IP addressing and IPv6

1
IP addressing and IPv6

• Sept. 13, 2004

2
TCP/IP Protocol Suite
TCP
UDP
ICMP
IP
IGMP
ARP
RARP
Ethernet
3
IP Packet Format
0
4
8
16
19
31
TOS
Length
V
ersion
HLen
Ident
Flags
Offset
TTL
Protocol
Checksum
SourceAddr
DestinationAddr
Pad
Options (variable)
(variable)
Data
4
Fragmentation and Reassembly
5
Addressing

• Ethernet address is flat.
• IP address is hierarchical.

7
24
(a)
Network
Host
0
14
16
(b)
Network
Host
1
0
21
8
(c)
Network
Host
1
1
0
6
Datagram Forwarding in IP
For a router if (NetworkNum of destination
NetworkNum of one of my interface) then
deliver packet to destination over that
interface else if (NetworkNum of destination
is in my forwarding table) then deliver
packet to NextHop router else deliver
packet to default router For a host if
(NetworkNum of destination my NetworkNum) then
deliver packet to destination directly else
deliver packet to default router
7
ICMP Features

• ICMP Used by IP to send error and control
  messages
• ICMP uses IP to send its messages
• ICMP does not report errors on ICMP messages.
• ICMP message are not required on datagram
  checksum errors. (Some implementations still do)

8
ICMP Message Format
9
ICMP Message Types

• Type description
• 0 echo reply (ping)
• 3 destination unreachable
• source quench
• redirect
• 8 echo request (ping)
• 9 route advertisement
• 10 router discovery
• 11 TTL expired
• bad IP header
• timestamp request
• timestamp reply
• information request
• information reply
• address mask request
• address mask reply

10
ICMP Messages

• Source Quench Please slow down! I just dropped
  one of your datagrams.
• Time Exceeded Time to live field in one of your
  packets became zero. or Reassembly timer expired
  at the destination.
• Fragmentation Required Datagram was longer than
  MTU and No Fragment bit was set.
• Address Mask Request/Reply What is the subnet
  mask on this net? Replied by Address mask agent
  

11
Destination Unreachable
12
Other ICMP Messages

• Redirect Please send to router X instead of me.
• 0 Redirect datagrams for the network
• 1 Redirect datagrams for the host
• 2 Redirect datagrams for the type of service
  and net
• 3 Redirect datagrams for the type of service
  and host
• Time Stamp Request/Reply

13
IP version 6- IP Next Generation (IPng)
14
Related RFCs
15
IPng Considerations

• Addressing
• the two level structure of the IP address is
  convenient but wasteful of address spaces.
• it is general practice to assign a unique network
  number to an IP network whether or not it is
  actually connected to the Internet.
• networks are proliferating rapidly.
• growth of TCP/IP usage in new areas will result
  in a rapid growth in the demand for unique IP
  addresses.
• Performance
• reduced number of fields in the IPv6 packet
  header
• fixed length of header extension header
• disabling fragmentation

16
IPng Considerations

• Network service
• should be possible to associate packets with
  particular services classes flow label
• Addressing flexibility
• anycast delivered to just one of a set of nodes
• multicast improved scalability by a scope filed
• Security capabilities
• providing authentication and privacy

17
IPv6 Packet Header
0
4
12
16
24
31
V
ersion
T
rafficClass
FlowLabel
PayloadLen
NextHeader
HopLimit
SourceAddress
DestinationAddress
Next header/data
18
Extension Headers

• Hop-by-hop options header
• defines special options that require hop-by-hop
  processing
• Routing header
• provides extended routing, similar to IPv4 source
  routing
• Authentication header
• provides packet integrity and authentication
• Encapsulating security payload header
• provides privacy
• Destination options header
• contains optional information to be examined by
  the destination node

19
Priority Field

• One bit for two classes
• congestion controlled traffic
• non-congestion controlled traffic
• Three bits for eight priorities in each class

20
Flow Label

• a flow is a sequence of packets that
• are generated from a single application instance
  from the sources point of view
• share attributes which affect how they are
  handled from the routers point of view
• Rules for flow label
• hosts or routers that do not support the flow
  label field must
• set the field to zero when originating a packet
• pass the filed unchanged when forwarding a packet
• ignore the filed when receiving a packet
• all the packets with the same non-zero flow label
  must have the same destination address, source
  address, priority, hop-by-hop options header
  contents and routing header contents.
• the source assigns a flow label to a flow.

21
Addressing

• 128 bit address space
• Address notation 47cd12344422ac0200221234a4
  560123

125

m

n

o

p
p
o
n
m
3
SubscriberID
ProviderID
RegistryID
010
InterfaceID
SubnetID
22
Address Prefix Assignment
23
Multicast Address
112
4
4
8
11111111
Scope
Flags
Group ID

• flags field
• consists of three zeros followed by a T bit with
• T 0 to indicates a permanently assigned or
  well-known multicast address, assigned by the
  global internet numbering authority
• T 1 to indicates a nunpermanently-assigned or
  transient multicast address
• Scope field to limit the scope of the multicast
  group
• 0reserved, 1node-local, 2link-local,
  5site-local, 8organization-local, 14global

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Anycast

• Delivery method
• unicast one-to-one
• multicast one-to-many
• broadcast one-to-all
• anycast one-to-one-of-many
• Anycast address an address assigned to multiple
  hosts
• Restrictions
• do not use in the source address field
• only assign to routers but not hosts
• Applications of anycast
• server selection
• service location

25
Challenges in Anycast

• Global routing
• anycast defeats the advantages of aggregated
  routing
• Global IP Anycast (GIA) has been proposed
• Supporting stateful connections
• anycast is naturally inappropriate for stateful
  connection such as TCP
• proposals
• use only stateless connection protocol such as
  UDP
• five-way handshake
• source id option

26
Evaluating IPv6

• Test setup
• Two Intel Pentium III 500 Mhz PCs
• 100 Mbps PCI Ethernet adapter
• Both Windows 2000 Professional and Solaris 8.0
• Metrics
• throughput
• round-trip time
• CPU utilization
• socket-creation time
• TCP-connection time
• client-server interactions

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Throughput
28
Latency
29
Socket Creation and TCP Connection