Tài liệu Infrastructure Quality of Service pptx

Copyright © 2000, Cisco Systems, Inc. 1
© 2000, Cisco Systems, Inc.
Infrastructure
Quality of Service
Infrastructure
Quality of Service
Copyright © 2000, Cisco Systems, Inc. 2
© 2000, Cisco Systems, Inc. www.cisco.com econ_0386_09_010.ppt
Keep All Graphics Inside This Box
Objectives
Objectives
Upon completion of this module, you will be
able to perform the following tasks:
• Describe the purpose of classification and marking
• Explain IP Precedence and Diff-Serv
• Describe Quality of Service policy using Modular
QoS Command Line Interface (CLI)
• Explain Network Based Application Recognition
(NBAR)
Copyright © 2000, Cisco Systems, Inc. 3
© 2000, Cisco Systems, Inc. www.cisco.com econ_0386_09_010.ppt
Keep All Graphics Inside This Box
Objectives
Objectives
• Describe forms of packet, frame, or cell marking
• Describe the purpose and benefits of Resource
Reservation Protocol (RSVP) and Common Open
Policy Service (COPS)
• Explain briefly how RSVP and COPS work
• Describe each of the Cisco QoS management
products

• Identify the functions of each product
• Recommend a full QoS management architecture
Copyright © 2000, Cisco Systems, Inc. 4
Quality of Service
Classification
and Marking
Quality of Service
Classification
and Marking
© 2000, Cisco Systems, Inc. www.cisco.com econ_0386_09_001.ppt
Copyright © 2000, Cisco Systems, Inc. 5
© 2000, Cisco Systems, Inc. www.cisco.com econ_0386_09_010.ppt
Keep All Graphics Inside This Box
Objectives
Objectives
Upon completion of this module section, you will
be able to perform the following tasks:
• Describe the purpose of classification and marking
• Explain IP Precedence and Diff-Serv
• Describe QoS policy using Modular QoSCLI
• Explain Network Based Application Recognition
(NBAR)
• Describe forms of packet, frame, or cell marking
The purpose of the lesson is to quickly survey the new Classification and Marking
features in Cisco IOS 12.1, and to describe the problems they solve.
Copyright © 2000, Cisco Systems, Inc. 6
© 2000, Cisco Systems, Inc. www.cisco.com econ_0386_09_010.ppt
Keep All Graphics Inside This Box
Enterprise QoS
Enterprise QoS

30 Kbps
300 Kbps
• Remote site has a 350 Kbps CIR FR link
• Bursty applications contending for bandwidth
reduce collective throughput. Customer needs
better throughput
• What can we do to improve things?
These are charts from Ganymede Chariot used in a lab based on FIFO (no
queuing). TCP traffic was going all over the chart. With nothing controlling the
traffic, throughput is horrible and completely unpredictable!
With Traffic Shaping, Frame Relay DE bit setting, Class-Based Weighted Fair
Queuing (CBWFQ), and Weighted Random Early Detection (WRED) enabled, the
network is much more well behaved.
We’ll discuss CBWFQ and WRED in the Queuing module.
In this section we’ll look at techniques for Classification and Marking. These are
the beginning of solving the example customer’s problem.
Classification and Marking do not in themselves solve the customer problem. They
do however allow us to apply queuing and shaping techniques, both in the edge
router doing the classification and marking, and in the downstream routers in the
network.
Classification and Marking will be further defined in the following slides.
Terminology:
CIR Committed Information Rate
Copyright © 2000, Cisco Systems, Inc. 7
© 2000, Cisco Systems, Inc. www.cisco.com econ_0386_09_010.ppt
Keep All Graphics Inside This Box
Internet
Classification and marking of packets at the
edge of the network makes the packets
accessible to QoS handling within the network

Classification and marking of packets at the
edge of the network makes the packets
accessible to QoS handling within the network
Network Management
Classifying and Marking
Classifying and Marking
In order for QoS methods to be used within the network, traffic must be classified
into higher and lower priorities. Each classification must then be marked so the
network knows which QoS methods to apply. This process is completed at the
ingress points to the network. Queuing and shaping methods can then be applied
throughout the network.
The Classification and Marking work is usually done at the edge of the network
where speeds are lower. This is because it can be more CPU and memory intense.
In general, at the edge we can use relatively complex access lists, flows, and other
techniques to recognize traffic. In the network core, where speeds are higher, we
keep things simpler, by using marked packets (simpler lookups) and Classes of
Service (several major categories of traffics rather than per-application or per-flow
handling).
Copyright © 2000, Cisco Systems, Inc. 8
© 2000, Cisco Systems, Inc. www.cisco.com econ_0386_09_010.ppt
Keep All Graphics Inside This Box
Classification
What Is it?
Classification
What Is it?
Classification is...
• The QoS feature component that recognizes
and distinguishes among different packet
streams
• The most fundamental QoS building block

