NAME

  reducePMTUonlink - Reduce PMTU On-link

TARGET

  Host and Router

SYNOPSIS

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

INITIALIZATION

        Common Test Setup 1.1

TEST PROCEDURE

Verify that a node properly processes a Packet Too Big message indicating a reduction in Path MTU for an on-link destination.

   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)

JUDGEMENT

  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.

CLEANUP

Common Test Cleanup

REFERENCE

RFC 8201 - Path MTU Discovery for IPv6