QOS

1. QOS Lecture 6- Classification and Marking

2. 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.

3. 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

4. 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.

5. Classification and Marking in the Enterprise

6. 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.

7. 7 6 5 4 3 2 1 0 Standard IPv4 IP Precedence Unused DiffServ Code Point (DSCP) IP ECN DiffServ Extensions Classification ToolsIP 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 ToS Byte Version Length Len ID Offset TTL Proto FCS IP SA IP DA Data IPv4 Packet

8. IP ToS Byte and DS Field Inside the IP Header

9. 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.

10. Per-Hop Behaviors • DSCP selects PHB throughout the network: Default PHB (FIFO, tail drop) Class-selector PHB (IP precedence) EF PHB AF PHB

11. Standard PHB Groups

12. 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

13. 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

14. 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.

15. Mapping CoS to Network Layer QoS

16. 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)

17. Implementing QoS Policy Using a QoS Service Class

18. 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.

19. Application L3 Classification L2 IPP PHB DSCP CoS Routing 6 CS6 48 6 Voice 5 EF 46 5 Video Conferencing 4 AF41 34 4 4 CS4 32 4 Streaming Video Mission-Critical Data 3 AF31* 26 3 Call Signaling 3 CS3* 24 3 2 AF21 18 2 Transactional Data Network Management 2 CS2 16 2 Bulk Data 1 AF11 10 1 Scavenger 1 CS1 8 1 Best Effort 0 0 0 0 Classification and Marking DesignQoS Baseline Marking Recommendations

20. 8 Class Model 11 Class Model Voice Voice Interactive-Video Video Streaming Video Call Signaling Call Signaling IP Routing Network Control Network Management Critical Data Mission-Critical Data Transactional Data Bulk Data Bulk Data Best Effort Best Effort Time Scavenger Scavenger How Many Classes of Service Do I Need? 4/5 Class Model Realtime Call Signaling Critical Data Best Effort Scavenger

21. 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

22. Trust Boundaries: Mark Where? • For scalability, marking should be done as close to the source as possible.

23. My application is too slow! Citrix 25% Netshow 15% Fasttrack 10% FTP 30% HTTP 20% Sample Link Utilization 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.

24. 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)

25. 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

26. 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.

27. 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). router(config)# ip nbar pdlm pdlm-name router(config)# ip nbar port-map protocol-name [tcp | udp] port-number • 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.

28. 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 router# show ip nbar port-map [protocol-name]

29. 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

30. 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 Configuring and Monitoring NBAR Protocol Discovery router(config-if)# ip nbar protocol-discovery router# show ip nbar protocol-discovery • Displays the statistics for all interfaces on which protocol discovery is enabled

31. 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 <output omitted>

32. 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.

33. 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. router(config-cmap)# match protocol protocol

34. 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.

35. 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.

36. 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 router(config-cmap)# match protocol http url url-string router(config-cmap)# match protocol http host hostname-string • Performs a regular expression match on the host field content inside an HTTP GET packet and classifies all packets from that host

37. Matches a packet containing the MIME type and all subsequent packets until the next HTTP transaction for stateful protocol. Special NBAR Configuration for HTTP and FastTrack router(config-cmap)# match protocol http mime MIME-type router(config-cmap)# match protocol fasttrack file-transferregular-expression • 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.

38. URL or HOST Specification String Options

39. 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 router(config-cmap)# match protocol rtp [audio | video | payload-type payload-string]

40. Classification of RTP Session