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IPv6 Addressing
Agenda
• OSI & TCP/IP Model
• IPv4 Addressing
• IPv6 Addressing
TCP/IP and OSI
• OSI is made of seven layers.
• TCP/IP protocol is made of five layers.
PHYSICAL
DATA LINK
NETWORK
TRANSPORT
APPLICATION
PHYSICAL
DATA LINK
NETWORK
TRANSPORT
SESSION
PRESENTATION
APPLICATION
OSI Model TCP/IP Model
Frame Head Trailer
Frame
Data Encapsulation
Data
Data
Data
TCP Header
TCP Segment
UDP Header
UDP Message
TCP-UDP DataIP Header
IP Datagram
IP Header TCP-UDP Data
Application
TPT Layer
NW Layer
Data Link
D
P
N
T
A
TCP/IPv4 Protocol Suite..
ICMP IGMPRARPARP
FTPSMTP
TELNETHTTP
TFTPNFS
SNMPDNS
TCP UDP
IP
Protocols defined by the underlying networks
IP Header..
HEADER CHECKSUMPROTOCOLTIME TO LIVE
DESTINATION ADDRESS OF HOST
SOURCE ADDRESS OF HOST
PADDINGOPTIONS
76543210765432107654321076543210
FRAGMENT OFFSETMF
DFIDENTIFICATION
TOTAL LENGTHTOSHLENVER
Octet +3Octet +2 Octet +1 Octet +0
ARP Operation
Request Ignored
Request Ignored
ARP Response Accepted
Give me MAC address of 129.1.1.4
That’s Me
Here is my MAC address
129.1.1.1 129.1.1.4
129.1.1.2 129.1.1.308-00-39-00-2F-C3
08-00-10-99-AC-54
08-00-5A-21-A7-2208-00-39-00-2F-AB
RARP Operation
Give me my IP address RARP Response
Diskless work
station RARPServer
08-00-39-00-2F-C3 08-00-10-99-AC-54
08-00-5A-21-A7-22
223.1.2.1223.1.2.2
223.1.2.3
08-00-39-00-2F-AB
IPv4 Header
Version(4)
Destination IP Address (32)
HeaderLength (4)
Priority & Type of Service (8) Total Length (16)
Identification (16)Flags
(3) Fragment offset (13)
Time to live (8) Protocol (8) Header checksum (16)
Source IP Address (32)
20Bytes
Removed Changed
IPv6 Header
Version(4)
Destination IP Address (128)
Traffic Class(8) Flow Label(20)
Payload Length(16) Next Header(8) Hop Limit(8)
Source IP Address (128)40
Bytes
New
Extension Header
04/18/23 14
IPv6 HeaderNext Header= TCP
TCP Header+ Data
IPv6 HeaderNext Header= Routing
Routing HeaderNext Header= TCP
TCP Header+ Data
TCP Header+ Data
IPv6 HeaderNext Header= Routing
Routing HeaderNext Header= ESP
ESP HeaderNext Header= TCP
• New way of doing options• Added after the basic IPv6 header• Daisy chained
Summary
• Comparison of IPv4 and IPv6 headers shows a longer
header, but less number of fields
• Header processing is simpler
• Options are handled by extension headers
• Routing header for source routing changes the destination
address in the IP header
04/18/23 18
ALTTC/DX/SC/IPADDRESSING 19
IPv4 Addressing
8 Bits8 Bits 8 Bits 8 Bits
Network Host
32 Bits
172 . 16 . 122 . 204
ALTTC/DX/SC/IPADDRESSING 20
IPv4 Address Scheme
• Two types of addressing schemes for IPv4– Classful– Classless
• Classful – Original style of addressing based on first few
bits of the address.– Generally used in customer sites.
• Classless– A new type of addressing that disregards the
class bit of an address and applies a variable prefix (mask) to determine the network number.
