%\begin{bwslide}
%\part	{SESSION SERVICES}\bf
%\end{bwslide}


\begin{bwslide}
\part	{SESSION SERVICES}\bf

\vskip.5in
\diagram[p]{figureA-6}
\end{bwslide}


\begin{bwslide}
\ctitle {SESSION LAYER\\PURPOSE}

\begin{nrtc}
\item	ADD STRUCTURE TO DATA CIRCUIT PROVIDED BY TRANSPORT
\item	MORE ``APPLICATIONS ORIENTED'' STREAM TO USER
\item	ADD CONTROL MECHANISMS TO DATA EXCHANGE
\end{nrtc}
\end{bwslide}


\begin{bwslide}
\ctitle {SESSION}

\vskip.5in
\diagram[p]{figureA-13}
\end{bwslide}


%\begin{bwslide}
%\ctitle {SESSION}
%
%\begin{nrtc}
%\item	22 SERVICES
%\item	50+ PRIMITIVES
%\item	COMPLEX STATE MACHINE RULES
%\item	QUITE COMPLEX COMPARED TO TRANSPORT SERVICE
%%\item	PRIMITIVES PREFIXED WITH {\em S--\ldots}
%\end{nrtc}
%\end{bwslide}


%\begin{bwslide}
%\ctitle {USERS}
%
%\begin{nrtc}
%\item	{\em SS--user} TYPICALLY A PRESENTATION ENTITY
%\item	NOT ALWAYS THE CASE
%	\begin{nrtc}
%	\item	1984 MHS (X.400) USED RELIABLE TRANSFER TO DIRECTLY 
%							ACCESS SESSION
%	\end{nrtc}
%\item	SESSION PROVIDER INTERACTS WITH A SINGLE {\em SS-user} ENTITY
%\end{nrtc}
%\end{bwslide}


%\begin{bwslide}
%\ctitle {\em SS-users}
%
%\begin{nrtc}
%\item	CONNECTION ESTABLISHMENT
%	\begin{nrtc}
%	\item	CALLING {\em SS-user}
%	\item	CALLED {\em SS-user}
%	\end{nrtc}
%\item	ACTION INITIATION
%	\begin{nrtc}
%	\item	REQUESTING {\em SS-user}
%	\item	ACCEPTING {\em SS-user}
%	\end{nrtc}
%\item	CONNECTIONS ARE SYMMETRIC
%\end{nrtc}
%\end{bwslide}


%\begin{bwslide}
%\ctitle {SESSION ADDRESSING}
%
%\begin{nrtc}
%\item	{\em SS-user} ADDRESSED AT SESSION SERVICE ACCESS POINT (SSAP) BY:
%\item	SSAP CONTENT:
%	\begin{nrtc}
%	\item	SESSION SELECTOR
%	\item	TRANSPORT ADDRESS
%	\end{nrtc}
%%\item	SELECTOR IS A STRING OF OCTETS
%\item	TRANSPORT ADDRESS IDENTIFIES A GIVEN SESSION ENTITY
%\item	SESSION SELECTOR IDENTIFIES A SPECIFIC USER OF THAT ENTITY
%\end{nrtc}
%\end{bwslide}


%\begin{bwslide}
%\ctitle {U.S. GOSIP SESSION SELECTOR}
%diagram
%\end{bwslide}


%\begin{bwslide}
%\ctitle {SESSION ADDRESSING (cont.)}
%
%\begin{nrtc}
%\item	DE-MULTIPLEXING ON nSAPs
%	\begin{nrtc}
%	\item	KERNEL
%	\item	USER
%	\end{nrtc}
%\item	IMPLEMENTATION CONSIDERATION
%\end{nrtc}
%\end{bwslide}


%\begin{bwslide}
%\ctitle {SERIAL NUMBERS}
%
%\begin{nrtc}
%\item	{\em OPTIONALLY} MAINTAINED DURING SESSION CONNECTION
%\item	AVAILABILITY DEPENDS ON CONNECTION FUNCTIONALITY NEGOTIATIONS
%\item	USED TO COORDINATE AND REFERENCE TRANSACTIONS ON CONNECTION
%\end{nrtc}
%\end{bwslide}


