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Cisco Catalyst 6500 Series Switches

Quality of Service on Cisco Catalyst 6500

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INTRODUCTION

Picture a busy bank branch. The queue of customers lining up to see the tellers is very long. When you arrive at the bank branch, you are immediately recognized as one of the bank's valued customers. You are escorted to a separate queue for "special" customers away from the hustle and bustle of the long queue. In this special queue you get served by the teller immediately. As a special customer, you have just been given a preferential level of service that exceeds what the average customer receives.
Like in the bank example above, quality of service (QoS) in Cisco ® Catalyst ® 6500 Family line cards is a tool that is used to provide preferential service for select traffic as it transits the switch. Over time and with the advancements in hardware and software technology, a number of QoS tools have now become available. QoS in itself is not one feature, but a collection of features that when combined provide a powerful way to identify different classes of traffic, prioritize them, and then service that traffic ahead of other lower priority traffic entering and leaving the switch.
This document will attempt to provide a high level overview of the QoS features found on the Cisco Catalyst 6500. It will explain what the features are, how they work, and where in hardware they are performed.

WHERE IS QoS PERFORMED?

The Cisco Catalyst 6500 performs QoS on the supervisor and the line card. The supervisor contains a daughter card called the policy feature card (PFC). Although the PFC is primarily responsible for the hardware forwarding of packets, it also performs a number of important QoS tasks. Since the Cisco Catalyst 6500 was introduced in 1999, a number of PFC models aligned with specific supervisor models have been introduced. Typically the introduction of a new PFC coincides with the arrival of new QoS features. This is especially true of the PFC3, which when introduced with the Cisco Catalyst 6500 Series Supervisor Engine 720 in 2003 added a number of new QoS features not found in earlier PFC models.
The Cisco Catalyst 6500 line card is the other component that performs QoS, and those QoS features are primarily influenced by the port application-specific integrated circuit (ASIC). The level of QoS support on the line card is dependent on the functionality built into the line-card port ASIC. For this reason, the QoS capabilities can differ between different generations of the Cisco Catalyst 6500 Family.
Toward the end of this paper, a set of tables give an overview of the QoS features available on each of the line cards and PFC versions.

A QUICK RECAP ON SETTING PRIORITY

When data is sent through a network, it can be tagged with a priority value. When the data passes through a network device, the priority value is used by that network device to determine how it should treat the packet. Data can be tagged with a priority value as described in the following sections.

Class of Service

When a packet is transmitted out an Ethernet port, it has an Ethernet header attached to it. This Ethernet header can include an optional VLAN tag (also referred to as an IEEE 802.1Q VLAN tag). Within the VLAN tag is a 3-bit field called the class-of-service (CoS) field. These 3 bits can be manipulated to yield eight different priority values. Figure 1 shows where in the Ethernet header the priority bits are found.

Figure 1. CoS Field

Cisco Systems ® supports the Inter-Switch Link (ISL) VLAN tagging option on selected Cisco Catalyst 6500 line cards. ISL is a Cisco proprietary VLAN tagging option that also supports an inbuilt 3-bit CoS field just like the IEEE 802.1Q option mentioned earlier.

Type of Service

Built into every IP packet is an IP header, and like in the Ethernet example earlier, the IP header also contains a field that defines a priority value for this packet. This field is the type-of-service (ToS) field. Unlike the CoS field, the ToS field is an 8-bit field. There are two ways to set a priority value in the ToS field. One method, called IP precedence, uses the 3 most significant bits of the ToS field to yield eight priority values. Differentiated Services Code Point (DSCP) is a second method for assigning a priority to an IP packet. DSCP uses the 6 most significant bits of the ToS field to yield 64 different priority values. Figure 2 shows where the ToS bits are found in the IP header.

Figure 2. Reading IP Precedence and DSCP from the ToS Byte

CATEGORIES OF QoS FEATURES

Explaining what QoS features are available on the Cisco Catalyst 6500 is best served by categorizing them into one of the following major groups. These groups are:

• Classification

• Queuing

• Congestion avoidance

• Policing

• Rewrite

• Scheduling

The use of classification provides a way for the switch to identify specific traffic so that it can determine what level of service needs to be applied to that data. Identification can be achieved by a number of means, such as inspecting primary fields in the packet header or looking at the port of arrival. The main set of classification tools provided by the Cisco Catalyst 6500 are the access control list (ACL) and per-port trust setting.
Queuing (also known as congestion management) provides a way to temporarily store data when the arrival rate of data is larger than what can be sent. Like in the earlier bank example, the switch port will use a queue to place data into a temporary holding area until the data can be processed and forwarded. Memory is allocated to each queue, which provides the buffer space for data awaiting service. The number of queues and the amount of buffering available are hardware dependent and are determined by the line card in use. A table later in this document provides the queue type and per-port memory with different line-card options.
Managing the queues and buffers is the primary goal of congestion avoidance. As a queue starts to fill up with transient data, it is important to try to ensure that the available memory in the queue does not fill up completely. If this happens, subsequent packets coming into the port will simply be dropped, irrespective of the priority that they could have received. This could have a detrimental effect on the performance of critical applications.
For this reason, congestion avoidance techniques are used to reduce the risk of a queue from filling up completely. Queue thresholds are used to trigger when certain levels of occupancy are met. After a threshold has been crossed, the system can start to randomly drop lower priority data while trying to keep as much of the higher priority data resident in the queue. Examples of congestion avoidance technologies include Weighted Random Early Detection (WRED), tail drop, and maps.
The act of policing in the switch provides a means to limit the amount of bandwidth that traffic traveling through a given port or collection of ports in a VLAN can use. Policing works by defining an amount of data that the switch is willing to send or receive in Kbps. The policing policy uses an ACL to identify the traffic to which the policer will be applied.
Multiple policing policies can be active in the switch at any one time, allowing an administrator to set different rates for different classes of traffic. Policing can be set up so that it rate limits all traffic entering a given port or VLAN to a given rate or by limiting each new flow to a given rate.
Rewrite is the action of changing the priority setting of the packet. Each packet consists of the data and a header. The header among other things contains information such as where the data has come from (that is, the sending device's source address) and where the data is destined (that is, the target device's destination address). Built into the header is the priority value that can be used to indicate to switches and routers in the network path of the priority of that piece of data. The Cisco Catalyst 6500 has the ability to change that priority value (increase or decrease it) if required based on any policies that may be set by the network administrator.
Scheduling is the QoS mechanism used to empty the queues of data and send the data onward to its destination. A number of scheduling options are available in the Cisco Catalyst 6500-for example, Weighted Round Robin (WRR), Deficit Weighted Round Robin (DWRR), Shaped Round Robin (SRR), and strict priority queuing.
Now that the major QoS groups have been explained, it is pertinent to point out where in the QoS processing path these actions take place. Figure 3 provides a high-level overview of where those actions occur.

Figure 3. Cisco Catalyst 6500 QoS Processing Model

The following section will attempt to provide some insight into the many QoS features that make up the QoS feature toolkit now available on the Cisco Catalyst 6500.

THE QoS FEATURE TOOLKIT

The Cisco Catalyst 6500 is primed with a number of QoS features that when combined provide an effective vehicle to better service higher priority traffic. The following section will attempt to present a high-level overview of the major QoS features in the Cisco Catalyst 6500.

Modular QoS Command-Line Interface

When a Cisco Catalyst 6500 runs native Cisco IOS ® Software, some (not all) of the QoS configuration on the switch follows the modular QoS command-line interface (MQC) structure that is also found in Cisco IOS Software running on Cisco routers. The normal rules of configuration are such that a class map is built incorporating the ACLs that identify the traffic that will have QoS applied to them. The class map is then referenced within a policy map, which contains the QoS policy that will be applied to the switch port (or VLAN). The policy is then applied to the physical or logical interface. A high-level view of this process is shown in Figure 4.

Figure 4. MQC

A primary differentiator between MQC on the Cisco Catalyst 6500 and router Cisco IOS Software is in the application of specific QoS features. The Cisco Catalyst 6500 implements much of its QoS functionality in hardware. Router Cisco IOS Software differs in that it primarily implements most features in software. For this reason, there are differences in how certain features are configured. More importantly, there are some QoS features that are found in router Cisco IOS Software that are not found in the Cisco Catalyst 6500 hardware.

Ingress QoS: Trust

A packet can arrive at an interface with a priority value already present in the packets header. A question then arises for the switch: Is this priority setting valid? Was it set by a valid application or network device according to predefined rules? Or maybe this priority setting was set by a user hoping to get better service from the network? Either way, the switch has to make that determination and decide whether to honor the priority valueµ or change it to another value. How the switch makes this determination is by using the port "trust" setting. (See Figure 5.)

Figure 5. Switch Port Trust Settings

When QoS is enabled on a switch, by default, all ports are placed into a state of untrusted. In this mode, any packet with an existing priority setting that is received on an untrusted port will have its priority setting reset to a default CoS value (the default CoS value is zero). It is the responsibility of the network administrator to identify ports where the priority value should be honored. For instance, connections to selected servers, IP telephones, and IP call managers are examples of ports that should be set to trust the incoming priority setting.
When setting trust, the switch port can be set to trust one of the three priority settings, CoS, IP precedence, or DSCP. If a port is going to be set to trust the incoming priority value, the network administrator has to make the determination of which of the three priority settings will be trusted.

