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2: Comparing IPv4 and IPv6 Rick Graziani Cabrillo College

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Presentation on theme: "2: Comparing IPv4 and IPv6 Rick Graziani Cabrillo College"— Presentation transcript:

1 2: Comparing IPv4 and IPv6 Rick Graziani Cabrillo College Rick.Graziani@cabrillo.edu

2 © For more information please check out my Cisco Press book and video series: IPv6 Fundamentals: A Straightforward Approach to Understanding IPv6 By Rick Graziani ISBN-10: 1-58714-313-5 IPv6 Fundamentals LiveLessons: A Straightforward Approach to Understanding IPv6 By Rick Graziani ISBN-10: 1-58720-457-6

3 2.1: Comparing the IPv4 and IPv6 Headers

4 © Let’s Begin with the IPv6 Header Understanding IPv6 begins with the IPv6 header. IPv6 takes advantage of 64-bit CPUs. Several differences between IPv4 and IPv6 headers. IPv4 IPv6 64-bit memory word Simpler IPv6 header. Fixed 40 byte IPv6 header. Lets look at the differences… Similar fields

5 © IPv6 Version IPv4 Version contains 4. IPv6 Version contains 6. Version 5? Internet Stream Protocol (ST2) IPv4 IPv6

6 © IPv4 Internet Header Length IPv4 Internet Header Length (IHL) Length of IPv4 header in 32-bit words including any Options or Padding. IPv6 IHL for IPv6 is not needed. IPv6 header is fixed at 40 bytes. IPv4 IPv6 8 bytes 40 bytes = 1 2 3 4 5 ?

7 © IPv6 Traffic Class IPv4 Type of Service IPv6 Traffic Class Not mandated by any IPv6 RFCs. Same functionality as IPv4. Uses same Differentiated Services technique (RFC 2474) as IPv4. IPv4 IPv6

8 © IPv6 Flow Label New field in IPv6 – not part of IPv4. Flow label is used to identify the packets in a common stream or flow. Traffic from source to destination share a common flow label. RFC 6437 IPv6 Flow Label Specification IPv4 IPv6 11001011000101100 10110010111000111

9 © IPv6 Payload Length IPv4 Total Length – Number of bytes of the IPv4 header (options) + data. IPv6 Payload Length – Number of bytes of the payload. Does not include the main IPv6 header. Includes extension headers + data IPv4 IPv6 IPv6 HeaderData IPv6 Extension Header (Optional) IPv4 HeaderData (Payload) Payload

10 © IPv4 Fragmentation IPv4 fields used for fragmentation and reassembly. Intermediate devices such as IPv6 routers do not perform fragmentation. Any fragmentation needed will be handled by the source using an extension header. IPv4 IPv6

11 © Source R1R2R3 PCB MTU of outgoing link smaller than packet size – fragment IPv4 packet. 12 PCA Destination IPv4 Fragmentation Link with smaller MTU IPv4 Packet It is my job to reassemble the packet fragments. 3 IPv4 Packet IPv4 requires that every link have a minimum MTU of 68 bytes. Every internet destination must be able to receive a packet of 576 bytes either in one piece or in fragments to be reassembled.

12 © MTU = 1500 MTU = 1350 MTU = 1500 R1R2R3 PCB MTU of outgoing link smaller than packet size. Drop packet. Send ICMPv6 Packet Too Big message, use MTU 1350. 2 3 PCA IPv6 No Fragmentation Link with smaller MTU IPv6 Packet – MTU 1500 Source Destination ICMPv6 Packet Too Big Use MTU 1350 1 IPv6 Packet MTU 1350 Packet received. No reassembly required. IPv6 requires that every link have a minimum MTU of 1280 bytes, with a recommended MTU of 1500 bytes. Path MTU Discovery uses this same process. Because intermediate devices do not fragment packets, Path MTU Discovery is used when their links are greater than 1280. I will use MTU of the interface.

