1. © 2006 Cisco Systems, Inc. All rights reserved. Optimizing Converged Cisco Networks (ONT) Module 4: Implement the DiffServ QoS Model

2. © 2006 Cisco Systems, Inc. All rights reserved. Module 4: Implement the DiffServ QoS Model Lesson 4.1: Introducing Classification and Marking

3. © 2006 Cisco Systems, Inc. All rights reserved. Objectives  Describe the classification and marking for QoS.  Explain the relationship between IP Precedence and DSCP.  Describe the standard Per Hop Behavior (PHB) groups and their characteristics.  Explain how a service class is used to implement QoS policies.  Describe a trust boundary and the guidelines used to establish this boundary.

4. © 2006 Cisco Systems, Inc. All rights reserved. Classification  Classification is the process of identifying and categorizing traffic into classes, typically based upon: Incoming interface IP precedence DSCP Source or destination address Application  Without classification, all packets are treated the same.  Classification should take place as close to the source as possible.

5. © 2006 Cisco Systems, Inc. All rights reserved. Marking  Marking is the QoS feature component that “colors” a packet (frame) so it can be identified and distinguished from other packets (frames) in QoS treatment.  Commonly used markers: Link layer: CoS (ISL, 802.1p) MPLS EXP bits Frame Relay Network layer: DSCP IP precedence

6. © 2006 Cisco Systems, Inc. All rights reserved. Classification and Marking in the LAN with IEEE 802.1Q  IEEE 802.1p user priority field is also called CoS.  IEEE 802.1p supports up to eight CoSs.  IEEE 802.1p focuses on support for QoS over LANs and 802.1Q ports.  IEEE 802.1p is preserved through the LAN, not end to end.

7. © 2006 Cisco Systems, Inc. All rights reserved. Classification and Marking in the Enterprise

8. © 2006 Cisco Systems, Inc. All rights reserved. DiffServ Model  Describes services associated with traffic classes, rather than traffic flows.  Complex traffic classification and conditioning is performed at the network edge.  No per-flow state in the core.  The goal of the DiffServ model is scalability.  Interoperability with non-DiffServ-compliant nodes.  Incremental deployment.

9. © 2006 Cisco Systems, Inc. All rights reserved. Classification Tools IP Precedence and DiffServ Code Points  IPv4: three most significant bits of ToS byte are called IP Precedence (IPP)—other bits unused  DiffServ: six most significant bits of ToS byte are called DiffServ Code Point (DSCP)—remaining two bits used for flow control  DSCP is backward-compatible with IP precedence 76543210 IDOffsetTTLProtoFCSIP SAIP DADataLen Version Length ToS Byte DiffServ Code Point (DSCP)IP ECN IPv4 Packet IP PrecedenceUnused Standard IPv4 DiffServ Extensions

10. © 2006 Cisco Systems, Inc. All rights reserved. IP ToS Byte and DS Field Inside the IP Header

11. © 2006 Cisco Systems, Inc. All rights reserved. IP Precedence and DSCP Compatibility  Compatibility with current IP precedence usage (RFC 1812)  Differentiates probability of timely forwarding: (xyz000) >= (abc000) if xyz > abc  That is, if a packet has DSCP value of 011000, it has a greater probability of timely forwarding than a packet with DSCP value of 001000.

12. © 2006 Cisco Systems, Inc. All rights reserved. Per-Hop Behaviors  DSCP selects PHB throughout the network: Default PHB (FIFO, tail drop) Class-selector PHB (IP precedence) EF PHB AF PHB

13. © 2006 Cisco Systems, Inc. All rights reserved. Standard PHB Groups

14. © 2006 Cisco Systems, Inc. All rights reserved. Expedited Forwarding (EF) PHB  EF PHB: Ensures a minimum departure rate Guarantees bandwidth—class guaranteed an amount of bandwidth with prioritized forwarding Polices bandwidth—class not allowed to exceed the guaranteed amount (excess traffic is dropped)  DSCP value of 101110: Looks like IP precedence 5 to non-DiffServ- compliant devices: Bits 5 to 7: 101 = 5 (same 3 bits are used for IP precedence) Bits 3 and 4: 11 = No drop probability Bit 2: Just 0

