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© MMII JW Ryder CS 428 Computer Networking 1
The Future of TCP/IP (IPv6) Chapter 33 Evolution of TCP/IP intertwined with
evolution of the global Internet Internet is largest installed internet Funding comes from organizations that are
Internet users Most researchers use Internet daily
Chapter purpose is to consider ongoing evolution of TCP/IP
© MMII JW Ryder CS 428 Computer Networking 2
Why Change? New computer and communication
technologies New technologies = new possibilities and needs
New applications New ways to use Internet means new protocols
needed Increases in size and load
Massive growth means old ways strained
© MMII JW Ryder CS 428 Computer Networking 3
Motivation for Changing IPv4 New countries with differing administrative policies IPv4 same for about 20 years Since IPv4 designed
Enhanced processor performance Memory size increased Network bandwidth for Internet backbone increased New LAN technologies Number of hosts on Internet risen to over 56 million
© MMII JW Ryder CS 428 Computer Networking 4
Road to New Version of IP Several suggested designs
Make IP more sophisticated at expense of increased complexity and processing overhead
Use a modification of OSI CLNS protocol Retain most of ideas in IP but make simple
extensions to accommodate larger addresses Simple IP – (SIP) Still include new ideas from other suggested protocols
© MMII JW Ryder CS 428 Computer Networking 5
Features of IPv6 Despite many conceptual similarities IPv6
changes most protocol details Completely revises datagram format
Replace IPv4 variable length fields with a series of fixed format headers
Still supports connectionless delivery Allows sender to choose datagram size but
requires sender to specify maximum hops
© MMII JW Ryder CS 428 Computer Networking 6
Features of IPv6 Includes facilities for fragmentation and source
routing Main changes introduced are1. Larger Addresses: IPv6 quadruples the size from 32
bits to 128 bits2. Extended Address Hierarchy: Creates ability to have
additional address levels on an internet IPv4 Addresses – 2 levels, Network and Host IPv6 Addresses – Can define a hierarchy of ISPs as well
as hierarchy within a site
© MMII JW Ryder CS 428 Computer Networking 7
Features of IPv63. Flexible Header Format: Datagram format
entirely different Defines a fixed size (40 octets) header with
optional extended headers
4. Improved Options: Has same options as IPv4 plus some new ones
5. Provision for Protocol Extension: Move away from protocol that fully specifies all
details to one that permits additional features
© MMII JW Ryder CS 428 Computer Networking 8
Features of IPv66. Support for Autoconfiguration and
Renumbering: Allows computers on an isolated network to
assign themselves addresses and begin communicating without depending on a router or manual configuration
Facility to permit a manager to renumber networks dynamically
© MMII JW Ryder CS 428 Computer Networking 9
Features of IPv67. Support for Resource Allocation:
Two facilities for pre-allocation of network resources a Flow abstraction a Differentiated Services specification
© MMII JW Ryder CS 428 Computer Networking 10
IPv6 Address Space How big is 2128 ? So large that everyone on earth will have enough
addresses to have their own internets with as many addresses as the current Internet has
So large that there would be 1024 internet addresses per each square meter on earth
So large that the address space is greater than 3.4 * 1038 If addresses are assigned at the rate of 1,000,000 every
microsecond (1/1,000,000th of a second), it would take more than 1020 years to assign all possible addresses
© MMII JW Ryder CS 428 Computer Networking 11
IPv6 Colon Hexadecimal Notation 128 bit number expressed as dotted decimal 104.230.140.100.255.255.255.255.0.0.17.128.150.10.255.255 becomes 68E6:8C64:FFFF:FFFF:0:1180:96A:FFFF
Hex notation allows zero compression A string of repeated zeros is replaced with a pair
of colons FF05:0:0:0:0:0:0:B3 becomes FF05::B3 Can be applied only once in any address
© MMII JW Ryder CS 428 Computer Networking 12
Zero Suppression 0:0:0:0:0:0:128.10.2.1 becomes ::128.10.2.1 Looks quite similar to IPv4 12AB::CD30:0:0:0:0/60 says use first 60 bits
and becomes 12AB00000000CD3
© MMII JW Ryder CS 428 Computer Networking 13
Basic IPv6 Address Types Unicast – Destination address specifies a
single computer. Route datagram along shortest path.
