1. Next Generation: IPv6 and ICMPv6
Also called , IPng – “IP next generation”
Next Generation:
IPv6 and ICMPv6
Recall IPv4 provides host-to-host or hop-to-hop communication
Recall UDP/TCP provide end-to-end or process-to-process communication
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2. Why IPv6 ? 3 major reasons
Recall that (1) subnetting, (2) classless addressing, (3) DHCP (dynamic address allocation) and (4) NAT all contributed to better utilization of the 32-bit address space
- despite these solutions, address depletion is still an issue
There are numerous applications on the rise that require streaming real-time audio and video – and real-time transmission requires minimum delay and reservation-of-resources strategies – and IPv4 isn’t designed for these strategies
Over the last few years, there has been a much greater demand for security and for the Internet to accommodate encryption and authentication of data for some applications – and IPv4 doesn’t provide encryption or authentication
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3. Why IPv6 ? IPv6 was proposed in overcoming IPv4’s deficiencies
IPv6 has these advantages over IPv4: 1. larger address space – 128 bits
2. better header format – options can be inserted or not
3. new options – additional functionalities 4. allowance for extension – protocol can be extended for newer technologies 5. support for resource allocation – enables the Tx to request special handling 6. support for more security – provides encryption and authentication
Related protocols were either modified or dropped for IPv6
- ICMP was modified (ICMPv6)
- ARP and IGMP in version 4 were combined in ICMPv6
- RARP was dropped
- RIP and OSPF were slightly modified
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4. IPv6 Address Abbreviated address
Uses hexadecimal colon notation, a 296 address increase over IPv4
Abbreviated address
Leading zeros can be omitted
If consecutive sections consist of zeros only, the zeros can be removed altogether and replaced with double semicolon
Only allowed once per address – if there were two runs of zero sections, only one can be abbreviated
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5. IPv6 Address 3 Categories of IPv6 Addresses
Like IPv4, IPv6 can use CIDR notation
3 Categories of IPv6 Addresses
Unicast Address – packet sent to a specific computer
Anycast Address – group of computers with addresses that have the same prefix (ie. all belong to the same physical network)
Multicast Address – packet sent to a group of computers with different address prefixes
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6. IPv6 Address Address structure Type prefixes for IPv6 addresses
Means 1/8 of the entire address spaces uses type prefix 010
The address space has many purposes
The address space is divided into 2 parts
The first part, called “type prefix”, is variable length, defines the purpose by using unique codes
Type prefixes for IPv6 addresses
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7. IPv6 Address Provider-based address structure
Type prefix 010 or provider-based address is generally used by a host as a unicast address
Provider-based address structure
Variable-length field identifies the provider for Internet access (ie ISP) – recommends this field be 16 bits
The provider (ISP) assigns a 24-bit subscriber id to the organization
Identifies one of many subnets under the subscriber’s control – recommends using 32-bits
Identifies the node connected to the subnet – recommends 48-bits (the same as the 48-bit physical Ethernet address)
Defines the address as a provider-based address
Indicates one of the three agencies that has registered the address.
INTERNIC – North America
RIPNIC – Europe
APNIC – Asia & Pacific
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8. IPv6 Address Address hierarchy
Can think of the provider-based address as a hierarchical identity with several prefixes
Address hierarchy
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9. IPv6 Address Unspecified address Loopback address
When the non-prefix part of the address is also zeros – this is called an Unspecified Address – this address is used when the host doesn’t know its own address and sends an inquiry and uses the Unspecified Address to represent itself – the address can not be used as a destination address
Loopback address
Recall the purpose of the loopback address – an address used by a host to test itself without going into the network.
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10. IPv6 Address Compatible address
During transition from IPv4 to IPv6, hosts can use their IPv4 addresses embedded in IPv6 addresses. Two formats have been designed for this – (1) compatible and (2) mapped
Compatible address
96 bits of zeros followed by 32 bits of IPv4 address
Compatible Address is used when a IPv6 Tx wants to send a message to an IPv6 Rx, but needs to pass through a region using IPv4 – the Tx must them use the compatible address while passing through the Ipv4 region
Binary
D E
Hexidecimal
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Decimal

11. IPv6 Address Mapped address
During transition from IPv4 to IPv6, hosts can use their IPv4 addresses embedded in IPv6 addresses. Two formats have been designed for this – (1) compatible and (2) mapped
Mapped address
80 bits of zeros followed by 16 bits of ones followed by 32 bits of IPv4 address
Mapped Address is used when a IPv6 Tx wants to send a message to an IPv4 Rx. The packet will mostly travel through an IPv6 region with a final destination of IPv4.
NOTE: when calculating the CHECKSUM, either the embedded address or total address can be used because the extra 0s or 1s (in multiples of 16) DO NOT have an effect on the checksum calculation.
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12. IPv6 Address Link local address Site local address
Addresses that use the reserved prefix ( ) are local addresses
Link local address
Used if the LAN uses the Internet protocols but is not connected to the Internet for security reasons – these addresses do not have a global effect
Site local address
Used if a site with several networks uses the Internet protocols but is not connected to the Internet for security reasons – these addresses do not have a global effect
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13. IPv6 Address Multicast address
Addresses used to define a group of hosts instead of just one.
