The connectivity and bandwidth requirements for Twilio's Client SDK (twilio.js) and mobile Programmable Voice SDKs can vary depending on the version in use. For a complete rundown of the connectivity needs for each SDK, see Voice Client JS and Mobile SDKs' Network Connectivity Requirements (Twilio Docs).
Note: For Twilio Programmable Video network requirements, please see Programmable Video IP Address Whitelisting (Twilio Docs).