13 © IPv6 Next Header IPv4 Protocol IPv6 Next Header For both protocols, the field indicates the type of header following the IP header. IPv4 IPv6 Common values: 6 = TCP 17 = UDP 58 = ICMPv6 88 = EIGRP 89 = OSPF IPv6 Header Next Header Data (Protocol: TCP, UDP, ICMPv6, etc.)

14 © IPv6 Hop Limit IPv4 TTL (Time to Live) IPv6 Hop Limit Renamed to more accurately reflect process. Set by source, every router in path decrements hop limit by 1. IPv4 IPv6 When 0, drop packet.

15 © IPv6 Source and Destination Addresses IPv6 Source and Destination addresses have the same basic functionality as IPv4. IPv4 – 32-bit addresses. IPv6 – 128-bit addresses. Some significant changes in IPv6. IPv4 IPv6

16 © IPv4 Header Checksum Not used in IPv6. Upper-layer protocols generally have a checksum (UDP and TCP). So, in IPv4 the UDP checksum is optional. IPv4 IPv6 Because it’s not in IPv6, the UDP checksum is now mandatory.

17 © IPv4 Options and Padding Not used in IPv6. Variable length, optional. IPv4 Options are handled using extension headers in IPv6. IPv4 IPv6 Padding makes sure IPv4 options fall on a 32-bit boundary. IPv6 header is fixed at 40 bytes. 40 bytes =

18 © IPv6 Extension Header Next Header identifies: The protocol carried in the data portion of the packet. IPv6 Main Header Next Header Extension Header Next Header Data (Protocol: TCP, UDP, ICMPv6, etc.) Extension headers are optional and follow the main IPv6 header. Provide flexibility and features to the main IPv6 header for future enhancements without having to redesign the entire protocol. Allows the main IPv6 header to have a fixed size for more efficient processing. The presence of an extension header.

19 © IPv6 Extension Header Next Header Value (Decimal) Extension Header Name Extension Header Description 0Hop-by-Hop OptionsUsed to carry optional information, which must be examined by every router along the path of the packet. 43RoutingAllows the source of the packet to specify the path to the destination. 44FragmentUsed to fragment IPv6 packets. 50Encapsulating Security Payload (ESP) Used to provide authentication, integrity, and encryption. 51Authentication Header (AH) Used to provide authentication and integrity. 60Destination OptionsUsed to carry optional information that only needs to be examined by a packet’s destination node(s). IPv6 Main Header Next Header 0 Hop-by-Hop Extension Header Next Header 51 TCP Header AH Extension Header Next Header 6 Data

20 2.2: A Brief Look at IPv6 Address Types

21 © IPv6 Address Types IPv6 Addresses FF00::/8FF02::1:FF00:0000/104 ::/128::1/1282000::/3FE80::/10FC00::/7::/80 Unicast Multicast Anycast Assigned Solicited Node Global Unicast Link-Local Loopback Unspecified Unique Local Embedded IPv4 More details in Lessons 3, 4, 5 & 6

22 2.3: A Brief Look at ICMPv6 Neighbor Discovery

23 © ICMPv6 Internet Control Message Protocol for IPv6 ICMPv6 is defined in RFC 4443. Similar to ICMPv4, describes two types of messages: Informational Error ICMPv6 Neighbor Discovery is described in RFC 4861. Much more robust than ICMP for IPv4. Contains new functionality and improvements. More than just “messaging” but “how IPv6 conducts business”. IPv6 Main Header Next Header 58 ICMPv6 Header Data All ICMPv6 messages

24 © ICMPv6 Neighbor Discover Protocol Router Solicitation Message Router Advertisement Message Used with dynamic address allocation Neighbor Solicitation Message Neighbor Advertisement Message Used with address resolution (IPv4 ARP) Redirect Message Similar to ICMPv4 redirect message Router-to-Device messaging Router-Device Messaging Device-Device Messaging ICMPv6 Neighbor Discovery defines 5 different packet types:

25 © Router Solicitation & Router Advertisement Messages Router Solicitation Message Router Advertisement Message Used with dynamic address allocation Neighbor Solicitation Message Neighbor Advertisement Message Used with address resolution (IPv4 ARP) Redirect Message Similar to ICMPv4 redirect message Router-to-Device messaging Router-Device Messaging Device-Device Messaging ICMPv6 Neighbor Discovery defines 5 different packet types:

26 © Dynamic Address Allocation in IPv4 DHCPv4 Server 1 1 2 2 I need IPv4 addressing information. Here is everything you need.