Multicast address
Defines the group address as either permanent or transient
Permanent Address – defined by the Internet authorities and can be accessed at all time
Transient Address – is temporary
Defines the scope of the group address
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14. Next Generation: IPv6 and ICMPv6
.. Continuing …
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15. IPv6 Packet
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16. Format of an IPv6 datagram
Defines the priority of the packet with respect to traffic congestion (discuss later)
24-bit field that provide special handling for a particular flow of data (discuss later)
Defines the version (IPv6 = 6)
8-bit field defining the header that follows the base header (discuss later)
8-bit field serves as the Time-To-Live (TTL)
2-byte field defines the length of the data excluding the base header
Source address
Usually identifies the destination address – if Source Routing is used, identifies the address of the next router
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17. Format of an IPv6 datagram
Next Header
The next header is either one of the optional extension headers used by IPv6 or the header of an encapsulated packet such as UDP or TCP.
Each extension header also contains the next header field.
For version 4, this field was called the protocol.
Next header codes
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18. Format of an IPv6 datagram
Priority
Defines the priority of each packet with respect to other packets from the same source.
IPv6 divides traffic into two categories: congestion-control and non-congestion-control
Priorities for congestion-controlled traffic
Process does not define a priority
If a source adapts itself to traffic slowdown when there is congestion, the traffic is called congestion-control traffic – example, TCP sliding window protocol
Defines data delivered in the background
User is not waiting for the data (ie. )
Protocol that transfer data while the user is waiting to receive the data (ie FTP, HTTP)
User interaction is needed (ie. TELNET)
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Protocols that control traffic (ie. OSPF, RIP, SNMP)

19. Format of an IPv6 datagram
Priority
Defines the priority of each packet with respect to other packets from the same source.
IPv6 divides traffic into two categories: congestion-control and non-congestion-control
Priorities for non congestion-controlled traffic
Refers to traffic that expects minimum delay – dropping packets is not desired – retransmission is impossible. Examples would be realtime audio and video
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20. IPv6 Packet
Flow Label
Recall how a routing-algorithm table lookup is performed for a packet using a router.
Sequence of packets sent from a Tx to Rx needing “special handling” is called a flow
Combo of the Tx address and a flow label uniquely identifies a flow of packets
The flow label is assigned to the packet by the Tx – randomly generated number
From a router perspective, a flow is a sequence of packets sharing the characteristics (using same resources, same security, , etc)
If the packet has a flow number, the router consults it flow label table for the next hop
This speeds up the process – much faster than going through the routing algorithm approach
Flow label approach is good for apps needing to reserve bandwidth and buffer space beforehand in minimizing delays (ie. realtime audio and video)
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21. Comparison between IPv4 and IPv6 packet header
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22. IPv6 Packet Extension header format
The base header is 40 bytes – in providing the IPv6 datagram more functionality, up to 6 extension headers can be added
There are 6 different extension header types
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23. Hop-by-hop option header format
Option used when the Tx needs to pass info to every router visited by the datagram (ie mgmt, debugging or control functions)
The various options for the Hop-by-Hop option are (1) Pad1, (2) PadN and (3) Jumbo payload.
The general format is
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24. Pad1
1 byte long and used for alignment or padding – some options need to start at specific bit. Pad1 doesn’t contain the option length field nor the data field – simply consists of the code field with all bits set to zeros. The Pad1 option can be inserted anywhere.
Action is 00 (skip over this option)
Change bit is 0 (does not change in transit)
Type is (Pad1)
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25. PadN
Similar to Pad1 however, PadN is used when 2 or bytes are needed for alignment or padding. Length contains the number of padding bytes
Data contains the zero padding bytes
Action is 00 (skip over this option)
Change bit is 0 (does not change in transit)
Type is (PadN)
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26. Jumbo payload
Maximum size of an IP payload is 65,535 bytes – but suppose a longer payload is needed – use the Jumbo Payload to define the longer payload
Action is 11 , change bit is 0, type is  Code =
Contains the size-in-bytes of this field (static 4 bytes)
Contains the size of the payload – can be a max size of because it can be a max of 32 bits (4x8)
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27. Source Routing
Recall the concepts of strict source routing and loose source routing for IPv4 – IPv6 combines the two.
Indicates the # hops needed to reach destination
Defines Source routing
Defines Strict (must follow exactly) or Loose (in addition to the routers in the header, can visit other routers)
For this option, the destination address is the next hop (versus the Rx) and it is not constant
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28. Fragmentation
Recall the concept of fragmentation for IPv4 – IPv6 fragmentation is similar however, ONLY the Tx can fragment – the TX uses Path MTU Discovery technique in finding the smallest MTU across the path – then it fragment based on this
If the Tx does not use the Path MTU Discovery technique, it fragments to 576 bytes or smaller – the minimum size MTU
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29. Authentication
Authentication extension header (1) validates the Tx and (2) ensures the integrity of the data – making sure the Tx is genuine and making sure the data sent wasn’t altered.
