From Sender:-

1. 	System receives ODATA packet. 
	Reads packet code and establishes that it is normal data.
	Does multicast address lookup and forwards data on all multicast group
	member interfaces.

2.	System receives SPM packet.
	Checks to see if TSI is already registered.
		if TRUE  - system checks upstream PGM next hop info. Updates if
		changed.
		if FALSE - system creates session entry. Records upstream PGM
		hop.

	System replaces SPM Path NLA with its own IP address and forwards SPM on
	all multicast group member interfaces.
	
3.	System receives RDATA packet.
	Does lookup to see if there is a Repair Sub-tree table entry for that
	packet Sequence No.:-
		if TRUE  - system multicasts RDATA packet on all listed
		interfaces. System deletes Repair Sub-Tree entry.
		if FALSE - system discards RDATA packet.

From Receiver:-
		
4.	System receives unicast NAK.
	Does lookup to see if there is a Repair Sub-tree table entry for that
	packet Sequence No.:-
		if TRUE  - system discards NAK. Checks to see if incoming packet
		interface is already registered in table entry.
			if FALSE - updates table entry with additional
			requesting interface ID.
		if FALSE - system creates entry in Repair Sub-tree table
		including:-
			PACKET_SEQ_NO
			INTERFACE ID
	
	System does PGM upstream source path element lookup and propagates NAK
	to upstream element.
	System begins retransmit request thread:-
		BEGIN TIMER
		TIMER INTERRUPT
		Check to see if Repair Sub-tree table entry NCF entry is updated
			if TRUE  - Resend NAK. Repeat loop.
			if FALSE - Kill thread
	
	Multicast NCF on same interface as NAK was received.
	
From Network Element:-

5.	System receives ODATA packet. 
	Reads packet code and establishes that it is normal data.
	Does multicast address lookup and forwards data on all multicast group
	member interfaces.
	
	
6.	System receives SPM packet.
	Checks to see if TSI is already registered.
		if TRUE  - system checks upstream PGM next hop info. Updates if
		changed.
		if FALSE - system creates session entry. Records upstream PGM
		hop.

	System replaces SPM Path NLA with its own IP address and forwards SPM on
	all multicast group member interfaces.
	

7.	System receives unicast NAK.
	Does lookup to see if there is a Repair Sub-tree table entry for that
	packet Sequence No.:-
		if TRUE  - system discards NAK. Checks to see if incoming packet
		interface is already registered in table entry.
			if FALSE - updates table entry with additional
			requesting interface ID.
		if FALSE - system creates entry in Repair Sub-tree table
		including:-
			PACKET_SEQ_NO
			INTERFACE ID
	
	System does PGM upstream source path element lookup and propagates NAK
	to upstream element.
	System begins retransmit request thread:-
		BEGIN TIMER
		TIMER INTERRUPT
		Check to see if Repair Sub-tree table entry NCF entry is updated
			if TRUE  - Resend NAK. Repeat loop.
			if FALSE - Kill thread
	
	Multicast NCF on same interface as NAK was received.
	
	
8.	System receives NCF.
	Does Repair Sub-tree table lookup to see if entry exists corresponding
	to packet request Seq. No.
		if TRUE  - Check NCF confirmation field in table entry. Update
		if necessary
		if FALSE - ignore NCF