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					Applied Cisco Networking
(CCNP BCMSN)
Unit 7
QoS




                           Author: Bill Buchanan
PoTs and IP Network

            PoTs (Plain Old Telephone
                                                         IP Network
                     System)


                    PSTN (Public
                       Switch                             Internet
                     Telephone
                      Network)




                                    Migration towards
                                   Integrated solution
        PBX
  (Private Branch
    eXchange)




                                                                      Author: Bill Buchanan
Base rate




              Sampler
            8000 times per   Analogue-to-digital
              seconds)           converter
            Once every 125        (12-bits)
            microSeconds




                                                    Compressor
                                                   (u-Law/A-Law)
                                                     12-to-8-bits




              64 kbps             Serialiser




                                                                    Author: Bill Buchanan
ISDN, E1 and T1




    64kbps                     64kbps                           64kbps
     (Data)                    (Data 1)                         (Data 1)


                   Base-rate
    64kbps                     64kbps                           64kbps
                     ISDN
     (Data)                    (Data 2)                         (Data 2)



    16 kbps                                   Primary-rate                     Primary-rate
    (Signal)                                      ISDN                             ISDN
                                                (T1 PRI)                         (E1 PRI)


         Total rate: 160kbps    64kbps                          64kbps
                               (Data 23)                       (Data 30)



                               64 kbps                          64 kbps
                               (Signal)                         (Signal)



                                  Total bit rate: 1.544 Mbps   Total bit rate: 2.048 Mbps




                                                                                              Author: Bill Buchanan
AVVID




        AVVID: Architecture
        for Voice, Video and
        Integrated Data
        Key focus:
        · Network Management
        · High availability
        · Security
        · QoS

        Key metrics (Voice):
        · Necessary bandwidth
        · Acceptable delay
        · Acceptable jitter
        · Acceptable loss




                                Author: Bill Buchanan
        Voice:
        · Constant requirement for         Data:
          bandwidth.                       · Bursty bandwidth
        · Delay sensitive.                   requirement.
        · Jitter sensitive.                · Delay insensitive
        · Relatively error                 · Jitter insensitive.
          insensitive                      · Error sensitive



                       QoS methods

                                                      Congestion
   Traffic
                         Traffic shaping              Avoidance
classification
                                                       Methods




                            Prioritised                Traffic
                             Queues                  compression




                                                                   Author: Bill Buchanan
      Bandwidth calculation


                         Voice:
                         · Constant requirement for
                                                                             Voice payload
                           bandwidth.
                         · Delay sensitive.
                                                                            [G.711 (64Kbps)]
                         · Jitter sensitive.                                   160 Bytes
                         · Relatively error
                           insensitive
                                                                             Voice payload
                                                                            [G.726 (32Kbps)]
                                                                               120 Bytes

 Ethernet              IP                                                                      Ethernet
                                      UDP (8 bytes)        RTP (12 bytes)                      (4 bytes)
(14 bytes)         (20 bytes)
                                                                             Voice payload
                                                                            [G.729 (8Kbps)]
                                                                                40 Bytes




       Total data frame size (G.711) = 14+20+8+12+160+4 = 218 bytes
        Packets generated by second (G.711) = 50 pps




                                                                                                       Author: Bill Buchanan
        Bandwidth required for each call (G.711) = 218x8x50 = 87.2kbps
Providing power to the phone over Ethernet




     4000-series switch with
     In-line Power module




                                 3524-PWR-XL
                                 (based on 3524XL switch)

   WS-PWR-PANEL
   (Patch panel in-line power)




                                                            Author: Bill Buchanan
Good design practices

          AVVID: Architecture for Voice,
          Video and Integrated Data
          Good practice (Layer 2)
          · Separate VLANs for data and
            voice.
          · STP features: PortFast,
            UpLinkFast UDLD and Root
            Guard.
          · 802.1P/802.1Q tagging.

          Good pratice (Layer 3)
          · OSPF/EIGRP for fast
            convergence.
          · Passive interfaces for access
            layer so that there is no routing
            updates sent to them.
          · HSRP/GLBP used for gateway
            redundancy.