%\begin{bwslide}
%\ctitle {CONNECTION IDENTIFIER}
%
%\begin{nrtc}
%\item	{\em SS-users} ASSIGN A UNIQUE IDENTIFIER TO A CONNECTION
%%\item	{NOT A LOCAL MECHANISM SUCH AS A FILE DESCRIPTOR}
%\item	TYPICALLY
%	\begin{nrtc}
%	\item	EACH SYSTEM PROVIDES A HOST NAME
%	\item	CURRENT UTC TIME IS PROVIDED IN A COMMON PORTION
%	\end{nrtc}
%\item	USED TO RE--ESTABLISH BROKEN CONNECTIONS
%\end{nrtc}
%\end{bwslide}


\begin{bwslide}
\ctitle {SESSION PROVIDES}

\begin{nrtc}
\item	DIALOGUE CONTROL (TOKENS)
\item	SYNCHRONIZATION (CHECKPOINTING)
\item	ACTIVITY MANAGEMENT
\item	EXCEPTION REPORTING
\item	{\em TRANSPORT FUNCTIONALITY}
\end{nrtc}
\end{bwslide}


%\begin{bwslide}
%\ctitle {TOKENS}
%
%\begin{nrtc}
%\item	MANY APPLICATION EXCHANGES ARE ACTUALLY HALF-DUPLEX
%\item	``TOKENS'' KEEP TRACK OF WHO MAY SEND DATA
%\item	REQUESTS FOR A TOKEN CARRY A PRIORITY
%\end{nrtc}
%\end{bwslide}


%\begin{bwslide}
%\ctitle	{TOKENS}
%
%\begin{nrtc}
%\item	CONTROL EXCLUSIVE ACCESS TO PARTICULAR SERVICE
%\item	TRAFFIC SIGNAL OF SESSION COMMUNICATIONS
%\item	TOKENS ARE ONE OF:
%	\begin{nrtc}
%	\item	AVAILABLE \& OWNED
%	\item	AVAILABLE \& NOT OWNED
%	\item	UNAVAILABLE
%	\end{nrtc}
%\item	EXCHANGED BETWEEN PEERS
%\item	MAINTAINED BY SS-PROVIDER
%\end{nrtc}
%\end{bwslide}


%\begin{bwslide}
%\ctitle {TOKENS (cont.)}
%
%\begin{nrtc}
%\item	4 TYPES OF TOKENS
%	\begin{nrtc}
%	\item	DATA, SYNC MINOR, MAJOR/ACTIVITY, RELEASE
%	\end{nrtc}
%\item	PERMITTED OPERATIONS
%	\begin{nrtc}
%	\item	GIVE TOKENS, PLEASE TOKENS, GIVE CONTROL
%	\end{nrtc}
%\end{nrtc}
%\end{bwslide}


%\begin{bwslide}
%\ctitle {CHECKPOINTING}
%
%\begin{nrtc}
%\item	MANY APPLICATIONS EXCHANGE LARGE AMOUNTS OF DATA
%\item	CHECKPOINTS MAY BE INSERTED IN THE DATA STREAM, SO THAT
%	\begin{nrtc}
%	\item	IF THE TRANSPORT CONNECTION BREAKS AND IS RE-ESTABLISHED,
%		DATA EXCHANGE MAY RESUME AT THE LAST CONFIRMED CHECKPOINT
%	\end{nrtc}
%\item	SEMANTICS PROVIDED BY SS-USER
%\item	THREE KINDS OF SYNCHRONIZATION
%	\begin{nrtc}
%	\item	MINOR CHECKPOINTS (NEED NOT BE CONFIRMED)
%	\item	MAJOR CHECKPOINTS
%	\item	RESYNCHRONIZATION
%	\end{nrtc}
%\end{nrtc}
%\end{bwslide}


%\begin{note}
%diagram sync example using ftam
%\end{note}


%\begin{bwslide}
%\ctitle {RESYNC}
%
%\begin{nrtc}
%\item	INITIATED BY EITHER SS-USER
%\item	SETS SESSION TO DEFINED STATE
%\item	3 OPTIONS
%	\begin{nrtc}
%	\item	ABANDON
%	\item	RESTART
%	\item	SET
%	\end{nrtc}
%\item	PERMITTED OPERATIONS
%	\begin{nrtc}
%	\item	RESYNC ACK
%	\end{nrtc}
%\end{nrtc}
%\end{bwslide}


\begin{bwslide}
\ctitle {RESYNCHRONIZATION EXAMPLE}

\vskip.5in
\diagram[p]{figureA-33}
\end{bwslide}


%\begin{bwslide}
%\ctitle {ACTIVITIES}
%
%\begin{nrtc}
%\item	MANY APPLICATION EXCHANGES CONSIST OF SEVERAL SMALLER EXCHANGES
%\item	LOGICALLY DIFFERENT TASKS
%	\begin{nrtc}
%	\item	ACTIVITIES CAN BE INTERRUPTED OR DISCARDED
%	\item	DIALOGS WITHIN AN ACTIVITY DISTINGUISH PARTS OF  ``TASK''
%	\end{nrtc}
%\end{nrtc}
%\end{bwslide}


