Download Introduction - Ceng Anadolu

IPv6
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IPv6
• Problem: 32-bit address space will be completely
allocated by 2008.
• Solution: Design a new IP with a larger address space,
called the IP version 6, IPv6
– Expanded Address Space: 128-bit addresses
– IP Address Auto-configuration: Stateless (no servers) host IP
Address Configuration (Plug-and-Play)
– Security Capabilities: IPSec required
– Better and hierarchical routing mechanisms: Current IPv4
routing infrastructure is a combination of flat and hierarchical
routing. Leads to bigger routing tables at the backbone routers.
– Improved Options Mechanism: Options are located between the
IPv4 main header and transport headers. Most routers do not
examine these option fields
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IPv6 Addressing
• 128-bit addresses
• IPv4 – dotted decimal representation
– 223.1.1.1
• IPv6 – 128-bit address divided along 16-bit
boundaries, each 16-bit block converted to a 4
digit hexadecimal number separated by colons
– 0010000111011010 0000000011010011 0000000000000000 0010111100111011
– 21DA:00D3:0000:2F3B:02AA:00FF:FE28:9C5A
– Can be simplified by removing leading 0’s within each 16-bit block
– 21DA:D3:0:2F3B:02AA:FF:FE28:9C5A
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IPv6 Addressing – Compressing 0’s
• Some type of addresses contain long sequences
of 0s. To further simplify the representation of
IPv6 addresses, a contiguous sequence of 16-bit
blocks set to 0 in the colon format can be
compressed to “::”, known as double colon
– Example1:
• FE80:0:0:0:2AA:FF:FE9A:4CA2
• FE80::2AA:FF:FE9A:4CA2
– Example2:
• FF02:0:0:0:0:0:0:2
• FF02::2
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Types of IPv6 Addresses
• 3 types of addresses
– Unicast Addresses
• Identifies a single interface within the whole IPv6 Network.
A packet sent to a unicast address is delivered to a single
interface
– Multicast Addresses
• Identifies multiple interfaces. A packet sent to a multicast
address is delivered to ALL multicast interfaces.
– Anycast Addresses
• Identifies multiple interfaces. A packet sent to a anycast
address is delivered to ANY one of the interfaces. Typically
the closest interface
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Unicast IPv6 Addresses
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Global unicast addresses
Link-Local addresses
Site-Local addresses -- deprecated
Special addresses
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Global Unicast IPv6 Addresses
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Link-Local Unicast IPv6 Addresses
• Always start with FE80::/64
• Equivalent to IPv4 169.254/16 address range
• An IPv6 router never forwards link-local traffic
beyond the link
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Site-Local Unicast IPv6 Addresses
• Always start with FEC0::/10
• Equivalent to IPv4 10/8, 172.16/12, 192.168/16
address ranges
• Scope of a site-local address is the site.
• Deprecated – Not to be used any longer!
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Special Unicast IPv6 Addresses
• 0:0:0:0:0:0:0:0 or ::
– Indicates the lack of an address
– Corresponds to IPv4
0.0.0.0
• 0:0:0:0:0:0:0:1 or ::1
– Loopback interface address
– Corresponds to IPv4 loopback IP address 127.0.0.1
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Interface ID Generation
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Interface ID Generation - Example
• MAC:
• EUI-64:
• Intf ID:
00-AA-00-3F-2A-1C
00-AA-00-FF-FE-3F-2A-1C
02-AA-00-FF-FE-3F-2A-1C
• Colon Hexadecimal Notation: 2AA:FF:FE3F:2A1C
• Link-Local Address: FE80::2AA:FF:FE3F:2A1C
• Notice that the above algorithm generates the same UID
from the same MAC
• To provide anonymity, RFC 3041 suggests an alternative
that generates IDs that change over time
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IPv6 Subnets – Example
INTERNET
2000::2:InterfaceID
2000::1:InterfaceID
2000::1:InterfaceID
2000::2:InterfaceID
2000::3:InterfaceID
2000::3:InterfaceID
2000::3:InterfaceID
• Similar to IPv4, an IPv6 subnet prefix (subnetID) is
assigned to a single link
• Multiple subnetIDs may be assigned to the same link
• 3 IPv6 Subnets in above network
– 2000::1/64, 2000::2/64, 2000::3/64
• No need for netmask
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IPv6 Datagram Format
Ver: 6
Priority: identify priority among datagrams in flow
Flow Label: identify datagrams in same “flow.”
Next header: identify upper layer protocol for data;
or the offset of the next options header
128-bit source & destination addresses
Fixed-length 40 byte header
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Other Changes from IPv4
• Checksum: removed entirely to reduce
processing time at each hop
• Options: allowed, but outside of header,
indicated by “Next Header” field
• ICMPv6: new version of ICMP
– additional message types, e.g. “Packet Too Big”
– multicast group management functions
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IPv6 Forwarding
• Similar to IPv4 Forwarding
• If the destination is on the same IPv6 Subnet
– Deliver the packet directly using LL
– Otherwise, deliver the packet to the default router
• IPv6 Address  MAC Resolution?
– No ARP in IPv6
– MAC resolution performed by ICMP Neighbor
solicitation messages sent to multicast solicited node
address
• Disturbs less nodes on the network
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IPv6 Fragmentation & Reassembly
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large IP datagram divided
(“fragmented”) ONLY at the source
– one datagram becomes several
datagrams
– “reassembled” ONLY at final
destination
– Optional Fragmentation header
is used if the packet is
fragmented.
fragmentation:
in: one large datagram
out: 3 smaller datagrams
reassembly
• What if the packet needs to be
fragmented within the network?
– Router drops the packet and
sends a “PACKET TOO BIG”
ICMP response back to the
sender.
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Host IPv6 Address Configuration
HIGH-LEVEL DESCRIPTION
1. Always configure a link-local address
2. Listen for router advertisements
1. If router advertisement indicates that a stateful
address configuration is to be used, then use DHCP
to get another address
2. If router advertisement indicates that a stateless
address configuration is to be used, then take the
routing prefix from the router advertisement and
configure an address
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