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Foundation Summary 405

Foundation Summary

The “Foundation Summary” is a collection of tables and ﬁgures that provide a convenient review of many key concepts in this chapter. For those of you already comfortable with the topics in this chapter, this summary could help you recall a few details. For those of you who just read this chapter, this review should help solidify some key facts. For any of you doing your ﬁnal prep before the exam, these tables and ﬁgures are a convenient way to review the day before the exam.

ISPs make the business choice of whether to police, and how aggressively to police. The options reduce to the following three basic options:

•Do not police. To support the trafﬁc, build the network to support the trafﬁc as if all customers will send and receive data at the clock rate of the access link. From a sales perspective, close deals by claiming that no policing will be done, but encourage customers who exceed their contracts to pay for more bandwidth.

•Police at the contracted rate. To support these trafﬁc levels, the network only needs to be built to support the collective contracted rates, although the core would be overbuilt to support new customers. From a sales perspective, encourage customers that are beginning to exceed their contracts to upgrade, and give incentives.

•Police somewhere in between the contracted rate and the access-link clock rate. For instance, ISP1 might police PB Tents at 5 Mbps, when the contract reads 2 Mbps. The network can be built to support the collective policed rates. The sales team can encourage customers to buy a larger contracted rate when they consistently exceed the contracted rate, but keep customer satisfaction higher by pointing out their generosity by only policing at rates much higher than the contracted rates.

Figure 5-24 points out two cases of egress blocking, using a Frame Relay network as an example.

Figure 5-24 PB Tents Network, Egress Blocking

All VCs 64 kbps CIR

Cumulative Traffic Can Be

24 * 128 kbps = 3.0 Mbps

AR 128 kbps

Main

AR 128 kbps

FRS1

FRS2

AR 1.5 Mbps

FRS3

AR 128 kbps

Speed Mismatch Between Main (1.5 Mbps)

R24

and R24 Access Rate (128 kbps) Causes Blocking

406 Chapter 5: Traffic Policing and Shaping

Table 5-27 summarizes some of the key points about when and where you should consider using policing and shaping.

Table 5-27 Policing and Shaping: When to Use Them, and Where

Topic	Rationale

Why police?	If a neighboring network can send more trafﬁc than the trafﬁc contract speciﬁes,
	policing can be used to enforce the contract, protecting the network from being
	overrun with too much trafﬁc.

Where to police?	Typically, policing is performed as packets enter the ﬁrst device in a network.
	Egress policing is also supported, although it is less typical.

Why shape?	The ﬁrst of two reasons for shaping is when the neighboring network is policing.
	Instead of waiting for the neighboring policer to discard trafﬁc, a shaper can
	instead delay trafﬁc so that it will not be dropped.
	The second reason has to do with the effects of egress blocking. By shaping,
	egress blocking can be avoided, or minimized, essentially moving the queues
	from inside the service provider cloud, and back into the enterprise routers. By
	doing so, the router queuing tools can selectively give better QoS performance to
	particular types of trafﬁc.

Where to shape?	Shaping is always an egress function. Typically, shaping is performed on packets
	exiting a router, going into another network. This may be the edge between a
	router and a multiaccess WAN, or possibly just a link to an ISP.

Trafﬁc shaping implements this basic logic by deﬁning a measurement interval, and a number of bits that can be sent in that interval, so that the overall shaped rate is not exceeded. Table 5-28 lists some related deﬁnitions.

Table 5-28 Shaping Terminology

Term	Deﬁnition

Tc	Time interval, measured in milliseconds, over which the committed burst (Bc) can be
	sent. With many shaping tools, Tc = Bc/CIR.

Bc	Committed burst size, measured in bits. This is the amount of trafﬁc that can be sent
	over the interval Tc. Typically also deﬁned in the trafﬁc contract.

CIR	Committed information rate, in bits per second, deﬁnes the rate deﬁned in the trafﬁc
	contract.

Shaped Rate	The rate, in bits per second, to which a particular conﬁguration wants to shape the
	trafﬁc. In some cases, the shaped rate is set to the same value as CIR; in others,
	the shaped rate is set to a larger value, with the hope of sending more trafﬁc through
	the network.