Anycast – Destination is a set of computers, possibly at different locations, that all share a single address. Route datagram along shortest path and deliver to exactly one member of the group (i.e. closest member)
© MMII JW Ryder CS 428 Computer Networking 14
Basic IPv6 Address Types Multicast - Destination is a set of computers,
possibly at different locations. One copy of the datagram will be delivered to each member of the group using hardware multicast or broadcast if viable.
© MMII JW Ryder CS 428 Computer Networking 15
Encoding IPv4 Addresses in IPv6
DATAGRAM IDENTIFICATION
16 bits
IPv4 Address 0000 . . . . . . . . . . . . . . . . . . . . . . . . 0000
RESERVED
0000
FFFF IPv4 Address 0000 . . . . . . . . . . .. . . . . . . . . . . . . . 0000
32 bits80 zero bits
• 16-bit field contains 0000 if node also has a conventional IPv6 address and FFFF if it does not.
© MMII JW Ryder CS 428 Computer Networking 16
General Form of IPv6 Datagram
Base
Header
Extension
Header 1
Extension
Header N Data
Optional
40 octets
© MMII JW Ryder CS 428 Computer Networking 17
IPv6 Base Header Format See Base Header figure Alignment changed from 32 bit to 64 bit multiples Header length eliminated – Replaced with
PAYLOAD LENGTH field Size of source and destination addresses changed to
16 octets Fragmentation information moved out of fixed fields
in base header to extension header
© MMII JW Ryder CS 428 Computer Networking 18
IPv6 Base Header Format TIME-TO-LIVE field changed to HOP
LIMIT SERVICE-TYPE field renamed to TRAFFIC
CLASS and extended with FLOW LABEL field
PROTOCOL field replaced with a field that specifies type of next header
© MMII JW Ryder CS 428 Computer Networking 19
Base Header Format
NEXT HEADER HOP LIMITPAYLOAD LENGTH
FLOW LABELTRAFFIC CLASSVERS
SOURCE ADDRESS
DESTINATION ADDRESS
160 4 12 24 31
Base Header Size: 4 + 4 + 16 + 16 = 40 Octets
© MMII JW Ryder CS 428 Computer Networking 20
Base Header Format PAYLOAD LENGTH is length of all
extension headers plus data i.e. Total length – 40 octets (Base Header)
IPv6 datagram can contain up to 64K octets of data
© MMII JW Ryder CS 428 Computer Networking 21
Traffic Class IPv4 SERVICE CLASS renamed to TRAFFIC
CLASS New IPv6 mechanism allows for resource
reservation! A router can associate with each datagram a given
resource allocation Abstraction called a FLOW
A FLOW is a path through an internet along which intermediate routers guarantee a certain level of quality of service
© MMII JW Ryder CS 428 Computer Networking 22
Traffic Class FLOW LABEL in the base header contains a
label that routers use to map a datagram to a certain specific flow and priority
Flows can also be used within an organization to manage network resources
Example Two applications that need to send and receive
video can establish a flow over which the bandwidth and delay are guaranteed
© MMII JW Ryder CS 428 Computer Networking 23
IPv6 Extension Headers
Base Header NEXT=ROUTE
Route Header NEXT=AUTH
Auth Header NEXT=TCP
TCP Segment
Base Header NEXT=TCP
TCP Segment
Base Header NEXT=ROUTE
Route Header NEXT=TCP
TCP Segment
One Base Header
Two Base Headers
Three Base Headers
© MMII JW Ryder CS 428 Computer Networking 24
IPv6 Fragmentation As with IPv4, IPv6 arranges for destination to
perform re-assembly In IPv6 however, changes were made that avoid
fragmentation by routers IPv4 requires intermediate routers to fragment any
datagram that is too large for the maximum transfer/transmission unit (MTU) of network over which it must travel
IPv6 fragmentation is end-to-end
© MMII JW Ryder CS 428 Computer Networking 25
IPv6 Fragmentation No fragmentation done on intermediate
routers Source which is responsible for fragmentation
has two choices Use guaranteed minimum MTU (1280 octets) Perform Path MTU Discovery
Identifies minimum MTU along path to the destination
© MMII JW Ryder CS 428 Computer Networking 26
IPv6 Fragmentation Either case, the source fragments data IPv6 fragmentation inserts a small extension
header after the base header in each fragment
DATAGRAM IDENTIFICATION
FRAG. OFFSETNEXT HEADER
160 8 24 31
RESERVED RS M
29
RS is set t 0 and reserved. M marks last fragment. ID unique for re-assembly. Fragments must be a multiple of 8 octets.