27 © Dynamic Address Allocation in IPv6 DHCPv6 Server ICMPv6 Router Advertisement ICMPv6 Router Solicitation To all IPv6 routers: I need IPv6 address information. To all IPv6 devices: Let me tell you how to do this … To all IPv6 devices: Let me tell you how to do this … 1. SLAAC 2. SLAAC with Stateless DHCPv6 3. Stateful DHCPv6 SLAAC (Stateless Address Autoconfiguration ) I might not be needed. Router Solicitations Router Advertisements

28 © Neighbor Solicitation & Neighbor Advertisement Messages Router Solicitation Message Router Advertisement Message Used with dynamic address allocation Neighbor Solicitation Message Neighbor Advertisement Message Used with address resolution (IPv4 ARP) Redirect Message Similar to ICMPv4 redirect message Router-to-Device messaging Router-Device Messaging Device-Device Messaging ICMPv6 Neighbor Discovery defines 5 different packet types:

29 © Ethernet ARP Request/Reply ICMPv6: Neighbor Solicitation/Advertisement IPv4: ARP over Ethernet PCA PCB ARP Request Neighbor Advertisement 1 1 2 2 Neighbor Solicitation 1 1 ARP Reply 2 2 Know IPv4, what is the MAC? My IPv4! Here is the MAC? Know IPv6, what is the MAC? My IPv6! Here is the MAC? ARP Request: Broadcast NS: MulticastNS: Solicited Node Multicast Ethernet IPv6 Header IPv6: ICMPv6 over IPv6 over Ethernet Address Resolution: IPv4 and IPv6 ARP Cache Neighbor Cache Neighbor Solicitations Neighbor Advertisements

30 © Redirect Message Router Solicitation Message Router Advertisement Message Used with dynamic address allocation Neighbor Solicitation Message Neighbor Advertisement Message Used with address resolution (IPv4 ARP) Redirect Message Similar to ICMPv4 redirect message Router-to-Device messaging Router-Device Messaging Device-Device Messaging ICMPv6 Neighbor Discovery defines 5 different packet types:

31 © ICMPv6 Redirect Similar functionality as ICMPv4. Like IPv4, a router informs an originating host of the IP address of a router that is on the local link and is closer to the destination. Unlike IPv4, a router informs an originating host that the destination host (on a different prefix/network) is on the same link as itself. Network X PCA PCB R1 R2 Destination: Network X Host Destination: PCB IPv6 Network A IPv6 Network B

32 © ICMPv6 Neighbor Discover Protocol Router Solicitation Message Router Advertisement Message Used with dynamic address allocation Neighbor Solicitation Message Neighbor Advertisement Message Used with address resolution (IPv4 ARP) Redirect Message Similar to ICMPv4 redirect message Router-to-Device messaging Router-Device Messaging Device-Device Messaging ICMPv6 Neighbor Discovery defines 5 different packet types: More details in Lessons 7, 8 & 10

33 © For more information please check out my Cisco Press book and video series: IPv6 Fundamentals: A Straightforward Approach to Understanding IPv6 By Rick Graziani ISBN-10: 1-58714-313-5 IPv6 Fundamentals LiveLessons: A Straightforward Approach to Understanding IPv6 By Rick Graziani ISBN-10: 1-58720-457-6

34 2: Comparing IPv4 and IPv6 Rick Graziani Cabrillo College Rick.Graziani@cabrillo.edu


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