NAME

  reducePMTUofflink - Reduce PMTU Off-link

TARGET

  Host and Router

SYNOPSIS

  reducePMTUofflink.seq [-tooloption ...] -pkt reducePMTUofflink.def
    -tooloption : v6eval tool option

INITIALIZATION

        Common Test Setup 1.1

TEST PROCEDURE

Verify that a node properly reduces its estimate of he MTU for a path due to a Packet Too Big message indicating a reduction in Path MTU for a global destination.

   TN2                    TR1                    NUT
    |                      |                      |
    |-------------------------------------------->|
    |   1.Echo Request     |                      |
    |   (1440 octets)      |                      |
    |                      |                      |
    |<--------------------------------------------|
    |   2.Echo Reply       |                      |
    |   (1440 octets)      |                      |
    |                      |                      |
    |                      +--------------------->|
    |                      |  3.Packet Too Big    |
    |                      |    (MTU 1400)        |
    |                      |                      |
    |-------------------------------------------->|
    |   4.Echo Request     |                      |
    |   (1500 octets)      |                      |
    |                      |                      |
    |<--------------------------------------------|
    | 5.Fragment Echo Reply|                      |
    |   (1st + 2nd = 1500) |                      |
    |                      |                      |
    |                      +--------------------->|
    |                      |  6.Packet Too Big    |
    |                      |    (MTU 1280)        |
    |                      |                      |
    |-------------------------------------------->|
    |   7.Echo Request     |                      |
    |   (1500 octets)      |                      |
    |                      |                      |
    |<--------------------------------------------|
    | 8.Fragment Echo Reply|                      |
    |   (1st + 2nd = 1500) |                      |
    |                      |                      |
    v                      v                      v

  1. Send Echo Request (Payload Length is 1400)
  2. Receive Echo Reply (Payload Length is 1400)<<Check 1>>
  3. Send Packet Too Big message (MTU is 1400)
  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 1280)
  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      = 1400 or 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    = (1392 or 1452 octets )

  Packet Too Big message is:

        IPv6 Header
            Version            = 6
            Traffic Class      = 0
            FlowLabel          = 0
            PayloadLength      = 1280
            NextHeader         = 58 (ICMPv6)
            SourceAddress      = TR1's Global Address
            DestinationAddress = NUT's Global Address

        ICMP Echo Request
            Type           = 2 (Packet Too Big)
            Code           = 0
            Checksum       = (auto)
            MTU            = 1400,1280
            PayloadData    = (1232 octets)

JUDGEMENT

  PASS: <<Check 1>> Echo Reply Received or Fragment Echo Reply Received
        <<Check 2>> Fragment Echo Reply Received. 1st and 2nd fragment no larger than 1400 octets.
        <<Check 3>> Fragment Echo Reply Received. 1st and 2nd fragment no larger than 1280 octets.

        IPv6 Header
            Version             = 6
            Traffic Class       = 0
            FlowLabel           = 0
            PayloadLength       = 1400,1460
            NextHeader          = 58 (ICMPv6)
            SourceAddress       = NUT's Global 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    = (1392 or 1452 octets ) (same as Echo Request)

CLEANUP

Common Test Cleanup

REFERENCE

RFC 8201 - Path MTU Discovery for IPv6