2.2.4 Packet Data Token and Tokenless Data Streams

The messages contained in packet data that pass between the client and the server can be one of two types: a "token stream" or a "tokenless stream". A token stream consists of one or more "tokens" each followed by some token-specific data. A "token" is a single byte identifier used to describe the data that follows it (for example contains token data type, token data length, and so on). Tokenless streams are typically used for simple messages. Messages that might require a more detailed description of the data within it are sent as a token stream. The following table highlights which messages, as described previously in sections 2.2.1 and 2.2.2, use token streams and which do not.

 Message type

 Client or server message

 Token stream?

Pre-Login

Client

No

Login

Client

No

Federated Authentication Token<14>

Client

No

SQL Command

Client

No

SQL Command with Binary Data

Client

Yes

Remote Procedure Call (RPC)

Client

Yes

Attention

Client

No

Transaction Manager Request

Client

No

Pre-Login Response

Server

No

Federated Authentication Information

Server

Yes

FeatureExtAck

Server

Yes

Login Response

Server

Yes

Row Data

Server

Yes

Return Status

Server

Yes

Return Parameters

Server

Yes

Response Completion

Server

Yes

Session State

Server

Yes

Error and Info

Server

Yes

Attention Acknowledgement

Server

No

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