increase0x1fffffff - Verify that a host does not increase its estimate
of the MTU for a path due to a Packet Too Big message
Host and Router
increase0x1fffffff.seq [-tooloption ...] -pkt increase0x1fffffff.def
-tooloption : v6eval tool option
If the NUT is a host, send a Router Advertisment.
If the NUT is a router, configure a default route with TN as the next hop.
And make state of Neighbor Cashe Entry for TN's addresses reachable.
TN2 TR1 NUT
| | |
|-------------------------------------------->|
| 1.Echo Request | |
| (1500 octets) | |
| | |
|<--------------------------------------------|
| 2.Echo Reply | |
| (1500 octets) | |
| | |
| +--------------------->|
| | 3.Packet Too Big |
| | (MTU 1304) |
| | |
|-------------------------------------------->|
| 4.Echo Request | |
| (1500 octets) | |
| | |
|<--------------------------------------------|
| 5.Fragment Echo Reply| |
| (1st + 2nd = 1500) | |
| | |
| +--------------------->|
| | 6.Packet Too Big |
| | (MTU 0x1FFFFFFF) |
| | |
|-------------------------------------------->|
| 7.Echo Request | |
| (1500 octets) | |
| | |
|<--------------------------------------------|
| 8.Fragment Echo Reply| |
| (1st + 2nd = 1500) | |
| | |
v v v
1. Send Echo Request (Payload Length is 1500)
2. Receive Echo Reply (Payload Length is 1500)<<Check 1>>
3. Send Packet Too Big message (MTU is 1304)
4. Send Echo Request (Packet size is 1500)
5. Receive fragmented Echo Reply (1st + 2nd Fragment size is 1500)<<Check 2>>
6. Send Packet Too Big message (MTU is 1500)
7. Send Echo Request (Packet size is 1500)
8. Receive fragmented Echo Reply (1st + 2nd Fragment size is 1500)<<Check 3>>
Echo Request Data is:
IPv6 Header
Version = 6
Traffic Class = 0
FlowLabel = 0
PayloadLength = 1460
NextHeader = 58 (ICMPv6)
SourceAddress = TN2's Global Address
DestinationAddress = NUT's Global Address
ICMP Echo Request
Type = 128 (Echo Request)
Code = 0
Checksum = (auto)
Identifier = 0xffff
SequenceNumber = 1
PayloadData = (1452 octets)
Packet Too Big message is:
IPv6 Header
Version = 6
Traffic Class = 0
FlowLabel = 0
PayloadLength = 1280
NextHeader = 58 (ICMPv6)
SourceAddress = NUT's Global Address
Destination Address = TN2's Global Address
ICMP Echo Request
Type = 2 (Packet Too Big)
Code = 0
Checksum = (auto)
MTU = 1304,0x1FFFFFFF
PayloadData = (1232 octets)
PASS: <<Check 1>> Echo Reply Received or Fragment Echo Reply Received
<<Check 2,3>> Fragment Echo Reply Received. 1st and 2nd fragment no larger than 1304 octets.
IPv6 Header
Version = 6
Traffic Class = 0
FlowLabel = 0
PayloadLength = 1460
NextHeader = 58 (ICMPv6)
SourceAddress = NUT's Address
Destination Address = TN2's Global Address
ICMP Echo Reply
Type = 129 (Echo Reply)
Code = 0
Checksum = (auto)
Identifier = 0xffff (same as Echo Request)
SequenceNumber = 1 (same as Echo Request)
PayloadData = (1452 octets) (same as Echo Request)
RFC 1981 - Path MTU Discovery for IPv6
perldoc V6evalTool