IP QoS Principles

1
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 1990s
• 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 theres 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
  (senderreceiver) 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. Theres 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 (its 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) dont
  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
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
Unused
D
T
R
Version
Length
Total Length
ToS Field

8
0
15
31
20
IP Precedence Values
21
DSCPDiffserv Code Point
DSCP (6 bits)
Unused
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
25
Basic MQC Commands

• 1. Create Class Map defines traffic selection
  criteria

Router(config) class-map class1 Router(config-cma
p) match ip precedence 5 Router(config-cmap)
exit

• 2. Create Policy Map- associates classes with
  actions

Router(config) policy-map policy1 Router(config-p
map) 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 64000 conform-action set-prec-transmit 1
  excess-action drop
• !
• ip access-list extended premium
• permit tcp host 10.0.0.1 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 attachedto interface
27
Classification Configuring Sample
CAR based

• ip cef
• !
• interface serial 2/1
• ip unnumbered loopback 0
• rate-limit input access-group 100 64000 8000
  8000 conform-action set-prec-transmit 1
  exceed-action set-prec-transmit 0
• !
• access-list 100 permit tcp host 10.0.0.1 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 192.168.0.1
• access-list 100 permit tcp host 10.0.0.1 any eq
  http

Route-map definitions
Route-map attachedto 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

• 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 Bcv?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 BcBe 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(1Be/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 exceedsCAR
  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 lengthL arrived
CAR Algorithm
ConformAction
Y
Bccur L gt 0
Bccur Bccur L
N
Dcur L - Bccur Bccur 0 Dcomp Dcomp
Dcur Dact Dact Dcur v?t
Y
ExceedAction
Dact gt Be
N
Y
Dcomp 0
Dcomp gt Be
N
38
Shaping Configuration Sample
GTS Based
interface serial 2/1 ip unnumbered loopback
0 traffic-shape rate 64000 8000 1000
256 ! interface serial 2/2 ip unnumbered
loopback 0 traffic-shape group 100 64000 8000
8000 512 ! access-list 100 permit tcp host
10.0.0.1 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 100
64000 8000 16000 conform-action transmit
excess-action drop ! interface serial 2/2 ip
unnumbered loopback 0 rate-limit input 128000
16000 32000 conform-action transmit
excess-action drop ! access-list 100 permit tcp
host 10.0.0.1 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 64000 8000 8000
conform-action transmit exceed-action drop
class shaped shape average 128000 ! 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 attachedto 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 gt 2Mbps (i.e.
  Ethernet)

46
FIFO
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 ltapplicationgt has traffic waiting, send it
  next
• Commonly implemented
• Defined behavior of IP precedence

49
Priority Queuing Implementation Approach

• Identify interesting traffic
• Access lists
• Place traffic in various queues
• Dequeue in order of queue precedence

50
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.)

51
Priority Queuing Scheme
Y
Y
Y
Y
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 10.0.0.1 any eq http
PQ Definition
PQ Attachedto 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 RoundRobin Scheduling (byte count)
Q Length Deferred by Queue Limit
Interface Buffer Resources

• Classification by
• Protocol (IP, IPX, AppleTalk, SNA, DecNet,
  Bridge, etc.)
• Incoming interface(EO, SO, S1, etc.)

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
  xyz and packet sizes qx, qy, qz.
• Calculate axx/qx, ayy/qy, azz/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 axqx bcy ayqy bcz
  azqz.
• 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 10.0.0.1 any
eq http
CQ List Definition
CQ Attachedto 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

59
TDM Message Arrival Sequence
6
4
1
5
2
Time Division Multiplexer
3
60
TDM Message Delivery Sequence
5
4
1
6
3
Time Division Multiplexer
2
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

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

64
What Weighting Does

• In TDM
• Channel speed determines message duration
• In WFQ
• Multiplier on message length changes simulated
  message duration
• Result
• Flows fair share predictably unfair

65
Weighted Fair Queuing (WFQ)
Traffic Destined for Interface
Transmit Queue
Output Line
Classify
Weighted Fair Scheduling
Configurable Number of Queues
Interface Buffer Resources

• Flow-Based Classification by
• Source and destination address
• Protocol
• Session identifier (port/socket)

• 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/(precedence1)
• 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

70
Weighted Fair Queuing (WFQ)
71
Weighted Fair Queuing (WFQ)
72
WFQ Configuration Sample
interface serial 2/1 ip unnumbered loopback
0 fair-queue 32 128 0
Queue Threshold (packets)
Number of reservable queues
Maximal numberof 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 16384 16383 256
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 10.0.0.1 any
Class definitions
LLQ policy definition
LLQ Policy attachedto 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-q
ueue 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
10.0.0.1 any
Class definitions
Qos policy definition
QoS Policy attachedto 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 class
class-default 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
10.0.0.1 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
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
86
Random Early Detection (RED)
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 transmitters 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 protocols 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 0 32 64
20 random-detect 1 32 64 20 random-detect 2 32
64 20 random-detect 3 32 64 20
?min
?max
?
92
WRED Configuration Sample
MQI based
policy-map red class class-default random-detec
t random-detect 0 32 64 20 random-detect 1 32
64 20 random-detect 2 32 64 20 random-detect
3 32 64 20 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 lt 128kbps
95
Link Fragmentation and Interleaving (LFI)

• 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 16384 1024 512
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)

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 10.0.0.1 remote-as 20 neighbor 10.0.0.1
send-community neighbor 10.0.0.1 route-map cout
out ! route-map cout permit 10 match ip address
20 set community 609 ! access-list 20 permit
192.168.0.0 0.0.0.255
ip bgp-community new-format ! router bgp 20
neighbor 10.0.0.2 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 609 ! interface Serial
0/1 ip unnumbered loopback 0 bgp-policy source
ip-prec-map
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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???