Transcript IPv6 Addresses

Introduction
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IETF RFC1752 – a specification for a next-generation
IP (IPng)
IETF RFC2460 – IPv6 specification
Designed to accommodate the highest speed network
and a mix of data stream.
Important driving force – need more IP addresses
Migration from today’s IPv4 to IPv6 – “change jet
engine while keeping it flying”
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IPv6 Addresses
• IPv6 uses 128 bits to support at least one billion networks
• IPv6 still uses the concept of network number and host number
with extension to several levels
• To convert existing IPv4 addresses to IPv6 addresses
– 32 bits of IPv4 address are kept as the lower bits of IPv6 address
– Adding a fixed prefix of 96 bits with 80 zero bits followed by 16 zero
bits or 16 one bits
• IPv6 addresses can use colon hexadecimal notation with a
colon to separate every 16 bits
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IPv6 Header Format
• 40 bytes basic fixed-size header
– Include 16 bytes each for source and destination IP addresses
• Optional extension header(s) follow the basic header
• Payload Length  216 bytes = 65536 bytes
Version
Flow Label (20 bits)
Traffic Class (8 bits)
Payload Length (16 bits)
TTL Time-to-Live
Hop Limit
>= ten 32-bit words
Source IP address (128 bits)
Destination IP address (128 bits)
Options (if any, <=40 bytes)
Optional Extension Headers
0
31
32-bit word
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IPv6 Header Format (cont.)
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40 bytes basic header
Optional extension headers include the following fields
Router processed headers
– Hop-by-hop options header
– Routing header
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Ethernet type value (hex-86dd) assigned for IPv6
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IPv6 Datagram Priority
• 4-bits priority field
– 0 – 7: lower priority traffic for which the source is providing
congestion control (e.g. TCP …)
– 8 – 15: higher priority traffic that does not back off in response to
congestion (e.g. real time traffic …)
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IPv6 Datagram Priority (cont.)
Priority Value
Meaning
0
Uncharacterized traffic
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“Filler” traffic (e.g. netnews)
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Unattended data transfer (e.g. e-mail)
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(Reserved)
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Attended bulk transfer (e.g. FTP, NFS)
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(Reserved)
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Interactive traffic (e.g. telnet)
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Internet control traffic (e.g. SNMP, routing protocols)
8
Most willing to have discarded under the condition of congestion
15
Lest willing to have discarded under the condition of congestion
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