[j-nsp] Big Size Packets on DS3

[Josef Buchsteiner]

>> trying to get to the default MTU. Getting bogged down at
>> about 4445 bytes. Tried another
>> channel on this CHOC-12 to no avail. The exact same setup works fine when tried with
>> Cisco.

> Keep in mind that if you use the "size" parameter on the juniper ping
> command to test what you are describing, it only counts the payload, not
> the IP or ICMP headers, so the maximum size you can ping with is your
> inet mtu (4470) - 28 bytes = 4442. So this is normal behaviour. You can
> see the same thing on an Ethernet interface with standard inet mtu of
> 1500, where 1472 is the largest size parameter to junipers ping you will
> get through the link with do-not-fragment set.


correct.  just  for  illustration  below.  Therefor  my  initial
question was how the mtu test has been performed.

thanks
Josef


  Logical interface t3-1/2/0:0.0 (Index 96) (SNMP ifIndex 155)
    Flags: Point-To-Point SNMP-Traps Encapsulation: Cisco-HDLC
    Protocol inet, MTU: 4470
      Flags: None
      Addresses, Flags: Is-Preferred Is-Primary
        Destination: 88.88.88/24, Local: 88.88.88.1, Broadcast: 88.88.88.255



josefb at Leeds-re0> ping bypass-routing interface t3-1/2/0:0 do-not-fragment size 4442 88.88.88.1 
PING 88.88.88.1 (88.88.88.1): 4442 data bytes
4450 bytes from 88.88.88.1: icmp_seq=0 ttl=255 time=4.040 ms
^C
--- 88.88.88.1 ping statistics ---
1 packets transmitted, 1 packets received, 0% packet loss
round-trip min/avg/max/stddev = 4.040/4.040/4.040/0.000 ms

josefb at Leeds-re0> ping bypass-routing interface t3-1/2/0:0 do-not-fragment size 4443 88.88.88.1    
PING 88.88.88.1 (88.88.88.1): 4443 data bytes
ping: sendto: Message too long
ping: sendto: Message too long


> /leg

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