Be	Excess burst size, in bits. This is the number of bits beyond Bc that can be sent after a
	period of inactivity.

Foundation Summary 407

The formulas IOS uses to calculate Tc when you conﬁgure both the shaping rate and the Bc are as follows:

Tc = Bc/CIR

Tc = Bc/Shaped rate

Figure 5-25 lists the overall process used by shaping, in terms of Tc, Bc, and Be.

Figure 5-25 Bc and Be, After a Period of Inactivity (Both Buckets Full)

			Bc = 8000, Be = 0
			Send 16,000 bits in each
	Bc = 8000, Be = 8000		Send 16,000 bits in each
	Bc = 8000, Be = 8000		interval, until Be can
	Send 16,000 bits in first interval		interval, until Be can
	Send 16,000 bits in first interval		accumulate
			accumulate

Period of inactivity — Be re-fills in 1 single totally dormant Tc

Sending Rate

128 kbps

0 kbps

0 125 250 375 500 625 750 875 1000 Time

(Ms)

In summary, most QoS policies call for shaping on each VC. The number of VCs, and how they are conﬁgured, dictates where the shaping tool needs to be enabled. Table 5-29 summarizes the options.

Table 5-29 Options of How to Enable Shaping for per-VC Shaping

Location	Requirements for Shaping per VC

No VCs	Shape on the main interface. Shaping occurs for all
	trafﬁc on interface.

Physical interface, 1 VC, no subinterfaces	Shaping shapes the individual VC associated with this
	interface. Shaping is enabled on the physical interface.

Physical interface, 1 VC, 1 subinterface	Shaping shapes the individual VC associated with this
	interface. Shaping can be enabled on the physical
	interface, the subinterface, or the VC (DLCI).

continues

408 Chapter 5: Traffic Policing and Shaping

Table 5-29 Options of How to Enable Shaping for per-VC Shaping (Continued)

Location	Requirements for Shaping per VC

Multiple VCs on 1 interface, point-to-point	Shaping can be enabled on the subinterface, or per
subinterfaces only	DLCI. Both methods work identically.

Multiple VCs on 1 interface, some	Must enable shaping on each DLCI to shape per VC.
multipoint subinterfaces with > 1 VC per
subinterface

Table 5-30 lists the trafﬁc-shaping tools, and the queuing tools supported by each for the shaping queues.

Table 5-30 Options for Queuing in Trafﬁc-Shaping Tools

Shaping Tool	Queuing Tools Supported for the Shaping Queue(s)

GTS	WFQ

CB shaping	FIFO, WFQ, CBWFQ, LLQ

DTS	FIFO, WFQ, CBWFQ, LLQ

FRTS	FIFO, WFQ, CBWFQ, LLQ, PQ, CQ,

When a shaper uses a queuing tool, instead of having a single shaping queue, multiple shaping queues exist. If FRTS were conﬁgured to use PQ, for example, up to four queues could be created for shaping. Figure 5-26 shows the basic idea, with shaping enabled on the physical interface, FIFO Queuing on the physical interface, and PQ conﬁgured for the shaping queue.

Figure 5-26 FIFO Queuing for the Physical Interface, Plus PQ for the Shaping Queue

Shaping Queues for a Single VC

PQ High –

Shaping Queue

PQ Medium –

Shaping Queue

PQ Normal –

Shaping Queue

	Bit Rate	Interface
	Limit		TX Ring
	x bps	Output Queue
			AR 128 kbps
	Down
Slow

Shape to PQ Low – 96 kbps Shaping Queue

Foundation Summary 409

Many QoS designs call for shaping per VC. For the same router, with two 64-kbps CIR VCs (each conﬁgured on a separate point-to-point subinterface) shaping queues are created for each subinterface, with the familiar output queues as well. Figure 5-27 depicts the overall idea.