Ingress and Egress QoS: Switch Port Queues

All line cards in the Cisco Catalyst 6500 provide a fixed set of ingress (also known as input or receive) queues and egress (also known as output or transmit) queues per port. The number of queues is fixed in hardware on the line card and cannot be changed. Associated with the queue is an amount of buffer memory that the queue uses to temporarily hold transient data. On some line cards, there is a dedicated amount of memory available to each port. On other line cards, a pool of memory is shared between a set group of ports. A table later in this paper provides a summary list of line cards, the queue structures on each, and the amount of buffering available to each port on the line card.
On select line cards, a strict priority queue is made available. This special queue can be used for latency-sensitive traffic and is designed to forward data immediately when a packet arrives in that queue. More information on the strict priority queue is detailed later in this paper.

Ingress and Egress QoS: Thresholds

Thresholds have multiple uses within a queue. They are used within a queue to identify when the memory buffers have reached a certain predefined utilization. After the threshold has been exceeded, the switch port will initiate a process to start dropping packets from the queue. One of two mechanisms-tail drop and WRED-is typically used to perform this duty. Both of these processes are described later in this paper.
The threshold is also used to associate itself with certain packets tagged with a priority value. When the threshold has been exceeded, the WRED process will attempt to drop packets associated with that breached threshold level. The network administrator also has the ability to set the threshold level.

Ingress and Egress QoS: Maps

The Cisco Catalyst 6500 uses maps in a number of forms to perform different duties. The following section summarizes the different maps available.

Maps: Mapping a Packet to a Queue or Threshold

Given that a switch port can have multiple queues, a way must be provided for the switch to determine in which queue a given piece of data should be placed. The way in which this is determined is by using a map. A map sets out a two-column table. The first column contains the priority value that would be found in the packet's header. The second column contains the queue (and threshold in that queue) to which the packet should be assigned. This is shown in Figure 6.

Figure 6. Mapping a Packet to a Queue or Threshold

Maps: Mapping Priority Values

When a packet arrives at a switch port, it can be primed with a priority value. The trust setting of the port will determine which priority setting (ToS or CoS) will be honored by the switch. As the packet passes through the switch (that is, after it has arrived on the input port and prior to it being sent out the output port), it is assigned a priority value that is only used internal to the switch. This internal priority value is referred to as the internal DSCP. A map is used to derive the internal DSCP from the incoming packet's priority setting. After the packet has passed through the switch, another map is used to derive what the CoS value will be written as for the packet when it is transmitted out the switch port. A summary of these maps is presented in Table 1.

Table 1. Map Summary

Map Name

Related Trust Setting

Used on Input or Output

Map Description

CoS to DSCP Map

Trust CoS

Input

Derives the internal DSCP from the incoming CoS value

IP Precedence to DSCP Map

Trust IP precedence

Input

Derives the internal DSCP from the incoming IP precedence value

DSCP to CoS Map

-

Output

Derives the CoS for the outbound packet from the internal DSCP

Figure 7 shows two of the maps (on ingress) that can be used to derive the internal DSCO priority value.

Figure 7. Mapping Priority to Internal DSCP

Maps: Policing Map

Although policing is primarily designed to limit traffic to a set amount of bandwidth, it also has the ability to reduce the priority value of any data that exceeds the set rate. When this option is configured, the policer uses a map to identify what priority it will mark the data down to.
The map used to perform this task is called the policed-dscp-map. It is a table that contains two columns: the left column is the original priority value, and the matching value in the column on the right is what value the packet will be marked down to.

Maps: Egress DSCP Mutation

When a packet arrives at a switch port, the trust setting of that port will derive an internal priority value (known as internal DSCP, as described earlier) that it uses to assign service to the packet while it transits the switch. When the packet is transmitted out a switch port, the actual DSCP value (written into the IP header) in the outgoing packet is derived from the internal DSCP value. (See Figure 8.)

Figure 8. Egress DSCP Mutation

Egress DSCP mutation provides a way to change the DSCP value in the outgoing packet. An egress DSCP map table is used to tell the switch what DSCP value to write in the outbound packet based on the packet's internal DSCP value. Egress DSCP mutation relies on the presence of a PFC3A, PFC3B, or PFC3BXL to support this feature.

Maps: Ingress CoS Mutation

Support for this feature is present on some of the newer Cisco Catalyst 6500 line cards. Specifically, it is supported on the CEF720 series 48 port GETX and SFP line card, the CEF720 series 4 port 10GE line card and the CEF720 series 24 port SFP line card. Each of these line cards in turn requires the presence of a Supervisor Engine 720 to work in the chassis.
When a port on one of these line cards is configured as an IEEE 802.1Q trunk port, ingress CoS mutation can be configured. What this feature allows the user to do is to change the incoming CoS value to another CoS value. A map is provided that lists what the incoming CoS value will be changed to. The administrator can change the map table to suit local policy requirements.

