“BYOD” is an acronym which stands for “Bring Your Own Device”. Essentially, a service provider who does not encypt or otherwise hide their SIP credentials, allowing you to configure virtually any SIP based device for use with their service, qualifies as “BYOD”.

There are many advantages to BYOD, with the most notable to be customer savings. In most, if not all cases, BYOD involves the client previously owning the device “brought”, meaning they only pay for subscribing to the hosting service. The one downside, is that the device will need to initially be configured with the assistance of the provider, which may be incredibly simple or on the more difficult side – it all depends greatly on the knowledge of the technical support staff and the flexibility of their service. Further, support for the device may be comprehensive or limited, which also depends on the expertise and commitment of a provider.

Not all VoIP service providers will offer special rate plans for subscribers with their own equipment. If a BYOD subscription is unavailable through a VoIP provider, the potential client will need to use the provider's recommended/compatible equipment instead of their own. Providers often offer this equipment for purchase at a discounted rate, or for lease, which involves monthly charges that a customer will see on their bill, or in some cases will include the equipment lease at no extra cost.

BYOD may not always be the best option, and potential subscribers should really consider whether their equipment is too outdated for them to fully enjoy all the features of their VoIP provider, whether that equipment has been locked by the prior subscription it was associated with, and if charges, such as fees to unlock the equipment overshadow the prospect of using the device with a new service. 

Related:
Top 7 Restriction Free BYOD Business VoIP Providers
BYOD Pros and Cons