http-mcache.tcl

对IEEE 802.11e里的分布式信道接入算法EDCA进行改进

# 
#  Copyright (c) 1997 by the University of Southern California
#  All rights reserved.
# 
#  Permission to use, copy, modify, and distribute this software and its
#  documentation in source and binary forms for non-commercial purposes
#  and without fee is hereby granted, provided that the above copyright
#  notice appear in all copies and that both the copyright notice and
#  this permission notice appear in supporting documentation. and that
#  any documentation, advertising materials, and other materials related
#  to such distribution and use acknowledge that the software was
#  developed by the University of Southern California, Information
#  Sciences Institute.  The name of the University may not be used to
#  endorse or promote products derived from this software without
#  specific prior written permission.
# 
#  THE UNIVERSITY OF SOUTHERN CALIFORNIA makes no representations about
#  the suitability of this software for any purpose.  THIS SOFTWARE IS
#  PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES,
#  INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
#  MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
# 
#  Other copyrights might apply to parts of this software and are so
#  noted when applicable.
# 
# Implementation of web cache, client and server which support 
# multimedia objects.
#
# $Header: /nfs/jade/vint/CVSROOT/ns-2/tcl/webcache/http-mcache.tcl,v 1.5 1999/11/18 23:14:36 haoboy Exp $

#
# Multimedia web client
#

# Override this method to change the default max size of the page pool
Http/Client/Media instproc create-pagepool {} {
	set pool [new PagePool/Client/Media]
	$self set-pagepool $pool
	return $pool
}

# Connection procedure:
# (1) Client ---(HTTP_REQUEST)--> Server
# (2) Client <--(HTTP_RESPONSE)-- Server
# (3) Client <----(RAP_DATA)----  Server
Http/Client/Media instproc get-response-GET { server pageid args } {
	eval $self next $server $pageid $args
	
	# XXX Enter the page into page pool, so that we can keep track of 
	# which segment has been received and know where to stop receiving. 
	if [$self exist-page $pageid] {
		error "Http/Client/Media: receives an \"active\" page!"
	}
	eval $self enter-page $pageid $args

	array set data $args
	if {[info exists data(pgtype)] && ($data(pgtype) == "MEDIA")} {
		# Create a multimedia connection to server
		$self media-connect $server $pageid
	}
}

# Don't accept an request if there is one stream still on transit
Http/Client/Media instproc send-request { server type pageid args } {
	$self instvar mmapp_ 
	if [info exists mmapp_($pageid)] {
		return
	}
	eval $self next $server $type $pageid $args
}

# Create a RAP connection to a server
Http/Client/Media instproc media-connect { server pageid } {

	# DEBUG ONLY
	#puts "Client [$self id] media-connect [$server id] $pageid"

	$self instvar mmapp_ ns_ node_ 
	Http instvar MEDIA_TRANSPORT_ MEDIA_APP_
	if [info exists mmapp_($pageid)] {
		puts "Media client [$self id] got a request for an existing stream"
		return
	}
	set agent [new Agent/$MEDIA_TRANSPORT_]
	$ns_ attach-agent $node_ $agent
	set app [new Application/$MEDIA_APP_ $pageid]
	$app attach-agent $agent
	$app target $self
	$server alloc-mcon $self $pageid $agent
	set mmapp_($pageid) $app
	$app set-layer [$self get-layer $pageid]
}

Http/Client/Media instproc media-disconnect { server pageid } {
	$self instvar mmapp_ ns_ node_

	if {![info exists mmapp_($pageid)]} {
		error "Media client [$self id] disconnect: not connected to \
server [$server id] with page $pageid"
	}
	set app $mmapp_($pageid)
	set agent [$app agent]
	$ns_ detach-agent $node_ $agent

	# DEBUG ONLY
#	puts "Client [$self id] disconnect from server [$server id]"

	# Disconnect the agent and app at the server side
	$server media-disconnect $self $pageid

	delete $agent
	delete $app
	unset mmapp_($pageid)

	$self stream-received $pageid
}


#
# Multimedia web server
#

# Create media pages instead of normal pages
Http/Server/Media instproc gen-page { pageid } {
	$self instvar pgtr_ 
	set pginfo [$self next $pageid]
	if [$pgtr_ is-media-page $pageid] {
		return [lappend pginfo pgtype MEDIA]
	} else {
		return $pginfo
	}
}

Http/Server/Media instproc create-pagepool {} {
	set pool [new PagePool/Client/Media]
	$self set-pagepool $pool
	# Set the pool size to "infinity" (2^31-1)
	$pool set max_size_ 2147483647
	return $pool
}

Http/Server/Media instproc medialog-on {} {
	$self instvar MediaLog_
	set MediaLog_ 1
}