          Typical prioritization:




                                                Author: Bill Buchanan
          1. Voice/video (highest priority)
          2. Transactional applications
          3. Data transfers (lowest priority)
Delay, Jitter and Packet Loss


               Transmission
                  system

                              Delay (<60ms)




               Transmission
                  system
                                Jitter (<20ms)




               Transmission
                  system




                                                                    Author: Bill Buchanan
                               Packet loss
                               Error on line, or when congestion:
                               Tail drop,
                               Random early detection (RED)
                               Weight RED
Delays

                Issues for QoS:
                · Bandwidth.
                · Delay.
                · Jitter.
                · Packet loss.




 Processing
                                                                        Processing


Packetization
                                                                       Packetization
                 Queuing            Processing           Propagation

Serialization
                                                                       Serialization
                      Fixed delay. Such as amount of time to
                      encapsulate/de-capsulate and propagation
                      delay.
                      Variable delay. Such as queuing time and




                                                                                       Author: Bill Buchanan
                      processing on the devices.
Jitter




                            Transmission
                               system
                                                     Jitter (<20ms)




                            Jitter buffers
                            - smooths-out
                                delays




                  Jitter
                 Overrun                                     Jitter
   Buffer cannot resize itself to handle                  Underrun




                                                                                      Author: Bill Buchanan
   changes in delay variation -> leads       Variation in delays is too large, that
           to dropped packets                  the buffer cannot smooth-out
QoS Methods
                   Issues for QoS:
                   · Bandwidth.
                   · Delay.
                   · Jitter.
                   · Packet loss.




                                     Marking. Adds tags to the           Traffic shaping. Tries to
  Classification. Sorts and                                              smooth-out traffic flows to
                                     packets/frames to classify/
  classifies traffic.                                                    remove jitter, or restrict
                                     prioritize flow.
                                                                         bandwidth usage.

                                     Policing. Analyse bandwidth,
  Forwarding. Switching traffic
                                     jitter, delay, and packet loss,     Dropping. Defines which
  from one interface to another
                                     and determine whether to            packets to drop, and when.
  (CEF/fast switching)
                                     drop or break.

                                     Scheduling. Defines how the
  Queuing. Determines the
                                     queues should be serviced …
  queue that the packets should
                                     highest priority first, or round-




                                                                                                       Author: Bill Buchanan
  be placing for egress queuing.
                                     robin?
IntServ and DiffServ


                        Best effort
                          No QoS.
                      First-in, first-out
                                            IntServ (Integrated
                                            Services)
                                            Connection reserved at
                                            start via RSVP for every
                                            connection.
                                            All the devices are
                                            enabled to support the
                                            connection.

                                            Strength: Guaranteed
                                            QoS
    DiffServ (Differentiated
    Services)                               Weakness: Not scaleable
    Done of a hop-to-hop basis.             and requires extra
    Mark TOS field in IP header.            bandwidth for RSVP.

    Strength: Easier to implement
    than IntServ and costs less.

    Weakness: Best effort.




                                                                       Author: Bill Buchanan
    Requires packet tagging.
 Classification
                             Queuing                 Conditioning
and marking of
                             method                     traffic
     traffic




 Classification methods
 · Policy-based routing. Route maps.
 · Priority and Custom Queuing – ACLs, ingress
   interface, Layer 3 protocol and/or packet size.
 · Committed Access Rate (CAR). ACLs, DSCP,
   QoS groups and rate limit ACLs.
 · All methods. Class maps.