Without classification, all packets will be
treated the same
Classification entails using a traffic descriptor to categorize a packet within a
specific group to define that packet and make it accessible for QoS handling on the
network. Using packet classification, you can partition network traffic into
multiple priority levels or classes of service. When traffic descriptors are used to
classify traffic, the source agrees to adhere to the contracted terms and the network
promises a quality of service. Traffic policers, such as Committed Access Rate's
(CARs) rate-limiting feature, and traffic shapers, such as Frame Relay Traffic
Shaping (FRTS) and Generic Traffic Shaping (GTS), use a packet's traffic
descriptor—that is, its classification—to ensure adherence to the contract.
Packet classification is pivotal to policy techniques that select packets traversing a
network element or a particular interface for different types ofQoS service. For
example, you can use classification to mark certain packets for IP Precedence and
you can identify others as belonging to a Resource Reservation Protocol (RSVP)
flow.
Methods of classification were once limited to use of the contents of the packet
header. Today's methods of marking a packet with its classification allow you to
set information in the Layer 2, 3, or 4 headers, or even to set information within
the packet's payload. Criteria for classification of a group might be as broad as
“traffic destined for subnetwork X” or as narrow as a single flow.
Copyright © 2000, Cisco Systems, Inc. 9
© 2000, Cisco Systems, Inc. www.cisco.com econ_0386_09_010.ppt
Keep All Graphics Inside This Box
Marking
What is it?
Marking
What is it?
Marking is…
• The QoS feature component that “colors” a

packet so that it can be identified and
distinguished among other packets in QoS
treatment:
–Differentiated Services Code Point (DSCP)
–IP Precedence
–QoS-Group
–802.1p
Packets entering the network may have been marked previously. If this marking is
from a trusted source, then classification may be based on the previous mark. If the
marking is not from a trusted source, then classification may be used to determine
what the new marking should be.
Marking can occur at Layer 2 or Layer 3, however many QoS features are based on
the IP Precedence bit or DSCP settings. There are methods of marking that will
map Layer 2 Class of Service (CoS) bits to Layer 3 IP Precedence or DSCP
settings.
A QoS-group is internal to a router. It allows us to virtually mark packets as they
come into a router, then use that virtual marking for outbound policy. The biggest
advantage to virtual marking is that it does not alter the traffic passing through the
router.
Copyright © 2000, Cisco Systems, Inc. 10
© 2000, Cisco Systems, Inc. www.cisco.com econ_0386_09_010.ppt
Keep All Graphics Inside This Box
Topics
Topics
Modular CLI for QoS
Classification
Marking
Copyright © 2000, Cisco Systems, Inc. 11
© 2000, Cisco Systems, Inc. www.cisco.com econ_0386_09_010.ppt
Keep All Graphics Inside This Box

What Is Modular QoS CLI
(MQC)?
What Is Modular QoS CLI
(MQC)?
Modular QoS CLI (MQC):
• Is how you configure QoS policy
• Separates the definition of classes from the
application of QoS mechanisms
MQC is template-based:
• Reduces configuration
• Configure policy, not “raw” per-interface
commands
Modular QoS CLI (MQC) is available across all main Cisco IOS-based platforms,
initially with Cisco IOS Release 12.0(5)T. MQC is a new feature, a new, more
advanced way of configuring QoS.
In the next few slides we will look briefly at MQC.
Copyright © 2000, Cisco Systems, Inc. 12
© 2000, Cisco Systems, Inc. www.cisco.com econ_0386_09_010.ppt
Keep All Graphics Inside This Box
Modular QoS CLI
Modular QoS CLI
Class maps:
• Access lists, input interface, protocol
• Class-default
Policy maps:
• Bandwidth, random-detect, queue-limit
Service maps:
• Input, output, applied at interface
The MQC allows users to specify a traffic class independently ofQoS policies.
The class-map command is used to define a traffic class. A traffic class contains three major

