3Com 2200 manual Pseudocode translates into the following packet filter, # XNS Filtering Section

Creating Packet Filters 12-13

The pseudocode translates into the following packet filter:

Name	“IP XNS ticker bcast filter”
			# Assign this filter in the multicast path
			# of a port only--this is very important
			#
			# XNS FILTERING SECTION
			#
pushField.w		12	# get the type field of the packet and
			# place it on top of the stack.
pushLiteral.w		0x0600	# put the	type value for XNS on top of
			# the stack.
eq			# if the two values on the top of the
			# stack are equal, then return a non-zero
			# value.
pushLiteral.w		0x76c	# put the lowest socket value on top of
			# the stack.
pushField.w		30	# put the value of the socket from the
			# packet on top of the stack.
ge			# compare if the value of the socket is
			# greater than or equal to lower bound.
pushLiteral.w		0x0898	# put the highest socket value on top of
			# the stack.
pushField.w		30	# put the value of the socket from the
			# packet on top of the stack.
lt			# compare if the value of the socket is
			# less than the upper bound
and			# “and” together with “ge” and “lt” test
			# to determine if the socket value is
			# “within” the range. If it is, a “one”
			# will be placed on the stack.
and			# compare if XNS & in range
			#
			# IP FILTERING SECTION
			#
pushField.w		12	# get the type field of the packet and
			# place it on top of the stack.
pushLiteral.w		0x0800	# put the type value for IP on top of
			# the stack.
eq			# if the two values on the top of the
			# stack are equal, then return a non-zero
			# value.
pushLiteral.w		0x76c	# put the lowest socket value on top of
			# the stack (1900).
pushField.w		24	# put the value of the socket from the
			# packet on top of the stack.
ge			# compare if the value of the socket is
			# greater than or equal to lower bound.
pushLiteral.w		0x0898	# put the highest socket value on top of
			# the stack (2200).
pushField.w		24	# put the value of the socket from the
			# packet on top of the stack.
lt			# compare if the value of the socket is
			# less than the upper bound
and			# “and” together with “ge” and “lt”.
			# test to determine if the socket value is
			# “within” the range. If it is in range, a
			# “one” will be placed on the stack.
and			# compare if IP and in range.
or			# determine if the type field is either
			# XNS or IP.
not			# discard if (IP & in range) and (XNS & in
			# range).