Figure 5-27 Fancy Queuing for the Physical Interface as well as for Two Sets of Shaping Queues

Shaping Queues for Subinterface 1

Bit Rate

Limit

Subint #1

x bps

Shaping Queue1

Slow

Down

Subint #1

Shaping Queue2

Shape

96 kbps

Shaping Queues for Subinterface 2

Bit Rate

Limit

Subint #2

Shaping Queue1

x bps

Slow

Down

Subint #2

Shaping Queue2

Shape to

64 kbps

Interface

Output

Queue#1

	TX Ring
	TX Ring	AR 128 kbps
Interface
Interface
Output
Output
Queue#2

One goal of policing when Be is being used is to discard some packets, hoping to avoid the point where all packets are discarded. Figure 5-28 shows the general idea of how policers accomplish that goal, using Da and Dc values.

Figure 5-28 Actual Debt and Compounded Debt with Policing

Point at Which Dc Caused Single

Packet Drop When Dc > Be Point at Which Be Has Been

Consumed; All Packets Dropped

Dc	Da

Tables 5-31 and 5-32 list the conﬁguration and show commands pertinent to GTS.

410 Chapter 5: Traffic Policing and Shaping

Table 5-31 Command Reference for Generic Trafﬁc Shaping

	Command	Mode and Function

	trafﬁc-shape rate bit-rate [burst-size	Interface conﬁguration mode; enables GTS for a shaped
	[excess-burst-size]]	rate, with optional Bc and Be settings, in bits

	trafﬁc-shape group access-list bit-rate	Interface conﬁguration mode; enables GTS for a shaped
	[burst-size [excess-burst-size]]	rate, only for trafﬁc permitted by the referenced ACL, with
		optional Bc and Be settings, in bits

	trafﬁc-shape adaptive bit-rate	Interface conﬁguration mode; enables adaptive shaping,
		and sets the minimum shaped rate

	trafﬁc-shape fecn-adapt	Interface conﬁguration mode; enables the reﬂection of
		BECN signals upon receipt of an FECN

Table 5-32 Exec Command Reference for Generic Trafﬁc Shaping

	Command	Function

	show trafﬁc-shape [interface-type	Lists information about the conﬁguration details
	interface-number]

	show trafﬁc-shape queue [interface-	Lists statistics about the queuing tool used on the shaping
	number [dlci dlci-number]]	queue

	show trafﬁc-shape statistics [interface-	Lists statistics about shaping operation
	type interface-number]

Tables 5-33 and 5-34 list the conﬁguration and show commands pertinent to CB shaping.

Table 5-33 Command Reference for Class-Based Shaping

Command	Mode and Function

shape [average \| peak] mean-rate [[burst-	Policy-map class conﬁguration mode; enables shaping
size] [excess-burst-size]]	for the class, setting the shaping rate, and optionally
	Bc and Be. The average option causes shaping as nor-
	mal; the peak option causes Bc + Be to be sent per Tc.

Shape adaptive min-rate	Policy-map class conﬁguration mode; enables the
	minimum rate for adaptive shaping. The maximum
	rate is conﬁgured with the shape average or shape
	peak command.

Shape fecn-adapt	Policy-map class conﬁguration mode; enables
	reﬂection of BECN signals upon receipt of an FECN.

service-policy {input \| output} policy-map-	Interface or subinterface conﬁguration mode; enables
name	CB shaping on the interface.

Foundation Summary 411

Table 5-33 Command Reference for Class-Based Shaping (Continued)

Command	Mode and Function

class-map class-map-name	Global conﬁg; names a class map, where classiﬁcation
	options are conﬁgured.

Match . . .	class-map subcommand; deﬁnes speciﬁc classiﬁcation
	parameters.

match access-group {access-group \| name	class-map subcommand; references either numbered
access-group-name}	or named ACL.

match source-address mac address	class-map subcommand; references the source MAC
	address that forwarded the packet to this router,
	typically the previous-hop router.

match ip precedence ip-precedence-value	class-map subcommand; references one or more IP
[ip-precedence-value ip-precedence-value ip-	precedence values. A packet with any of the listed
precedence-value]	values matches.

match mpls experimental number	class-map subcommand; references MPLS
	Experimental bits.

match cos cos-value [cos-value cos-value	class-map subcommand; references one or more class
cos-value]	of service (CoS) values. A packet with any of the listed
	values matches.

match destination-address mac address	class-map subcommand; references the destination
	MAC address of the device to which the packet will be
	forwarded next.

