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Examples: Configuring Bandwidth Management

Understanding Bandwidth Management for Multicast

Bandwidth management enables you to control the multicast flows that leave a multicast interface. This control enables you to better manage your multicast traffic and reduce or eliminate the chances of interface oversubscription or congestion.

Bandwidth management ensures that multicast traffic oversubscription does not occur on an interface. When managing multicast bandwidth, you define the maximum amount of multicast bandwidth that an individual interface can use as well as the bandwidth individual multicast flows use.

For example, the routing software cannot add a flow to an interface if doing so exceeds the allowed bandwidth for that interface. Under these circumstances, the interface is rejected. This rejection, however, does not prevent a multicast protocol (for example, PIM) from sending a join message upstream. Traffic continues to arrive on the router, even though the router is not sending the flow from the expected outgoing interfaces.

You can configure the flow bandwidth statically by specifying a bandwidth value for the flow in bits per second, or you can enable the flow bandwidth to be measured and adaptively changed. When using the adaptive bandwidth option, the routing software queries the statistics for the flows to be measured at 5-second intervals and calculates the bandwidth based on the queries. The routing software uses the maximum value measured within the last minute (that is, the last 12 measuring points) as the flow bandwidth.

For more information, see the following sections:

Bandwidth Management and PIM Graceful Restart

When using PIM graceful restart, after the routing process restarts on the Routing Engine, previously admitted interfaces are always readmitted and the available bandwidth is adjusted on the interfaces. When using the adaptive bandwidth option, the bandwidth measurement is initially based on the configured or default starting bandwidth, which might be inaccurate during the first minute. This means that new flows might be incorrectly rejected or admitted temporarily. You can correct this problem by issuing the clear multicast bandwidth-admission operational command.

If PIM graceful restart is not configured, after the routing process restarts, previously admitted or rejected interfaces might be rejected or admitted in an unpredictable manner.

Bandwidth Management and Source Redundancy

When using source redundancy, multiple sources (for example, s1 and s2) might exist for the same destination group (g). However, only one of the sources can actively transmit at any time. In this case, multiple forwarding entries—(s1,g) and (s2,g)—are created after each goes through the admission process.

With redundant sources, unlike unrelated entries, an OIF that is already admitted for one entry—for example, (s1,g)—is automatically admitted for other redundancy entries—for example, (s2,g). The remaining bandwidth on the interface is deducted each time an outbound interface is added, even though only one sender actively transmits. By measuring bandwidth, the bandwidth deducted for the inactive entries is credited back when the router detects no traffic is being transmitted.

For more information about defining redundant sources, see Example: Configuring a Multicast Flow Map.

Logical Systems and Bandwidth Oversubscription

You can manage bandwidth at both the physical and logical interface level. However, if more than one logical system shares the same physical interface, the interface might become oversubscribed. Oversubscription occurs if the total bandwidth of all separately configured maximum bandwidth values for the interfaces on each logical system exceeds the bandwidth of the physical interface.

When displaying interface bandwidth information, a negative available bandwidth value indicates oversubscription on the interface.

Interface bandwidth can become oversubscribed when the configured maximum bandwidth decreases or when some flow bandwidths increase because of a configuration change or an actual increase in the traffic rate.

Interface bandwidth can become available again if one of the following occurs:

  • The configured maximum bandwidth increases.

  • Some flows are no longer transmitted from interfaces, and bandwidth reserves for them are now available to other flows.

  • Some flow bandwidths decrease because of a configuration change or an actual decrease in the traffic rate.

Interfaces that are rejected for a flow because of insufficient bandwidth are not automatically readmitted, even when bandwidth becomes available again. Rejected interfaces have an opportunity to be readmitted when one of the following occurs:

  • The multicast routing protocol updates the forwarding entry for the flow after receiving a join, leave, or prune message or after a topology change occurs.

  • The multicast routing protocol updates the forwarding entry for the flow due to configuration changes.

  • You manually reapply bandwidth management to a specific flow or to all flows using the clear multicast bandwidth-admission operational command.

In addition, even if previously available bandwidth is no longer available, already admitted interfaces are not removed until one of the following occurs:

  • The multicast routing protocol explicitly removes the interfaces after receiving a leave or prune message or after a topology change occurs.

  • You manually reapply bandwidth management to a specific flow or to all flows using the clear multicast bandwidth-admission operational command.

Example: Defining Interface Bandwidth Maximums

This example shows you how to configure the maximum bandwidth for a physical or logical interface.