elements: a name, a series of match commands, and an instructionon how to evaluate these
match commands. The traffic class is named in the class-mapcommand line; for instance, if
you enter the class-map don command while configuring the traffic class in the command-
line interface, the traffic class would be named don.
The policy-mapcommand is used to associate a traffic class, which was defined by the
class-map command, with one or more QoS policies. The result of this association is called
a service policy. A service policy contains three elements: a name, a traffic class (specified
with the class command), and the QoS policies. The purpose of the service policy is to
associate a traffic class with one or more QoS policies. The name of a service policy is
specified in the policy-mapcommand-line interface (for example, issuing the policy-map
gary command would create a service policy named gary).
The service-policy command is used to attach the service policy, as specified with the
policy-mapcommand, to an interface. Because the elements of the service policy can be
applied to packets entering and leaving the interface, users are required to specify whether
the service policy characteristics should be applied to incoming or outgoing packets. For
instance, the service-policy output gary command would attach all the characteristics of
the service policy named gary to the specified interface. All packets leaving the specified
interface are evaluated according to the criteria specified in the service policy named gary.
/>Copyright © 2000, Cisco Systems, Inc. 13
© 2000, Cisco Systems, Inc. www.cisco.com econ_0386_09_010.ppt
Keep All Graphics Inside This Box
Topics
Topics
Modular QoS CLI
Classification
Marking
We will now look at the tools for recognizing certain types of traffic, or
classification.
Copyright © 2000, Cisco Systems, Inc. 14
© 2000, Cisco Systems, Inc. www.cisco.com econ_0386_09_010.ppt

Keep All Graphics Inside This Box
Classification through
Modular QoS CLI
Classification through
Modular QoS CLI
match input-interface
match source-address
(MAC)
match destination-
address (MAC)
match access-group
match ip dscp/prec
match qos-group
match protocol (NBAR)
match mpls experimental
match any
match not …..
Using MQC, various match criteria may be used to define a class of service. This is
classification.
• class-map match-all class-name: specifies a logical AND operator for all matching
statements under this traffic class. When neither match-all nor match-any is
specified, the default is match-all.
• class-map match-any class-name: specifies a logical OR operator for all matching
statements under this traffic class.
• match input-interface interface-name: specifies the name of the input interface used
as a match criterion against which packets are checked to determine if they belong to
the class.
• match source-address mac address: specifies the name of the source MAC address
used as a match criterion against which packets are checked to determine if they
belong to the class.

• match destination-address mac address: specifies the name of the destination MAC
address used as a match criterion against which packets are checked to determine if
they belong to the class.
• match access-group access-list-number: specifies the numbered access list against
whose contents packets are checked to determine if they belong to the class.
• match ip dscp number: specifies up to eight differentiated services code point
(DSCP) values used as match criteria. The value of each service code point is from 0
to 63.
• match ip precedence number: specifies up to eight IP precedence values used as
match criteria.
Copyright © 2000, Cisco Systems, Inc. 15
© 2000, Cisco Systems, Inc. www.cisco.com econ_0386_09_010.ppt
Keep All Graphics Inside This Box
Hidden slide for notes. Do not delete.
Classification through
Modular QoS CLI
Classification through
Modular QoS CLI
Using MQC, various match criteria may be used to define a class of service. This is
classification (continued).
• match qos-group number: specifies the number of the QoS group index used as a
match criterion against which packets are checked to determine if they belong to the
class.
• match protocol protocol: specifies the name of the protocol used as a match criterion
against which packets are checked to determine if they belong to the class.
• match class-map class-name: specifies the name of a traffic class to be used as a
matching criterion (for nesting traffic class [nested class maps] within one another).
• match any: specifies that all packets will be matched.
• match not match-criteria: specifies a match criterion value that prevents packets
from being classified as members of a specified traffic class. All other values of that

particular match criterion belong to the class.
/>d121129
Copyright © 2000, Cisco Systems, Inc. 16
© 2000, Cisco Systems, Inc. www.cisco.com econ_0386_09_010.ppt
Keep All Graphics Inside This Box
Network Based Application
Recognition (NBAR)
Network Based Application
Recognition (NBAR)
Mark Citrix sub-applications as
GOLD service and police FTP
Guarantee bandwidth for Citrix!
19200 bps / user
My application
is too slow!
• Protocol Discovery analyzes
application traffic patterns in
real time
• NBAR classifies network traffic
using application information
• Enables downstream actions
based on QoS policies through
random early detection, class-
based queuing, and policing
• New applications easily
supported by loading Packet
Description Language Modules
Available now on
7100 and 7200
routers