Ingress and Egress QoS: Policing

The PFC on the supervisor engine implements policing in a number of forms. The following sections provide an insight into the different policing actions available on the PFC.

Policing: Aggregate Policing

An aggregate policer is a term used to define a rate-limiting policy that applies to all traffic on a given port or VLAN that matches a set of classification criteria. This type of policer can be applied to traffic traveling in either direction-that is, for inbound traffic or outbound traffic. The aggregate policer can be applied to a single port or to a VLAN containing multiple ports. The PFC allows up to 1023 aggregate policers to be defined and active in the system at any one time.

Policing: Microflow Policing

The microflow policer differs slightly from an aggregate in that it applies a rate-limiting policy to each discrete flow. The question then becomes: What is a flow, and how is it defined by the Cisco Catalyst 6500? A flow is defined as a unidirectional flow of data that is uniquely identified by primary fields in the packet's IP and TCP/User Datagram Protocol (UDP) headers. Microflow policing, by default, identifies a unique flow by its source and destination IP address as well as its source and destination TCP/UDP ports. To explain this further, if a user were to start up two applications-for example, an e-mail client and an FTP session-each session would kick off a set of unique flows. In this mode, if a microflow policer were applied with a limit set to 2 Mb, then the e-mail session would be limited to 2 Mb, and the FTP session would be limited to 2 Mb. This would equate to a total of 4 Mb of traffic. Comparing this to an aggregate policer of 2 Mb, then the combined volume of traffic from the FTP and e-mail sessions would be limited to 2 Mb.

Policing: User-Based Rate Limiting

User-based rate limiting (UBRL) is an enhancement to microflow policing introduced with the PFC3. It provides a configuration option to change the way in which a flow is viewed by the system. In the previous section, the example showed that for the user initiating the FTP and e-mail applications, two discrete flows would be seen by the system. In this sense, each flow would be limited to the stated rate. UBRL takes advantage of a new enhancement in the PFC that allows a flow to be viewed as everything originating from a unique source or destination IP address. In technical speak, this enhancement is known as a source IP only flow mask or destination IP only flow mask. What this means is that a microflow policer can now be applied to limit traffic originating to or from each user. It allows the administrator to put in place some rules that allow policies limiting traffic on a per-user basis, something microflow policing was not able to do on earlier PFC models. Using the preceding example, if each user initiated multiple sessions (e-mail, Telnet, FTP, HTTP, and so on), each user (all data for that user) would be limited to 2 Mb of data.

Congestion Avoidance: Tail Drop

As a switch port queue begins to fill with data, thresholds can be used to identify what traffic can be dropped when the threshold is breached. A packet is primed with a priority value, and the priority value identifies with which threshold this packet is going to be associated. When that threshold is breached, any packet arriving at the queue with that priority value will be dropped. Packets with that priority value will continue to be dropped while the amount of data in the queue exceeds that threshold. Figure 9 provides a pictorial view of how thresholds are viewed on a given queue.

Figure 9. Tail Drop

Congestion Avoidance: WRED

WRED is less aggressive than tail drop, and it targets fewer flows when it initially begins its drop process. When the first (low) threshold is exceeded, the WRED algorithm will start to randomly drop packets tagged with a particular priority value. The algorithm will attempt to minimize the impact to multiple flows by only targeting a few select flows. As the queue continues to approach the second threshold the WRED algorithm begins to more aggressively drop data, and more flows are susceptible to having packets dropped. (See Figure 10.)

Figure 10. WRED

WRED is built into the port ASIC and is performed in hardware. There is no performance penalty applied when WRED is in use.

Scheduling: WRR

With multiple queues on each switch port, WRR (see Figure 11) provides a way to schedule and send data held in those queues onto the wire. Used on the egress port, the configuration of WRR allows a weighting to be assigned to each queue, which is then used to determine the amount of bandwidth to which each queue has access. The "round-robin" aspect of the algorithm allows each queue to be serviced in turn, sending a set amount of data before moving onto the next queue.

Figure 11. WRR

Scheduling: DWRR

DWRR is a feature that is used on egress (transmit) queues. Explaining DWRR is best served by using an example. Assume a switch port has three queues. Queue 1 has been given access to 50 percent of the bandwidth, queue 2 has 30 percent, and queue 3 has 20 percent. If the WRR algorithm is servicing queue 2, and on this service pass it has used 99.9 percent of its allotted bandwidth, the WRR algorithm will still send out the next packet in the queue as the queue's allotted bandwidth allocation has not yet been used up. When it sends the next packet, it will exceed the amount of bandwidth that was configured for this queue. Statically over time, queue 2 may end up using a lot more bandwidth than it was initially configured for when using WRR. (See Figure 12.)