15. © 2006 Cisco Systems, Inc. All rights reserved. Assured Forwarding (AF) PHB  AF PHB: Guarantees bandwidth Allows access to extra bandwidth, if available  Four standard classes: AF1, AF2, AF3, and AF4  DSCP value range of aaadd0: aaa is a binary value of the class dd is drop probability

16. © 2006 Cisco Systems, Inc. All rights reserved. AF PHB Values  Each AF class uses three DSCP values.  Each AF class is independently forwarded with its guaranteed bandwidth.  Congestion avoidance is used within each class to prevent congestion within the class.

17. © 2006 Cisco Systems, Inc. All rights reserved. Mapping CoS to Network Layer QoS

18. © 2006 Cisco Systems, Inc. All rights reserved. QoS Service Class  A QoS service class is a logical grouping of packets that are to receive a similar level of applied quality.  A QoS service class can be: A single user (such as MAC address or IP address) A department, customer (such as subnet or interface) An application (such as port numbers or URL) A network destination (such as tunnel interface or VPN)

19. © 2006 Cisco Systems, Inc. All rights reserved. Implementing QoS Policy Using a QoS Service Class

20. © 2006 Cisco Systems, Inc. All rights reserved. QoS Service Class Guidelines  Profile applications to their basic network requirements.  Do not over engineer provisioning; use no more than four to five traffic classes for data traffic: Voice applications: VoIP Mission-critical applications: Oracle, SAP, SNA Interactive applications: Telnet, TN3270 Bulk applications: FTP, TFTP Best-effort applications: E-mail, web Scavenger applications: Nonorganizational streaming and video applications (Kazaa, Yahoo)  Do not assign more than three applications to mission-critical or transactional classes.  Use proactive policies before reactive (policing) policies.  Seek executive endorsement of relative ranking of application priority prior to rolling out QoS policies for data.

21. © 2006 Cisco Systems, Inc. All rights reserved. Classification and Marking Design QoS Baseline Marking Recommendations Application L3 Classification DSCPPHBIPPCoS Transactional Data 18AF2122 Call Signaling24CS3*33 Streaming Video 32CS444 Video Conferencing34AF4144 Voice46EF55 Network Management16CS222 L2 Bulk Data10AF1111 Scavenger8CS111 Routing48CS666 Mission-Critical Data26AF31*33 Best Effort0000

22. © 2006 Cisco Systems, Inc. All rights reserved. How Many Classes of Service Do I Need? 4/5 Class Model Scavenger Critical Data Call Signaling Realtime 8 Class Model Critical Data Video Call Signaling Best Effort Voice Bulk Data Network Control Scavenger 11 Class Model Network Management Call Signaling Streaming Video Transactional Data Interactive-Video Voice Best Effort IP Routing Mission-Critical Data Scavenger Bulk Data Time Best Effort

23. © 2006 Cisco Systems, Inc. All rights reserved. Trust Boundaries: Classify Where?  For scalability, classification should be enabled as close to the edge as possible, depending on the capabilities of the device at: Endpoint or end system Access layer Distribution layer

24. © 2006 Cisco Systems, Inc. All rights reserved. Trust Boundaries: Mark Where?  For scalability, marking should be done as close to the source as possible.

25. © 2006 Cisco Systems, Inc. All rights reserved. Self Check 1.Which PHB would be used for voice traffic? 2.How many bits are used for IP Precedence? For DSCP? 3.Which PHB can allow access to extra bandwidth if it is available? 4.How is CDP used to establish trust boundaries?

