Using classifiers to configure QoS for outbound traffic

When you use TCP or UDP and a layer 4 Application port number as a global QoS classifier, traffic carrying the specified TCP/UDP port numbers is marked with a specified priority level, without regard for any other QoS classifiers in the switch.

You can configure up to 50 TCP/UDP application port numbers as QoS classifiers.

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Operating notes on using TCP/UDP port ranges

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• Only six concurrent policies are possible when using unique ranges. The number of policies allowed is less if ACLs are also using port ranges.

• No ranges allowed that include any port numbers configured as part of another QoS application port number policy.

• An error message is generated if there are not enough hardware resources available when configuring a policy.

• The entire range of configured port numbers must be specified when using the no form of the command, for example:

  switch(config)#: qos udp-port range 1300 1399 dscp 001110
  
  switch(config)#: no qos range 1300 1399

The following example displays the following configuration for TCP and UDP port prioritization:

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Configuration for TCP and UDP port prioritization

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TCP/UDP port	802.1p priority for TCP	802.1p priority for UDP
TCP Port 23 (Telnet)	7	7
UDP Port 23 (Telnet)	7	7
TCP Port 80 (World Wide Web HTTP)	2	2
UDP Port 80 (World Wide Web HTTP)	1	1

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Configuring 802.1p priority assignments on TCP/UDP ports

The global IP-device classifier enables you to configure up to 300 IP addresses to select IP packets according to source or destination address.

Where a particular device-IP address classifier has the highest precedence in the switch for traffic addressed to or from that device, then traffic received on the switch with that address is marked with the IP address classifier’s configured priority level. Different IP device classifiers can have differing priority levels.

	NOTE: QoS IP-device restriction: The switch does not allow a QoS IP-device priority for the Management VLAN IP address (if configured). If no Management VLAN is configured, then the switch does not allow configuring a QoS IP-device priority for the default VLAN IP address.

The packet-marking options for global IP-device classifiers include:

For a given IP address or subnet mask, you can assign only one of the above options at a time. However, for different IP addresses, you can use different options.

This global QoS packet-marking option assigns an 802.1p priority to all IP packets that have the specified IP address as either a source or destination. If both the source and destination addresses match, the priority configured for the IP destination address has precedence.​

​Syntax (IPv4):

​Syntax (IPv6):

	NOTE: The global IP-device classifier priority feature for IPv6 is not supported on switches J9779A, J9780A, J9782A, and J9783A.

switch(config)#: qos device-priority 10.28.31.1 priority 7
switch(config)#: qos device-priority 10.28.31.130 priority 5
switch(config)#: qos device-priority ipv4 10.28.32.100/24 priority 1
switch(config)#: qos device-priority 2001:db8:2:1:212:79ff:fe88:a100 priority
switch(config)#: qos device-priority ipv6 2001:db8:3:3::/64 priority 1
switch(config)#: show qos device-priority

  Device priorities

  Device Address                                Apply rule | DSCP  Priority
  --------------------------------------------  ---------- + ------ -----------
  10.28.31.1                                    Priority   |        7
  10.28.31.130                                  Priority   |        5
  10.28.32.100/24                               Priority   |        1
  2001:db8:2:1:212:79ff:fe88:a100               Priority   |        3
  2001:db8:3:3::/64                             Priority   |        1

You can assign a maximum of 64 ToS rules. This feature applies only to IPv4 traffic and performs either of the following:

Unless IP-Precedence mode and Diffserv mode are both disabled (the default setting), enabling one automatically disables the other.

	NOTE: “Mixing” ToS DSCP policies and 802.1p priorities is not recommended. See the ‘Note’ in Packet classifiers and evaluation order.

If a device or application upstream of the switch sets the precedence bits in the ToS byte of IPv4 packets, you can use this feature to apply that setting for prioritizing packets for outbound port queues. If the outbound packets are in a tagged VLAN, this priority is carried as an 802.1p value to the adjacent downstream devices.

​Syntax:

Using the IP-precedence classifier, prioritization of outbound packets relies on the IP-Precedence bit setting that IP packets carry with them from upstream devices and applications. To configure and verify this option:

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Enabling ToS IP-precedence prioritization

To replace this option with the ToS diff-services option, configure diff-services as described below, which automatically disables IP-Precedence. To disable IP-Precedence without enabling the diff-services option, use this command: no qos type-of-service

One of the best uses for this option is on an interior switch where you want to honor (continue) a policy set on an edge switch. That is, it enables you to select incoming packets having a specific DSCP and forward these packets with the desired 802.1p priority. For example, if an edge switch “A” marks all packets received on port 5 with a particular DSCP, you can configure a downstream (interior) switch “B” to handle such packets with the desired priority (regardless of whether 802.1Q tagged VLANs are in use).

