Internet Protocol version 6
Devpratim Chakraborty
Ayaz Lalani
ECE 4605
Prof: Siva
Outline



Introduction – IPv6
Header Format
Extension Headers
 Several




types of extension headers
Packet Size
Flow Labels
Upper-Layer Protocols
IPv4 vs. IPv6
Introduction


Next generation protocol designed by IETF
Improvised IPv4
 Backwards

compatibility
Growing applicability
 Mail
Clients
 DNS
 Multimedia
 Remote Access
Header Format
0
Version
4
12
24
16
Traffic class
31
Flow label
Payload length
Next header
Source address
Destination address
Hop limit
Extension Headers
All extension headers start with “next header” field
- Hop-by-hop header
- Destination Options header
- Routing header: specifies nodes to be visited on the way
- Fragment header
Why
Extension
Headers
- Authentication header
- Encapsulating security payload header
- Destination Options header: information to be examined only by the destination host
- Upper-Layer Header
Options
Pad1, PadN
• Option Type
• First two bits (00, 01, 10, 11)
• Third bit (0, 1)
• Padding (Pad1, PadN)
Examples:
• Hop-by-Hop
-0
• Destination Options
- 60
Routing Header
Identified by Next Header value of 43
Type-specific
data
Routing (example)
Fragment Header
• Fragmentation at Source to fit path MTU
• Identification values for each packet
• Reassembly at Destination
Fragmented Packets
• Unfragmentable Part
• IPv6 Header
• Routing Header
• Hop-by-Hop Options Header
Fragment Header contd.

Reassembly
 Same
source, destination, identifier

Payload Length

Possible errors during reassembly
 Fragment
Reassembly Time Exceeded
 Inconsistent Payload Length

Inconsistent Fragment Headers
No Next Header

The value 59 in the Next Header field of an IPv6
header or any extension header indicates there
is nothing following that header.

If the Payload Length of IPv6 header indicates
the presence of more octets whose Next Header
field contains a 59, those octets must be
ignored, and forwarded unchanged.
Packet Size

Minimum MTU of 1280 octets (default)
 If
unable, fragment at lower layer
 Destination can reassemble up to 1500 octets


Path MTU Discovery – Efficiency!!
IPv6 Source - IPv4 Destination
 ICMP
Packet Too Big message
 Include Fragment Header


Payload Length reduced to 1232
Same Fragment ID => problem?!?
Flow Labels

Type of Service (TOS)
 “Real-Time”

Flow Label
 Random

and Uniform between 1 & FFFFF
Why?
 zero

service
(non-supportive nodes, routers)
Default routers do not distinguish between
flows
Traffic Classes
Prioritization of packets by originating
node
 Differentiate services without explicit flow
setup
 Replaces ToS in IPv4
 General requirements

 Upper-layer
protocol compatibility
 Leniency to change per use
Upper-Layer Protocol

Upper Layer Checksums
 Computation modified for
128-bit IPv6 addresses vs.
32-bit IPv4 addresses
 UDP checksum is not
optional for IPv6
 Next Header identifies the
Upper-layer protocol



Checksum includes the
Pseudo-Header!!


IPv6 Pseudo-Header
TCP – 6
UDP – 17

Different from IPv4
Why?
Protect from misdelivery or
corruption of IPv6 header
fields.
Upper-Layer Protocols contd.

Maximum Packet Lifetime
 IPv6 nodes are not required to enforce maximum
packet lifetime
 “Time to Live” of IPv4  “Hop Limit” of IPv6

Maximum Payload Size
 IPv4: Max packet size – 40 octets
 IPv6: Max packet size – 60 octets
Why IPv6?

Improvements over IPv4:






Expanded address space
Security and authentication
Improved option mechanism: separate optional headers
Mechanism for dynamic assignments of addresses
Improved addressing flexibility, including unicast
support for resource allocation: instead of TOS in IPv4,
labeling of packets according to a traffic flow (sourcedestination) with predefined service characteristics
Questions or comments?
Puzzle

Suppose you have milk and coffee in equal
quantities in two different cups. You pour some
of the milk into the coffee then pour back some
of the mixture back into the milk cup so that
there is the same total amount of liquid in both
cups once again. Is there more, less or an equal
amount of milk in the coffee cup than there is in
the milk cup?