Figure 12. DWRR

DWRR prevents this problem from occurring. If the queue uses more bandwidth than it was allotted, DWRR keeps a tally of the extra bandwidth used on that pass. On the next pass through the queues, the DWRR algorithm will subtract the extra bandwidth used on the last pass for this turn. This means statistically over a period of time that each queue will use bandwidth that is much closer to the configured amount for that queue.

Scheduling: SRR

SRR is a recent addition to the scheduling capabilities of the Cisco Catalyst 6500 Family. At the time of writing this paper, support for SRR is only available on the uplink ports of the Cisco Catalyst 6500 Series Supervisor Engine 32. SRR is different from WRR in that the SRR algorithm provides a way to shape outbound traffic to a stated rate. In some respects, it is similar to a policer except that traffic in excess of the rate will be buffered rather than dropped as with a policer.
The shaper is implemented on a per-queue basis and has the effect of smoothing transient bursts of data that pass through that port. SRR also modifies the way in which it schedules data when compared to the WRR algorithm. This can be seen in Figure 13, which shows a representation of the packet scheduling order for both algorithms.

Figure 13. SRR Compared to WRR

Scheduling: Strict Priority Queuing

Select line cards support a strict priority queue on a per-port basis. The purpose of a strict priority queue is to facilitate support for latency-sensitive traffic that gets queued on the line card. When a packet is placed into a strict priority queue, scheduling of packets from WRR queues will cease, and the packet(s) in the strict priority queue will be transmitted. Only when the strict priority queue is empty will the scheduling process recommence sending packets from WRR queues. (See Figure 14.)

Figure 14. Strict Priority Queuing Process

AUTO-QoS

The concept of auto-QoS was designed to simplify the configuration and implementation of specific QoS features on the Cisco Catalyst 6500. Auto-QoS puts in place a set of macros that can be implemented from the Cisco Catalyst 6500 command line. In its initial implementation, the application of auto-QoS is focused on setting the QoS configuration for a given port to support an attached Cisco IP Phone. The QoS settings applied conform to the IETF settings for attached telephony devices.
Auto-QoS is applied in two steps. The first step is to enable it at a system level. This sets in place a series of defaults, which will become active when a given port has auto-QoS applied. For each port that has an attached Cisco IP Phone, an auto-QoS macro is applied that sets in place a number of port-specific QoS settings specific for the device telephony type. At the time of writing, there are two auto-QoS macros that can be applied to a switch port. The ciscoiphone macro is used when a physical Cisco IP Phone is connected to the switch port. The other macro is ciscosoftphone, which is used when a user attaches a PC to a switch port to run the software version of the IP telephone.

QoS FEATURE SUMMARY

Table 2 provides a summary of the QoS features found in the Cisco Catalyst 6500, where the feature is processed, and if the feature is applied on ingress or egress.

Table 2. QoS Feature Summary

QoS Feature

Processed in . . .?

Applied on Ingress or Egress

Supported PFC

Port Trust

Line-card port ASIC

Ingress

-

Default CoS Assignment

Line-card port ASIC

Ingress

-

CoS to DSCP Map

Line-card port ASIC

Ingress

-

IP Precedence to DSCP Map

Line-card port ASIC

Ingress

-

CoS Mutation

Line-card port ASIC

Ingress

-

Ingress Classification

PFC

Ingress

PFC1, 2, 3A, 3B, 3BXL

Ingress Aggregate Policing

PFC

Ingress

PFC1, 2, 3A, 3B, 3BXL

Egress Classification

PFC

Egress

PFC3A, 3B, 3BXL

Egress Aggregate Policing

PFC

Egress

PFC3A, 3B, 3BXL

Microflow Policing

PFC

Ingress

PFC1, 2, 3A, 3B, 3BXL

UBRL

PFC

Ingress

PFC3A, 3B, 3BXL

DSCP to CoS Map

Line-card port ASIC

Egress

-

Egress DSCP Mutation

PFC

Egress

PFC3A, 3B, 3BXL

WRR

Line-card port ASIC

Egress

-

DWRR

Line-card port ASIC

Egress

-

SRR

Line-card port ASIC

Egress

-

Strict Priority Queuing

Line-card port ASIC

Egress

-

Tail Drop

Line-card port ASIC

Egress

-

WRED

Line-card port ASIC

Egress

-

LINE-CARD QoS SUMMARY

Table 3 provides a summary of the QoS capabilities for each of the line cards in the Cisco Catalyst 6500 Family.

