How VeloCloud SD-WAN is measuring the Latency and Loss in a WAN link?

Products

• VMware SD-WAN by VeloCloud

Issue/Introduction

This document explains how the VeloCloud SD-WAN measuring the Latency and Loss in a WAN link.

Environment

VMware SD-WAN by VeloCloud

Resolution

VeloCloud uses VeloCloud multi-path (VCMP) which connects from the SD-WAN edge to the VeloCloud gateways (VCGs) via the WAN link.

VCMP tunnel uses UDP port 2426 for the encapsulation. When sending packets from the edge to the VCG, the edge time stamps, and sequences these packets. When the VCG receives these packets, it checks the time stamps and sequence number and uses that information to determine latency and loss.

The time difference between consecutive packets is the measured latency, and if a sequence number doesn't arrive, that is measured as a loss. Packets sent from the edge to the VCG are used to measure upstream latency and loss.

Packets from the VCG to the edge (sequenced and time stamped the same way) are used to measure downstream latency and loss.  There are multiple VCGs that the edge connects to, and the VCO QOE graph will show the best path.