# Allocate a media connection
Http/Server/Media instproc alloc-mcon { client pageid dst_agent } {
	$self instvar ns_ node_ mmapp_ 
	Http instvar MEDIA_TRANSPORT_ MEDIA_APP_

	set agent [new Agent/$MEDIA_TRANSPORT_]
	$ns_ attach-agent $node_ $agent
	set app [new Application/$MEDIA_APP_ $pageid]
	$app attach-agent $agent
	$app target $self 
	set mmapp_($client/$pageid) $app
	# Set layers
	$app set-layer [$self get-layer $pageid]

	# Associate $app with $client and $pageid
	$self register-client $app $client $pageid

	# DEBUG ONLY
	# Logging MediaApps, only do it for sender-side media apps
	$self instvar MediaLog_
	if [info exists MediaLog_] {
		set lf [$self log]
		if {$lf != ""} {
			$app log $lf
		}
	}
#	puts "Server [$self id] allocated a connection to client [$client id] using agent $agent"

	# Connect two RAP agents and start data transmission
	$ns_ connect $agent $dst_agent
	$agent start
}

Http/Server/Media instproc media-disconnect { client pageid } { 
	$self instvar mmapp_ ns_ node_

	# DEBUG ONLY
#	puts "At [$ns_ now] Server [$self id] disconnected from client [$client id]"

	if {![info exists mmapp_($client/$pageid)]} {
		error "Media server [$self id] disconnect: not connected to \
client [$client id] with page $pageid"
	}
	set app $mmapp_($client/$pageid)
	set agent [$app agent]
	$ns_ detach-agent $node_ $agent

	$self unregister-client $app $client $pageid

	# DEBUG ONLY 
#	puts "Server [$self id] deleting agent $agent"

	delete $agent
	delete $app
	unset mmapp_($client/$pageid)
}

# Tell the client that a stream has been completed. Assume that there is 
# an open connection between server and client
Http/Server/Media instproc finish-stream { app } {
	$self instvar mmapp_ 
	foreach n [array names mmapp_] {
		if {$mmapp_($n) == $app} {
			set tmp [split $n /]
			set client [lindex $tmp 0]
			set pageid [lindex $tmp 1]
			$self send $client [$self get-reqsize] \
				"$client media-disconnect $self $pageid"
			return
		}
	}
}

# If the page is a media page, set the response size to that of the request
Http/Server/Media instproc handle-request-GET { pageid args } {
	set pginfo [eval $self next $pageid $args]
	if {[$self get-pagetype $pageid] == "MEDIA"} {
		set pginfo [lreplace $pginfo 0 0 [$self get-reqsize]]
	}
	return $pginfo
}

Http/Server/Media instproc gen-pageinfo { pageid } {
	set pginfo [eval $self next $pageid]
	# Create contents for media page
	$self instvar pgtr_
	if [$pgtr_ is-media-page $pageid] {
		return [lappend pginfo pgtype MEDIA layer \
				[$pgtr_ get-layer $pageid]]
	} else {
		return $pginfo
	}
}

# Map a media application to the HTTP application at the other end
#Http/Server/Media instproc map-media-app { app } {
#	$self instvar mmapp_
#	foreach n [array names mmapp_] {
#		if {$mmapp_($n) == $app} {
#			return [lindex [split $n /] 0]
#		}
#	}
#}

# Handle prefetching of designated segments
Http/Server/Media instproc get-request { client type pageid args } {
	if {$type == "PREFSEG"} {
		# XXX allow only one prefetching stream from any single client
		# Records this client as doing prefetching. 
		# FAKE a connection to the client without prior negotiation
		set pagenum [lindex [split $pageid :] 1]
		set conid [lindex $args 0]
		set layer [lindex $args 1]
		set seglist [lrange $args 2 end]
		eval $self register-prefetch $client $pagenum $conid \
				$layer $seglist
		$client start-prefetch $self $pageid $conid
		$self evTrace S PREF p $pageid l $layer [join $seglist]
		# DEBUG only
#		$self instvar ns_
#		puts "At [$ns_ now] server [$self id] prefetches $args"
	} elseif {$type == "STOPPREF"} {
		set pagenum [lindex [split $pageid :] 1]
		set conid [lindex $args 0]
		# DEBUG only
#		$self instvar ns_
#		puts "At [$ns_ now] server [$self id] stops prefetching $pageid conid $conid"
		if [$self stop-prefetching $client $conid $pagenum] {
			# Tear down pref channel iff we don't have remaining 
			# clients sharing the channel
			$client media-disconnect $self $pageid $conid
		}
	} elseif {$type == "OFFLPREF"} {
		# Simply send the page back through TCP channel
		if ![$self exist-page $pageid] {
			error "Server [$self id] offline-prefetch non-existent page $pageid!"
		}
		set size [$self get-size $pageid]
		$self send $client $size "$client offline-complete $pageid"
	} else {
		eval $self next $client $type $pageid $args
	}
}



#
# Multimedia web cache
#