Table 3. QoS Capability Summary for Line Cards

xCEF720 Modules

Description

Receive Queue Structure

Transmit Queue Structure

Buffer Size

WS-X6704-10GE

Cisco Catalyst 6500 4-port 10-GbE

1q8t ` 8q8t with DFC3

1p7q8t

16 MB per port

WS-X6724-SFP

Cisco Catalyst 6500 24-port GbE SFP

1q8t ; 2q8t with DFC3a

1p3q8t

1 MB per port

WS-X6748-GE-TX

Cisco Catalyst 6500 48-port 10/100/1000 RJ45

1q8t ; 2q8t with DFC3a

1p3q8t

1 MB per port

WS-X6748-SFP

Cisco Catalyst 6500 48-port GbE SFP

1q8t ; 2q8t with DFC3a

1p3q8t

1 MB per port

WS-X6024-10FL-MT

Cisco Catalyst 6500 24-port 10BaseFL MT-RJ module

1q4t

2q2t

64 KB per port

WS-X6148-RJ21

Cisco Catalyst 6500 48-port 10/100 upgradable to voice; RJ-21

1q4t

2q2t

128 KB per port

WS-X6148-RJ21V

Cisco Catalyst 6500 48-port 10/100 inline power module; RJ-21

1q4t

2q2t

128 KB per port

WS-X6148-RJ45

Cisco Catalyst 6500 48-port 10/100; upgradable to voice; RJ-45

1q4t

2q2t

128 KB per port

WS-X6148A-TJ45

Cisco Catalyst 6500 48-port 10/100 inline power enhanced; RJ-45

1q2t

1p3q8t

5.2 Mb per port

WS-X6148-RJ45V

Cisco Catalyst 6500 48-port 10/100 inline power; RJ-45

1q4t

2q2t

128 KB per port

WS-X6148-FE-SFP

Cisco Catalyst 6500 48-port 100-Mb mod.; SFP

1q2t

1p3q8t

5.2 Mb per port

WS-X6148-GE-TX

Cisco Catalyst 6500 48-port 10/100/1000 GE mod.; RJ-45

1q2t

1p2q2t

1 MB per 8 ports

WS-X6148A-GE-TX

Cisco Catalyst 6500 48-port 10/100/1000 GE mod enhanced; RJ-45

1q2t

1p3q8t

5.2 Mb per port

WS-X6148V-GE-TX

Cisco Catalyst 6500 48-port 10/100/1000 inline power module; RJ-45

1q2t

1p2q2t

1 MB per 8 ports

WS-X6148X2-RJ-45

Cisco Catalyst 6500 96-port 10/100TX mod.; RJ-45

1p1q0t

1p3q1t

1088 Kb per port

WS-X6196-RJ-21

Cisco Catalyst 6500 96-port 10/100 mod.; RJ-21

1p1q0t

1p3q1t

1088 Kb per port

WS-X6316-GE-TX

Cisco Catalyst 6500 16-port 1000TX GE mod.; RJ-45

1p1q4t

1p2q2t

512 KB per port

WS-X6324-100FX-MM

Cisco Catalyst 6000 24-port 100FX; enh QoS; MT-RJ; MMF

1q4t

2q2t

128 KB per port

WS-X6324-100FX-SM

Cisco Catalyst 6000 24-port 100FX; enh QoS; MT-RJ; SMF

1q4t

2q2t

128 KB per port

WS-X6348-RJ-21

Cisco Catalyst 6000 48-port 10/100; RJ-21

1q4t

2q2t

128 KB per port

WS-X6348-RJ21V

Cisco Catalyst 6000 48-port 10/100; inline power; RJ-21

1q4t

2q2t

128 KB per port

WS-X6348-RJ-45

Cisco Catalyst 6500 48-port 10/100; upgradable to voice; RJ-45

1q4t

2q2t

128 KB per port

WS-X6348-RJ45V

Cisco Catalyst 6500 48-port 10/100; inline power; RJ-45

1q4t

2q2t

128 KB per port

WS-X6408A-GBIC

Cisco Catalyst 6000 8-port GE; enhanced QoS (req. GBICs)

1p1q4t

1p2q2t

512 KB per port

WS-X6416-GBIC

Cisco Catalyst 6000 16-port Gig-Ethernet mod. (req. GBICs)

1p1q4t

1p2q2t

512 KB per port

WS-X6416-GE-MT

Cisco Catalyst 6000 16-port Gig-Ethernet mod.; MT-RJ

1p1q4t

1p2q2t

512 KB per port

WS-X6501-10GEX4

Cisco Catalyst 6500 1-port 10GbE module

1p1q8t

1p2q1t

64 MB per port

WS-X6502-10GE

Cisco Catalyst 6500 10-Gigabit Ethernet base module (req. OIM)

1p1q8t

1p2q1t

64 MB per port

WS-X6516A-GBIC

Cisco Catalyst 6500 16-port GigE mod; fabric-enabled (req. GBICs)

1p1q4t

1p2q2t

1 MB per port

WS-X6516-GBIC

Cisco Catalyst 6500 16-port GigE mod: fabric-enabled (req. GBICs)