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Interior switch B honors the policy established in edge switch A

To do so, assign the desired 802.1p priority to the same codepoint that the upstream or edge switch assigns to the selected packets. When the downstream switch receives an IPv4 packet carrying one of these codepoints, it assigns the configured priority to the packet and sends it out the appropriate priority queue. (The packet retains the codepoint it received from the upstream or edge switch). You can use this option concurrently with the diffserv DSCP Policy option (described later in this section), as long as the DSCPs specified in the two options do not match.

	NOTE: Regarding DSCP use: Different applications may use the same DSCP in their IP packets. Also, the same application may use multiple DSCPs if the application originates on different clients, servers, or other devices. Using an edge switch enables you to select the desired packets and mark them with predictable DSCPs that can be used by downstream switches to honor policies set in the edge switch. When enabled, the switch applies direct 802.1p prioritization to all packets having codepoints that meet these prerequisites: The codepoint is configured with an 802.1p priority in the DSCP table. (Codepoints configured with No-override are not used.) The codepoint is not configured for a new DSCP policy assignment. Thus, the switch does not allow the same incoming codepoint (DSCP) to be used simultaneously for directly assigning an 802.1p priority and also assigning a DSCP policy. For a given incoming codepoint, if you configure one option and then the other, the second overwrites the first.

To use this option:

​Syntax:

For example, an edge switch “A” in an untagged VLAN assigns a DSCP of 000110 on IP packets it receives on port 6, and handles the packets with high priority (7). When these packets reach interior switch “B” you want the switch to handle them with the same high priority. To enable this operation, you would configure an 802.1p priority of 7 for packets received with a DSCP of 000110. ToS diff-services must be enabled:

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Viewing the codepoints available for 802.1p priority assignments

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ToS configuration that enables both 802.1p priority and DSCP policy assignment

The preceding section describes how to forward a policy set by an edge (or upstream) switch. This option changes a DSCP policy in an IPv4 packet by changing its IP ToS codepoint and applying the priority associated with the new codepoint. (A DSCP policy consists of a differentiated services codepoint and an associated 802.1p priority.) You can use this option concurrently with the diffserv 802.1p priority option (above), as long as the DSCPs specified in the two options do not match.

To use this option to configure a change in policy:

​Syntax:

​Syntax:

​Syntax:

​Syntax:

​Syntax:

For example, suppose that you want to configure the following two DSCP policies for packets received with the indicated DSCPs.

IP packets include a Type of Service (ToS) byte. The ToS byte includes:

The ToS codepoint and precedence bits shows an example of the ToS byte in the header for an IPv4 packet, and illustrates the diffserv bits and precedence bits in the ToS byte. (Note that the Precedence bits are a subset of the Differentiated Services bits.)

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The ToS codepoint and precedence bits

When a global Layer-3 Protocol classifier is configured as the highest-precedence classifier and the switch receives traffic carrying the specified protocol, matching packets are assigned the priority configured for the classifier.

This global QoS packet-marking option assigns an 802.1p priority to outbound packets having the specified Layer-3 protocol.

​Syntax:

​Syntax:

​Syntax:

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Configuring global Layer-3 protocol classifiers

To configure the following global Layer-3 protocol classifiers:

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1. Configure QoS protocol classifiers with IP at 0 (normal), ARP at 5 (medium), and AppleTalk at 7 (high) and display the QoS protocol configuration.

2. Disable the QoS IP protocol classifier, downgrade the ARP priority to 4, and again display the QoS protocol configuration.

The following example shows the necessary configuration commands.

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Adding, viewing, removing, and changing QoS protocol classifiers

Where a particular VLAN-ID classifier has the highest precedence in the switch for traffic in that VLAN, then traffic received in that VLAN is marked with the VID classifier’s configured priority level. Different VLAN-ID classifiers can have differing priority levels.

Priority control options for packets carrying a specified VLAN-ID include:

(For operation when other QoS classifiers apply to the same traffic, see Classifiers for prioritizing outbound packets.)

	NOTE: QoS with VID priority applies to static VLANs only, and applying QoS to dynamic VLANs created by GVRP operation is not supported. A VLAN must exist while a subject of a QoS configuration, and eliminating a VLAN from the switch causes the switch to clear any QoS features configured for that VID.

This option assigns a priority to all outbound packets having the specified VLAN-ID (VID). You can configure this option by either specifying the VID ahead of the qos command or moving to the VLAN context for the VLAN you want to configure for priority.

