The Net Sync industry has consolidated over the past 20+ years with many mergers & acquisitions. Big names were gone and new names appear.

In the early 90s, there were 4 prominent vendors in Net Sync market, namely: 
⤇ Datum, USA
⤇ Hewlett-Packard/HP/Agilent, USA
⤇ Oscilloquartz, Switzerland
⤇ Symmetricom, USA

For instance, HP5071A Cesium Clock designed by Hewlett-Packard used to be the dominating the market as the most high precision atomic cesiums clock that was used primarily as the PRC/PRS in a telecom network. And than Hewlett-Packard was spun off to become HP and Agilent. 

Symmetricom later acquired the entire Datum and part of the NetSync product lines from HP/Agilent to become the main US-based player against Oscilloquartz of Switzerland. But in 2013, Symmetricom was acquired by Microsemi (which later became part of Microchip Inc of USA in 201x) and in 201x, Oscilloquartz became of part of ADVA. Obviously, this trend was due to the market forces - competition, market share and cost/revenue pressure.

As of now, Microsemi (part of Microchip, USA) and Oscilloquartz (part of Adva, Germany) seem like the two major competing players in the Net Sync market. There are also a few new players from Europe. 

While most (if not all) of these players sell the Net Sync products as an independent product line to the network operators and to the network equipment manufacturers, Huawei Net Sync products are normally bundled in with the sales of transmission equipment (in particular SDH equipment) or mobile network equipment (in particular 3G/4G and upcoming 5G) to the network operators.