match input-interface interface-name	class-map subcommand; matches based on the inter-
	face in which the packet was received.

match ip dscp ip-dscp-value [ip-dscp-value	class-map subcommand; references one or more IP
ip-dscp-value ip-dscp-value ip-dscp-value ip-	DSCP values. A packet with any of the listed values
dscp-value ip-dscp-value ip-dscp-value]	matches.

match ip rtp starting-port-number port-	class-map subcommand; references a range of UDP
range	ports, only matching the even numbered ports, which
	carry voice payload.

match qos-group qos-group-value	class-map subcommand; matches based on QoS
	group.

match protocol protocol-name	class-map subcommand; matches based on NBAR-
	deﬁned protocol types.

match protocol citrix [app application-	class-map subcommand; matches based on NBAR-
name-string].	deﬁned Citrix application types.

match protocol http [url url-string \| host	class-map subcommand; matches based on NBAR-
hostname-string \| mime MIME-type]	discovered details inside the host name or URL string.

continues

412 Chapter 5: Traffic Policing and Shaping

Table 5-33 Command Reference for Class-Based Shaping (Continued)

	Command	Mode and Function

	match any	class-map subcommand; matches all packets.

	policy-map policy-map-name	Global conﬁg; names a policy, which is a set of actions
		to perform.

	class name	policy-map subcommand; identiﬁes which packets on
		which to perform some action by referring to the
		classiﬁcation logic in a class map.

Table 5-34 Exec Command Reference for Class-Based Shaping

	Command	Function

	show policy-map policy-map-name	Lists conﬁguration information about all MQC-based
		QoS tools

	show policy-map interface-spec [input \|	Lists statistical information about the behavior of all
	output] [class class-name]	MQC-based QoS tools

Tables 5-35 and 5-36 list the conﬁguration and show commands pertinent to FRTS.

Table 5-35 Command Reference for Frame Relay Trafﬁc Shaping

Command	Mode and Function

frame-relay trafﬁc-shaping	Interface subcommand; enables FRTS on the interface.

class name	Interface DLCI subcommand; enables a speciﬁc FRTS
	map class for the DLCI.

frame-relay class name	Interface or subinterface command; enables a speciﬁc
	FRTS map class for the interface or subinterface.

map-class frame-relay map-class-name	Global conﬁguration mode; names a map class, and
	places CLI into map-class conﬁguration mode

frame-relay priority-group list-number	Map-class conﬁguration mode; enables PQ for the
	shaping queues associated with this map class

frame-relay custom-queue-list list-number	Map-class conﬁguration mode; enables CQ for the
	shaping queues associated with this map class

frame-relay fair-queue	Map-class conﬁguration mode; enables WFQ for the
[congestive_discard_threshold	shaping queues associated with this map class
[number_dynamic_conversation_queues
[number_reservable_conversation_queues
[max_buffer_size_for_fair_queues]]]]

Foundation Summary 413

Table 5-35 Command Reference for Frame Relay Trafﬁc Shaping (Continued)

Command	Mode and Function

service-policy {input \| output} policy-map-	Map-class conﬁguration mode; enables LLQ or
name	CBWFQ on the shaping queues associated with the
	map class.

frame-relay trafﬁc-rate average [peak]	Map-class conﬁguration mode; sets the shaped rate,
	and the EIR*. Bc and Be are calculated from these,
	based on Tc of 125ms.

frame-relay bc {in \| out} bits	Map-class conﬁguration mode; sets the Bc value.
	Alternative conﬁguration option to frame-relay
	trafﬁc-rate.

frame-relay be {in \| out} bits	Map-class conﬁguration mode; sets the Be value.
	Alternative conﬁguration option to frame-relay
	trafﬁc-rate.

frame-relay cir {in \| out} bps	Map-class conﬁguration mode; sets the CIR value.
	Alternative conﬁguration option to frame-relay
	trafﬁc-rate.

frame-relay adaptive-shaping {becn \|	Map-class conﬁguration mode; enables adaptive
foresight}	shaping, specifying either BECN or Foresight for
	signaling.

frame-relay mincir {in \| out} bps	Map-class conﬁguration mode; sets the minimum CIR
	used for adaptive shaping.

frame-relay tc milliseconds	Map-class conﬁguration mode; for 0 CIR VCs, sets the
	Tc value.

frame-relay qos-autosense	Interface conﬁguration mode; uses ELMI to automati-
	cally discover CIR, Bc, and Be settings for each VC.

