IPv6. CM0255 Course Omer Rana

Transcription

1 IPv6 CM0255 Course Omer Rana Issues IPv4, defines a 32-bit address (4,294,967,296) IPv4 addresses available The first problem is concerned with the eventual depletion of the IP address space. Scarceness of IPv4 addresses Some use a Network Address Translation mechanism (makes reuse of private address space) Traditional model of classful addressing does not allow the address space to be used to its maximum potential. 1

2 Classful Addressing When IP was first standardized in Sep 1981, each system attached to the IP based Internet had to be assigned a unique 32-bit address The 32-bit IP addressing scheme involves a two level addressing hierarchy Network Number/Prefix Host Number Issues 2 Increase in internet-connected devices/appliances Difficulty in routing traffic Can have large routing tables (over 85K routes of Internet Backbone Routers) Better support for Quality of Service (QoS) Lack of support for real-time traffic in IPv4 (e.g. IPv4 Type of Service field has limited functionality) 2

3 Features of IPv6 Larger Address Space Aggregation-based address hierarchy Efficient backbone routing Efficient and Extensible IP datagram Stateless Address Autoconfiguration Security (IPsec mandatory) Mobility Addresses 128-bit = 3.4 x addresses = 340,282,366,920,938,463,463,374,607,431,768,211,456 possible addresses 655,570,793,348,866,943,898,599 (6.5 x ) addresses for every square meter of the Earth s surface Stateless and Stateful Address Configuration Stateful: Use of a DHCP server Stateless: hosts automatically configure themselves (link-local addresses) and with addresses derived from prefixes advertised by local routers 3

4 128-bit IPv6 Address 3FFE:085B:1F1F:0000:0000:0000:00A9: groups of 16-bit hexadecimal numbers separated by : Leading zeros can be removed 3FFE:85B:1F1F::A9:1234 :: = all zeros in one or more group of 16-bit hexadecimal numbers Another Example DA:00D3:0000:2F3B:02AA:00FF:FE28:9C5A 21DA:D3:0:2F3B:2AA:FF:FE28:9C5A 4

5 Compressing Zeros A contiguous section of 16-bit block set to 0 s :: FE80:0:0:0:2AA:FF:FE9A:4CA2 FE80::2AA:FF:FE9A:4CA2 Multicast address: FF02:0:0:0:0:0:0:2 FF02::2 FF02:30:0:0:0:0:0:5 as FF02:3::5 (incorrect) FF02:30:0:0:0:0:0:5 as FF02:30::5 (correct) How many zero bits represented by ::? FF02::2 (count number of blocks, in this case 2) Calculate = (8 number of blocks) * 16 = 96 Zero compression can only be used once in a given address otherwise, cannot determine number of 0 bits represented by each :: Type of Addresses Unicast: delivery to a single interface Multicast: delivery to multiple interfaces (one-to-many communication) IPv6 multicast addresses have first 8 bits set to 1 Anycast delivery to one of many potential interfaces (one-to-one-of-many communication) 5

6 Link-Local Address Used by hosts to communicate on the same link (i.e. within the same router) IPv6 router does not forward link-local traffic beyond the link Required for Neighbour Discovery process always automatically configured Link-local addresses begin with FE80. With 64-bit interface identifier, prefix for link-local address is always FE80::/64 Site Local Address Similar to private internet i.e. networks not directly connected to external internet For traffic restricted to a site (behind a NAT) Unlike link-local addresses are not automatically assigned 6

7 Ipconfig output Ethernet adapter Local Area Connection: Connection-specific DNS Suffix. : wcoast.example.com IP Address : Subnet Mask : IP Address : 3ffe:ffff:2a1c:2:1cc8:ef1d:1dd9:8066 IP Address : 3ffe:ffff:2a1c:204:5aff:fe56:f5b IP Address : fe80::204:5aff:fe56:f5b%4 Default Gateway : fe80::20a:42ff:feb0:5400%4 IPv6 Packet over LAN 7