26. © 2006 Cisco Systems, Inc. All rights reserved. Summary  Classification, marking, and queuing are critical functions of any successful QoS implementation.  Classification allows network devices to identify traffic as belonging to a specific class with the specific QoS requirements determined by an administrative QoS policy.  The DiffServ model uses classes to describe services offered to network traffic, rather than traffic flows.  DiffServ uses DSCP to establish Per Hop Behaviors (PHBs) to classify and service traffic.

27. © 2006 Cisco Systems, Inc. All rights reserved. Resources  DiffServ -- The Scalable End-to-End QoS Model http://www.cisco.com/en/US/partner/products/ps6610/products_ white_paper09186a00800a3e2f.shtml  Quality of Service - The Differentiated Services Model http://www.cisco.com/en/US/partner/products/ps6610/products_ data_sheet0900aecd8031b36d.html

28. © 2006 Cisco Systems, Inc. All rights reserved. Module 4: Implement the DiffServ QoS Model Lesson 4.2: Using NBAR for Classification

29. © 2006 Cisco Systems, Inc. All rights reserved. Network-Based Application Recognition  Used in conjunction with QoS class- based features, NBAR is an intelligent classification engine that: Classifies modern client-server and web- based applications Discovers what traffic is running on the network Analyzes application traffic patterns in real time  NBAR functions: Performs identification of applications and protocols (Layer 4–7) Performs protocol discovery Provides traffic statistics  New applications are easily supported by loading a PDLM. My application is too slow! Sample Link Utilization Citrix25% Netshow 15% Fasttrack10% FTP30% HTTP20%

30. © 2006 Cisco Systems, Inc. All rights reserved. NBAR Functions & Features  NBAR performs the following two functions: Identification of applications and protocols (Layer 4 to Layer 7) Protocol discovery  Some examples of class-based QoS features that can be used on traffic after the traffic is classified by NBAR include: Class-Based Marking (the set command) Class-Based Weighted Fair Queueing (the bandwidth and queue-limit commands) Low Latency Queueing (the priority command) Traffic Policing (the police command) Traffic Shaping (the shape command)

31. © 2006 Cisco Systems, Inc. All rights reserved. NBAR Application Support  NBAR can classify applications that use: Statically assigned TCP and UDP port numbers Non-UDP and non-TCP IP protocols Dynamically assigned TCP and UDP port numbers negotiated during connection establishment (requires stateful inspection) Subport and deep packet inspection classification

32. © 2006 Cisco Systems, Inc. All rights reserved. Packet Description Language Module  PDLMs allow NBAR to recognize new protocols matching text patterns in data packets without requiring a new Cisco IOS software image or a router reload.  An external PDLM can be loaded at run time to extend the NBAR list of recognized protocols.  PDLMs can also be used to enhance an existing protocol recognition capability.  PDLMs must be produced by Cisco engineers.

33. © 2006 Cisco Systems, Inc. All rights reserved. PDLM Command Syntax  Used to enhance the list of protocols recognized by NBAR through a PDLM.  The filename is in the URL format (for example, flash://citrix.pdlm). ip nbar pdlm pdlm-name router(config)# ip nbar port-map protocol-name [tcp | udp] port-number router(config)#  Configures NBAR to search for a protocol or protocol name using a port number other than the well-known port.  Up to 16 additional port numbers can be specified.

34. © 2006 Cisco Systems, Inc. All rights reserved. NBAR Protocol-to-Port Maps  Displays the current NBAR protocol-to-port mappings router#show ip nbar port-map port-map bgp udp 179 port-map bgp tcp 179 port-map cuseeme udp 7648 7649 port-map cuseeme tcp 7648 7649 port-map dhcp udp 67 68 port-map dhcp tcp 67 68 port-map dns udp 53 port-map dns tcp 53 show ip nbar port-map [protocol-name] router#

35. © 2006 Cisco Systems, Inc. All rights reserved. NBAR Protocol Discovery  Analyzes application traffic patterns in real time and discovers which traffic is running on the network  Provides bidirectional, per-interface, and per-protocol statistics  Important monitoring tool supported by Cisco QoS management tools: Generates real-time application statistics Provides traffic distribution information at key network locations