*EIR = excess information rate

Table 5-36 Exec Command Reference for Frame Relay Trafﬁc Shaping

Command	Function

show frame-relay pvc [interface interface]	Shows PVC statistics, including shaping statistics
[dlci]

show trafﬁc-shape [interface-type interface-	Shows information about FRTS conﬁguration per VC
number]

show trafﬁc-shape queue [interface-number	Shows information about the queuing tool used with
[dlci dlci-number]]	the shaping queue

show trafﬁc-shape statistics [interface-type	Shows trafﬁc-shaping statistics
interface-number]

414 Chapter 5: Traffic Policing and Shaping

Frame Relay fragmentation (FRF) can be used with FRTS. Figure 5-29 outlines the basic idea, with FRTS on two subinterfaces.

Figure 5-29 Interaction Between Shaping Queues and Frame Relay Fragmentation Queues

Shaping Queues for Subinterface 1

			Bit Rate
			Limit
	Subint #1		x bps
	Shaping Queue1	Slow	Down
			Down
	Subint #1
	Shaping Queue2
	Shaping Queue2		Shape	to
			96 kbps

Shaping Queues for Subinterface 2
			Bit Rate
			Bit Rate
	Subint #2		Limit
	Shaping Queue1		x bps
			x bps

		Slow	Down


	Subint #2
	Subint #2
	Shaping Queue2
	Shaping Queue2	Shape to


		64 kbps

Dual FIFO Interface Queues

Unfragmented

Frames; PQ-

Like Service

TX Ring

AR 128 kbps

Fragmented

Frames

Table 5-37 summaries the key points for comparison between the various trafﬁc-shaping tools.

Table 5-37 Comparison of Trafﬁc Shaping Tools: GTS, CB Shaping, DTS, and FRTS

Feature	GTS	CB Shaping	DTS	FRTS

Supports ATM, FR, HDLC, PPP, LAN	Yes	Yes	Yes	No
interfaces

Can be enabled on interfaces and	Yes	Yes	Yes	Yes
subinterfaces

Can be enabled per Frame Relay DLCI	No	No	No	Yes
to support per-VC shaping on multipoint
interfaces

Supports adaptive shaping	Yes	Yes	Yes	Yes

Supports concurrent FRF.12 Frame	No	No	No	Yes
Relay fragmentation

Queuing methods in shaping queue	WFQ	FIFO, WFQ,	FIFO, WFQ,	FIFO, WFQ,
		CBWFQ,	CBWFQ,	CBWFQ,
		LLQ	LLQ	LLQ, PQ, CQ

Concurrent queuing methods on	All	All	All	FIFO, FRF*
Physical interface

Foundation Summary 415

Table 5-37 Comparison of Trafﬁc Shaping Tools: GTS, CB Shaping, DTS, and FRTS (Continued)

Feature	GTS	CB Shaping	DTS	FRTS

Can be conﬁgured using MQC	No	Yes	Yes	No
commands

Can classify trafﬁc to shape a subset of	Yes	Yes	Yes	No
the trafﬁc on an interface/VC

Default Tc	Variable	125 ms	125 ms	125 ms

Distributes shaping processing to VIPs	No	No	Yes	No
in 7500 series routers

*The Cisco QoS course claims WFQ is supported on the physical interface. In addition, FRF is not technically a queuing tool, although its feature of using two queues does achieve the same effect.

Table 5-38 lists the matchable ﬁelds for classiﬁcation for CB policing and CAR.

Table 5-38 Classiﬁcation Fields Used by CAR and CB Policing

Field	Tool	Comments

Anything matched with an	CAR, CB policing	N/A
IP ACL

Source MAC Address	CAR, CB policing	CAR uses a special access-rate ACL; CB
		marking uses the match command.

IP Precedence	CAR, CB policing	CAR uses a special access-rate ACL speciﬁc to
		CAR; CB marking uses the match command;
		Both can match a subset of values.