                                                                    Author: Bill Buchanan
        Marking options
        · Layer 2. CoS field in IEEE 802.1P frame. Values: 0
          (Best effort), 1 (Medium), 2 (High), and so on. 3 bits.
        · Layer 3. TOS field in IP header for DiffServ. 6-bits
          gives 64 levels. 2 bits used for congestion.
           DiffServ values
                                                           Original TOS field definition (RFC 791)

                                                                  P2       P1       P0        T2      T1      T0     CU1     CU0
     Classification
                                                                           ·    IP precedence—three bits (P2 to
    and marking of                                                              P0)
         traffic                                                           ·    Delay, Throughput and
                                                                                Reliability—three bits (T2 to T0)
                                                                           ·    CU (Currently Unused)—two
                                                                                bits(CU1-CU0)


                                                           DiffServ TOS field definition (RFC 2474/2475)

                                                                   D5      D4       D3      D2      D1      D0      ECN     ECN
Marking options
· Layer 3. TOS field in IP header for DiffServ. 6-bits               ·   DSCP - six bits (DS5-DS0)
  gives 64 levels. 2 bits used for congestion.                       ·   ECN (Explicit Congestion
                                                                         Notification)- two bits

                                                     (config)# class-map match-all VOIP
  Drop     Class 1   Class 2   Class 3   Class 4      1751-uut1(config-cmap)# match ip dscp ?
                                                        <0-63>   Differentiated services codepoint value
           001010    010010    011010    100010
                                                        af11     Match packets with AF11 dscp (001010)
           AF11      AF21      AF31      AF41           af12     Match packets with AF12 dscp (001100)
  Low
           DSCP      DSCP      DSCP      DSCP           af13     Match packets with AF13 dscp (001110)
           10        18        26        34             af21     Match packets with AF21 dscp (010010)
                                                        af22     Match packets with AF22 dscp (010100)
           001100    010100    011100    100100         af23     Match packets with AF23 dscp (010110)
           AF12      AF 22     AF32      AF42           af31     Match packets with AF31 dscp (011010)
  Medium
           DSCP      DSCP      DSCP      DSCP           af32     Match packets with AF32 dscp (011100)
           12        20        28        36             af33     Match packets with AF33 dscp (011110)
                                                        af41     Match packets with AF41 dscp (100010)
           001110    010110    011110    100110         af42     Match packets with AF42 dscp (100100)
           AF13      AF23      AF33      AF43           af43     Match packets with AF43 dscp (100110)
  High
           DSCP      DSCP      DSCP      DSCP           cs1      Match packets with CS1(precedence 1) dscp                 (001000)




                                                                                                                                      Author: Bill Buchanan
           14        22        30        38             cs2      Match packets with CS2(precedence 2) dscp                 (010000)
                                                        cs3      Match packets with CS3(precedence 3) dscp                 (011000)
                                                        cs4      Match packets with CS4(precedence 4) dscp                 (100000)
                                                        cs5      Match packets with CS5(precedence 5) dscp                 (101000)
                                                        cs6      Match packets with CS6(precedence 6) dscp                 (110000)
                                                        cs7      Match packets with CS7(precedence 7) dscp                 (111000)
                                                        default Match packets with default dscp (000000)
                                                        ef       Match packets with EF dscp (101110)
                                                     (config-cmap)# match ip dscp af31
      Queuing methods


 Priority Queuing (PQ)
 Queuing method which has four queues of high,
 medium, normal and low priorities. Always empty
 the highest priority queue first.
                                                           Weighted Fair Queuing (WFQ)
                                                           Queuing method that examines the traffic flow, such
                                                           as for source and destination addresses, to
                                                           determine the type of queuing.


       Weighted Round-Robin Queuing (WRRQ)
       Queuing method which priorities based on the IP
       precedence value, but still gives low priority a
       chance.




                                                          Low Latency Queuing (LLQ)
                                                          Checks the classification of the egress traffic and if
                                                          the priority is high, it is process first, otherwise it
Class-based Weighted Fair Queuing (CB-WFQ)                uses a class-based weighted-fair queue
Decides queuing method automatically determines
what should go into higher and lower priority queues




                                                                                                                    Author: Bill Buchanan
Congestion Avoidance



                                         Interface
      Route
    Processor
                                Packet




                                Packet
                Buffer is
                full. Next
                packets         Packet

                will be
                dropped
                unless the
                buffer is
                emptied