36. © 2006 Cisco Systems, Inc. All rights reserved. Configuring and Monitoring NBAR Protocol Discovery  Configures NBAR to discover traffic for all protocols known to NBAR on a particular interface  Requires that CEF be enabled before protocol discovery  Can be applied with or without a service policy enabled ip nbar protocol-discovery router(config-if)# show ip nbar protocol-discovery router#  Displays the statistics for all interfaces on which protocol discovery is enabled

37. © 2006 Cisco Systems, Inc. All rights reserved. Configuring and Monitoring Protocol Discovery Output router#show ip nbar protocol-discovery Ethernet0/0 Input Output Protocol Packet Count Packet Count Byte Count Byte Count 5 minute bit rate (bps) 5 minute bit rate (bps) ---------- ------------------------ ------------------------ realaudio 2911 3040 1678304 198406 19000 1000 http 19624 13506 14050949 2017293 0 0

38. © 2006 Cisco Systems, Inc. All rights reserved. Steps for Configuring NBAR for Static Protocols  Required steps: Enable NBAR Protocol Discovery. Configure a traffic class. Configure a traffic policy. Attach the traffic policy to an interface. Enable PDLM if needed.

39. © 2006 Cisco Systems, Inc. All rights reserved. Configuring NBAR for Static Protocols Commands  Configures the match criteria for a class map on the basis of the specified protocol using the MQC configuration mode.  Static protocols are recognized based on the well-known destination port number.  A match not command can be used to specify a QoS policy value that is not used as a match criterion; in this case, all other values of that QoS policy become successful match criteria. match protocol protocol router(config-cmap)#

40. © 2006 Cisco Systems, Inc. All rights reserved. Configuring NBAR Example  HTTP is a static protocol using a well-known port number 80. However, other port numbers may also be in use.  The ip nbar port-map command will inform the router that other ports are also used for HTTP.

41. © 2006 Cisco Systems, Inc. All rights reserved. Steps for Configuring Stateful NBAR for Dynamic Protocols  Required steps: Configure a traffic class. Configure a traffic policy. Attach the traffic policy to an interface.

42. © 2006 Cisco Systems, Inc. All rights reserved. Enhanced NBAR Classification for HTTP  Recognizes the HTTP GET packets containing the URL, and then matches all packets that are part of the HTTP GET request  Include only the portion of the URL following the address or host name in the match statement match protocol http url url-string router(config-cmap)# match protocol http host hostname-string router(config-cmap)#  Performs a regular expression match on the host field content inside an HTTP GET packet and classifies all packets from that host

43. © 2006 Cisco Systems, Inc. All rights reserved. match protocol http mime MIME-type router(config-cmap)# match protocol fasttrack file-transfer regular-expression router(config-cmap)# Special NBAR Configuration for HTTP and FastTrack  Matches a packet containing the MIME type and all subsequent packets until the next HTTP transaction for stateful protocol.  Stateful mechanism to identify a group of peer-to-peer file-sharing applications.  Applications that use FastTrack peer-to-peer protocol include Kazaa, Grokster, Gnutella, and Morpheus.  A Cisco IOS regular expression is used to identify specific FastTrack traffic.  To specify that all FastTrack traffic will be identified by the traffic class, use asterisk (*) as the regular expression.

44. © 2006 Cisco Systems, Inc. All rights reserved. URL or HOST Specification String Options OptionsDescription * Match any zero or more characters in this position. ? Match any one character in this position. | Match one of a choice of characters. (|) Match one of a choice of characters in a range. For example, xyz.(gif | jpg) matches either xyz.gif or xyz.jpg. [ ] Match any character in the range specified, or one of the special characters. For example, [0-9] is all of the digits; [*] is the "*" character, and [[] is the "[" character.