%\begin{bwslide}
%\ctitle {ACTIVITIES (cont.)}
%
%\begin{nrtc}
%\item	TRANSFER OF LOGICALLY RELATED DATA
%\item	SEVERAL CONSECUTIVE ACTIVITIES ALLOWED
%\item	OPERATIONS
%	\begin{nrtc}
%	\item	START, END, INTERRUPT, RESUME, DISCARD
%	\end{nrtc}
%\item	SEMANTICS PROVIDED BY SS-USER
%\end{nrtc}
%\end{bwslide}


%\begin{note}
%diagram activities example
%\end{note}


%\begin{bwslide}
%\ctitle	{ACTIVITIES (cont.)}
%
%\begin{nrtc}
%\item	IMPLEMENTATION CONCERNS
%	\begin{nrtc}
%	\item	INTERRUPT/RESUME = SAVE/RESTORE STATE
%	\item	BURDEN ON SS-USER
%	\end{nrtc}
%\end{nrtc}
%\end{bwslide}


%\begin{bwslide}
%\ctitle {EXCEPTIONS}
%
%\begin{nrtc}
%\item	SOME APPLICATIONS MAY EXPERIENCE ABNORMAL EVENTS REQUIRING DRASTIC ACTION
%\item	AN EXCEPTION CAN BE REPORTED INSTEAD OF ABORTING THE CONNECTION
%\item	THE CONNECTION MUST BE BROUGHT TO A KNOWN STATE TO CLEAR AN EXCEPTION AND
%	REQUIRES EXPLICIT ACTION ON THE OTHER SIDE
%\end{nrtc}
%\end{bwslide}


%\begin{bwslide}
%\ctitle {SESSION QUALITY OF SERVICE (QOS)}
%
%\begin{nrtc}
%\item	MOST PARAMETERS PASSED TO TRANSPORT SERVICE
%\item	OF CONCERN TO SESSION ENTITY:
%	\begin{nrtc}
%	\item	BATCH SEVERAL PRIMITIVES FOR SENDING
%	\item	ALLOW FLOW--CONTROL BYPASS
%	\end{nrtc}
%\end{nrtc}
%\end{bwslide}


%\begin{bwslide}
%\ctitle {SESSION QUALITY OF SERVICE (cont.)}
%
%\begin{nrtc}
%\item	RULES FOR NEGOTIATION
%\item	NOT REFLECTED IN PROTOCOL!
%\end{nrtc}
%\end{bwslide}


%\begin{bwslide}
%\ctitle {TRANSPORT FUNCTIONALITY}
%\end{bwslide}


%\begin{bwslide}
%\ctitle {CONNECTION ESTABLISHMENT}
%
%\begin{nrtc}
%\item	NEGOTIATES
%	\begin{nrtc}
%	\item	FUNCTIONAL UNITS
%	\item	INITIAL TOKEN POSITIONS
%	\item	MAXIMUM TSDU SIZE
%	\item	OPTIONS/VERSION/...
%	\end{nrtc}
%\item	TWO WAY EXCHANGE
%\item	LITTLE ADDED FUNCTIONALITY OVER TRANSPORT, {\bf BUT A LOT MORE WORK!}
%\end{nrtc}
%\end{bwslide}


