© 2006 Cisco Systems, Inc. All rights reserved. QOS Lecture 6- Classification and Marking

© 2006 Cisco Systems, Inc. All rights reserved.

QOS

Lecture 6- Classification and Marking


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.


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


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.


Classification and Marking in the Enterprise


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.


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

7 6 5 4 3 2 1 0

ID Offset TTL Proto FCS IP SA IP DA DataLenVersion Length

ToSByte

DiffServ Code Point (DSCP) IP ECN

IPv4 Packet

IP Precedence UnusedStandard IPv4

DiffServ Extensions


IP ToS Byte and DS Field Inside the IP Header


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.


Per-Hop Behaviors

DSCP selects PHB throughout the network:Default PHB (FIFO, tail drop)

Class-selector PHB (IP precedence)

EF PHB

AF PHB


Standard PHB Groups


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


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


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.


Mapping CoS to Network Layer QoS


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)


Implementing QoS Policy Using a QoS Service Class


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.


Classification and Marking DesignQoS Baseline Marking Recommendations

ApplicationL3 Classification

DSCPPHBIPP CoS

Transactional Data 18AF212 2

Call Signaling 24CS3*3 3

Streaming Video 32CS44 4

Video Conferencing 34AF414 4

Voice 46EF5 5

Network Management 16CS22 2

L2

Bulk Data 10AF111 1

Scavenger 8CS11 1

Routing 48CS66 6

Mission-Critical Data 26AF31*3 3

Best Effort 000 0


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


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


Trust Boundaries: Mark Where?

For scalability, marking should be done as close to the source as possible.


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 applicationsDiscovers what traffic is running on the networkAnalyzes application traffic patterns in real time

NBAR functions:Performs identification of applications and protocols (Layer 4–7)Performs protocol discoveryProvides traffic statistics

New applications are easily supported by loading a PDLM.

My application is too slow!

Sample Link Utilization

Citrix 25%Netshow 15%Fasttrack 10%FTP 30%HTTP 20%


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)


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


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.


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.


NBAR Protocol-to-Port Maps

Displays the current NBAR protocol-to-port mappings

router#show ip nbar port-map

port-map bgp udp 179port-map bgp tcp 179port-map cuseeme udp 7648 7649port-map cuseeme tcp 7648 7649port-map dhcp udp 67 68port-map dhcp tcp 67 68port-map dns udp 53port-map dns tcp 53

show ip nbar port-map [protocol-name]

router#


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


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


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>


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.


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)#


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.


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.


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


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


match protocol http mime MIME-type


match protocol fasttrack file-transferregular-expression


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.


URL or HOST Specification String Options

Options Options DescriptionDescription * * 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.


match protocol rtp [audio | video | payload-type payload-string]


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


Classification of RTP Session

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© 2006 Cisco Systems, Inc. All rights reserved. QOS Lecture 6- Classification and Marking