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ME60 V800R010C10SPC500 Feature Description - IP Multicast 01

This is ME60 V800R010C10SPC500 Feature Description - IP Multicast
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NG MVPN Public Network Tunnel Principle

NG MVPN Public Network Tunnel Principle

NG MVPN devices exchange routing information through BGP and establishes an MVPN tunnel based on MPLS P2MP to carry multicast traffic.

The establishment of NG MVPN tunnels is affected by the network deployed on the public network, including whether the public network contains multiple ASs and whether different MPLS protocols are deployed in different areas. According to the two factors, NG MVPN deployment scenarios can be classified into the following types:
  • Intra-AS non-segmented NG MVPN: The public network contains only one AS, and only one MPLS protocol is deployed.
  • Intra-AS segmented NG MVPN: The public network contains only one AS but contains multiple areas. Different MPLS protocols are deployed in adjacent areas.
  • Inter-AS non-segmented NG MVPN: The public network contains multiple ASs, and only one MPLS protocol is deployed in the ASs.

For details about the NG MVPN deployment scenarios, see NG MVPN Typical Deployment Scenarios on the Public Network.

Tunnel establishment includes the following basic steps and slightly differs in different scenarios:
  1. MVPN membership autodiscovery

    MVPN membership autodiscovery is a process that automatically discovers MVPN peers and establishes MVPN peer relationships. A sender PE and a receiver PE on the same MVPN can exchange control messages that carry MVPN NLRI to establish a PMSI tunnel only after they establish an MVPN peer relationship. In ME60, PEs use BGP as the signaling protocol to exchange control messages.

  2. I-PMSI tunnel establishment

    PMSI tunnels are logical tunnels used by a public network to transmit VPN multicast traffic.

  3. Switching between I-PMSI and S-PMSI tunnels

    After switching between I-PMSI and S-PMSI tunnels is configured, if the multicast data forwarding rate exceeds the switching threshold, multicast data is switched from the I-PMSI tunnel to an S-PMSI tunnel. Unlike the I-PMSI tunnel that sends multicast data to all PEs on an NG MVPN, an S-PMSI tunnel sends multicast data only to PEs interested in the data, reducing bandwidth consumption and PEs' burdens.

  4. Transmitting multicast traffic on an NG MVPN

    After a public network PMSI tunnel is created, multicast users can join the multicast group and apply for multicast services from the multicast source. The multicast source can send multicast traffic to multicast users through the PMSI tunnel.

The concepts and protocols related to the multicast traffic carried by the public network tunnel are as follows:

PMSI Tunnel

Public tunnels (P-tunnels) are transport mechanisms used to forward VPN multicast traffic across service provider networks. In ME60, PMSI tunnels can be carried over RSVP-TE P2MP or mLDP P2MP tunnels. Table 8-22 lists the differences between RSVP-TE P2MP tunnels and mLDP P2MP tunnels.

Table 8-22 Differences between RSVP-TE P2MP tunnels and mLDP P2MP tunnels

Tunnel Type

Tunnel Establishment Method

Characteristic

RSVP-TE P2MP tunnel

Established from the root node.

RSVP-TE P2MP tunnels support bandwidth reservation and can ensure service quality during network congestion. Use RSVP-TE P2MP tunnels to carry PMSI tunnels if high service quality is required.

mLDP P2MP tunnel

Established from a leaf node.

mLDP P2MP tunnels do not support bandwidth reservation and cannot ensure service quality during network congestion. Configuring an mLDP P2MP tunnel, however, is easier than configuring an RSVP-TE P2MP tunnel. Use mLDP P2MP tunnels to carry PMSI tunnels if high service quality is not required.

Theoretically, a P-tunnel can carry the traffic of one or multiple MVPNs. However, in ME60, a P-tunnel can carry the traffic of only one MVPN.

On an MVPN that uses BGP as the signaling protocol, a sender PE distributes information about the P-tunnel in a new BGP attribute called PMSI. PMSI tunnels are the logical tunnels used by the public network to transmit VPN multicast data, and P-tunnels are the actual tunnels used by the public network to transmit VPN multicast data. A sender PE uses PMSI tunnels to send specific VPN multicast data to receiver PEs. A receiver PE uses PMSI tunnel information to determine which multicast data is sent by the multicast source on the same MVPN as itself. There are two types of PMSI tunnels: I-PMSI tunnels and S-PMSI tunnels.Table 8-23 lists the differences between I-PMSI and S-PMSI tunnels.
Table 8-23 I-PMSI and S-PMSI

PMSI Tunnel Type

Description

Characteristic

I-PMSI tunnel

An I-PMSI tunnel connects to all PEs on an MVPN.

Multicast data sent over an I-PMSI tunnel can be received by all PEs on the MVPN. In a VPN instance, one PE corresponds to only one I-PMSI tunnel.

S-PMSI tunnel

An S-PMSI tunnel connects to the sender and receiver PEs of specific sources and multicast groups.

Multicast data sent over an S-PMSI tunnel is received by only PEs interested in the data. In a VPN instance, one PE can correspond to multiple S-PMSI tunnels.

A public network tunnel can consist of one PMSI logical tunnel or multiple interconnected PMSI tunnels. The former is a non-segmented tunnel, and the latter forms a segmented tunnel.
  • For a non-segment tunnel, the public network between the sender PE and receiver PE uses the same MPLS protocol. Therefore, an MPLS P2MP tunnel can be used to set up a PSMI logical tunnel to carry multicast traffic.
  • For a segmented tunnel, different areas on the public network between the sender PE and receiver PE use different MPLS protocols. Therefore, PMSI tunnels need to be established in each area based on the MPLS protocol type and MPLS P2MP tunnel type. In addition, tunnel stitching must be configured on area connection nodes to stitch PMSI tunnels in different areas into one tunnel to carry the data traffic of the MVPN. Currently, the ME60 supports intra-AS segmented tunnels, not inter-AS segmented tunnels.

MVPN Targets

MVPN targets are used to control MVPN A-D route advertisement. MVPN targets function in a similar way as VPN targets used on unicast VPNs and are also classified into two types:
  • Export MVPN target: A PE adds the export MVPN target to an MVPN instance before advertising this route.
  • Import MVPN target: After receiving an MVPN A-D route from another PE, a PE matches the export MVPN target of the route against the import MVPN targets of its VPN instances. If the export MVPN target matches the import MVPN target of a VPN instance, the PE accepts the MVPN A-D route and records the sender PE as an MVPN member. If the export MVPN target does not match the import MVPN target of any VPN instance, the PE drops the MVPN A-D route.
NOTE:

By default, if you do not configure MVPN targets for an MVPN, MVPN A-D routes carry the VPN target communities that are attached to unicast VPN-IPv4 routes. If the unicast and multicast network topologies are congruent, you do not need to configure MVPN targets for MVPN A-D routes. If they are not congruent, configure MVPN targets for MVPN A-D routes.

MVPN Membership Autodiscovery

To exchange control messages and establish PMSI tunnels, a PE on an MVPN must be capable of discovering other PEs on the MVPN. The discovery process is called MVPN membership autodiscovery. An NG MVPN uses BGP to implement this process. To support MVPN membership autodiscovery, BGP defines a new address family, the BGP-MVPN address family.

On the network shown in Figure 8-25, BGP and MVPN are configured on PE1, PE2, and PE3 in a way that PE1 can negotiate with PE2 and PE3 to establish BGP MVPN peer relationships. A PE newly added to the service provider's backbone network can join the MVPN so long as this PE can establish BGP MVPN peer relationships with existing PEs on the MVPN.

Figure 8-25 Typical NG MVPN networking scenario

To transmit multicast traffic from multicast sources to multicast receivers, sender PEs must establish BGP MVPN peer relationships with receiver PEs. On the network shown in Figure 8-25, PE1 serves as a sender PE, and PE2 and PE3 serve as receiver PEs. Therefore, PE1 establishes BGP MVPN peer relationships with PE2 and PE3.

PEs on an NG MVPN use BGP Update messages to exchange MVPN information. MVPN information is carried in the network layer reachability information (NLRI) field of a BGP Update message. The NLRI containing MVPN information is also called the MVPN NLRI. For more information about the MVPN NLRI, see MVPN NLRI.

I-PMSI Tunnel Establishment

When establishing an I-PMSI tunnel, you must specify the P-tunnel type. The process of establishing an I-PMSI tunnel varies according to the P-tunnel type. In ME60, PEs can use only the following types of P-tunnels to carry I-PMSI tunnels:
  • RSVP-TE P2MP tunnels: A sender PE sends an intra-AS PMSI A-D route to each receiver PE. Upon receipt, each receiver PE sends a reply message. Then, the sender PE collects P2MP tunnel leaf information from received reply messages and establishes an RSVP-TE P2MP tunnel for each MVPN based on the leaf information of the MVPN. For more information about RSVP-TE P2MP tunnel establishment, see "P2MP TE" in ME60 Feature Description - MPLS.
  • mLDP P2MP tunnels: Receiver PEs directly send Label Mapping messages based on the root node address (sender PE address) and opaque value information carried in the Intra-AS PMSI A-D route sent by the sender PE to establish an mLDP P2MP tunnel. For more information about mLDP P2MP tunnel establishment, see "mLDP" in ME60 Feature Description - MPLS.
NOTE:

For comparison between RSVP-TE and mLDP P2MP tunnels, see Table 8-22 in NG MVPN Public Network Tunnel Principle.

The following example uses the network shown in Figure 8-26 to describe how to establish PMSI tunnels. Because RSVP-TE P2MP tunnels and mLDP P2MP tunnels are established differently, the following uses two scenarios, RSVP-TE P2MP Tunnel and mLDP P2MP Tunnel, to describe how to establish PMSI tunnels.

This example presumes that:

  • PE1 has established BGP MVPN peer relationships with PE2 and PE3, but no BGP MVPN peer relationship is established between PE2 and PE3.
  • The network administrator has configured MVPN on PE1, PE2, and PE3 in turn.
Figure 8-26 Typical NG MVPN networking scenario

RSVP-TE P2MP Tunnel

Figure 8-27 shows the time sequence for establishing an I-PMSI tunnel with the P-tunnel type as RSVP-TE P2MP LSP.

Figure 8-27 Time sequence for establishing an I-PMSI tunnel with the P-tunnel type as RSVP-TE P2MP LSP

Table 8-24 briefs the procedure for establishing an I-PMSI tunnel with the P-tunnel type as RSVP-TE P2MP LSP.

Table 8-24 Procedure for establishing an I-PMSI tunnel with the P-tunnel type as RSVP-TE P2MP LSP

Step

Device

Prerequisites

Key Action

PE1

BGP and MVPN have been configured on PE1.

PE1 has been configured as a sender PE.

The P-tunnel type for I-PMSI tunnel establishment has been specified as RSVP-TE P2MP LSP.

As a sender PE, PE1 initiates the I-PMSI tunnel establishment process. The MPLS module on PE1 reserves resources for the corresponding RSVP-TE P2MP tunnel. Because PE1 does not know RSVP-TE P2MP tunnel leaf information, the RSVP-TE P2MP tunnel is not established in a real sense.

PE1

BGP and MVPN have been configured on PE2.

PE1 has established a BGP MVPN peer relationship with PE2.

PE1 sends a Type 1 BGP A-D route to PE2. This route carries the following information:
  • MVPN Targets: used to control A-D route advertisement. The Type 1 BGP A-D route carries the export MVPN target information configured on PE1.
  • PMSI Tunnel Attribute: specifies the P-tunnel type (RSVP-TE P2MP LSP in this case) used for PMSI tunnel establishment. This attribute carries information about resources reserved for the RSVP-TE P2MP tunnel in Step .

PE2

-

  1. PE2 sends a BGP A-D route that carries the export MVPN target to PE1. Because PE2 is not a sender PE configured with PMSI tunnel information, the BGP A-D route sent by PE2 does not carry the PMSI Tunnel attribute.
  2. After PE2 receives the BGP A-D route from PE1, PE2 matches the export MVPN target of the route against its local import MVPN target. If the two targets match, PE2 accepts this route, records PE1 as an MVPN member, and joins the P2MP tunnel that is specified in the PMSI Tunnel attribute carried in this route (at the moment, the P2MP tunnel has not been established yet).

PE1

-

After PE1 receives the BGP A-D route from PE2, PE1 matches the export MVPN target of the route against its local import MVPN target. If the two targets match, PE1 accepts this route, records PE2 as an MVPN member, and instructs the MPLS module to send an MPLS message to PE2 and add PE2 as a leaf node of the RSVP-TE P2MP tunnel to be established.

PE1

-

After PE1 receives a reply from PE2, the MPLS module on PE1 completes the process of establishing an RSVP-TE P2MP tunnel with PE1 as the root node and PE2 as a leaf node. For more information about RSVP-TE P2MP tunnel establishment, see "P2MP TE" in ME60 Feature Description - MPLS.

PE2

-

After PE2 receives the MPLS message from PE1, PE2 joins the established RSVP-TE P2MP tunnel.

PE3 joins the RSVP-TE P2MP tunnel rooted at PE1 in a similar way as PE2. After PE2 and PE3 both join the RSVP-TE P2MP tunnel rooted at PE1, the I-PMSI tunnel is established and the MVPN service becomes available.

mLDP P2MP Tunnel

Figure 8-28 shows the time sequence for establishing an I-PMSI tunnel with the P-tunnel type as mLDP LSP.

Figure 8-28 Time sequence for establishing an I-PMSI tunnel with the P-tunnel type as mLDP P2MP LSP

Table 8-25 briefs the procedure for establishing an I-PMSI tunnel with the P-tunnel type as mLDP P2MP LSP.

Table 8-25 Procedure for establishing an I-PMSI tunnel with the P-tunnel type as mLDP P2MP LSP

Step

Device

Prerequisites

Key Action

PE1

BGP and MVPN have been configured on PE1.

PE1 has been configured as a sender PE.

The P-tunnel type for I-PMSI tunnel establishment has been specified as mLDP P2MP LSP.

As a sender PE, PE1 initiates the I-PMSI tunnel establishment process. The MPLS module on PE1 reserves resources (FEC information such as the opaque value and root node address) for the corresponding mLDP P2MP tunnel. Because PE1 does not know leaf information of the mLDP P2MP tunnel, the mLDP P2MP tunnel is not established in a real sense.

PE1

BGP and MVPN have been configured on PE2.

PE1 has established a BGP MVPN peer relationship with PE2.

PE1 sends a Type 1 BGP A-D route to PE2. This route carries the following information:
  • MVPN Targets: used to control A-D route advertisement. The Type 1 BGP A-D route carries the export MVPN target configured on PE1.
  • PMSI Tunnel Attribute: specifies the P-tunnel type (mLDP P2MP in this case) used for PMSI tunnel establishment. This attribute carries information about resources reserved by MPLS for the mLDP P2MP tunnel in Step .

PE2

-

After PE2 receives the BGP A-D route from PE1, the MPLS module on PE2 sends a Label Mapping message to PE1. This is because the PMSI Tunnel attribute carried in the received route specifies the P-tunnel type as mLDP, meaning that the P2MP tunnel must be established from leaves.

After PE2 receives the MPLS message replied by PE1, PE2 becomes aware that the P2MP tunnel has been established. For more information about mLDP P2MP tunnel establishment, see "mLDP" in ME60 Feature Description - MPLS.

PE2

-

PE2 creates an mLDP P2MP tunnel rooted at PE1.

PE2

-

PE2 sends a BGP A-D route that carries the export MVPN target to PE1. Because PE2 is not a sender PE configured with PMSI tunnel information, the BGP A-D route sent by PE2 does not carry the PMSI Tunnel attribute.

After PE1 receives the BGP A-D route from PE2, PE1 matches the export MVPN target of the route against its local import MVPN target. If the two targets match, PE1 accepts this route and records PE2 as an MVPN member.

PE3 joins the mLDP P2MP tunnel and MVPN in a similar way as PE2. After PE2 and PE3 both join the mLDP P2MP tunnel rooted at PE1, the I-PMSI tunnel is established and the MVPN service becomes available.

Switching Between I-PMSI and S-PMSI Tunnels

Background

An NG MVPN uses the I-PMSI tunnel to send multicast data to receivers. The I-PMSI tunnel connects to all PEs on the MVPN and sends multicast data to these PEs regardless of whether these PEs have receivers. If some PEs do not have receivers, this implementation will cause redundant traffic, wasting bandwidth resources and increasing PEs' burdens.

To solve this problem, S-PMSI tunnels are introduced. An S-PMSI tunnel connects to the sender and receiver PEs of specific multicast sources and groups on an NG MVPN. Compared with the I-PMSI tunnel, an S-PMSI tunnel sends multicast data only to PEs interested in the data, reducing bandwidth consumption and PEs' burdens.

NOTE:

For comparison between I-PMSI and S-PMSI tunnels, see NG MVPN Public Network Tunnel Principle in Table 8-23.

Implementation

The following example uses the network shown in Figure 8-29 to describe switching between I-PMSI and S-PMSI tunnels on an NG MVPN.

Figure 8-29 Typical NG MVPN networking
Table 8-26 Switching between I-PMSI and S-PMSI tunnels

Item

Occurring Condition

Description

Switching from the I-PMSI tunnel to an S-PMSI tunnel

The multicast data forwarding rate is consistently above the specified switching threshold.

S-PMSI tunnels are classified as RSVP-TE S-PMSI tunnels or mLDP S-PMSI tunnels, depending on the bearer tunnel type. For details about switching from the I-PMSI tunnel to an S-PMSI tunnel, see:
Switching from an S-PMSI tunnel to the I-PMSI tunnel

The multicast data forwarding rate is consistently below the specified switching threshold.

-
NOTE:
  • After multicast data is switched from the I-PMSI tunnel to an S-PMSI tunnel, if the S-PMSI tunnel fails but the I-PMSI tunnel is still available, multicast data will be switched back to the I-PMSI tunnel.
  • After multicast data is switched from the I-PMSI tunnel to an S-PMSI tunnel, if the multicast data forwarding rate is consistently below the specified switching threshold but the I-PMSI tunnel is unavailable, multicast data still travels along the S-PMSI tunnel.
Switching from the I-PMSI Tunnel to an S-PMSI Tunnel
  • Switching from the I-PMSI Tunnel to an RSVP-TE S-PMSI Tunnel

    Figure 8-30 shows the time sequence for switching from the I-PMSI tunnel to an RSVP-TE S-PMSI tunnel. Table 8-27 describes the specific switching procedure.

    Figure 8-30 Time sequence for switching from the I-PMSI tunnel to an RSVP-TE S-PMSI tunnel
    Table 8-27 Procedure for switching from the I-PMSI tunnel to an RSVP-TE S-PMSI tunnel

    Step

    Device

    Key Action

    PE1

    After PE1 detects that the multicast data forwarding rate exceeds the specified switching threshold, PE1 initiates switching from the I-PMSI tunnel to an S-PMSI tunnel by sending a BGP S-PMSI A-D route to its BGP peers. In the BGP S-PMSI A-D route, the Leaf Information Require flag is set to 1, indicating that a PE that receives this route needs to send a BGP Leaf A-D route in response if the PE wants to join the S-PMSI tunnel to be established.

    PE2

    Upon receipt of the BGP S-PMSI A-D route, PE2, which has downstream receivers, sends a BGP Leaf A-D route to PE1.

    PE3

    Upon receipt of the BGP S-PMSI A-D route, PE3, which does not have downstream receivers, does not send a BGP Leaf A-D route to PE1 but records the BGP S-PMSI A-D route information.

    PE1

    Upon receipt of the BGP Leaf A-D route from PE2, PE1 establishes an S-PMSI tunnel with itself as the root node and PE2 as a leaf node.

    PE2

    After PE2 detects that the RSVP-TE S-PMSI tunnel has been established, PE2 joins this tunnel.

    After PE3 has downstream receivers, PE3 will send a BGP Leaf A-D route to PE1. Upon receipt of the route, PE1 adds PE3 as a leaf node of the RSVE-TE S-PMSI tunnel. After PE3 joins the tunnel, PE3's downstream receivers will also be able to receive multicast data.

  • Switching from the I-PMSI Tunnel to an mLDP S-PMSI Tunnel

    Figure 8-31 shows the time sequence for switching from the I-PMSI tunnel to an mLDP S-PMSI tunnel. Table 8-28 describes the specific switching procedure.

    Figure 8-31 Time sequence for switching from the I-PMSI tunnel to an mLDP S-PMSI tunnel
    Table 8-28 Procedure for switching from the I-PMSI tunnel to an mLDP S-PMSI tunnel

    Step

    Device

    Key Action

    PE1

    After PE1 detects that the multicast data forwarding rate exceeds the specified switching threshold, PE1 initiates switching from the I-PMSI tunnel to an S-PMSI tunnel by sending a BGP S-PMSI A-D route to its BGP peers. In the BGP S-PMSI A-D route, the Leaf Information Require flag is set to 0.

    PE2

    Upon receipt of the BGP S-PMSI A-D route, PE2, which has downstream receivers, directly joins the mLDP S-PMSI tunnel specified in the BGP S-PMSI A-D route.

    PE3

    Upon receipt of the BGP S-PMSI A-D route, PE3, which does not have downstream receivers, does not join the mLDP S-PMSI tunnel specified in the BGP S-PMSI A-D route, but records the BGP S-PMSI A-D route information.

    After PE3 has downstream receivers, PE3 will also directly join the mLDP S-PMSI tunnel. Then, PE3's downstream receivers will also be able to receive multicast data.

NOTE:

PE1 starts a switch-delay timer upon the completion of S-PMSI tunnel establishment and determines whether to switch multicast data to the S-PMSI tunnel as follows: If the S-PMSI tunnel fails to be established, PE1 still uses the I-PMSI tunnel to send multicast data. If the multicast data forwarding rate is consistently below the specified switching threshold throughout the timer lifecycle, PE1 still uses the I-PMSI tunnel to transmit multicast data. If the multicast data forwarding rate is consistently above the specified switching threshold throughout the timer lifecycle, PE1 switches data to the S-PMSI tunnel for transmission.

Switching from an S-PMSI Tunnel to the I-PMSI Tunnel

Figure 8-32 shows the time sequence for switching from an S-PMSI tunnel to the I-PMSI tunnel. Table 8-29 describes the specific switching procedure.