Requirements

Before you begin:

Overview

The maximum bandwidth setting applies admission control either against the configured interface bandwidth or against the native speed of the underlying interface (when there is no configured bandwidth for the interface).

If you configure several logical interfaces (for example, to support VLANs or PVCs) on the same underlying physical interface, and no bandwidth is configured for the logical interfaces, it is assumed that the logical interfaces all have the same bandwidth as the underlying interface. This can cause oversubscription. To prevent oversubscription, configure bandwidth for the logical interfaces, or configure admission control at the physical interface level.

You only need to define the maximum bandwidth for an interface on which you want to apply bandwidth management. An interface that does not have a defined maximum bandwidth transmits all multicast flows as determined by the multicast protocol that is running on the interface (for example, PIM).

If you specify maximum-bandwidth without including a bits-per-second value, admission control is enabled based on the bandwidth configured for the interface. In the following example, admission control is enabled for logical interface unit 200, and the maximum bandwidth is 20 Mbps. If the bandwidth is not configured on the interface, the maximum bandwidth is the link speed.

Topology

Configuration

Procedure

CLI Quick Configuration

To quickly configure this example, copy the following commands, paste them into a text file, remove any line breaks, change any details necessary to match your network configuration, copy and paste the commands into the CLI at the [edit] hierarchy level, and then enter commit from configuration mode.

Step-by-Step Procedure

The following example requires you to navigate various levels in the configuration hierarchy. For information about navigating the CLI, see Using the CLI Editor in Configuration Mode in the Junos OS CLI User Guide.

To configure a bandwidth maximum:

  1. Configure the a logical interface bandwidth.

  2. Enable admission control on the logical interface.

  3. On a physical interface, enable admission control and set the maximum bandwidth to 60 Mbps.

  4. For a logical interface on the same physical interface shown in Step 3, set a smaller maximum bandwidth.

Results

Confirm your configuration by entering the show interfaces and show routing-options commands.

Verification

To verify the configuration, run the show multicast interface command.

Example: Configuring Multicast with Subscriber VLANs

This example shows how to configure an MX Series router to function as a broadband service router (BSR).

Requirements

This example uses the following hardware components:

  • One MX Series router or EX Series switch with a PIC that supports traffic control profile queuing

  • One DSLAM

Before you begin:

Overview and Topology

When multiple BSR interfaces receive IGMP and MLD join and leave requests for the same multicast stream, the BSR sends a copy of the multicast stream on each interface. Both the multicast control packets (IGMP and MLD) and the multicast data packets flow on the same BSR interface, along with the unicast data. Because all per-customer traffic has its own interface on the BSR, per-customer accounting, call admission control (CAC), and quality-of-service (QoS) adjustment are supported. The QoS bandwidth used by multicast reduces the unicast bandwidth.

Multiple interfaces on the BSR might connect to a shared device (for example, a DSLAM). The BSR sends the same multicast stream multiple times to the shared device, thus wasting bandwidth. It is more efficient to send the multicast stream one time to the DSLAM and replicate the multicast streams in the DSLAM. There are two approaches that you can use.

The first approach is to continue to send unicast data on the per-customer interfaces, but have the DSLAM route all the per-customer IGMP and MLD join and leave requests to the BSR on a single dedicated interface (a multicast VLAN). The DSLAM receives the multicast streams from the BSR on the dedicated interface with no unnecessary replication and performs the necessary replication to the customers. Because all multicast control and data packets use only one interface, only one copy of a stream is sent even if there are multiple requests. This approach is called reverse outgoing interface (OIF) mapping. Reverse OIF mapping enables the BSR to propagate the multicast state of the shared interface to the customer interfaces, which enables per-customer accounting and QoS adjustment to work. When a customer changes the TV channel, the router gateway (RG) sends an IGMP or MLD join and leave messages to the DSLAM. The DSLAM transparently passes the request to the BSR through the multicast VLAN. The BSR maps the IGMP or MLD request to one of the subscriber VLANs based on the IP source address or the source MAC address. When the subscriber VLAN is found, QoS adjustment and accounting are perfomed on that VLAN or interface.