1p1q4t

1p2q2t

512 KB per port

WS-X6516-GE-TX

Cisco Catalyst 6500 16-port Gig/copper module; x-bar

1p1q4t

1p2q2t

512 KB per port

WS-X6524-100FX-MM

Cisco Catalyst 6500 24-port 100FX; MT-RJ; fabric-enabled

1p1q0t

1p3q1t

1 MB per port

WS-X6548-RJ-21

Cisco Catalyst 6500 48-port 10/100; RJ-21; fabric-enabled

1p1q0t

1p3q1t

1 MB per port

WS-X6548-RJ-45

Cisco Catalyst-6500 48-port 10/100; RJ-45; x-bar

1p1q0t

1p3q1t

1 MB per port

WS-X6548V-GE-TX

Cisco Catalyst 6500 48-port fab-enabled 10/100/1000 inline pwr mod

1q2t

1p2q2t

1 MB per 8 ports

WS-X6548-GE-TX

Cisco Catalyst 6500 48-port fabric-enabled 10/100/1000 module

1q2t

1p2q2t

1 MB per 8 ports

WS-X6816-GBIC

Cisco Catalyst 6500 16-port GigE mod: fabric-enabled (req. GBICs)

1p1q4t

1p2q2t

512 KB per port

COMPARISON OF QoS FEATURES BETWEEN PFC VERSIONS

Over the years a number of different PFC versions have been released. Table 4 provides a high-level overview of the major differences between the QoS capabilities of each PFC.