2600, 3600 and 7500 support in
2nd half of CY2000
Link Utilization
Napster 25%
Netshow 15%
Oracle 10%
FTP 30%
HTTP 20%
In some networks critical applications do not get the bandwidth they need. Rather than throwing
bandwidth at the problem (increasing bandwidth in the hope it solves the problem), you can use
existing bandwidth more efficiently.
NBAR can determine the mix of traffic on the network and isolate the problem. In the case shown
in the slide, too much point-cast traffic is overloading the link.
NBAR Capabilities:
A new IP packet classifier capable of classifying…
• Those Layer 4 to Layer 7 protocols which dynamically assign TCP/UDP ports
• HTTP (Web) traffic by URL or MIME (Multipurpose Internet Mail Extension) type using
regular expressions (*, ?, [ ])
• “Sub-port” criteria such as transaction types
NBAR classification is used by QoS features:
• Guarantee minimum bandwidth (CBWFQ)
• Control congestion differentially (WRED)
• Enforce a maximum bandwidth usage (Policing)
• Set IP Precedence/DSCP values
NBAR is supported on Cisco 7100 and 7200 routers starting with Cisco IOS Release 12.0(5)XE2.
/>Copyright © 2000, Cisco Systems, Inc. 17
© 2000, Cisco Systems, Inc. www.cisco.com econ_0386_09_010.ppt
Keep All Graphics Inside This Box
Applications Supported by
NBAR

Applications Supported by
NBAR
Statefully Inspected
Protocols
FTP
Exchange
HTTP
(URL and MIME)
Netshow
Realaudio
r-commands
Oracle SQL*NET
SunRPC
TFTP
StreamWorks
VDOLive
Static Protocols
EGP
GRE
ICMP
IPINIP
IPSec
EIGRP
BGP
CU-SeeMe
DHCP/BOOTP
DNS
Finger
Gopher
HTTP

HTTPS
IMAP
IRC
Kerberos
L2TP
LDAP
MS-PPTP
MS-SQLServer
NetBIOS
NFS
NNTP
Notes
NTP
PCAnywhere
POP3
PPTP
RIP
RSVP
SFTP
SHTTP
SIMAP
SIRC
SLDAP
SNNTP
SMTP
SNMP
SOCKS
SPOP3
SSH
STELNET

Syslog
Telnet
X Windows
The real win with NBAR is simpler configuration coupled withstateful recognition
of flows. The simpler configuration means you don’t have to do a protocol analyser
capture to figure out ports and so on. Stateful recognition means smarter deeper
packet recognition.
NBAR can classify application traffic by looking beyond the TCP/UDP port
numbers of a packet. This is sub-port classification. NBAR looks into the
TCP/UDP payload itself and classifies packets on content within the payload such
as transaction identifier, message type, or other similar data.
Classification of HTTP by URL or MIME type is an example of subport
classification. NBAR classifies HTTP traffic by text within the URL using regular
expression matching. NBAR uses the UNIX filename specification as the basis for
the URL specification format. The NBAR engine then converts the specification
format into a regular expression.
NBAR recognizes HTTP GET packet(s) containing the URL and classifies all
packets that are sent to the source of the HTTP GET request.
Memory Management:
NBAR uses approximately 150 bytes of DRAM for each flow that requires stateful
inspection. When NBAR is configured, it allocates 1 MB of DRAM to support up
to 5000 concurrent flows. NBAR determines if it needs more memory to handle
additional concurrent stateful flows. If such a need is detected, NBAR expands its
memory usage in increments of 200 KB to 400 KB.
Copyright © 2000, Cisco Systems, Inc. 18
© 2000, Cisco Systems, Inc. www.cisco.com econ_0386_09_010.ppt
Keep All Graphics Inside This Box
Packet Description Language
Module (PDLM)
Packet Description Language