The second approach is for the DSLAM to continue to send unicast data and all the per-customer IGMP and MLD join and leave requests to the BSR on the individual customer interfaces, but to have the multicast streams arrive on a single dedicated interface. If multiple customers request the same multicast stream, the BSR sends one copy of the data on the dedicated interface. The DSLAM receives the multicast streams from the BSR on the dedicated interface and performs the necessary replication to the customers. Because the multicast control packets use many customer interfaces, configuration on the BSR must specify how to map each customer’s multicast data packets to the single dedicated output interface. QoS adjustment is supported on the customer interfaces. CAC is supported on the shared interface. This second approach is called multicast OIF mapping.

OIF mapping and reverse OIF mapping are not supported on the same customer interface or shared interface. This example shows how to configure the two different approaches. Both approaches support QoS adjustment, and both approaches support MLD/IPv6. The reverse OIF mapping example focuses on IGMP/IPv4 and enables QoS adjustment. The OIF mapping example focuses on MLD/IPv6 and disables QoS adjustment.

The first approach (reverse OIF mapping) includes the following statements:

  • flow-map—Defines a flow map that controls the bandwidth for each flow.

  • maximum-bandwidth—Enables CAC.

  • reverse-oif-mapping—Enables the routing device to identify a subscriber VLAN or interface based on an IGMP or MLD join or leave request that it receives over the multicast VLAN.

    After the subscriber VLAN is identified, the routing device immediately adjusts the QoS (in this case, the bandwidth) on that VLAN based on the addition or removal of a subscriber.

    The routing device uses IGMP and MLD join or leave reports to obtain the subscriber VLAN information. This means that the connecting equipment (for example, the DSLAM) must forward all IGMP and MLD reports to the routing device for this feature to function properly. Using report suppression or an IGMP proxy can result in reverse OIF mapping not working properly.

  • subscriber-leave-timer—Introduces a delay to the QoS update. After receiving an IGMP or MLD leave request, this statement defines a time delay (between 1 and 30 seconds) that the routing device waits before updating the QoS for the remaining subscriber interfaces. You might use this delay to decrease how often the routing device adjusts the overall QoS bandwidth on the VLAN when a subscriber sends rapid leave and join messages (for example, when changing channels in an IPTV network).

  • traffic-control-profile—Configures a shaping rate on the logical interface. The configured shaping rate must be configured as an absolute value, not as a percentage.

The second approach (OIF mapping) includes the following statements:

  • map-to-interface—In a policy statement, enables you to build the OIF map.

    The OIF map is a routing policy statement that can contain multiple terms. When creating OIF maps, keep the following in mind:

    • If you specify a physical interface (for example, ge-0/0/0), a ".0" is appended to the interface to create a logical interface (for example, ge-0/0/0.0).

    • Configure a routing policy for each logical system. You cannot configure routing policies dynamically.

    • The interface must also have IGMP, MLD, or PIM configured.

    • You cannot map to a mapped interface.

    • We recommend that you configure policy statements for IGMP and MLD separately.

    • Specify either a logical interface or the keyword self. The self keyword specifies that multicast data packets be sent on the same interface as the control packets and that no mapping occur. If no term matches, then no multicast data packets are sent.

  • no-qos-adjust—Disables QoS adjustment.

    QoS adjustment decreases the available bandwidth on the client interface by the amount of bandwidth consumed by the multicast streams that are mapped from the client interface to the shared interface. This action always occurs unless it is explicitly disabled.

    If you disable QoS adjustment, available bandwidth is not reduced on the customer interface when multicast streams are added to the shared interface.

    Note:

    You can dynamically disable QoS adjustment for IGMP and MLD interfaces using dynamic profiles.

  • oif-map—Associate a map with an IGMP or MLD interface. The OIF map is then applied to all IGMP or MLD requests received on the configured interface. In this example, subscriber VLANs 1 and 2 have MLD configured, and each VLAN points to an OIF map that directs some traffic to ge-2/3/9.4000, some traffic to ge-2/3/9.4001, and some traffic to self.

    Note:

    You can dynamically associate OIF maps with IGMP interfaces using dynamic profiles.

  • passive—Defines either IGMP or MLD to use passive mode.

    The OIF map interface should not typically pass IGMP or MLD control traffic and should be configured as passive. However, the OIF map implementation does support running IGMP or MLD on an interface (control and data) in addition to mapping data streams to the same interface. In this case, you should configure IGMP or MLD normally (that is, not in passive mode) on the mapped interface. In this example, the OIF map interfaces (ge-2/3/9.4000 and ge-2/3/9.4001) are configured as MLD passive.

    By default, specifying the passive statement means that no general queries, group-specific queries, or group-source-specific queries are sent over the interface and that all received control traffic is ignored by the interface. However, you can selectively activate up to two out of the three available options for the passive statement while keeping the other functions passive (inactive).

