Slice Creation Error&Guidance on Network Service Choice for Multi-Sit

[Yuanhao Chang]

Hello,

I am working on building a slice for a 5G core network experiment and would appreciate your guidance on the most appropriate network service to use for my specific topology.

My Required Topology(l25gcplus-yuanhao5, figure 1):

My experiment requires a 3-site topology with three separate, isolated, point-to-point network links:

1. Link 1 (Data Plane): Between a NIC on my AN (Access Network) node at DALL and a NIC on my CN (Core Network) node at ATLA.
2. Link 2 (Control Plane): A separate link between another NIC on the AN node at DALL and another NIC on the CN node at ATLA.
3. Link 3 (Data Plane): Between a third NIC on my CN node at ATLA and a NIC on my DN (Data Network) node at WASH.

The Problem & Troubleshooting Steps:

My primary question is to understand the best network service for this setup (L2PTP, L2Bridge, L2STS, or FABNetv4).

My first attempt was to implement this using three separate L2PTP services. This resulted in a “StableError”(figure 2) in my slice named l25gcplus-yuanhao4 (Slice ID: 99f62323-fd59-4cd2-a8d7-acf3838605c0). The error message for all three links was:

failed lease update- all units failed priming: Exception during create for unit: ... l2ptp - interface ... must be tagged (with vlan label in 1..4095)#

The error indicates that the L2PTP interfaces require a VLAN tag, but I was unable to find the correct method in the Slice Builder to assign one.

After the L2PTP attempt failed, I created my currently active slice, l25gclplus-yuanhao5 (ID: da3da8d7-7b53-4c72-bde1-ae9c552b3b65), using L2STS for the links. While this slice reached the “Active” state without an error, I am not confident this is the correct approach. My intention is to create private, internal links between my own nodes, not to stitch my slice to an external facility(or L2STS works for my situtation?).

My Questions:

Could you please provide guidance on the following?

1. What is the officially recommended network service for creating multiple, independent, point-to-point links between nodes at different sites, as per my topology?
2. If L2PTP is the correct choice, how can I properly specify the required VLAN tag for each link using the Slice Builder?
3. Is my current L2STS configuration in slice l25gclplus-yuanhao5 a valid and recommended way to achieve internal point-to-point connectivity?

Thank you for your time and assistance.

Best regards,

Yuanhao

[Komal Thareja]

Hello Yuanhao,

Thank you for the detailed description of your experiment and topology — that’s very helpful.

For your described setup with multiple independent, point-to-point internal links between your own nodes across sites, using L2STS is perfectly valid and appropriate. L2STS provides private Layer-2 connectivity between nodes within your slice and is generally recommended when you want internal point-to-point links without stitching to external networks.

L2PTP, on the other hand, is typically used when:

• You are connecting Dedicated NICs,
• You need guaranteed QoS (bandwidth reservation), or
• You want to explicitly control the path (e.g., define intermediate hop sites).

Given that, your current L2STS-based slice (l25gclplus-yuanhao5) is indeed a good configuration for your 5G experiment.

Regarding the L2PTP error, you’re correct — the message indicates that the interface must be tagged with a VLAN ID. There appears to be a bug in the portal’s Slice Builder that currently prevents specifying VLAN tags for L2PTP connections. Thank you for helping us identify that and we will work to address it.

In the meantime, you can continue using L2STS, which should meet your needs for internal connectivity.

For additional context and examples, please refer to our Network Services documentation:
https://learn.fabric-testbed.net/knowledge-base/network-services-in-fabric/

Also, I’d recommend checking out the example notebooks available under the JupyterHub tab on the FABRIC Portal — they provide working examples of various network configurations, including multi-site and point-to-point topologies.

Best regards,
Komal Thareja

1 user thanked author for this post.

Yuanhao Chang

[Yuanhao Chang]

Thank you so much for your detailed and prompt response, Komal!

Also wish the little tag bug could be fixed soon.

Thank you again for your detailed answer!

[Author]

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