Getting Started with the WebSockets API : 2 Login : 2.1 Definition of the Login Domain
 
2.1 Definition of the Login Domain
The Login domain is used to create a context within a system access point. You must use this special model to access all other domain models. A Login must be the very first request and be streaming so that user context is maintained.
Access points use special logic in handling Logins and utilize them to retrieve the user’s permission information. The user’s permissions profile is used to authorize all other domain model interactions for that user.
Regarding the Login Response, MaxMsgSize is the maximum supported message size as configured by the Refinitiv Real-Time Advanced Distribution Server. Any message greater in size is rejected and results in a disconnection.