                                Packet




                             Egress
                             buffer




                                                     Author: Bill Buchanan
          Tail Dropping
RED and WRED




                                       Interface
     Route
   Processor
                                          Weighted RED. Uses
                              Packet
                                          CoS value to drop
                              Packet      backs.
               Random         Packet

                 Early                    Threshold 1 (50%)
               Detection                  CoS=0,1
                                          Random drop.
                              Packet
               Randomly
               delete
                                          Threshold 2 (80%)
                                          CoS=2,3
                           Egress         Random drop.
                           buffer




                                                               Author: Bill Buchanan
                                          CoS 2,3 has higher
                                          priority.
         RED and WRED
Example of Modular QoS



  (config)# access-list 1 permit 192.168.0.0 0.0.0.255       Class-map
  (config)# class-map class1                               Classification of
  (config-cmap)# match access-group 101                         traffic
  (config-cmap)# exit


  (config)# policy-map policy1                        Traffic policy
  (config-pmap)# class class1                          Marking of
  (config-pmap-c)# bandwidth 3000
                                                     traffic, policing
  (config-pmap-c)# queue-limit 30
  (config-pmap-c)# set dscp AF12                     and queue type
  (config-pmap)# exit


  (config)# interface e1
  (config-if)# service-policy output policy1
                                                         Apply policy
  (config-if)# exit




                                                                               Author: Bill Buchanan
First define Class Map
(config)# access-list 108 permit ip 162.78.102.0 0.0.255.255
     247.226.90.0 0.0.255.255
(config)# class-map tayside
(config-cmap)# ?
QoS class-map configuration commands:
  description Class-Map description
  exit         Exit from QoS class-map configuration mode
  match        classification criteria
  no           Negate or set default values of a command
  rename       Rename this class-map
(config-cmap)# match ?
  access-group         Access group
  any                  Any packets
  class-map            Class map
  destination-address Destination address
  input-interface      Select an input interface to match
  ip                   IP specific values
  mpls                 Multi Protocol Label Switching specific values
  not                  Negate this match result
  protocol             Protocol
  source-address       Source address
  vlan                 VLANs to match




                                                                                            Author: Bill Buchanan
(config-cmap)# match access-group 108
(config-cmap)# exit
                                                            Policy-map
                                           Class-map
                                                             Define the      Service-policy
                                           Define traffic
                                                            policy for the   Apply the policy
                                          characteristics
                                                                traffic
Next define Policy map
(config)# policy-map ankle
(config-pmap)# ?
QoS policy-map configuration commands:
  class        policy criteria
  description Policy-Map description
  exit         Exit from QoS policy-map configuration mode
  no           Negate or set default values of a command
  rename       Rename this policy-map
(config-pmap)# class tayside
(config-pmap-c)# ?
QoS policy-map class configuration commands:
  bandwidth Bandwidth
  exit       Exit from QoS class action configuration mode
  no         Negate or set default values of a command
  trust      Set trust value for the class
  <cr>
  police     Police
  set        Set QoS values
(config-pmap-c)# bandwidth 128
(config-pmap-c)# queue-limit 21
(config-pmap-c)# exit
(config-pmap)# exit




                                                                                           Author: Bill Buchanan
                                                           Policy-map
                                          Class-map
                                                            Define the      Service-policy
                                          Define traffic
                                                           policy for the   Apply the policy
                                         characteristics
                                                               traffic
Finally apply the policy map
(config)# int fa0/1
(config-if)# service-policy ?
  history Keep history of QoS metrics
  input    Assign policy-map to the input of an interface
  output   Assign policy-map to the output of an interface
(config-if)# service-policy output ?
  WORD policy-map name
(config-if)# service-policy output ankle




                                                                                           Author: Bill Buchanan
                                                           Policy-map
                                          Class-map
                                                            Define the      Service-policy
                                          Define traffic
                                                           policy for the   Apply the policy
                                         characteristics
                                                               traffic
Finally apply the policy map
(config)# int fa0/1
(config-if)# service-policy ?
  history Keep history of QoS metrics
  input    Assign policy-map to the input of an interface
  output   Assign policy-map to the output of an interface
(config-if)# service-policy output ?
  WORD policy-map name
(config-if)# service-policy output ankle