    These options include the following:

    • send-general-query—When specified, the interface sends general queries.

    • send-group-query—When specified, the interface sends group-specific and group-source-specific queries.

    • allow-receive—When specified, the interface receives control traffic.

Topology

Figure 3 shows the scenario.

In both approaches, if multiple customers request the same multicast stream, the BSR sends one copy of the stream on the shared multicast VLAN interface. The DSLAM receives the multicast stream from the BSR on the shared interface and performs the necessary replication to the customers.

In the first approach (reverse OIF mapping), the DSLAM uses the per-customer subscriber VLANs for unicast data only. IGMP and MLD join and leave requests are sent on the multicast VLAN.

In the second approach (OIF mapping), the DSLAM uses the per-customer subscriber VLANs for unicast data and for IGMP and MLD join and leave requests. The multicast VLAN is used only for multicast streams, not for join and leave requests.

Figure 3: Multicast with Subscriber VLANsMulticast with Subscriber VLANs

Configuration

Configuring a Reverse OIF Map

CLI Quick Configuration

To quickly configure this example, copy the following commands, paste them into a text file, remove any line breaks, change any details necessary to match your network configuration, copy and paste the commands into the CLI at the [edit] hierarchy level, and then enter commit from configuration mode. .

Step-by-Step Procedure

The following example requires you to navigate various levels in the configuration hierarchy. For information about navigating the CLI, see Using the CLI Editor in Configuration Mode in the Junos OS CLI User Guide.

To configure reverse OIF mapping:

  1. Configure a logical interface for unicast data traffic.

  2. Configure a logical interface for subscriber control traffic.

  3. Configure two logical interfaces on which QoS adjustments are made.

  4. Configure a policy.

  5. Enable a flow map that references the policy.

  6. Enable OIF mapping on the logical interface that receives subscriber control traffic.

  7. Configure PIM and IGMP.

  8. Configure the hierarchical scheduler by configuring a shaping rate for the physical interface and a slower shaping rate for the logical interfaces on which QoS adjustments are made.

Results

From configuration mode, confirm your configuration by entering the show class-of-service, show interfaces, show policy-options, show protocols, and show routing-options commands. If the output does not display the intended configuration, repeat the instructions in this example to correct the configuration.

If you are done configuring the device, enter commit from configuration mode.

Configuring an OIF Map

CLI Quick Configuration

To quickly configure this example, copy the following commands, paste them into a text file, remove any line breaks, change any details necessary to match your network configuration, copy and paste the commands into the CLI at the [edit] hierarchy level, and then enter commit from configuration mode.

Step-by-Step Procedure

The following example requires you to navigate various levels in the configuration hierarchy. For information about navigating the CLI, see the Junos OS CLI User Guide.

To configure reverse OIF mapping:

  1. Configure a logical interface for unicast data traffic.

  2. Configure logical interfaces for subscriber VLANs.

  3. Configure two map-to logical interfaces.

  4. Configure the OIF map.

  5. Disable QoS adjustment on the subscriber VLANs.

  6. Configure PIM and MLD. Point the MLD subscriber VLANs to the OIF map.

Results

From configuration mode, confirm your configuration by entering the show interfaces, show policy-options, show protocols, and show routing-options commands. If the output does not display the intended configuration, repeat the instructions in this example to correct the configuration.

If you are done configuring the device, enter commit from configuration mode.

Verification

To verify the configuration, run the following commands:

  • show igmp statistics

  • show class-of-service interface

  • show interfaces statistics

  • show mld statistics

  • show multicast interface

  • show policy

Configuring Multicast Routing over IP Demux Interfaces

In a subscriber management network, fields in packets sent from IP demux interfaces are intended to correspond to a specific client that resides on the other side of an aggregation device (for example, a Multiservice Access Node [MSAN]). However, packets sent from a Broadband Services Router (BSR) to an MSAN do not identify the demux interface. Once it obtains a packet, it is up to the MSAN device to determine which client receives the packet.

Depending on the intelligence of the MSAN device, determining which client receives the packet can occur in an inefficient manner. For example, when it receives IGMP control traffic, an MSAN might forward the control traffic to all clients instead of the one intended client. In addition, once a data stream destination is established, though an MSAN can use IGMP snooping to determine which hosts reside in a particular group and limit data streams to only that group, the MSAN still must send multiple copies of the data stream to each group member, even if that data stream is intended for only one client in the group.