Module (PDLM)
• PDLMs define applications that are
recognizable by NBAR
• New applications easily supported by adding
new PDLMs
• No Cisco IOS software upgrade or reboot
required when adding new PDLMs
• PDLMs must be produced by Cisco
engineers
NBAR addresses IP QoS classification requirements by classifying application-
level protocols so that QoS policies can be applied to the classified traffic. NBAR
addresses the ongoing need to extend the classification engine for the many
existing and emerging application protocols by providing an extensible Packet
Description Language (PDL). NBAR can determine which protocols and
applications are currently running on a network so that an appropriate QoS policy
can be created based upon the current traffic mix and application requirements.
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 allow NBAR to recognize new protocols without
requiring a new Cisco IOS image or a router reload.
New PDLMs will only be released by Cisco and can be loaded from flash memory.
To extend or enhance the list of protocols recognized by NBAR through a Cisco-
provided PDLM, use the ip nbar pdlmconfiguration command. Use the no form
of this command to unload a PDLM if it was previously loaded.
/>xtocid45828
Copyright © 2000, Cisco Systems, Inc. 19
© 2000, Cisco Systems, Inc. www.cisco.com econ_0386_09_010.ppt
Keep All Graphics Inside This Box
NBAR Protocol Discovery
NBAR Protocol Discovery

Discovers what traffic is
running on the network
Provides per-interface, per-
protocol,bidirectionalstatistics:
Packet and byte counts
Bit rates
How much bandwidth
should I guarantee to my
mission-critical applications?
Are there any non mission-critical
applications I should police?
So that QoS policies can be developed and applied, NBAR includes a Protocol
Discovery feature that provides an easy way to discover application protocols
transiting an interface. The Protocol Discovery feature discovers any protocol
traffic supported by NBAR. Protocol Discovery may be applied to interfaces and
can be used to monitor both input and output traffic. Protocol Discovery maintains
the following per-protocol statistics for enabled interfaces: total number of input
and output packets and bytes, and input and output bit rates.
Preliminary performance data: T3 with an average number of flows resulted in
18 % CPU load, some sensitivity to the number of flows. The comment from a
TME in class was that this is probably not something you do in a Service Provider
core.
Copyright © 2000, Cisco Systems, Inc. 20
© 2000, Cisco Systems, Inc. www.cisco.com econ_0386_09_010.ppt
Keep All Graphics Inside This Box
Topics
Topics
Modular QoS CLI
Classification
Marking

We will now take a look at marking.
Copyright © 2000, Cisco Systems, Inc. 21
© 2000, Cisco Systems, Inc. www.cisco.com econ_0386_09_010.ppt
Keep All Graphics Inside This Box
Packet Marking
Packet Marking
Layer 3
• IP Precedence
• Diff-Serv (DSCP)
Layer 2
• ATM CLP bit marking
• FR DE bits
• MPLS EXP bits
• Ethernet 802.1P
Marking and VPNs
The discussion of marking starts with IP Precedence and Diff-Serv (DSCP), then
goes briefly into related Layer 2 features. We will finish with VPN tunnel-related
preservation of markings already on packets.
Copyright © 2000, Cisco Systems, Inc. 22
© 2000, Cisco Systems, Inc. www.cisco.com econ_0386_09_010.ppt
Keep All Graphics Inside This Box
Version
Length
ToS
1 Byte
Len
Standard IPV4: Three MSB Called IP Precedence
(Diff-ServWill Use 6 DS Bits Plus 2 for Flow Control)
Layer 3
IPV4

ID offset TTL Proto FCS IP-SA IP-DA Data
PREAM. SFD DA SA
TAG
4 Bytes
PT DATA FCS
3 bits used for CoS
(User Priority)
Layer 2
802.1Q/p
Data
Packet
Traffic Differentiation Mechanisms
IP Precedence and 802.1p
Traffic Differentiation Mechanisms
IP Precedence and 802.1p
• Layer 2 mechanisms are not assured end-to-end
• Layer 3 mechanisms provide end-to-end classification
Layer 2 marking sets bits or alters the header of the frame. This is for possible use
by LAN switches and other Layer 2 devices. The frame in the slide shows a Layer
2 802.1Q (and 802.1P) header, with extra space to hold a tag with priority
information embedded in it.
The slide also shows the Layer 3 IP header, with 3 IP Precedence bits in the Type
of Service (ToS) field . The newer Diff-Serv specification (DSCP) uses instead 6
of the ToS bits, plus the other two bits for flow control.
Although Layer 3 mechanisms provide end-to-end classification, they are not
recognized by switches, hence the need for additional Layer 2 mechanisms to
provide continuous quality of service into the LAN segments.
The Layer 2 mechanisms only provide for drop priority if queues begin reaching
predefined thresholds. The Layer 2 CoS bits can, however, be mapped to Layer 3
DSCP or IP Precedence values at the first Layer 3 device the packet hits in the

