCP Flow Control
Packet drops from all TCP sessions simultaneously
High probability of multiple drops from the same TCP session
Uniformly distributed drops from high volume and interactive flows
Result: Low average throughput!

84. Random Early Detection (RED)
Developed by Van Jacobson in 1993
Starts randomly dropping packets before actual congestion occurs
Keeps average queue depth low
Increases average throughput

85. Global Synchronization Removed
Load t
Link Capacity
Avg. Throughput

86. Random Early Detection (RED)p 1
qavg
 max
 min 
RED
Adjustable p 1
qavg
qmax
Tail Drop

87. Random Early Detection (RED)
RED Parameters:
min – Minimal threshold after which RED starts packet drops. Minimal recommended value is 5 packets.
max – Maximal threshold after which all packets are dropped. Recommended value is 2-3 times min.
 - Mark probability denominator denotes packet drop probability at max average queue depth. Optimal value – 0.1 .
 - Exponential weighting factor determines the level of backward value-dependence in average queue depth calculation: qavg = (qold · (1 - 2-)) + (qcur · 2-) General recommendation  = 9.

88. TCP Rate Control - 1
In TCP, the spacing of ACKs and the window size in the ACKs controls the transmitter’s rate.
Rate Control manipulates the ACKs as they pass through the rate control device by:
Adjusting the size of TCP ACK window
Inserting new ACKs
Re-spacing existing ACKs
Rate Control works only with TCP; other methods, such as Token Bucket, must be used with UDP.
Rate Control violates the protocol layering design, as it allows network devices to manipulate a higher-layer protocol’s operation. Nevertheless, it usually functions well and provides fine-grained control.

89. TCP Rate Control - 2
Example:

90. Weighted Random Early Detection (WRED)
Modified version of RED
Weights determine the set of parameters: min , max and  .
Weight depends on ToS field value
Interactive flows are preserved

91. WRED Configuration Sample
Interface based
interface serial 2/1
ip unnumbered loopback 0
random-detect
random-detect
random-detect
random-detect
random-detect …
min
max 

92. WRED Configuration Sample
MQI based
policy-map red
class class-default
random-detect
random-detect
random-detect
random-detect
random-detect …
interface Serial2/1
ip unnumbered loopback 0
service-policy output red
min
max 
WRED is incompatible with LLQ feature!

93. Link Optimization

94. Link Fragmentation and Interleaving (LFI)
For links < 128kbps
Voice Packet
Jumbogram
64 kbps
1500 bytes  190ms

95. Link Fragmentation and Interleaving (LFI)
64 kbps
Supported interfaces:
Multilink PPP
Frame Relay DLCI
ATM VC

96. LFI Configuration Sample
MLP version
interface virtual-template 1
ip unnumbered loopback 0
ppp multilink
ppp multilink interleave
ppp multilink fragment-delay 30
ip rtp interleave …

97. Signaling

98. Resource Reservation Protocol (RSVP)
End-to-end QoS signaling protocol
Used to establish dynamic reservations over the network
Always establishes simplex reservation
Supports unicast and multicast traffic
Actually uses WFQ and WRED mechanisms

99. Resource Reservation Protocol (RSVP)

100. Resource Reservation Protocol (RSVP)

101. Resource Reservation Protocol (RSVP)
Reservation Types:
Guaranteed Rate (uses WFQ and LLQ)
Controlled Load (uses WRED)
Distinct
Shared
Explicit
Fixed Filter (FF)
Shared Explicit (SE)
Wildcard X
Wildcard Filter (WF)

102. Resource Reservation Protocol (RSVP)

103. QoS Policy Propagation over BGP
QoS policy can be shared inside single AS or among different ASs.
Community attribute is usually used for color assignments
Prevents manual policy changes in network devices

104. QoS Policy Propagation over BGP

105. QPPB Configuration Sample
Router A
Router B
ip bgp-community new-format !
router bgp 10
neighbor remote-as 20
neighbor send-community
neighbor route-map cout out
route-map cout permit 10
match ip address 20
set community 60:9
access-list 20 permit
ip bgp-community new-format !
router bgp 20
neighbor remote-as 10
table-map mark-pol
route-map mark-pol permit 10
match community 1
set ip precedence flash
ip community-list 1 permit 60:9
interface Serial 0/1
ip unnumbered loopback 0
bgp-policy source ip-prec-map

106. Topics not Covered Multiprotocol Label Switching (MPLS)
Frame Relay QoS
ATM QoS
Distributed Queuing Algorithms
Multicast

107. Conclusion QoS is not an exotic feature any more
QoS allows specific applications (VoIP, VC) to share network infrastructure with best-effort traffic
QoS in IP networks simplifies their functionality avoiding Frame Relay and ATM usage

108. ?
Questions???