MPLS Experimental	CAR, CB policing	CAR uses a special access-rate ACL speciﬁc to
		CAR; CB marking uses the match command.
		Both can match a subset of values.

IP DSCP	CAR, CB policing	Can check for multiple values using multiple
		match commands.

QoS Group	CAR, CB policing	The QoS Group ﬁeld is used to tag packets
		internal to a single router.

Class of Service (CoS)	CB policing	Checks incoming ISL/802.1P CoS bits. Can
		match multiple values.

Destination MAC Address	CB policing	N/A

Input interface	CB policing	N/A

continues

416 Chapter 5: Traffic Policing and Shaping

Table 5-38 Classiﬁcation Fields Used by CAR and CB Policing (Continued)

Field	Tool	Comments

RTP’s UDP port-number	CB policing	RTP uses even numbered UDP ports from
range		16384–32767 for voice payload. This matching
		option allows matching a subset of the port
		numbers, and it matches only the even-numbered
		ports.

NBAR protocol types	CB policing	Refer to the coverage in Chapter 3 for more
		details.

NBAR Citrix applications	CB policing	NBAR can recognize different types of Citrix
		applications; CB marking can use NBAR to
		classify based on these application types.

Host Name and URL string	CB policing	NBAR can match URL strings using regular
		expressions, including the host name. CB
		marking can use NBAR to match these strings
		for classiﬁcation.

Table 5-39 lists the various actions associated with CB policing and CAR.

Table 5-39 Policing Actions Used by CAR and CB Policing

			CB
Action Keyword	Meaning	CAR?	Policer?

drop	Discards the packet	Yes	Yes

transmit	Forwards the packet	Yes	Yes

set-prec-transmit	Forwards the packet after marking the IP precedence	Yes	Yes
	value.

set-qos-transmit	Forwards the packet after marking the QoS group	Yes	Yes

set-dscp-transmit	Forwards the packet after marking the IP DSCP value	Yes	Yes

set-mpls-exp-transmit	Forwards the packet after marking the MPLS	Yes	Yes
	Experimental bits

set-frde-transmit	Forwards the packet after marking the Frame Relay	No	Yes
	discard eligibility (DE) bit

set-clp-transmit	Forwards the packet after marking the ATM cell loss	No	Yes
	priority (CLP) bit

set-prec-continue	Marks the IP precedence value, and continues to the	Yes	No
	next nested (cascaded) CAR command

set-dscp-continue	Marks the QoS group, and continues to the next	Yes	No
	nested (cascaded) CAR command

Foundation Summary 417

Table 5-39 Policing Actions Used by CAR and CB Policing (Continued)

			CB
Action Keyword	Meaning	CAR?	Policer?

set-mpls-exp-continue	Marks the IP precedence value, and continues to the	Yes	No
	next nested (cascaded) CAR command

set-qos-continue	Marks the QoS group, and continues to the next	Yes	No
	nested (cascaded) CAR command

continue	Just continues to the next nested (cascaded) CAR	Yes	No
	command

Tables 5-40 and 5-41 list the CB policing conﬁguration and show commands, respectively.

Table 5-40 Command Reference for Class-Based Policing

Command	Mode and Function

police bps burst-normal burst-max	Policy-map class subcommand; enables policing for the
conform-action action exceed-action	class, setting the police rate, Bc, and Bc + Be values,
action [violate-action action]	and actions taken. Actions are drop, set-clp-transmit,
	set-dscp-transmit, set-prec-transmit, set-qos-
	transmit, transmit.

service-policy {input \| output} policy-	Interface or subinterface conﬁguration mode; enables
map-name	CB shaping on the interface.

class-map class-map-name	Global conﬁg; names a class map, where classiﬁcation
	options are conﬁgured.

