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REVENUE RECOGNITION (Tables) | 9 Months Ended
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Sep. 30, 2025
REVENUE RECOGNITION |
Schedule of timing of performance obligation | ​
​ | ​ | ​ | ​ | ​
​ |  | When Performance Obligation is Typically |  | ​
Performance Obligation | ​ | Satisfied | ​ | When Payment is Typically Due
Software and Product Revenue | ​ | ​ | ​ | ​
Software licenses (perpetual or term) |  | For perpetual licenses, typically when made available for download (point in time); for term-based licenses, at the beginning of the specified term (point in time) |  | Generally, within 30-60 days of invoicing, except for term licenses which may be paid for over time
Software licenses (subscription) |  | Upon activation of hosted site (over time) | ​ | Generally, within 30-60 days of invoicing
Hardware |  | When control of the hardware passes to the customer; typically, upon delivery (point in time) |  | Generally, within 30-60 days of invoicing
Software upgrades |  | Upon transfer of control; typically, when made available for download (point in time) |  | Generally, within 30-60 days of invoicing
Customer Support Revenue |  |  |  |
Customer support |  | Ratably over the course of the support contract (over time) |  | Generally, within 30-60 days of invoicing
Professional Services |  |  |  |
Other professional services (excluding training services) |  | As work is performed (over time), typically on the input method based on hours incurred |  | Generally, within 30-60 days of invoicing (upon completion of services)
Training |  | As the training is delivered (over time), typically one to five days |  | Generally, within 30-60 days of services being performed
Schedule of disaggregation of revenue | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | ​ | ​ |  | ​ | ​ |  | Service revenue |  | ​ | ​
​ | ​ | Product | ​ | Service revenue | ​ | (professional | ​ | ​ | ​
Three months ended September 30, 2025 | ​ | revenue | ​ | (maintenance) | ​ | services) | ​ | Total revenue
United States | ​ | $ | 39,515 | ​ | $ | 35,191 | ​ | $ | 21,967 | ​ | $ | 96,673
Europe, Middle East and Africa | ​ | ​ | 35,765 | ​ | ​ | 18,045 | ​ | ​ | 9,082 | ​ | ​ | 62,892
Asia Pacific | ​ | ​ | 30,337 | ​ | ​ | 9,723 | ​ | ​ | 3,191 | ​ | ​ | 43,251
Other | ​ | ​ | 4,362 | ​ | ​ | 6,556 | ​ | ​ | 1,637 | ​ | ​ | 12,555
​ | ​ | $ | 109,979 | ​ | $ | 69,515 | ​ | $ | 35,877 | ​ | $ | 215,371
​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | ​ | ​ |  | ​ | ​ |  | Service revenue |  | ​ | ​
​ | ​ | Product | ​ | Service revenue | ​ | (professional | ​ | ​ | ​
Three months ended September 30, 2024 | ​ | revenue | ​ | (maintenance) | ​ | services) | ​ | Total revenue
United States | ​ | $ | 58,198 | ​ | $ | 33,670 | ​ | $ | 17,690 | ​ | $ | 109,558
Europe, Middle East and Africa | ​ |  | 24,708 | ​ |  | 17,918 | ​ |  | 7,141 | ​ |  | 49,767
Asia Pacific | ​ |  | 25,590 | ​ |  | 10,262 | ​ |  | 2,388 | ​ |  | 38,240
Other | ​ |  | 3,655 | ​ |  | 7,169 | ​ |  | 1,849 | ​ |  | 12,673
​ | ​ | $ | 112,151 | ​ | $ | 69,019 | ​ | $ | 29,068 | ​ | $ | 210,238
​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | ​ | ​ |  | ​ | ​ |  | Service revenue |  | ​ | ​
​ | ​ | Product | ​ | Service revenue | ​ | (professional | ​ | ​ | ​
Nine months ended September 30, 2025 | ​ | revenue | ​ | (maintenance) | ​ | services) | ​ | Total revenue
United States | ​ | $ | 127,957 | ​ | $ | 102,061 | ​ | $ | 65,572 | ​ | $ | 295,590
Europe, Middle East and Africa | ​ |  | 80,759 | ​ | ​ | 53,790 | ​ | ​ | 25,955 | ​ |  | 160,504
Asia Pacific | ​ |  | 89,342 | ​ | ​ | 28,831 | ​ | ​ | 10,009 | ​ |  | 128,182
Other | ​ |  | 8,969 | ​ | ​ | 19,552 | ​ | ​ | 4,436 | ​ |  | 32,957
​ | ​ | $ | 307,027 | ​ | $ | 204,234 | ​ | $ | 105,972 | ​ | $ | 617,233
​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | ​ | ​ |  | ​ | ​ |  | Service revenue |  | ​ | ​
​ | ​ | Product | ​ | Service revenue | ​ | (professional | ​ | ​ | ​
Nine months ended September 30, 2024 | ​ | revenue | ​ | (maintenance) | ​ | services) | ​ | Total revenue
United States | ​ | $ | 120,173 | ​ | $ | 99,156 | ​ | $ | 42,812 | ​ | $ | 262,141
