Mailing List Archive

Tuesday, December 2, 2003, 10:04:28 PM, you wrote:
> Good Afternoon Everyone!

> Hopefully a quick one if there is something to it. Is
> anybody aware of any bugs/issues
> with transporting pkts bigger than, say 444x bytes, through
> a DS3 interface on JunOS 5.1R3
> running on an M40 with the following simple config:


Since the default MTU is 4474 you know where the default limit
is and if you want to send bigger mtu size packets what about
increasing the MTU size ?

josefb@M10-xxx> show interfaces t3-1/1/0
Physical interface: t3-1/1/0, Enabled, Physical link is Down
Interface index: 132, SNMP ifIndex: 23
Link-level type: PPP, MTU: 4474, Clocking: Internal, Speed: T3,



> [edit interfaces t3-0/3/0:4]
> xxx@calif# show
> clocking internal;
> encapsulation cisco-hdlc;
> t3-options {
> fcs 32;
> }
> unit 0 {
> family inet {
> address 1.2.3.2/30;
> }
> }


> Pinging across the ckt apparently that is as high as we are able to go.

> Thanks!
> +++The information transmitted is intended only for the
> person or entity to which it is
> addressed and may contain confidential and/or privileged material. Any review,
> retransmission, dissemination or other use of, or taking of any action in reliance upon,
> this information by persons or entities other than the
> intended recipient is prohibited.
> If you received this in error, please contact the sender and destroy any copies of this
> document.+++
> _______________________________________________
> juniper-nsp mailing list juniper-nsp@puck.nether.net
> http://puck.nether.net/mailman/listinfo/juniper-nsp

> Tuesday, December 2, 2003, 10:04:28 PM, you wrote:
> > Good Afternoon Everyone!
>
> > Hopefully a quick one if there is something to it. Is
> > anybody aware of any bugs/issues
> > with transporting pkts bigger than, say 444x bytes, through
> > a DS3 interface on JunOS 5.1R3
> > running on an M40 with the following simple config:

> Since the default MTU is 4474 you know where the default
> limit is and if you want to send bigger mtu size packets
> what about increasing the MTU size ?
>
> josefb@M10-xxx> show interfaces t3-1/1/0
> Physical interface: t3-1/1/0, Enabled, Physical link is Down
> Interface index: 132, SNMP ifIndex: 23
> Link-level type: PPP, MTU: 4474, Clocking: Internal, Speed: T3,

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.
+++The information transmitted is intended only for the person or entity to which it is
addressed and may contain confidential and/or privileged material. Any review,
retransmission, dissemination or other use of, or taking of any action in reliance upon,
this information by persons or entities other than the intended recipient is prohibited.
If you received this in error, please contact the sender and destroy any copies of this
document.+++

> trying to get to the default MTU. Getting bogged down at
> about 4445 bytes. Tried another
> channel on this CHOC-12 to no avail.

can you illustrate/demonstrate how you verified the MTU settings and also
the output of the interface in question ?

thanks
Josef


> The exact same setup works fine when tried with
> Cisco.
> +++The information transmitted is intended only for the
> person or entity to which it is
> addressed and may contain confidential and/or privileged material. Any review,
> retransmission, dissemination or other use of, or taking of any action in reliance upon,
> this information by persons or entities other than the
> intended recipient is prohibited.
> If you received this in error, please contact the sender and destroy any copies of this
> document.+++
> _______________________________________________
> juniper-nsp mailing list juniper-nsp@puck.nether.net
> http://puck.nether.net/mailman/listinfo/juniper-nsp

On Wed, 2003-12-03 at 16:58, Kashif.Khawaja@Broadwing.com wrote:

> > Since the default MTU is 4474 you know where the default
> > limit is and if you want to send bigger mtu size packets
> > what about increasing the MTU size ?
> >
> > josefb@M10-xxx> show interfaces t3-1/1/0
> > Physical interface: t3-1/1/0, Enabled, Physical link is Down
> > Interface index: 132, SNMP ifIndex: 23
> > Link-level type: PPP, MTU: 4474, Clocking: Internal, Speed: T3,
>
> 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.

/leg

>> 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@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@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

> _______________________________________________
> juniper-nsp mailing list juniper-nsp@puck.nether.net
> http://puck.nether.net/mailman/listinfo/juniper-nsp

> > trying to get to the default MTU. Getting bogged down at about 4445
> > bytes. Tried another channel on this CHOC-12 to no avail.
>
> can you illustrate/demonstrate how you verified the MTU
> settings and also
> the output of the interface in question ?
>
> thanks
> Josef
>

Is there any other way definite way apart from this?

> show interfaces t3-0/3/0:4
Physical interface: t3-0/3/0:4, Enabled, Physical link is Down
Interface index: 17, SNMP ifIndex: 43
Description: XXXX
Link-level type: Cisco-HDLC, MTU: 4474, SONET mode, Speed: T3, Loopback: None, SONET
Loopback: None, FCS: 32, Mode: C/Bit parity
Device flags : Present Running Down
+++The information transmitted is intended only for the person or entity to which it is
addressed and may contain confidential and/or privileged material. Any review,
retransmission, dissemination or other use of, or taking of any action in reliance upon,
this information by persons or entities other than the intended recipient is prohibited.
If you received this in error, please contact the sender and destroy any copies of this
document.+++

> 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.
>
> /leg
>

Absolutely right. I was told when our provisioners were trying to bring the circuit up
they did not set the do-not-fragment bit. I have asked them to setup it up again so that I
can see whats going on. Will let ya guys know how it goes. Appreciate the help. Thanks
Lars!

-Kashif
+++The information transmitted is intended only for the person or entity to which it is
addressed and may contain confidential and/or privileged material. Any review,
retransmission, dissemination or other use of, or taking of any action in reliance upon,
this information by persons or entities other than the intended recipient is prohibited.
If you received this in error, please contact the sender and destroy any copies of this
document.+++