                                                                                           Author: Bill Buchanan
                                                           Policy-map
                                          Class-map
                                                            Define the      Service-policy
                                          Define traffic
                                                           policy for the   Apply the policy
                                         characteristics
                                                               traffic
         Priority Queuing (PQ)

          Priority Queuing (PQ)



Packet
                  High
                          (config)# priority-list 1 qUeue-limit 20 40 60 80
                          (config)# priority-list 1 protocol http high
                          (config)# priority-list 1 protocol ipx low
                          (config)# int serial0
                Medium    (config-if)# priority-group 1
                          (config-if)# exit
                          (config)# Exit
                          # show priority queuing


                 Normal
                                 High priority queue is
                                 always serviced first,
                                 followed by medium,
                               then by normal, and then
                  Low                   by low




                                                                              Author: Bill Buchanan
PQ

(config)# priority-list ?
  <1-16> Priority list number
(config)# priority-list 1 ?
  default      Set priority queue for unspecified datagrams
  interface    Establish priorities for packets from a named interface
  protocol     priority queueing by protocol
  queue-limit Set queue limits for priority queues
(config)# int fa0/1
(config)# priority-list 1 q ?
  <0-32767> High limit
(config)# priority-list 1 q 20 ?
  <0-32767> Medium limit
(config)# priority-list 1 q 20 40 ?
  <0-32767> Normal limit
(config)# priority-list 1 q 20 40 60 ?
  <0-32767> Lower limit
(config)# priority-list 1 q 20 40 60 80 ?
  <cr>
(config)# priority-list 1 q 20 40 60 80




                                                                    Author: Bill Buchanan
PQ
(config)# prio 1 p ?
  aarp              AppleTalk ARP
  appletalk         AppleTalk
  arp               IP ARP
  bridge            Bridging
  bstun             Block Serial Tunnel
  cdp               Cisco Discovery Protocol
  clns              ISO CLNS
  clns_es           ISO CLNS End System
  clns_is           ISO CLNS Intermediate System
  cmns              ISO CMNS
  compressedtcp     Compressed TCP (VJ)
  decnet            DECnet
  decnet_node       DECnet Node
  decnet_router-l1 DECnet Router L1
  decnet_router-l2 DECnet Router L2
  dlsw              Data Link Switching (Direct encapsulation only)
  http              HTTP
  ip                IP
  ipv6              IPV6
  ipx               Novell IPX
  llc2              llc2




                                                                      Author: Bill Buchanan
  pad               PAD links
  pppoe             PPP over Ethernet
  qllc              qllc protocol
  rsrb              Remote Source-Route Bridging
  snapshot          Snapshot routing support
PQ
(config)# priority-list 1 protocol http ?
  high
  medium
  normal
  low
(config)# priority-list 1 protocol http high
(config)# priority-list 1 protocol ipx low
(config)# int serial0
(config-if)# prority-group 1




                                               Author: Bill Buchanan
    Custom Queuing (CQ)

         Custom Queuing (CQ)



Packet
                1
                      (config)# queue-list 1 protocol ip 1
                      (config)# queue-list 1 protocol cdp 2
                      (config)# queue-list 1 queue 1 limit 40
                      (config)# queue-list 1 queue 2 limit 20
                2     (config)# int fa0/1
                      (config-if)# Custom-queue-list 1




                             CQ can use up to 16
                            queues in a round-robin
                                   manner.
                16




                                                                Author: Bill Buchanan
CQ
(config)# queue-list ?
  <1-16> Queue list number

(config)# queue-list 1 ?
  default        Set custom queue for unspecified datagrams
  interface      Establish priorities for packets from a named interfac
  lowest-custom Set lowest number of queue to be treated as custom
  protocol       priority queueing by protocol
  queue          Configure parameters for a particular queue
  stun           Establish priorities for stun packets
(config)# queue-list 1 protocol ?
  arp            IP ARP
  bridge         Bridging
  bstun          Block Serial Tunnel
  cdp            Cisco Discovery Protocol
  compressedtcp Compressed TCP
  dlsw           Data Link Switching (Direct encapsulation only)
  ip             IP
  ipv6           IPV6
  llc2           llc2
  pad            PAD links
  pppoe          PPP over Ethernet




