IPV6

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IPv6 Header Key

  • Mac Header
  • IPv6 Header
  • IPv6 Header
  • Data

IPv6 Header

0001020304050607 0809101112131415 1617181920212223 2425262728293031
Version Version - (4 bits) - The IPv6 version number Traffic Class Traffic Class - (8 bits) - The six most significant bits are used to classify packets. The other two bits are used for priority values. Priority Values are subdivided into ranges where one is for congestion control, and the other is for non-congestion control. Flow Label Flow Label - (20 bits) - When non-zero setting is is used for keeping packets on path. This serves as the informant to the routers and switches with multiple paths that these particular packets are meant to stay on the same path. This keeps them from being reordered. It also assists in defending against Off-Path Spoofing Attacks
Payload Length Payload Length - (16 bits) - Is the size of the payload in octets including any existing extension headers. If set to 0 there is a hop-by-hop extension header. Next Header Next Header - (8 bits) Hop Limit Hop Limit - (8 bits)
Source address Source address - (128 bits) - IP Address of the sending
Destination address Destination address - (128 bits) - IP Address of the destination
Data

IPV6 Next Header Values info on RCF4443

Value ( hex ) Value (decimal) Ext. Header
00 0 Hop-By-Hop
01 1 ICMPv4
02 2 IGMPv4
04 4 IP Encapsulation
06 6 TCP
08 8 EGP
11 17 UDP
29 41 IPv6
2B 43 Routing
2C 44 Fragmentation
2E 46 Resource Reservation Protocol RSVP
32 50 Security Payload
33 51 Authentication
3A 58 ICMPv6
3B 59 No Next Header
3C 60 Destination Options Extension Header
Version (4 bits)
The IPv6 version number
Traffic Class (8 bits)
The six most significant bits are used to classify packets. The other two bits are used for priority values. Priority Values are subdivided into ranges where one is for congestion control, and the other is for non-congestion control.
Flow Label (20 bits)
Used for keeping packets on path and inform routers of desired special handling of a packet(s).
Payload Length (16 bits)
Length of the data field
Next Header (8 bits)
If extension headers exist, this field points (contains an identifier) to the first Extension Header. Each extension header has its own Next Header pointing to the next Extension header as well. The last Extension Headers Next Header will point to the Data Field.
Hop Limit (8 bits)
The Maximum number of "hops" a router can use in the advertisements and in all the packets. (1 to 255) default 64
Source address (128 bits)
IP Address of the sending
Destination address (128 bits)
IP Address of the destination

IPv6 gets its roots from version 4 but has improved in various ways such as:

  • A more simple header
  • Flow labeling
  • Allows for more options and extending to help with future proofing
  • Improved Security - Extensions for security and authentication
  • Moved from 32 bits (IPv4) to 128 bits (IPv6)
  • Abilities of Multicasting have been improved
  • Anycast Addressing has been added

Address Formats

Generic IPV6 Address Format
1st 16 bit : 2nd 16 bit : 3rd 16 bit : 4th 16 bit : 5th 16 bit : 6th 16 bit : 7th 16 bit : 8th 16 bit
1234 : DEC4 : 2134 : FA43 : 32FD : DC21 : FD33 : 23DF
Network ID 48-bit subnet ID 16-bit SUBNET ID 64-bit
General unicast address format
bits 48 (or more) 16 (or fewer) 64
field Network ID subnet ID interface ID
Link-Local address format
bits 10 54 64
field prefix zeros Interface ID
General Multicast address format
bits 8 4 4 112
field prefix flag scope Group ID