Europe, Middle East and Africa | ​ |  | 99,636 | ​ |  | 53,105 | ​ |  | 23,027 | ​ |  | 175,768
Asia Pacific | ​ |  | 68,304 | ​ |  | 30,262 | ​ |  | 7,912 | ​ |  | 106,478
Other | ​ |  | 10,781 | ​ |  | 22,397 | ​ |  | 4,957 | ​ |  | 38,135
​ | ​ | $ | 298,894 | ​ | $ | 204,920 | ​ | $ | 78,708 | ​ | $ | 582,522
​ The Company’s product revenue from its direct sales program and from indirect sales through its channel partner program for the three and nine months ended September 30, 2025 and 2024 was as follows (in thousands):
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Three months ended | ​ | Nine months ended |
​ | ​ | September 30, | ​ | September 30, | ​ | September 30, | ​ | September 30, | ​
​ |  | 2025 |  | 2024 |  | 2025 |  | 2024 |
Indirect sales through channel partner program | ​ | $ | 28,488 | ​ | $ | 38,000 | ​ | $ | 90,211 | ​ | $ | 114,958 | ​
Direct sales | ​ |  | 81,491 | ​ |  | 74,151 | ​ |  | 216,816 | ​ |  | 183,936 | ​
​ | ​ | $ | 109,979 | ​ | $ | 112,151 | ​ | $ | 307,027 | ​ | $ | 298,894 | ​
​ The Company’s product revenue from sales to enterprise customers and from sales to service provider customers for the three and nine months ended September 30, 2025 and 2024 was as follows (in thousands):
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | Three months ended | ​ | Nine months ended |
​ | ​ | September 30, | ​ | September 30, | ​ | September 30, | ​ | September 30, | ​
​ |  | 2025 |  | 2024 |  | 2025 |  | 2024 |
Sales to enterprise customers | ​ | $ | 37,467 | ​ | $ | 40,002 | ​ | $ | 99,751 | ​ | $ | 115,912 | ​
Sales to service provider customers | ​ |  | 72,512 | ​ |  | 72,149 | ​ |  | 207,276 | ​ |  | 182,982 | ​
​ | ​ | $ | 109,979 | ​ | $ | 112,151 | ​ | $ | 307,027 | ​ | $ | 298,894 | ​
​ The Company’s product revenue and service revenue components by segment for the three and nine months ended September 30, 2025 and 2024 were as follows (in thousands):
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Three months ended | ​ | Nine months ended | ​
​ | ​ | September 30, | ​ | September 30, | ​ | September 30, | ​ | September 30, | ​
​ |  | 2025 |  | 2024 |  | 2025 |  | 2024 |
Product revenue: | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Cloud and Edge |  | $ | 46,097 |  | $ | 53,455 |  | $ | 134,070 |  | $ | 124,554 |
IP Optical Networks |  | ​ | 63,882 |  | ​ | 58,696 |  | ​ | 172,957 |  | ​ | 174,340 |
Total product revenue |  | $ | 109,979 |  | $ | 112,151 |  | $ | 307,027 |  | $ | 298,894 |
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Service revenue: |  | ​ |  |  | ​ |  |  | ​ |  |  | ​ |  |
Maintenance: |  | ​ |  |  | ​ |  |  | ​ |  |  | ​ |  |
Cloud and Edge |  | $ | 52,315 |  | $ | 53,595 |  | $ | 154,899 |  | $ | 159,454 |
IP Optical Networks |  | ​ | 17,200 |  | ​ | 15,424 |  | ​ | 49,335 |  | ​ | 45,466 |
Total maintenance revenue |  | ​ | 69,515 |  | ​ | 69,019 |  | ​ | 204,234 |  | ​ | 204,920 |
Professional services: |  | ​ |  |  | ​ |  |  | ​ |  |  | ​ |  |
Cloud and Edge |  | ​ | 26,026 |  | ​ | 21,028 |  | ​ | 80,108 |  | ​ | 56,294 |
IP Optical Networks |  | ​ | 9,851 |  | ​ | 8,040 |  | ​ | 25,864 |  | ​ | 22,414 |
Total professional services revenue |  | ​ | 35,877 |  | ​ | 29,068 |  | ​ | 105,972 |  | ​ | 78,708 |
Total service revenue |  | $ | 105,392 |  | $ | 98,087 |  | $ | 310,206 |  | $ | 283,628 |
Schedule of customer assets and liabilities | The changes in the Company’s accounts receivable, unbilled receivables and deferred revenue balances for the nine months ended September 30, 2025 were as follows (in thousands): ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | ​ | ​ | ​ | Unbilled | ​ | Deferred | ​ | Deferred
​ | ​ | Accounts | ​ | accounts | ​ | revenue | ​ | revenue
​ |  | receivable |  | receivable |  | (current) |  | (long-term)
Balance at January 1, 2025 | ​ | $ | 176,575 | ​ | $ | 78,143 | ​ | $ | 119,295 | ​ | $ | 20,991
Increase (decrease), net | ​ |  | (22,861) | ​ |  | (13,545) | ​ |  | (12,598) | ​ |  | 8,757
Balance at September 30, 2025 | ​ | $ | 153,714 | ​ | $ | 64,598 | ​ | $ | 106,697 | ​ | $ | 29,748
​

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