%\begin{bwslide}
%\ctitle {CONNECTION RELEASE}
%\end{bwslide}


%\begin{bwslide}
%\ctitle {DATA TRANSFER\\SESSION USER DATA}
%
%\begin{nrtc}
%\item	SESSION SERVICE DATA UNIT (SSDU)
%\item	COMPOSED OF OCTETS (1 OR MORE)
%\item	PASS OPAQUELY THROUGH SESSION SERVICE
%\item	3 TYPES OF SSDUs, WE WILL JUST CALL THEM SSDUs
%\end{nrtc}
%\end{bwslide}


\begin{bwslide}
\ctitle {SESSION USER DATA (cont.)}

\begin{nrtc}
\item	ORIGINAL RESTRICTIONS ON SSDU SIZE FOR CONNECTION ESTABLISHMENT
	\begin{nrtc}
	\item	LIMIT OF 512 OCTETS
	\item	SESSION VERSION 1
	\end{nrtc}
\item	TOO RESTRICTIVE FOR MANY OSI APPLICATIONS
	\begin{nrtc}
	\item	e.g., PASSING OSI DIRECTORY NAMES ON CONNECTIONS
	\end{nrtc}
\item	RECENT ADDENDA REMOVE THIS LIMIT
	\begin{nrtc}
	\item	PRACTICAL LIMIT OF 10K OCTETS USED
	\item	SESSION VERSION 2
	\end{nrtc}
\item	VERSION 1 \& 2 DO \underline{NOT} INTERWORK
	\begin{nrtc}
	\item	NO NEGOTIATION POSSIBLE
	\item	VERSION 2 MAY DOWNGRADE TO VERSION 1
	\end{nrtc}
\end{nrtc}
\end{bwslide}




%\begin{bwslide}
%\ctitle{DATA UNITS}
%
%\begin{nrtc}
%\item	SSDU --- PASSED BETWEEN SS-USERS
%\item	SPDU --- PASSED BETWEEN SS-PROVIDERS
%\end{nrtc}
%\end{bwslide}


%\begin{bwslide}
%\ctitle {SPDU STRUCTURE}
%
%\begin{nrtc}
%\item	4 COMPONENTS
%\item	USER DATA vs. USER INFORMATION
%\item	USER INFORMATION PRESENT ONLY ON NORMAL \& TYPED DATA SPDUs
%\end{nrtc}
%\end{bwslide}


%\begin{note}
%diagram spdu structure
%\end{note}


%\begin{bwslide}
%\ctitle {SESSION FUNCTIONAL UNITS}
%
%\begin{tabular}{ll}
%KERNEL			&	CAPABILITY DATA	\\
%NEGOTIATED RELEASE	&	MINOR SYNC	\\
%DUPLEX			&	MAJOR SYNC	\\
%HALF DUPLEX		&	RESYNC		\\
%EXPEDITED DATA		&	ACTIVITY	\\
%TYPED DATA		&	EXCEPTIONS	\\
%\end{tabular}
%\end{bwslide}


%\begin{bwslide}
%\ctitle	{FUNCTIONAL UNIT SUBSETS}
%
%\begin{nrtc}
%\item	FOR SOME TIME ``POPULAR'' FUNCTIONAL UNIT SUBSETS WERE DEFINED:
%	\begin{nrtc}
%	\item	BCS --- BASIC COMBINED SUBSET
%	\item	BSS --- BASIC SYNCHRONIZATION SUBSET
%	\item	BAS --- BASIC ACTIVITY SUBSET
%	\end{nrtc}
%\item	NO LONGER USED, REFERENCE INDIVIDUAL FUNCTIONAL UNITS
%\end{nrtc}
%\end{bwslide}


\begin{bwslide}
\ctitle {IMPLEMENTATION CONSIDERATIONS}

\begin{nrtc}
\item	SIMILAR TO OTHER UPPER LAYERS
\item	WHERE
	\begin{nrtc}
	\item	USER LIBRARY
	\item	DISTINCT PROCESS
	\item	KERNEL RESIDENT
	\end{nrtc}
\end{nrtc}
\end{bwslide}


%\begin{bwslide}
%\ctitle {SESSION VERSION 2}
%
%\begin{nrtc}
%\item	``UNLIMITED'' USER DATA ON CONNECT
%	\begin{nrtc}
%	\item	STANDARDS LIMIT IS 64K OCTETS IN SINGLE SPDU
%	\item	PRACTICAL LIMIT IS 10K OCTETS ON CONNECTION ESTABLISHMENT
%	\end{nrtc}
%\end{nrtc}
%\end{bwslide}


%\begin{bwslide}
%\ctitle {SESSION}
%
%\center{\huge ``The sewer of OSI''}
%\end{bwslide}


%\begin{bwslide}
%\ctitle {REFERENCES}
%
%\begin{description}
%\item[ISO/IEC 8326:]	Basic Connection Oriented Session Service Definition
%\item[ISO/IEC 8327:]	Basic Connection Oriented Session Protocol Specification
%\end{description}
%\end{bwslide}