8 IPv6 Header Minimise header overhead IPv4 and IPv6 headers cannot work together (i.e. are not compatible) IPv6 header is only twice as large as IPv4, whereas IPv6 addresses are four times as large as IPv4 Header comparison 20 bytes 40 bytes vers hlen TOS total length identification flags flag-offset TTL protocol header checksum source address destination address options and padding IPv4 vers traffic class flow-label payload length next header hop limit source address destination address IPv6 Removed (6) ID, flags, flag offset TOS, hlen header checksum Changed (3) total length => payload protocol => next header TTL => hop limit Added (2) traffic class flow label Expanded address 32 to 128 bits 8

9 IPv6 Header Version (4 bits): set to 6 (for IPv6) Traffic Class (8 bits): class/priority of IPv6 packet similar to ToS in IPv4 Flow Label (20 bits): indicates a sequence of packets between source and destination requiring special handling by IPv6 routers Payload Length (16 bits): indicates what is carried (Protocol Data Unit, Extension Header, etc) IPv6 Header 2 Next Header (8 bits): first extension header (if present) or the PDU (TCP, UDP, ICMP) Hop Limit (8 bits): maximum number of links over which the packet can be carried before being discarded (similar to IPv4 Time To Live (TTL)) Source/Destination Address (128 bits each) 9

10 Extension Header Value (in decimal) Header Hop-by-Hop Options Header TCP UDP Encapsulated IPv6 Header Routing Header Fragment Header Resource ReSerVation Protocol Encapsulating Security Payload Authentication Header ICMPv6 No next header Destination Options Header Major Improvements of IPv6 Header No option field: Replaced by extension header. Result in a fixed length, 40- byte IP header. No header checksum: Result in fast processing. No fragmentation at intermediate nodes: Result in fast IP forwarding. 10

11 Extension Headers Routing Extended routing, like IPv4 loose list of routers to visit Fragmentation Fragmentation and reassembly Authentication Integrity and authentication, security Encapsulation Confidentiality Hop-by-Hop Option Special options that require hop-by-hop processing Destination Options Optional information to be examined by the destination node Stateless Address Autoconfiguration 3 ways to configure network interfaces: Manually, Stateful, Stateless IPSAA IPv6 addr. Separated into 2 2 parts: network and interface id. Link- local addresses: prefix FE80::0 + interface identifier Obtain network id through Router solicitation (RS) 11

12 IPv4 32 bits (4 byte) addresses IPSec is optional Fragmentation by both routers and sender ARP uses broadcast for resolution Internet Group Management Protocol for local subnet group membership IPv6 128 bits (16 byte) addresses IPsec support is required Fragmentation by sender only Use of multicast Neighbour Solicitation messages (part of ICMPv6) Use of Multicast Listener Discovery messages (part of ICMPv6) IPv4 to IPv6 Need for both: (1) migration; (2) coexistence of both types of hosts IPv6/IPv4 nodes: support both protocols. IPv4 compatible address can be used as an IPv6 destination IPv6 traffic automatically encapsulated within an IPv4 header (over IPv4 routers) 12

13 IPv4-compatible address 0:0:0:0:0:0:w.x.y.z or ::w.x.y.z IPv4-mapped address IPv4 to IPv6 0:0:0:0:0:FFFF:w.x.y.z or ::FFFF:w.x.y.z Not used as a source or destination Represents an IPv4-only node to an IPv6 node 6to4 address Tunnelling technique: communicate between two nodes running both IPv4 and IPv6 over an IPv4 routing infrastructure Combine prefix 2002::/16 with the 32 bits of an IPv4 address Overlay Tunnels 13

14 Material here is based on Introduction to IPv6 by Minal Mishra IPv6 by Mohamed Ezzat Introduction to IPv6 by Microsoft Corporation, Feb