45. © 2006 Cisco Systems, Inc. All rights reserved. match protocol rtp [audio | video | payload-type payload-string] router(config-cmap)# Configuring Stateful NBAR for RTP  Identifies real-time audio and video traffic in the class-map mode of MQC  Differentiates on the basis of audio and video codecs  The match protocol rtp command has these options: audio: Match by payload type values 0 to 23, reserved for audio traffic video: Match by payload type values 24 to 33, reserved for video traffic payload-type: Match by a specific payload type value; provides more granularity than the audio or video options

46. © 2006 Cisco Systems, Inc. All rights reserved. Classification of RTP Session

47. © 2006 Cisco Systems, Inc. All rights reserved. Resources  Network-Based Application Recognition, Q&A http://www.cisco.com/en/US/partner/products/ps6616/products_ qanda_item09186a00800a3ded.shtml  Network-Based Application Recognition and Distributed Network-Based Application Recognition http://www.cisco.com/en/US/partner/products/ps6350/products_ configuration_guide_chapter09186a0080455985.html

48. © 2006 Cisco Systems, Inc. All rights reserved. Module 4: Implement the DiffServ QoS Model Lesson 4.3: Introducing Queuing Implementations

49. © 2006 Cisco Systems, Inc. All rights reserved. Objectives  Describe the common causes of congestion on a link.  Compare and contrast various queuing methods used to relieve congestion.  Describe the purpose and functionality of software queues.  Describe the function and purpose of the hardware queue.

50. © 2006 Cisco Systems, Inc. All rights reserved.  Congestion can occur at any point in the network where there are points of speed mismatches or aggregation.  Queuing manages congestion to provide bandwidth and delay guarantees. Congestion and Queuing

51. © 2006 Cisco Systems, Inc. All rights reserved. Speed mismatches are the most typical cause of congestion. Possibly persistent when going from LAN to WAN. Usually transient when going from LAN to LAN. Speed Mismatch

52. © 2006 Cisco Systems, Inc. All rights reserved. Aggregation

53. © 2006 Cisco Systems, Inc. All rights reserved. What is Queuing?  Queuing is a congestion-management mechanism that allows you to control congestion on interfaces.  Queuing is designed to accommodate temporary congestion on an interface of a network device by storing excess packets in buffers until bandwidth becomes available.

54. © 2006 Cisco Systems, Inc. All rights reserved. Congestion and Queuing.

55. © 2006 Cisco Systems, Inc. All rights reserved. Queuing Algorithms  First-in, first-out (FIFO)  Priority queuing (PQ)  Round robin  Weighted round robin (WRR)

56. © 2006 Cisco Systems, Inc. All rights reserved. FIFO  First packet in is first packet out  Simplest of all  One queue  All individual queues are FIFO

57. © 2006 Cisco Systems, Inc. All rights reserved. Priority Queuing  Uses multiple queues  Allows prioritization  Always empties first queue before going to the next queue:  Empty queue number 1.  If queue number 1 is empty, then dispatch one packet from queue number 2.  If both queue number 1 and queue number 2 are empty, then dispatch one packet from queue number 3.  Queues number 2 and number 3 may “starve”

58. © 2006 Cisco Systems, Inc. All rights reserved. Round Robin Queuing  Uses multiple queues  No prioritization  Dispatches one packet from each queue in each round: One packet from queue number 1 One packet from queue number 2 One packet from queue number 3 Then repeat

59. © 2006 Cisco Systems, Inc. All rights reserved. Weighted Round Robin Queuing  Allows prioritization  Assign a weight to each queue  Dispatches packets from each queue proportionately to an assigned weight:  Dispatch up to four from queue number 1.  Dispatch up to two from queue number 2.  Dispatch 1 from queue number 3.  Go back to queue number 1.

60. © 2006 Cisco Systems, Inc. All rights reserved. Problems with Weighted Round Robin Queuing  Problem with WRR: Some implementations of WRR dispatch a configurable number of bytes (threshold) from each queue for each round—several packets can be sent in each turn. The router is allowed to send the entire packet even if the sum of all bytes is more than the threshold.