network.
Copyright © 2000, Cisco Systems, Inc. 23
© 2000, Cisco Systems, Inc. www.cisco.com econ_0386_09_010.ppt
Keep All Graphics Inside This Box
IP Precedence
IP Precedence
Number Name
0 routine
1 priority
2 immediate
3 flash
4 flash-override
5 critical
6 internet – reserved
7 network – reserved
IP Precedence marks packets
into six classes (two reserved):
IP Precedence is used to determine the weight
for QoS policy, for example for WFQ, WRED
7500
PBX
Server
7200
8500
3600
Handset
8500
Server
GSR
IP is normally thought of as being a “best effort” only protocol. But IP has always

had a mechanism for supporting differentiated services. The IP Type of Service
(ToS) field, and the IP Precedence bits provide this capability. Because the
majority of applications today are IP-based, why not leverage IP for end-to-end
QoS policy signaling?
IP Precedence takes advantage of in-band signaling. The ToS field can be used to
bind business policies into network behavior.
IP Precedence utilizes the three precedence bits in the IP header ToS field to
specify class of service for each packet. You can partition traffic in up to six
classes of service using IP Precedence (two others are reserved for internal
network use). The queuing technologies throughout the network can then use this
signal to provide the appropriate expedited handling.
IP Precedence enables service classes to be established using existing network
queuing mechanisms with no changes to existing applications and with no
complicated network requirements. And, this same approach is easily extended to
the next generation of IP, IP version 6, using its Priority field.
For historical reasons, each precedence corresponds to a name. These names,
which continue to evolve, are defined in the RFC 791 document.
Currently Cisco is using precedence 5 for voice traffic, and 4 down to 0 for
prioritized applications. The higher the precedence, the more quickly the packet
should get sent across the network.
Copyright © 2000, Cisco Systems, Inc. 24
© 2000, Cisco Systems, Inc. www.cisco.com econ_0386_09_010.ppt
Keep All Graphics Inside This Box
DSCP CU
DS field
DSCP
DSCP
DS field is the ex-ToS Field for IPv4 (RFC 791) and
Traffic Class octet for IPv6
• There is a DS field in header of every IPv4 and IPv6 packet

DSCP is the field identifying what treatment the packet
should receive
• DSCP : Differentiated Service Code Point, 6 bits
• CU: Currently Unused, 2 bits
The Internet Engineering Task Force (IETF) defines the six most significant bits of
the 1-byte ToS field as the Differentiated Services Code Point, DSCP. The priority
represented by a particular DSCP value is configurable. DSCP values range from 0
to 63.
The slide shows the breakout of the DSCP field. Six bits are used for the
Differentiated Service Code Point, and 2 bits are currently unused.
Layer 3 IP packets can carry either an IP Precedence value or a DSCP value. MQC
supports the use of either value in set and match commands. The recommended
settings of the DSCP field are backwards-compatible with IP precedence (see the
following material).
RFC2474, Definition of the Differentiated Services Field (DS Field) in the IPv4
and IPv6 Headers, Dec 98
/>Copyright © 2000, Cisco Systems, Inc. 25
© 2000, Cisco Systems, Inc. www.cisco.com econ_0386_09_010.ppt
Keep All Graphics Inside This Box
Cisco’s Diff-Serv
Implementation
Cisco’s Diff-Serv
Implementation
Until recently…
• ToS = Pre-Diff-Serv
implementation (IP Precedence),
not compliant with DS-byte
encoding (RFC2474)
• Compliant with:
– Diff-Serv Architecture (RFC

2475)
– Default forwarding, class
selectors, assured
forwarding, expedited
forwarding
• Now compliant if use
DSCP
Data
IP Precedence
Type of Service (ToS)
Diff-Serv Code Point (DSCP)
Data, Voice, Video
Until recently, Cisco IOS software only really supported IP Precedence, because it
represented a pre-Diff-Serv implementation. This followed the general Diff-Serv
architecture (RFC 2475) in terms of behavior, but the actual Diff-Serv byte
encoding was really a special use, namely using the 3-bit Precedence bit encoding
and not really using all 6 Diff-Serv bits.
/>