Match …	Class-map subcommand; deﬁnes speciﬁc classiﬁcation
	parameters.

match access-group {access-group \| name	Access-control list (ACL).
access-group-name}

match source-address mac address-	Source MAC address.
destination

match ip precedence ip-precedence-value	IP precedence.
[ip-precedence-value ip-precedence-value
ip-precedence-value]

match mpls experimental number	MPLS Experimental.

match cos cos-value [cos-value cos-value	CoS.
cos-value]

match destination-address mac address	Destination MAC address.

match input-interface interface-name	Input interface.

continues

418 Chapter 5: Traffic Policing and Shaping

Table 5-40 Command Reference for Class-Based Policing (Continued)

	Command	Mode and Function

	match ip dscp ip-dscp-value [ip-dscp-	IP DSCP.
	value ip-dscp-value ip-dscp-value ip-dscp-
	value ip-dscp-value ip-dscp-value ip-dscp-
	value]

	match ip rtp starting-port-number port-	RTP’s UDP port-number range.
	range

	match qos-group qos-group-value	QoS group.

	match protocol protocol-name	NBAR protocol types.

	match protocol citrix [app application-	NBAR Citrix applications.
	name-string].

	match protocol http [url url-string \| host	Host name and URL string.
	hostname-string \| mime MIME-type]

	match any	All packets.

	policy-map policy-map-name	Global conﬁg; names a policy, which is a set of actions
		to perform.

	class name	policy-map subcommand; identiﬁes which packets on
		which to perform some action by referring to the
		classiﬁcation logic in a class map.

Table 5-41 Exec Command Reference for Class-Based Policing

	Command	Function

	show policy-map policy-map-name	Lists conﬁguration information about all MQC-based
		QoS tools

	show policy-map interface-spec [input \|	Lists statistical information about the behavior of all
	output] [class class-name]	MQC-based QoS tools

Tables 5-42 and 5-43 list the CAR conﬁguration and show commands, respectively.

		Foundation Summary 419

Table 5-42 Conﬁguration Command Reference for CAR

	Command	Mode and Function

	rate-limit {input \| output} [access-group	Interface mode; conﬁgures classiﬁcation, marking,
	[rate-limit] acl-index] bps burst-normal	policing, and enables CAR on the interface
	burst-max conform-action conform-action
	exceed-action exceed-action

	access-list rate-limit acl-index	Global mode; creates a CAR ACL, which can match IP
	{precedence \| mac-address \| exp mask	precedence, MAC addresses, and MPLS Experimental
	mask}	bits

	The remaining entries describe the possible actions in the rate-limit command:

	continue	Evaluates the next rate-limit command

	drop	Drops the packet

	set-dscp-continue	Sets the differentiated services code point (DSCP)
		(0 to 63) and evaluates the next rate-limit command.

	set-dscp-transmit	Sends the DSCP and transmits the packet

	set-mpls-exp-continue	Sets the MPLS Experimental bits (0 to 7) and evaluates
		the next rate-limit command

	set-mpls-exp-transmit	Sets the MPLS Experimental bits (0 to 7) and sends the
		packet

	set-prec-continue	Sets the IP precedence (0 to 7) and evaluates the next
		rate-limit command

	set-prec-transmit	Sets the IP precedence (0 to 7) and sends the packet.

	set-qos-continue	Sets the QoS group ID (1 to 99) and evaluates the next
		rate-limit command

	set-qos-transmit	Sets the QoS group ID (1 to 99) and sends the packet

	transmit	Sends the packet

Table 5-43 Exec Command Reference for CAR

	Command	Function

	show interfaces [interface-type interface-	Displays CAR statistics on the interface speciﬁed, or on
	number] rate-limit	all interfaces if the interface is not speciﬁed

	show access-lists rate-limit [acl-index]	Lists information about the conﬁguration of rate-limit
		ACLs

420 Chapter 5: Traffic Policing and Shaping

Table 5-44 summarizes the CAR features, comparing them with CB policing.

Table 5-44 CAR and CB Policing Features Compared

Feature	CB Policing	CAR

Allows conform and exceed action categories	Yes	Yes

Allows violate action category	Yes	No

Polices either all trafﬁc, or a subset through	Yes	Yes
classiﬁcation

Uses MQC for conﬁguration	Yes	No

Allows nested or cascaded policing logic	No	Yes

Can be enabled per subinterface	Yes	Yes

Can be enabled per DLCI on multipoint	No	No
subinterfaces

Can set ATM CLP bit	Yes	No

Can set FR DE bit	Yes	No

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