​Syntax:

​Syntax:

​Syntax:

This option assigns a previously configured DSCP policy (codepoint and 802.1p priority) to outbound IP packets having the specified VLAN-ID (VID). The switch performs the following:

​Steps for creating a policy based on VLAN-ID classifier:

​Syntax:

​Syntax:

​Syntax:

For example, suppose that you wanted to assign this set of priorities:

Assign the DSCP policies to the selected VIDs and display the result.

switch(config)# vlan 1 qos dscp 17
switch(config)# vlan 20 qos dscp 17
switch(config)# vlan 30 qos dscp 16
switch(config)# vlan 40 qos dscp 15

switch(config)# show qos vlan-priority

 VLAN priorities

  VLAN ID Apply rule  | DSCP   Priority
  ------- ----------- + ------ -----------
  1       DSCP        | 010001 1
  20      DSCP        | 010001 1
  30      DSCP        | 010000 5
  40      DSCP        | 001111 7

The switch will now apply the DSCP policies in The completed VID-DSCP priority configuration to packets received on the switch with the specified VLAN-IDs. This means the switch will:

The QoS source-port option enables you to use a packet’s source-port on the switch as a QoS classifier. Where a particular source-port classifier has the highest precedence in the switch for traffic entering through that port, then traffic received from the port is marked with the source-port classifier’s configured priority level. Different source-port classifiers can have different priority levels.

Priority control options for packets from a specified source-port include:

(For operation when other QoS classifiers apply to the same traffic, see Classifiers for prioritizing outbound packets.)

You can use a RADIUS server to impose a QoS source-port priority during an 802.1X port-access authentication session. See the RADIUS chapter in the Access Security Guide for your switch.

This option assigns a priority to all outbound packets having the specified source-port. You can configure this option by either specifying the source-port ahead of the qos command or moving to the port context for the port you want to configure for priority. (If you are configuring multiple source-ports with the same priority, you may find it easier to use the interface <port-list> command to go to the port context instead of individually configuring the priority for each port.)

​Syntax:

​Syntax:

​Syntax:

For example, suppose that you want to prioritize inbound traffic on the following source-ports:

You would then execute the following commands to prioritize traffic received on the above ports.

switch(config)# interface e 1-3 qos priority 2
switch(config)# interface e 4 qos priority 3
switch(config)# show qos port-priority

  Port priorities
  
  Port Apply rule  | DSCP  Priority    Radius Override
  ---- ----------    ----  --------    ---------------
  1    Priority    |       2           No-override
  2    Priority    |       2           No-override
  3    Priority    |       2           No-override
  4    Priority    |       3           No-override
  5    No-override |       No-override No-override
  .    .                   .           .
  .    .                   .           .

If you then decided to remove port 1 from QoS prioritization:

switch(config)# no interface e 1 qos
switch(config)# show qos port-priority

  Port priorities
  
  Port Apply rule  | DSCP  Priority    Radius Override
  ---- ----------    ----  --------    ---------------
  1    No-override |       No-override No-override
  2    Priority    |       2           No-override
  3    Priority    |       2           No-override
  4    Priority    |       3           No-override
  5    No-override |       No-override No-override
  .    .                   .           .
  .    .                   .           .

This option assigns a previously configured DSCP policy (codepoint and 802.1p priority) to outbound IP packets (received from the specified sourceports). That is, the switch:

​Steps for creating a policy based on source-port classifier:

	NOTE: You can select one DSCP per source-port. Also, configuring a new DSCP for a source-port automatically overwrites (replaces) any previous DSCP or 802.1p priority configuration for that port.)

​Syntax:

​Syntax:

​Syntax:

For example, suppose that you wanted to assign this set of priorities that have been configured on the switch:

Assign the DSCP policies to the selected source-ports and display the result.

switch(config)# int 4,5
switch(eth-4,5)# qos dscp 17
switch(eth-4,5)# int 1,3
switch(eth-1,3)# qos dscp 16
switch(eth-1,3)# int 2
switch(eth-2)# qos dscp 15

switch(eth-2)# show qos port-priority

Port priorities

  Port Apply rule  | DSCP   Priority    Radius Override
  ---- ----------- + ------ ----------- ---------------
  1    DSCP        | 010000 5           No-override
  2    DSCP        | 001111 7           No-override
  3    DSCP        | 010000 5           No-override
  4    DSCP        | 010001 1           No-override
  5    DSCP        | 010001 1           No-override
  6    No-override |        No-override No-override
  7    No-override |        No-override No-override
  .         .         .          .           .
  .         .         .          .           .