CSE4213 Computer Networks II Supplementary Material (VLSM and IPv6) Course page: http://www.cs.yorku.ca/course/4213

Variable Length Subnet Mask Let’s say there is a company with a Class C network 202.145.225.0/24. Subnet 1 requires 10 hosts Subnet 2 requires 10 hosts Subnet 3 requires 10 hosts Subnet 4 requires 10 hosts Subnet 5 requires 50 hosts Subnet 6 requires 100 hosts How to subnet?

IPv6 Header Format

IPv6 Extension Header The general form of an IPv6 datagram. Extension headers are optional -- the minimum datagram has a base header followed by data

Example Two IPv6 datagrams in which (a) contains a base header plus data, and (b) contains a base header, route header, and data. The NEXT HEADER field in each header specifies the type of the item that follows.

IPv6 Options Extension Header Because the size of the options header can vary from one datagram to another, the HEADER LEN field specifies the exact length.

IPv6 Fragmentation In IPv4 a router performs fragmentation In IPv6 a sending host performs fragmentation. How? A sending host sends a packet to the size of the first link. If a router along the path cannot handle, it will drop the packet and send ICMPv6 packet too big. The sending host then resend with smaller size. Or simply send a minimum MTU size that all routers should support – 1280 bytes

IPv6 Fragmentation (2)

IPv6 Addressing http://www.tcpipguide.com/free/t_IPv6AddressandAddressNotationandPrefixRepresentati.htm

IPv4-Compatible IPv6 Addresses For devices that speak both IPv4 and IPv6: dual stack http://www.tcpipguide.com/free/t_IPv6IPv4AddressEmbedding.htm

IPv4-Mapped IPv6 Addresses Used for mapping IPv4 devices that are not compatible with IPv6 into the IPv6 address space; it begins with 80 zeroes followed by 16 ones. (only IPv4-capable) http://www.tcpipguide.com/free/t_IPv6IPv4AddressEmbedding-2.htm