ALTTC/DX/SC/IPADDRESSING 21
IPv4 Address classes
H H HNClass-A:
H HN NClass-B:
HN N NClass-C:
Class-D: For Multicast
Class-E: For Research
•N=Network number assigned by IR.•H=Host number assigned by network administrator.
ALTTC/DX/SC/IPADDRESSING 22
Identifying a class of address
Address Identifier Network Address Host Address
0 7 bits Network Address 24 bits Host AddressA
10 14 bits Network Address 16 bits Host AddressB
110 21 bits Network Address 8 bits Host AddressC
1110 Multicast address (224.0.0.0-239.255.255.255)D
1111 Reserved for future useE
ALTTC/DX/SC/IPADDRESSING 23
IP Address Bit Patterns
8 Bits8 Bits 8 Bits 8 Bits
Class-A:
Class-B:
Class-C:
Class-D:
Class-E:
0-127
128-191
192-223
224-239
240-255
0 0 0 0 0 0 0 0
1 0 0 0 0 0 0 0
1 1 0 0 0 0 0 0
1 1 1 0 0 0 0 0
1 1 1 1 0 0 0 0
0 1 1 1 1 1 1 1
1 0 1 1 1 1 1 1
1 1 0 1 1 1 1 1
1 1 1 0 1 1 1 1
1 1 1 1 1 1 1 1
ALTTC/DX/SC/IPADDRESSING 24
Networks Vs Hosts
• In Classless environment we can have232=4294967296 Hosts
• Class Networks Hosts/Network• A 126 16777214• B 16384 65354• C 2097152 254
ALTTC/DX/SC/IPADDRESSING 25
Private Address Space
• IANA has reserved the following three blocks of the IP address space for private internets (RFC 1918):– 10.0.0.0 - 10.255.255.255 (10.0.0.0/8 prefix)
• 24-bit block• Complete class-A network number
– 172.16.0.0 - 172.31.255.255 (172.16.0.0/12 prefix)• 172.0001/0000.0.0-172.0001/1111.255.255• 20-bit block• Set of 16 contiguous class-B network numbers
– 192.168.0.0 - 192.168.255.255 (192.168.0.0/16 prefix)• 16-bit block• Set of 256 contiguous class-C network numbers
IPv6 Addressing
• IPv6 addresses
• Format
• Unicast
• Multicast
• Anycast
• Required Node Addresses
• Address Selection
• Addressing Architecture
04/18/23 26
Addresses
• IPv4 = 32 bits
• IPv6 = 128 bits– This is not 4 times the number of addresses
– This is 4 times the number of bits
– ~3,4 * 1038 possible addressable nodes
– 1030 addresses per person on the planet
– Well, as with any numbering scheme, we will be using only a
portion of the full address space
04/18/23 27
Address Format
• x:x:x:x:x:x:x:x
– Where x is a 16 bits hexadecimal field
• 2001:0000:1234:0000:0000:C1C0:ABCD:0876
• Case insensitive
• 2001:0000:1234:0000:0000:c1c0:abcd:0876
• Leading zeros in a field are optional:
• 2001:0:1234:0:0:C1C0:ABCD:876
04/18/23 28
Address format
• Successive fields of 0 are represented as ::, but only once
in an address:– 2001:0:1234::C1C0:ABCD:876
– Not valid: 2001::1234::C1C0:ABCD:876
• Other examples:– FF02:0:0:0:0:0:0:1 => FF02::1
– 0:0:0:0:0:0:0:1 => ::1
– 0:0:0:0:0:0:0:0 => ::
04/18/23 29
Addresses in URL
• In a URL, it is enclosed in brackets– http://[2001:1:4F3A::206:AE14]:8080/index.html
– URL parsers have to be modified
– Cumbersome for users
• Mostly for diagnostic purposes
• Should use Fully Qualified Domain Names (FQDN)
04/18/23 30
Address Types
• Unicast– Unspecified
– Loopback
– Scoped addresses:• Link-local
• Site-local (Deprecated now)• Unique-Local
– Aggregatable Global:
• Multicast– Broadcast: none in IPv6
• Anycast
31
Unspecified
• Used as a placeholder when no address available– Initial DHCP request
– Duplicate Address Detection (DAD)
• Like 0.0.0.0 in IPv4
0:0:0:0:0:0:0:0 or ::
04/18/23 32
Loopback
