TCP/IP protocols are the middle two two tiers of the Internetprotocol. 
IP protocol used to move packets between any two nodes on network.
TCP protocol used for the overall trip between source and destination systems.

* Internet Packets or Datagrams (conceptual) 
  Packet consists of source & destination address, data, & control.
    (also check out www.freesoft.org/CIE/Course/Section3/7.htm)

  Version (IPv4)
    IPv4 up to 64KiB

    IPv6 - requires sender find the smallest packet size of path and limits
      packet size, usually 1500 bytes (compatible Ethernet frame size)

    IPv6 - does support Jumbo (< 4GiB) on IPv6 only networks.
 
  IHL, Internet header length (helps to find the data portion of packet). 
  * IPv6 uses a fixed header length but supports chained extensions.

  DSCP - differential services code point.
    Type of service (reliability, speed, delay acceptability).
    i.e is the packet handing audio/visual or important data.

  ECN - Explicit Congestion Notification. Can be used by endpoints to
    monitor and adjust for congestion. Not usually used.

  Total length
    Minimum 576 (all hops should provide).
    Maximum (IPv4) 65535.
     
  ID  (used to help assemble fragments across a hop). IDs fragments
    belonging to a single fragmented packet.

  Flags (type of fragmentation allowed)

  Fragment offset - sequences the fragmented portions of a packet so it
    can be reassembled.

  TTL - time to live, counter used to guard against lost packets. 
    Both total time and number of node hops monitored. TTL decremented
    accordingly. If it hits zero, packet is destroyed. If packet TCP, an
    ICMP error packet returned to sender.

    IPv6 uses hop count, does not bother with time (lost in queue). 

  Protocol - type of information being sent. ssh 22, http 80, etc.

  Header checksum - error checking for header only. As packet moved between
    nodes, some info regenerated and this is a check.

  Source and destination IP addresses.

  Options - various options for ip transport.

  Data - information being transferred.

  ***********
IPv6
  * Always 40 byte header.   

  Version (4 bits)

  Traffic class (8 bits) - similar to DSCP/ECN in IPv4 

  Flow label (20 bits) - used for real time streaming to 
    ecourage routers to use the same path to avoid sequence
    scrambling of packets.

  Payload Length (16 bits) - 64 KiB,  0 if using Jumbogram.

  Next Header flag - the primary header of IPv6 is always 40 bytes.
    If additional info is needed, it is placed in and at the start
    of the data portion of the packet.

  Hop limit - similar to TTL but doesn't note time only hop counts.

  Source and destination IP addresses.

  * Additional 'extension headers' can be added after the primary 
    header. Except for a type 0, hop by hop header, extension 
    headers are only handled by the destination node.

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  Internet packet encapsulated in the network frame.
 
  As packet moves from network to network, frame stripped and frames
    appropriate to specific technology applied.

  Also IP packet modified to handle variations of TCP/IP implementation 
    at this particular jump.
    

See wikipedia.org for topics :  
   "tcp/ip", "IPv4", "IPv6" "4in6" "4on6"