Various multicast features, when combined, enable you to avoid the inefficiencies mentioned above. These features include the following:

  • The ability to configure the IP demux interface family statement to use inet for either the numbered or unnumbered primary interface.

  • The ability to configure IGMP on the primary interface to send general queries for all clients. The demux configuration prevents the primary IGMP interface from receiving any client IGMP control packets. Instead, all IGMP control packets go to the demux interfaces. However, to guarantee that no joins occur on the primary interface:

    • For static IGMP interfaces—Include the passive send-general-query statement in the IGMP configuration at the [edit protocols igmp interface interface-name] hierarchy level.

    • For dynamic IGMP demux interfaces—Include the passive send-general-query statement at the [edit dynamic-profiles profile-name protocols igmp interface interface-name] hierarchy level.

  • The ability to map all multicast groups to the primary interface as follows:

    • For static IGMP interfaces—Include the oif-map statement at the [edit protocols igmp interface interface-name] hierarchy level.

    • For dynamic IGMP demux interfaces—Include the oif-map statement at the [edit dynamic-profiles profile-name protocols igmp interface interface-name] hierarchy level.

    Using the oif-map statement, you can map the same IGMP group to the same output interface and send only one copy of the multicast stream from the interface.

  • The ability to configure IGMP on each demux interface. To prevent duplicate general queries:

    • For static IGMP interfaces—Include the passive allow-receive send-group-query statement at the [edit protocols igmp interface interface-name] hierarchy level.

    • For dynamic demux interfaces—Include the passive allow-receive send-group-query statement at the [edit dynamic-profiles profile-name protocols igmp interface interface-name] hierarchy level.

    Note:

    To send only one copy of each group, regardless of how many customers join, use the oif-map statement as previously mentioned.

Classifying Packets by Egress Interface

For Juniper Networks M320 Multiservice Edge Routers and T Series Core Routers with the Intelligent Queuing (IQ), IQ2, Enhanced IQ (IQE), Multiservices link services intelligent queuing (LSQ) interfaces, or ATM2 PICs, you can classify unicast and multicast packets based on the egress interface. For unicast traffic, you can also use a multifield filter, but only egress interface classification applies to multicast traffic as well as unicast traffic. If you configure egress classification of an interface, you cannot perform Differentiated Services code point (DSCP) rewrites on the interface. By default, the system does not perform any classification based on the egress interface.

On an MX Series router that contains MPCs and MS-DPCs, multicast packets are dropped on the router and not processed properly if the router contains MLPPP LSQ logical interfaces that function as multicast receivers and if the network services mode is configured as enhanced IP mode on the router. This behavior is expected with LSQ interfaces in conjunction with enhanced IP mode. In such a scenario, if enhanced IP mode is not configured, multicasting works correctly. However, if the router contains redundant LSQ interfaces and enhanced IP network services mode configured with FIB localization, multicast works properly.

To enable packet classification by the egress interface, you first configure a forwarding class map and one or more queue numbers for the egress interface at the [edit class-of-service forwarding-class-map forwarding-class-map-name] hierarchy level:

For T Series routers that are restricted to only four queues, you can control the queue assignment with the restricted-queue option, or you can allow the system to automatically determine the queue in a modular fashion. For example, a map assigning packets to queue 6 would map to queue 2 on a four-queue system.

Note:

If you configure an output forwarding class map associating a forwarding class with a queue number, this map is not supported on multiservices link services intelligent queuing (lsq-) interfaces.

Once the forwarding class map has been configured, you apply the map to the logical interface by using the output-forwarding-class-map statement at the [edit class-of-service interfaces interface-name unit logical-unit-number ] hierarchy level:

All parameters relating to the queues and forwarding class must be configured as well. For more information about configuring forwarding classes and queues, see Configuring a Custom Forwarding Class for Each Queue.

This example shows how to configure an interface-specific forwarding-class map named FCMAP1 that restricts queues 5 and 6 to different queues on four-queue systems and then applies FCMAP1 to unit 0 of interface ge-6/0/0:

Note that without the restricted-queue option in FCMAP1, the example would assign FC1 and FC2 to queues 2 and 1, respectively, on a system restricted to four queues.

Use the show class-of-service forwarding-class forwarding-class-map-name command to display the forwarding-class map queue configuration:

Use the show class-of-service interface interface-name command to display the forwarding-class maps (and other information) assigned to a logical interface: