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Configuring Micro-SIDs in EVPN-VPWS

The segment routing headers (SRHs)for SRv6 can have a long list of SIDs when data packets are routed through many SRv6 nodes before it reaches its destination address (DA). A long list of segment identifiers (SIDs) adds overhead to the data payload and reduces the efficiency of the payload. Starting with Junos Evolved Release 24.2R1, you can configure micro-SIDs on the ACX7000 family. Micro-SIDs (uSIDs) extend SRv6 network programming by compressing up to 6 SRv6 SIDs into one SRv6 address within an SRH.

For uSID, the router divides the 128-bit SID into the following:

  • Prefix/Block—The prefix contains the locator address of the network.

  • List of uSID instructions—The list of uSID contains either micro-node IDs or a uSID function/behavior.

  • Argument—The argument is an optional field in the SRH.

Figure 1 shows the DA as a packet moves through different nodes in SRv6 topology 1. The nodes, ID/function, and SIDs advertised by the nodes are listed in Table 1.

Figure 1: Micro-SID in an SRv6 Network Micro-SID in an SRv6 Network
Table 1: SRv6 micro-SID

Node

Micro-Node ID/Micro-Node Function

SIDs Advertised by each Node

R1

300

2001:db8:300:0:0:0:0:0

R3

400

2001:db8:400:0:0:0:0:0

PE2

700

2001:db8:700:0:0:0:0:0

PE2

f001

2001:db8:700:f001:0:0:0:0

  1. At the ingress router, PE1 compresses the micro-SIDs for the nodes (R1, R3, and PE2) into one DA. 2001:db8:300:400:700:f001.

  2. R1 processes the DA by consuming its own uSID 300 and forwards the packet with a DA of 2001:db8:400:700:f001:0.

  3. R3 processes the DA by consuming its own uSID of 400 and forwards the packet with a DA 2001:db8:700:f001:0:0.

  4. At the egress router, PE2 consumes its own uSID of 700 and processes the microservices function.

Benefits of uSIDs

  • Reduces network bandwidth by reducing the number of SRv6 addresses in the SRH.

  • Reduces the SRH processing overhead on the node.

Configuring EVPN-VPWS over SRv6 Network with uSIDs

CLI Quick Configuration

To quickly configure EVPN-VPWS over SRv6 with uSIDs, copy the following commands, paste them into a text file, remove any line breaks, change any details necessary to match your configuration, copy and paste the commands into the CLI at the [edit] hierarchy level. Enter commit from configuration mode.

We describe the uSID configuration on PE1 with different configurations that are called out for PE2. To provision a static uSID, you must first a static local range of addresses that can be used by the devices. Include the additional configurations on the routers:

  1. Enable enhanced-ip support on all MX devices.

  2. Enable expanded next-hop hierarchy support for source packet routing.

  3. Enable an evpn-vpws routing instance.

  4. Configure the SRv6 encapsulation type for the EVPN-VPWS1 routing instance.

  5. Configure the interface with the local and remote VPWS SID for the EVPN-VPWS1 routing instance.

    PE1

    PE2

  6. Enable uSID for the EVPN-VPWS routing instance.

  7. Configure a block for the uSID by specifying the prefix and length for a block of IPv6 address. This reserves the block for local static micro-SIDs. For maximum compression, all nodes should have same block prefix.

  8. Specify the maximum number of static SID that will be used as micro-SIDs.

  9. Configure a locator and the uSID function for the locator. The uSID function for micro-dx2 is 0xF900.

    Note:

    The micro-SID value must be in the static SID range of local micro-SIDs. You can check that the static SID range for the local micro-SID with the show srv6 block command. See Checking the Static SID Range

    .
  10. Configure a range of address that the locator can use.

    PE1

    PE2

  11. Enable the uSID locator by specifying the name of the locator and block name that was reserved for the uSID.

Checking the Static SID Range

You must assign a uSID value that is inside the static SID range of the local uSIDs. To display the range of local static SIDs in the local uSID, use the show srv6 block command. The acceptable uSID value is between 0xF830-0xFFFF.

Dynamic uSID Allocation

The following is a sample configuration for configuring dynamically allocated uSID EVPN-VPWS instance. It builds on the EVPN-VPWS dynamic SID allocation configuration EVPN-VPWS.