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TCP/IP Tutorial and Technical Overview - IBM Redbooks

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The peer who starts the negotiation process is the initiator <strong>and</strong> the other peer is<br />

the responder. The initiator only proposes a set of capabilities. The responder<br />

agrees or rejects the proposal.<br />

Negotiations are about capabilities, such as:<br />

► A list of alternate addresses for the same requested service<br />

► An agreement on size of the largest size of transaction data<br />

► Header code pages<br />

► Maximum outst<strong>and</strong>ing method requests<br />

► Maximum outst<strong>and</strong>ing push requests<br />

WSP connection-mode: Operations<br />

Figure 18-14 on page 689 shows a sample of a successful session<br />

establishment process through the client with subsequent invocation of an action<br />

in a server. Several service primitives are used on the client <strong>and</strong> the server side:<br />

► S-Connect<br />

Used to initiate the session establishment <strong>and</strong> to notify the successful<br />

execution. Several parameters are provided, such as client address (session<br />

originator), server address (session target), client <strong>and</strong> server headers<br />

(application-level parameters to indicate that request <strong>and</strong> response headers<br />

of both partners are used throughout the session), <strong>and</strong> requested <strong>and</strong><br />

negotiated capabilities for the duration of the session (for example, list of<br />

alias-addresses, client send data unit size, server send data unit size,<br />

maximum outst<strong>and</strong>ing method requests, <strong>and</strong> maximum outst<strong>and</strong>ing push<br />

requests).<br />

► S-MethodInvoke<br />

Used to request an operation to be executed by a server. This service<br />

primitive can be used only together with S-MethodResult, which returns the<br />

result from the server to the client after the execution. The following<br />

parameters are valid: client <strong>and</strong> server transaction ID (to distinguish between<br />

several pending transactions over the same session), method (to tell which<br />

operation has to be used, either an HTTP method such as GET or PUT, or<br />

one of the extension methods established during capability negotiation),<br />

request Uniform Resource Identifier (URI) (to determine to which entity the<br />

operation applies), request headers (equivalent to HTTP headers), <strong>and</strong><br />

request body (to contain the data associated with the request).<br />

688 <strong>TCP</strong>/<strong>IP</strong> <strong>Tutorial</strong> <strong>and</strong> <strong>Technical</strong> <strong>Overview</strong>

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