Chapter 8 D IPv6

NEXT GENERATION INTERNET

IPV6

REASONS FOR IPV6

• Number of addresses is huge• IPv4 limited to 4.3 billion host addresses (232)• IPv6 will have about 340 undecillion addresses (2128)

• Improve route aggregation

• IPv6 addresses integrate IP and MAC addresses• First 64 bits are the network address• Second 64 bits are the MAC address• The traditional 48 bit address with some added bits to bring it

up to 64 bits.

ADDRESS EXAMPLE

2001:cdba:0000:0000:0000:0000:3257:9652

Network portion Device portion

ABBREVIATIONS

• Leading zero’s can be omitted• A double colon can be used to denote a string of

zeros, but can only be used once• Ex: FE80:0000:0000:0000:00CF:0000:EA98:1234

becomes FE80::CF:0:EA98:1234• IPV6 Loopback address is ::1

NETWORK/LOCAL LINK ADDRESSES

• Local Link Address is a variation of the MAC address plus the network address• Network address/MAC address + modifications

• Any computer running IPV6 gives itself a local link address even if IPV6 is not being used on the network.• The default network portion of the generated

local link address is FE80::/64• The local link address is a computer’s unique IP

address (before formal network assignment if the network is connected to the Internet)

LOCAL LINK ADDRESS/EUI-64 (EXTENDED UNIQUE IDENTIFIER)

• MAC address: 40-61-86-99-E5-11• Strip dashes, split in half: 406186 99E511• Add FFFE to the middle: 406186FFFE99E511• Convert 2nd Hexadecimal digit to binary, compliment

the 3rd binary digit and convert back to Hex• 0 hex to 0000 bin• 0000 becomes 0010• 0010 bin becomes 2 hex• EUI-64 address: 426186FFFE99E511• Local Link address: FE80::426186FFFE99E511

• MS Windows Vista and 7 generate EUI-64 number as a random number, but this can be disabled

END OF BROADCAST

• IPV6 does not have a broadcast address like IPV4• Unicast: just like IPV4, send to one computer• Multicast: just like IPV4, send to a group of

computers• FF02::1 – broadcast to all hosts • FF02::2 – broadcast to all routers only

• Anycast: An IPV6 address can be assigned to a group of computers and IPV6 routes will send to the closest available one (DNS is an example)

IPv4 versus IPv6 packet

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8.12: IPV6 PACKET HEADER

IP Version 6 Packet

Source IP Address (128 bits)

Bit 0 Bit 31

Hop Limit(8 bits)

Next Header(8 bits) Nameof next header

Payload Length(16 bits)

Version(4 bits)Valueis 6(0110)

Diff-Serv(8 bits)

Flow Label (20 bits)Marks a packet as part of a specific flow

Destination IP Address (128 bits)

Next Header or Payload (Data Field)

Version fieldis 6 (0110).

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IP Version 6 Packet


Bit 0 Bit 31

Hop Limit(8 bits)




Diff-Serv(8 bits)




Diff-Serv (Differentiated Services) fieldspecifies the quality of service

requested for this packet.


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IP Version 6 Packet


Bit 0 Bit 31

Hop Limit(8 bits)




Diff-Serv(8 bits)

Flow Label (20 bits)Marks a packet as part of a specific flow of packets



Flow Label specifies that this packetis part of a specific flow of packetsto be treated in a particular waydefined at the start of the flow.


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IP Version 6 Packet


Bit 0 Bit 31

Hop Limit(8 bits)




Diff-Serv(8 bits)



Next Header or Payload (Data Field)IPv6 header is always 40 octets long.Payload Length is the length of theremainder of the packet in octets.


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IP Version 6 Packet


Bit 0 Bit 31

Hop Limit(8 bits)




Diff-Serv(8 bits)




IPv6 Hop Limit works exactly likethe Time-to-Live field in IPv4.

The name change wasdone to confuse students.


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IP Version 6 Packet


Bit 0 Bit 31

Hop Limit(8 bits)




Diff-Serv(8 bits)


Destination IP Address (128 bits)Next Header or Payload (Data Field)

Source and Destination Addressesare 128 bits long.


• IP Version 4• 32-bit addresses• 232 possible addresses• 4,294,967,296 (about 4 billion)• Running out of these

• IP Version 6• 128-bit addresses• 2128 possible addresses• 340,282,366,920,938,000,000,000,000,000,000,000,000

addresses


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8.12: NEXT HEADERS IN IPV6 PACKET HEADERS

IP Version 6 Packet


Bit 0 Bit 31

Hop Limit(8 bits)




Diff-Serv(8 bits)




IPv6 has many subheaders,each is linked to the nextvia the Next Header field


8.13: NEXT HEADERS IN IPV6 PACKET HEADERS


Main Header

Hop-by-Hop Options Header (0)

TCP Segment (6)

0

6

Next Header

Next Header

Header Type Value

Extension HeaderHop-by-Hop Options Header 0Routing Header 43Fragmentation Header 44Authentication Header 51Encapsulating Security Protocol Header 50Destination Options Header 60Mobility Header 135No Next Header 59

8.14: IPV6 NEXT HEADER VALUES


Header Type Value

Upper Layer messagesTCP 6UDP 17ICMPv6 58

8.14: IPV6 NEXT HEADER VALUES


AGGREGATION

• IPV6 Network addresses are distributed dynamically (not frequently though) from Tier 1 routers down their chain of sub routers unlike IPV4.• Upstream routes can reconfigure downstream

routers with new network addresses• IANA passes out /32 bit subnets to large ISP’s.

ISP’s in tern pass out /48 and /64 subnets to end users

OTHER ASPECTS VS. IPV4

• NAT is no longer used• DHCP is used in IPV6 even though hosts receive

the network address portion of the address in router advertisements from the IPV6 router upon host startup.• DHCP servers in IPV6 still provide DNS info for

hosts and can operate in one of two modes:• Stateful: IPV6 address, subnet masks, default gateway

and DNS server(s) address• Stateless: DNS server(s) address

• Stateless is the most common mode

SECURITY ASPECTS OF IPV6

• IPv6 was originally intended to use IPsec for encrypting packets.• Not widely implemented in applications except for VPN’s• Also can be done in IPv4.

• Biggest advantage is the sheer number of IP addresses that are impossible to scan like can be done with IPv4.

• IPv4 addresses are written in dotted decimal notation.• Divide the 32-bit address into four 8-bit segments.• Convert each segment to a decimal number.• Place dots between the segments.

WRITING IPV6 ADDRESSES


Chapter 8 D IPv6

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