                                                                    Author: Bill Buchanan
  qllc           qllc protocol
  rsrb           Remote Source-Route Bridging
  snapshot       Snapshot routing support
  stun           Serial Tunnel
CQ
(config)# queue-list 1 protocol ip ?
  <0-16> queue number

(config)# queue-list 1   protocol ip 1 ?
  gt Classify packets    greater than a specified size
  lt Classify packets    less than a specified size
  <cr>
(config)# queue-list 1   protocol ip 1

(config)# que 1 queue ?
  <0-16> queue number

(config)# que 1 q 1 ?
  byte-count Specify size in bytes of a particular queue
  limit       Set queue entry limit of a particular queue

(config)# que 1 q 1 limit ?
  <0-32767> number of queue entries

(config)# que 1 q 1 l 40 ?
  byte-count Specify size in bytes of a particular queue
  <cr>




                                                            Author: Bill Buchanan
(config)# que 1 q 1 l 40
(config)# int fa0/1
(config-if)# custom-queue-list 1
WRRQ
(config-if)#   wrr-queue bandwidth ?
  <1-65536>    enter bandwidth weight for   qid 1
(config-if)#   wrr-queue bandwidth 3 ?
  <1-65536>    enter bandwidth weight for   qid 2
(config-if)#   wrr-queue bandwidth 3 8 ?
  <1-65536>    enter bandwidth weight for   qid 3
(config-if)#   wrr-queue bandwidth 3 8 10   ?
  <1-65536>    enter bandwidth weight for   qid 4
(config-if)#   wrr-queue bandwidth 3 8 10   12


In this case the bandwidth is:

Queue 1: 3/(3+8+10+12) = 9.1%
Queue 2: 3/(3+8+10+12) = 24.2%
Queue 3: 3/(3+8+10+12) = 30.3%
Queue 4: 3/(3+8+10+12) = 36.4%




                                                    Author: Bill Buchanan
WRRQ
(config-if)# wrr-queue cos-map ?
  <1-4> enter cos-map queue id
(config-if)# wrr-queue cos-map 1 ?
  <0-7> 8 cos values separated by spaces
(config-if)# wrr-queue cos-map 3 4 5

(config-if)# wrr-queue cos-map 1 0 1 2 4
(config-if)# wrr-queue cos-map 3 4 5

Queue 1 has CoS of 0, 1, 2 and 4 allocated to it
Queue 3 has CoS of 4 and 5 allocated to it.

(config-if)# wrr-queue random-detect 1 max-threshold 50 100
(config-if)# wrr-queue random-detect 3 max-threshold 80 100

Queue 1 has a min threshold of 50% and a max of 100%
Queue 3 has a min threshold of 80% and a max of 100%

To assign DSCP values to queues:

(config-if)# wrr-queue dscp-map 1 0 1 2 3 4 5 6 7
(config-if)# wrr-queue dscp-map 1 8 9




                                                              Author: Bill Buchanan
(config-if)# wrr-queue dscp-map 2 10 11 12 13 14
SPAN




            All the received traffic from FA0/1
             and FA0/2 are sent to this node




       (config)# monitor session 1 source interface fa0/1 - 2 rx
       (config)# monitor session 1 destination interface fa0/14




                                                                   Author: Bill Buchanan
Remote SPAN (RSPAN)




            All the received traffic from FA0/1
             and FA0/2 are sent to a remote
                          station
         (config)# int vlan 10
         (config-vlan)# remote-span
         (config-vlan)# exit
         (config)# monitor session 1 source interface fa0/1 - 2 rx
         (config)# monitor session 1 destination remote vlan 10




         (config)# monitor session 1 remote vlan 10
         (config)# monitor session 1 destination interface fa0/14




                                                                     Author: Bill Buchanan

				
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