61. © 2006 Cisco Systems, Inc. All rights reserved. Router Queuing Components  Each physical interface has a hardware and a software queuing system.

62. © 2006 Cisco Systems, Inc. All rights reserved. Hardware and Software Router Queuing Components  The hardware queuing system always uses FIFO queuing.  The software queuing system can be selected and configured depending on the platform and Cisco IOS version.

63. © 2006 Cisco Systems, Inc. All rights reserved. The Software Queue  Generally, a full hardware queue indicates interface congestion, and software queuing is used to manage it.  When a packet is being forwarded, the router will bypass the software queue if the hardware queue has space in it (no congestion).

64. © 2006 Cisco Systems, Inc. All rights reserved. The Hardware Queue  Routers determine the length of the hardware queue based on the configured bandwidth of the interface.  The length of the hardware queue can be adjusted with the tx- ring-limit command.  Reducing the size of the hardware queue has two benefits: It reduces the maximum amount of time that packets wait in the FIFO queue before being transmitted. It accelerates the use of QoS in Cisco IOS software.  Improper tuning of the hardware queue may produce undesirable results: A long transmit queue may result in poor performance of the software queuing system. A short transmit queue may result in a large number of interrupts, which causes high CPU utilization and low link utilization.

65. © 2006 Cisco Systems, Inc. All rights reserved. Monitoring Hardware Queue Transmit Queue Length  The show controllers serial 0/1/0 command shows the length of the hardware queue. R1#show controllers serial 0/1/0 Interface Serial0/1/0 Hardware is GT96K DCE V.11 (X.21), clock rate 384000 1 sdma_rx_reserr, 0 sdma_tx_reserr 0 rx_bogus_pkts, rx_bogus_flag FALSE 0 sdma_tx_ur_processed tx_limited = 1(2), errata19 count1 - 0, count2 - 0 Receive Ring rxr head (27)(0x075BD090), rxr tail (0)(0x075BCEE0) rmd(75BCEE0): nbd 75BCEF0 cmd_sts 80800000 buf_sz 06000000 buf_ptr 75CB8E0 rmd(75BCEF0): nbd 75BCF00 cmd_sts 80800000 buf_sz 06000000 buf_ptr 75CCC00

66. © 2006 Cisco Systems, Inc. All rights reserved. Congestion on Software Interfaces  Subinterfaces and software interfaces (dialers, tunnels, Frame Relay subinterfaces) do not have their own separate transmit queue.  Subinterfaces and software interfaces congest when the transmit queue of their main hardware interface congests.  The tx-ring state (full, not-full) is an indication of hardware interface congestion.  The terms “TxQ” and “tx-ring” both describe the hardware queue and are interchangeable.

67. © 2006 Cisco Systems, Inc. All rights reserved. Self Check 1.When does the router use a software queue? 2.What are the typical causes of congestion? 3.When would FIFO queuing be appropriate in a network? 4.What is the “worst case scenario” for Priority Queuing (PQ)? 5.How does Weighted Round Robin (WRR) improve on Round Robin queuing?

68. © 2006 Cisco Systems, Inc. All rights reserved. Summary  Speed mismatch and aggregation are the most common causes of congestion on a network link.  When network links experience congestion, queuing methods can be used to sort the traffic and then determine some method of prioritizing it onto an output link. Each queuing algorithm was designed to solve a specific network traffic problem and has a particular effect on network performance.  Software queuing is activated when the hardware queue fills. If the hardware queue is not full, software queuing is bypassed and packets are sent directly to the hardware output queue.

69. © 2006 Cisco Systems, Inc. All rights reserved. Q and A

70. © 2006 Cisco Systems, Inc. All rights reserved. Resources  Congestion Management Overview http://www.cisco.com/en/US/partner/products/ps6350/products_ configuration_guide_chapter09186a00800b75a9.html

71. © 2006 Cisco Systems, Inc. All rights reserved.