reducePMTUonlink - Verify that a node properly processes a Packet
Too Big message indicating a reduction in Path MTU
for a link-local and global destination
Host and Router
reducePMTUonlink.seq [-tooloption ...] -pkt reducePMTUonlink.def
-tooloption : v6eval tool option
Common Test Setup 1.1
Summary: This minimal setup procedure provides the NUT with
a default router TR1, a global prefix,
and ensures that the NUT can communicate with TR1.
1. If the NUT is a host, TR1 transmits a Router Advertisement to the all-nodes multicast address.
The Router Advertisement includes a Prefix Advertisement with a global prefix and the L and A bits sets.
This should cause the NUT to add TR1 to its Default Router List,
configure a global address, and compute Reachable Time.
The Router and Prefix Lifetimes are long enough such that they do not expire during the test.
2. If the NUT is a router,
configure a default route with TR1 as the next hop.
3. TR1 transmits an Echo Request to the NUT and responds to Neighbor Solicitations from the NUT.
Wait for an Echo Reply from the NUT.
This should cause the NUT to resolve the address of TR1 and create a Neighbor Cache entry for TR1 in state REACHABLE.
TR1 NUT
| |
|-------------------------->|
| 1.Echo Request |
| (1500 octets) |
| |
|<--------------------------|
| 2.Echo Reply |
| (1500 octets) |
| |
|-------------------------->|
| 3.Packet Too Big |
| (MTU is 1280) |
| |
|-------------------------->|
| 4.Echo Request |
| (1500 octets) |
| |
|<--------------------------|
| 5.Fragmented Echo Reply |
| (1st + 2nd = 1500) |
| |
v v
1. TR1 transmits a 1500 byte link-local Echo Request to the NUT.
2. Observe the packets transmitted by the NUT. <<Check 1>>
3. Even though TR1 is configured with a link MTU associated with its media type (1500 for Ethernet),
TR1 transmits a Packet Too Big message to the NUT with an MTU of 1280.
4. TR1 transmits a 1500 byte link-local fragmented Echo Request to the NUT.
The fragmented packets are no larger than 1280 octets in size.
5. Observe the packets transmitted by the NUT. <<Check 2>>
6. Repeat Steps 1 through 5,
transmitting an on-link global Echo Request to the NUT for both Steps 1 and 4.
Echo Request Data is:
IPv6 Header
Version = 6
Traffic Class = 0
FlowLabel = 0
PayloadLength = 1460
NextHeader = 58 (ICMPv6)
SourceAddress = TR1's Link-Local Address
DestinationAddress = NUT's Link-Local 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 = TR1's Link-Local Address
DestinationAddress = NUT Link-Local Address
ICMP Echo Request
Type = 2 (Packet Too Big)
Code = 0
Checksum = (auto)
MTU = 1280
PayloadData = (1232 octets)
PASS: <<Check 1>> The NUT should respond to the Echo Request.
<<Check 2>> The NUT should correctly fragment its response to the Echo Request,
indicating the NUT processed the Packet Too Big mesage.
The Fragmented packets must not be larger than 1280 octets in size.
RFC 1981 - Path MTU Discovery for IPv6
perldoc V6evalTool