Identifies which authentication algorithm is used
Contains the data generated from the algorithm
The way the authentication data is generated by the TX is by passing the key first, then the IP datagram with the changing and authentication fields removed, and them passing the key again
Using the secret key, the RX performs the same operation and if there is a match, fine, if there is no match, the datagram is discarded.
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30. Encrypted Security Payload
ESP extension header provides confidentiality and guards against eavesdropping.
32-bit word that defines the type of encryption/decryption used
Encrypted data with any extra parameters needed by the algorithm
Encryption can be implemented in 2 ways: transport mode or tunnel mode
For the transport mode, a TCP segment or UDP datagram is first encrypted and then encapsulated in the IPv6 packet – typically used to encrypt from host to host
For the tunnel mode, entire datagram with base header and extension header is encrypted and then encapsulated into a NEW datagram – most used by security gateways
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31. Destination option
Option used when the Tx needs to pass info to the Rx only
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32. Comparison between IPv4 options and IPv6 extension headers
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33. Next Generation: IPv6 and ICMPv6 final …
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34. Comparison of network layers in version 4 and version 6
Recall that ICMP is used for:
Error reporting
Host and management queries
Related protocols were either modified or dropped for IPv6
- ICMP was modified (ICMPv6)
- ARP and IGMP in version 4 were combined in ICMPv6
- RARP was dropped
- RIP and OSPF were slightly modified
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35. Categories of ICMPv6 messages
- Still divided into 2 categories
Report problems that a router or a host (destination) may encounter when it processes an IP packet.
Help a host or network manager get specific info from a router or another host.
New
New
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36. General format of ICMP messages
First 4 bytes are common to all
Type – type of message
Code – reason for the particular message type
Checksum
For error messages, this carries info for finding the original packet that had the error
For query messages, this carries extra info based on the type of the query
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37. Comparison of error-reporting messages in ICMPv4 and ICMPv6
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38. Destination-unreachable message format
Same as in version 4
Used when a router cannot route a datagram or a host cannot deliver a datagram
So the datagram is dropped and the host or router sends this message
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39. Packet-too-big message format
New in version 6
Router receives a datagram larger than the MTU
So the datagram is dropped and the host or router sends this message to the source
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40. Time-exceeded message format
Same as in version 4
When the hop limit is violated
So the datagram is dropped and the host or router sends this message to the source
The only difference is that the type is 3
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41. Parameter-problem message format
Same as in version 4
When a router or host discovers ambiguous or missing value in any field
Datagram is dropped and this error message is sent
The only differences are that the type is 4 and the size of the offset was increased to 4 bytes
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42. Redirection message format
Same as in version 4
When a host sends a datagram to the wrong router
The datagram IS NOT dropped – but rather “redirected” to the correct router
The only differences are:
It accommodates the larger IPv6 addresses
Has an option to let the host know the physical address of the target router
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43. Comparison of query messages in ICMPv4 and ICMPv6
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44. Echo request and reply messages
Same as in version 4
Used to identify network problems
The only difference is that the type was changed to 128 or 129
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45. Router-solicitation and advertisement message formats
Same as in version 4
Used by host to determine if routers are alive and functioning
The only differences are: (1) it can announce its physical address, (2) router can announce the MTU size, and (3) allows the router to define valid lifetime
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46. Neighbor-solicitation and advertisement message formats
New in version 6
Performs IPv4’s ARP function
Used to find the physical address of the Rx (given the network address of the Rx)
The only option announces the sender physical address for convenience of the Rx
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47. Four situations of group-membership operation
Group-membership message formats
New in version 6
Performs IPv4’s IGMP function
Four situations of group-membership operation
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48. TRANSITION FROM IPv4 TO IPv6
Three strategies have been devised by the IETF to provide for a smooth transition from IPv4 to IPv6.
1. Dual Stack
2. Tunneling
3. Header Translation
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49. Dual stack All host have both IPv4 and IPv6 protocols running
The host would query the DNS in determining the type of address (ie IPv4 or IPv6)
Depending on the type of address, the host would invoke the corresponding IP version
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50. Tunneling Automatic Tunneling Configured tunneling
Given an IPv6 Tx wants to send a packet to an IPv6 but needs to traverse across an IPv4 network – the IPv6 packet can be encapsulated into the IPv4 packet in traversing across the IPv4 network and “unpackaged” after reaching across the IPv4
Automatic Tunneling
If the Rx is IPv6, automatic tunneling is perform and the “compatible IPv6” address is used (recall this)
Configured tunneling
If the Rx doesn’t support a compatible IPv6 address, the initial IPv4 router uses it address as the source address
And the final IPv4 router address is used as the destination address
The final IPv4 router performs the decap and send the packet on the IPv6 Rx
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51. Header translation
Header Translation will be used when the majority of the Internet is IPv6 with some systems still using IPv4.
When the final destination is IPv4, tunneling will not work because the Rx only understands IPv4
Therefore, the IPv6 header must be translated to an IPv4 header
Header translation uses the “mapped address” (recall) to translate IPv6 address to a IPv4 address
Some of the rules used in the translation are:
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