Table 4. Major Differences Between PFC QoS Capabilities

Feature

PFC1

PFC2

PFC3A

PFC3B

PFC3BXL

ACL Classification

Yes

Yes

Yes

Yes

Yes

Microflow Policing

Yes

Yes

Yes

Yes

Yes

Ingress Aggregate Policing

Yes

Yes

Yes

Yes

Yes

Egress Aggregate Policing
   

Yes

Yes

Yes

UBRL
   

Yes

Yes

Yes

Egress DSCP Mutation
   

Yes

Yes

Yes

Ingress CoS Mutation
   

Yes

Yes

Yes

Number of QoS ACLs

16 K

32 K

32 K

32 K

32 K

Number of QoS Masks

2 K

4 K

4 K

4 K

4 K

Number of QoS Labels

512

512

512

4096

4096

SUMMARY

With the continued convergence of multiple technologies on IP networks, QoS is becoming more important in the successful operation of customer networks. As a collection of technologies, distinct QoS features can be applied in different combinations to solve an assortment of problems in a network. The richness of the QoS feature set on the Cisco Catalyst 6500 provides network managers with a means to facilitate convergence and prioritize mission-critical application data. More importantly, the nature of the Cisco Catalyst 6500 platform means that incremental changes in QoS features can be accommodated, allowing the platform to grow to meet the new demands of the networks of the future.
Text Box:  Corporate HeadquartersCisco Systems, Inc.170 West Tasman DriveSan Jose, CA 95134-1706USAwww.cisco.comTel:	408 526-4000	800 553-NETS (6387)Fax:	408 526-4100	European HeadquartersCisco Systems International BVHaarlerbergparkHaarlerbergweg 13-191101 CH AmsterdamThe Netherlandswww-europe.cisco.comTel:	31 0 20 357 1000Fax:	31 0 20 357 1100	Americas HeadquartersCisco Systems, Inc.170 West Tasman DriveSan Jose, CA 95134-1706USAwww.cisco.comTel:	408 526-7660Fax:	408 527-0883	Asia Pacific HeadquartersCisco Systems, Inc.168 Robinson Road#28-01 Capital TowerSingapore 068912www.cisco.comTel: +65 6317 7777Fax: +65 6317 7799Cisco Systems has more than 200 offices in the following countries and regions. Addresses, phone numbers, and fax numbers are listed onthe Cisco Website at www.cisco.com/go/offices.Argentina · Australia · Austria · Belgium · Brazil · Bulgaria · Canada · Chile · China PRC · Colombia · Costa Rica · Croatia · Cyprus Czech Republic · Denmark · Dubai, UAE · Finland · France · Germany · Greece · Hong Kong SAR · Hungary · India · Indonesia · Ireland · Israel Italy · Japan · Korea · Luxembourg · Malaysia · Mexico · The Netherlands · New Zealand · Norway · Peru · Philippines · Poland · Portugal Puerto Rico · Romania · Russia · Saudi Arabia · Scotland · Singapore · Slovakia · Slovenia · South Africa · Spain · Sweden · Switzerland · Taiwan Thailand · Turkey · Ukraine · United Kingdom · United States · Venezuela · Vietnam · ZimbabweCopyright  2005 Cisco Systems, Inc. All rights reserved. CCSP, CCVP, the Cisco Square Bridge logo, Follow Me Browsing, and StackWise are trademarks of Cisco Systems, Inc.; Changing the Way We Work, Live, Play, and Learn, and iQuick Study are service marks of Cisco Systems, Inc.; and Access Registrar, Aironet, ASIST, BPX, Catalyst, CCDA, CCDP, CCIE, CCIP, CCNA, CCNP, Cisco, the Cisco Certified Internetwork Expert logo, Cisco IOS, Cisco Press, Cisco Systems, Cisco Systems Capital, the Cisco Systems logo, Cisco Unity, Empowering the Internet Generation, Enterprise/Solver, EtherChannel, EtherFast, EtherSwitch, Fast Step, FormShare, GigaDrive, GigaStack, HomeLink, Internet Quotient, IOS, IP/TV, iQ Expertise, the iQ logo, iQ Net Readiness Scorecard, LightStream, Linksys, MeetingPlace, MGX, the Networkers logo, Networking Academy, Network Registrar, Packet, PIX, Post-Routing, Pre-Routing, ProConnect, RateMUX, ScriptShare, SlideCast, SMARTnet, StrataView Plus, TeleRouter, The Fastest Way to Increase Your Internet Quotient, and TransPath are registered trademarks of Cisco Systems, Inc. and/or its affiliates in the United States and certain other countries.All other trademarks mentioned in this document or Website are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (0502R)	205529.O_ETMG_JR_12.05Printed in the USA Text Box:  Corporate HeadquartersCisco Systems, Inc.170 West Tasman DriveSan Jose, CA 95134-1706USAwww.cisco.comTel:	408 526-4000	800 553-NETS (6387)Fax:	408 526-4100	European HeadquartersCisco Systems International BVHaarlerbergparkHaarlerbergweg 13-191101 CH AmsterdamThe Netherlandswww-europe.cisco.comTel:	31 0 20 357 1000Fax:	31 0 20 357 1100	Americas HeadquartersCisco Systems, Inc.170 West Tasman DriveSan Jose, CA 95134-1706USAwww.cisco.comTel:	408 526-7660Fax:	408 527-0883	Asia Pacific HeadquartersCisco Systems, Inc.168 Robinson Road#28-01 Capital TowerSingapore 068912www.cisco.comTel: +65 6317 7777Fax: +65 6317 7799Cisco Systems has more than 200 offices in the following countries and regions. Addresses, phone numbers, and fax numbers are listed onthe Cisco Website at www.cisco.com/go/offices.Argentina · Australia · Austria · Belgium · Brazil · Bulgaria · Canada · Chile · China PRC · Colombia · Costa Rica · Croatia · Cyprus Czech Republic · Denmark · Dubai, UAE · Finland · France · Germany · Greece · Hong Kong SAR · Hungary · India · Indonesia · Ireland · Israel Italy · Japan · Korea · Luxembourg · Malaysia · Mexico · The Netherlands · New Zealand · Norway · Peru · Philippines · Poland · Portugal Puerto Rico · Romania · Russia · Saudi Arabia · Scotland · Singapore · Slovakia · Slovenia · South Africa · Spain · Sweden · Switzerland · Taiwan Thailand · Turkey · Ukraine · United Kingdom · United States · Venezuela · Vietnam · ZimbabweCopyright  2005 Cisco Systems, Inc. All rights reserved. CCSP, CCVP, the Cisco Square Bridge logo, Follow Me Browsing, and StackWise are trademarks of Cisco Systems, Inc.; Changing the Way We Work, Live, Play, and Learn, and iQuick Study are service marks of Cisco Systems, Inc.; and Access Registrar, Aironet, ASIST, BPX, Catalyst, CCDA, CCDP, CCIE, CCIP, CCNA, CCNP, Cisco, the Cisco Certified Internetwork Expert logo, Cisco IOS, Cisco Press, Cisco Systems, Cisco Systems Capital, the Cisco Systems logo, Cisco Unity, Empowering the Internet Generation, Enterprise/Solver, EtherChannel, EtherFast, EtherSwitch, Fast Step, FormShare, GigaDrive, GigaStack, HomeLink, Internet Quotient, IOS, IP/TV, iQ Expertise, the iQ logo, iQ Net Readiness Scorecard, LightStream, Linksys, MeetingPlace, MGX, the Networkers logo, Networking Academy, Network Registrar, Packet, PIX, Post-Routing, Pre-Routing, ProConnect, RateMUX, ScriptShare, SlideCast, SMARTnet, StrataView Plus, TeleRouter, The Fastest Way to Increase Your Internet Quotient, and TransPath are registered trademarks of Cisco Systems, Inc. and/or its affiliates in the United States and certain other countries.All other trademarks mentioned in this document or Website are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (0502R)	205529.O_ETMG_JR_12.05Printed in the USA