• Identifies self
• Localhost
• Like 127.0.0.1 in IPv4
• 0:0:0:0:0:0:0:1 or ::1
• To find if your IPv6 stack works:
– Ping6 ::1
04/18/23 33
Link-Local
• Scoped address (new in IPv6)
• Scope = local link (i.e. VLAN, subnet)– Can only be used between nodes of the same link
– Cannot be routed
• Automatically configured on each interface– Uses the interface identifier (based on MAC address)
• Format:– FE80:0:0:0:<interface identifier>
• Gives every node an IPv6 address to start communications
04/18/23 34
Site-Local( now ULA)
• Scoped address
• Scope = site (a network of links)– Can only be used between nodes of the same site
– Cannot be routed outside the site (i.e. the Internet)
– Very similar to IPv4 private addresses
• Not configured by default
04/18/23 35
Unique local address
• ULA is an IPv6 address in the block fc00::/7 defined in RFC 4193.
• To be used for systems that are not connected to the Internet.
• Divided into two /8 address groups – assigned and random– valid /48 prefixes are derived
04/18/23 36
Aggregatable Global
• Generic use. Globally reachable.
• Allocated by IANA– To Regional Registries
– Then to Tier-1 Providers• Called Top-level Aggregator (TLA)
– Then to Intermediate Providers• Called Next-level Aggregator (NLA)
– Then to sites
– Then to subnets
04/18/23 37
Aggregatable Global• Structure:
04/18/23 38
TLA RES NLAs SLA Interface ID TLA RES NLAs SLA Interface ID
48 bits 16 bits 64 bits
• 128 bits as the total• 48 bits prefix to the site• 16 bits for the subnets in the site• 64 bits for host part
Aggregatable Global
• Consists of the following (left to right):– 3 bits: 001 (10% of the total address space reserved)
– 13 bits for the TLA• 213 TLAs ~ 8K TLAs
– 8 bits reserved
– 24 bits for the NLAs• 224 NLAs per TLA ~ 16M NLAs per TLA
– 16 bits for the site subnets• 216 subnets per site = 65536 subnets
– 64 bits for the interface identifier
– Total = 128 bits.
04/18/23 39
Multicast
• Multicast = one-to-many
• No broadcast in IPv6. Multicast is used instead, mostly on local links
• Scoped addresses:– Node, link, site, organisation, global
– No TTL as in IPv4
• Format:– FF<flags><scope>::<multicast group>
04/18/23 40
Multicast assigned Addresses
• Some reserved multicast addresses:
04/18/23 41
Address Scope Use
FF01::1 Interface-local All Nodes
FF01::2 Interface-local All Routers
FF02::1 Link-local All Nodes
FF02::2 Link-local All Routers
FF05::2 Site-local All Routers
FF02::1:FFxx:xxxx Link-local Solicited-Node
Anycast
• One-to-nearest: great for discovery functions
• Anycast addresses are indistinguishable from unicast
addresses– Allocated from the unicast addresses space
– Some anycast addresses are reserved for specific uses
• Few uses:– Router-subnet
– MobileIPv6 home-agent discovery
– discussions for DNS discovery
04/18/23 42
Required Node Addresses
• Any IPv6 node should recognize the following addresses
as identifying itself:– Link-local address for each interface
– Assigned (manually or automatically) unicast/anycast addresses
– Loopback address
– All-nodes multicast address
– Solicited-node multicast address for each of its assigned unicast
and anycast address
– Multicast address of all other groups to which the host belongs
04/18/23 43
Thanks
04/18/23 44
