IPv6 Jumbograms

What is IPv6 jumbogram? Jumbogram: a packet or datagram larger than the size limit of a given technology such as udp packet larger than 65,535 octet. IPv6 Jumbogram: IPv6 packet containing payload larger than 65,535 octets.

Jumbogram requirements: IP layer: as known IPv4 and IPv6 has payload length of 16 bits which restricts the maximum payload length to 2^16 in IPv4 but in IPv6 by using extension headers the problem can be solved. so by using hop-by-hop option header with Jumbo Payload Option the problem solved at IPv6.

By setting the payload lengh and next header fields to zero it means IPv6 jumpogram,the next header will be hop-by-hop options header.

Extension Header : Next Header 8 bit L=(HEL+1)*8 byte Header Ext Length 8bits Options Option type 8bit TLV format Option length 8bit Options data Options begin with 4n+2 octet

HPH Ext Header with jumbogram option: Options type=0xC2 Option length=0x04 (4 octets:payload length) Options value:payload length 0xC2 0x04 32 bit jumbo payload length

IPv6 Jumbogram requirements cont: Transport layer: UDP: the 16bit length field limit the maximum UDP segment size to 65,535 octets including UDP header and data,so to make UDP jumbograms set the length to zero. TCP: MSS will be 65,535 wich means infinity.

IPv6 Jumbogram requirements cont Data Link Layer: Jumbograms are relevant only to IPv6 nodes that may be attached to links with a link MTU greater than 65,575 octets, and need not be implemented or understood by IPv6 nodes that do not support attachment to links with such large MTUs.

Conclusion IPv6 jumbograms are intended for futuere use because MTU currently available are 9KB and exists in private networks for research purposes.