Figure 8-32 Time sequence for switching from an S-PMSI tunnel to the I-PMSI tunnel
Table 8-29 Procedure for switching from an S-PMSI tunnel to the I-PMSI tunnel

Step

Device

Key Action

PE1

After PE1 detects that the multicast data forwarding rate is consistently below the specified switching threshold, PE1 starts a switchback hold timer:
  • If the multicast data forwarding rate is consistently above the specified switching threshold throughout the timer lifecycle, PE1 still uses the S-PMSI tunnel to send traffic.
  • If the multicast data forwarding rate is consistently below the specified switching threshold throughout the timer lifecycle, PE1 switches multicast data to the I-PMSI tunnel for transmission. Meanwhile, PE1 sends a BGP Withdraw S-PMSI A-D route to PE2, instructing PE2 to withdraw bindings between multicast entries and the S-PMSI tunnel.

PE2

Upon receipt of the BGP Withdraw S-PMSI A-D route, PE2 withdraws the bindings between its multicast entries and the S-PMSI tunnel. If PE2 has sent a BGP Leaf A-D route to PE1, PE2 will send a BGP Withdraw Leaf A-D route to PE1 in this step.

PE2

After PE2 detects that none of its multicast entries is bound to the S-PMSI tunnel, PE2 leaves the S-PMSI tunnel.

PE1

PE1 deletes the S-PMSI tunnel after waiting for a specified period of time.

NOTE:
In an RSVP-TE P2MP tunnel dual-root 1+1 protection scenario, S-PMSI tunnels must be carried over RSVP-TE P2MP tunnels. The I-PMSI/S-PMSI switching processes in this scenario are similar to those described above except that the leaf PEs need to start a tunnel status check delay timer:
  • Before the timer expires, leaf PEs delete tunnel protection groups to skip the status check of the primary I-PMSI or S-PMSI tunnel. The leaf PEs select the multicast data received from the primary tunnel and discard the multicast data received from the backup tunnel.
  • After the timer expires, leaf PEs start to check the primary I-PMSI or S-PMSI tunnel status again. Leaf PEs select the multicast data received from the primary tunnel only if the primary tunnel is Up. If the primary tunnel is Down, Leaf PEs select the multicast data received from the backup tunnel.

Transmitting multicast traffic on an NG MVPN

After a multicast receiver joins a multicast group, the multicast source can send multicast traffic to the multicast receiver over a BGP/MPLS IP VPN if the corresponding P-tunnel has been established. Figure 8-33 shows a typical NG MVPN networking scenario, and Figure 8-34 shows how an IP multicast packet is encapsulated and transmitted on the network shown in Figure 8-33.
Figure 8-33 Typical NG MVPN networking scenario
Figure 8-34 IP multicast packet transmission on an NG MVPN

Table 8-30 describes how an IP multicast packet is transmitted on an NG MVPN.

Table 8-30 IP multicast packet transmission on an NG MVPN

Step

Device

Action

Multicast Forwarding Table Information

1

CE1

After CE1 receives an IP multicast packet from the multicast source, CE1 searches its multicast forwarding table to forward the packet to PE1.

2

PE1

After PE1 receives the IP multicast packet, PE1 searches its VPN instance multicast forwarding table for the corresponding (C-S, C-G) entry, adds an MPLS label to the packet, and sends the packet over a P2MP tunnel to the P.

3

P

After the P receives the MPLS packet, the P duplicates the packet after removing the MPLS label of the packet. Then, the P adds a new MPLS label to each copy and sends one copy to PE2 and one copy to PE3.

-

4

PE2/PE3

After PE2 and PE3 receive the MPLS packet, PE2 and PE3 remove the MPLS label, search their VPN instance multicast forwarding tables for the corresponding (C-S, C-G) entries, and forward the IP multicast packet to CE2 and CE3 respectively.

5

CE2/CE3

After CE2 and CE3 receive the IP multicast packet, CE2 and CE3 search their multicast forwarding tables to forward the IP multicast packet to all receivers in the multicast group.

NG MVPN Typical Deployment Scenarios on the Public Network

An NG MVPN uses a PMSI tunnel established on the public network BGP/MPLS VPN network to transmit multicast traffic. The NG MVPN deployment mode varies according to the public network architecture. According to whether the public network crosses ASs and whether the tunnel is segmented, there are the following scenarios:
  • Intra-AS non-segmented NG MVPN: The public network contains only one AS, and only one MPLS protocol is deployed.
  • Inter-AS non-segmented NG MVPN: The public network contains multiple ASs, and only one MPLS protocol is deployed in the ASs.
  • Intra-AS segmented NG MVPN: The public network contains only one AS but multiple areas, and different MPLS protocols are deployed in adjacent areas.
Intra-AS Non-segmented NG MVPN
The public network that the multicast service traverses contains only one AS, and only one MPLS protocol is used between PE1 on the multicast source side and PE2 on the multicast user side, as shown in Figure 8-35.
Figure 8-35 Intra-AS non-segmented NG MVPN
The NG MVPN is established as follows:
  • Establish an I-BGP peer relationship between PEs.
  • Deploy MVPN on the PEs, so that the PEs in the same MVPN can automatically discover each other and use BGP to transmit BGP C-multicast routes.
  • Configure a P2MP tunnel and use BGP to transmit BGP A-D routes to each other, so that PE1 and PE2 can establish a PMSI tunnel based on the P2MP tunnel to transmit multicast traffic.
Inter-AS Non-segmented NG MVPN
The public network that the multicast service traverses contains multiple ASs, and only one MPLS protocol is used between PE1 on the multicast source side and PE2 on the multicast user side, as shown in Figure 8-36.
Figure 8-36 Inter-AS non-segmented NG MVPN

This scenario supports three VPN modes: Option A, Option B, and Option C. In Option A mode, ASBRs use each other as CEs. The establishment process is similar to that in the intra-AS non-segment scenario.

In Option B mode, the NG MVPN is established as follows:
  • Establish an IBGP peer relationship between a PE and an ASBR in the same AS. Establish an EBGP peer relationship between ASBRs in different ASs.
  • Deploy MVPN on the PEs, so that the PEs in the same MVPN can automatically discover each other and use BGP to transmit BGP C-multicast routes through ASBRs.
  • Configure a P2MP tunnel and use BGP to transmit BGP A-D routes to each other through ASBRs, so that PE1 and PE2 can establish a PMSI tunnel based on the P2MP tunnel to transmit multicast traffic.
In Option C mode, the NG MVPN is established as follows:
  • Establish an IBGP peer relationship between a PE and an ASBR in the same AS. Establish an EBGP peer relationship between ASBRs in different ASs. Establish an MP-EBGP peer relationship between PE1 and PE2.
  • Deploy MVPN on the PEs, so that the PEs in the same MVPN can automatically discover each other and use BGP to directly transmit BGP C-multicast routes over ASBRs.
  • Configure a P2MP tunnel and use BGP to directly transmit BGP A-D routes to each other over ASBRs, so that PE1 and PE2 can establish a PMSI tunnel based on the P2MP tunnel to transmit multicast traffic.
Intra-AS Segmented NG MVPN
The public network that the multicast service traverses contains only one AS, and MPLS areas of different types are used between PE1 on the multicast source side and PE2 on the multicast user side, as shown in Figure 8-37.
Figure 8-37 Intra-AS segmented NG MVPN
The NG MVPN is established as follows:
  • Establish an I-BGP peer relationship between the PE and ABR.
  • Deploy MVPN on the PEs, so that the PEs in the same MVPN can automatically discover each other and use BGP to transmit BGP C-multicast routes.
  • Configure a P2MP tunnel and use BGP to transmit BGP A-D routes to each other so that PE1 and the ABR can establish a PMSI tunnel based on the P2MP tunnel. The ABR and PE2 establish a PMSI tunnel based on the P2MP tunnel. The two tunnels are stitched on the ABR to carry the multicast traffic transmitted from PE1 to PE2.
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Updated: 2019-01-04

Document ID: EDOC1100059456

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