tier 1 vendor

1. In information technology, a tier 1 vendor is a large and well-known vendor, often enjoying national or international recognition and acceptance. Tier 1 vendors may be both manufacturers and value-added resellers (VARs). For example, Cisco Systems Inc. is regarded as a tier 1 vendor in storage area network switching equipment and related technical certifications. Tier 1 vendors may also be a "preferred" vendor that provides products and services to you at appealing prices or other favorable terms.

2. A tier 1 vendor is a company that is a direct supplier for an original equipment manufacturer (OEM).  A tier 2 vendor, in contrast, is a subcontractor for the tier 1 vendor.