[j-nsp] J6350 Jumbo frame MTU and OSPF setting

Harris Hui harris.hui at hk1.ibm.com
Sat Oct 2 00:21:01 EDT 2010


Thanks Jonathan for the good tips. :-)

- Harris


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  |Jonathan Lassoff <jof at thejof.com>                                                                                                                 |
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  |Harris Hui/Hong Kong/IBM at IBMHK                                                                                                                    |
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  |juniper-nsp at puck.nether.net                                                                                                                       |
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  |10/02/2010 AM 12:14                                                                                                                               |
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  |Re: [j-nsp] J6350 Jumbo frame MTU and OSPF setting                                                                                                |
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While having an increased MTU across your WAN can improve throughout
greatly, I would suggest tuning your TCP stack for a "Long Fat Pipe", as
many operating systems are not designed to work well with high-throughput,
high-latency links.


There are some good tips here: http://fasterdata.es.net/


Cheers,
jof


      On Sep 30, 2010 10:38 PM, "Harris Hui" <harris.hui at hk1.ibm.com>
      wrote:



      Dear all,

      We had subscribed a private line circuit between 2 different data
      center
      for Data Backup and replication. The bandwidth of the private line is
      100Mbps.

      According to the provider, The Circuit is Built across their
       Network as 2 STS1's or High Speed DS3's which equals 100meg.

      Their GE port setting as follows.

      MTU Size - 9600
      Auto Negotiation - OFF
      Remote Client Fail - Disabled.

      The private circuit is connected directly to the fiber module of our
      J6350
      Services router at each Data Center. The Circuit is up and running
      but when
      we perform some TCP throughput test, we only get ~3Mbps for a Single
      TCP
      session with iPerf and the latency between two data center across the
      private circuit is ~80ms.

      I am trying to configure our J6350 fiber interface to MTU 9192 to get
      a
      better TCP throughput. However, I can only able to configure the MTU
      size
      below 1500, when I configure the MTU to 9192 and commit the changes,
      it
      still shows MTU 1500 on the physical interface.

      Do you have any experience on using Jumbo frame MTU size on the
      J6350? We
      are also running OSPF across the private circuit, is JUNOS support
      "OSPF
      ignore-mtu" like cisco?

      Please advise.

      Fiber module
      ================================================
      FPC 3            REV 18   750-013599   AAAH7361          FPC
       PIC 0                                                  1x GE SFP
         Xcvr 0       REV 02   740-011614   PG336CS           SFP-LX10

      show interfaces ge-3/0/0
      speed 1g;
      mtu 1400;
      link-mode full-duplex;
      gigether-options {
         no-auto-negotiation;
      }
      unit 0 {
         family inet {
             address xxx.xxx.xxx.253/30;
         }
      }

      harris at J6350# run show interfaces ge-3/0/0
      Physical interface: ge-3/0/0, Enabled, Physical link is Up
       Interface index: 152, SNMP ifIndex: 184
       Link-level type: Ethernet, MTU: 1400, Speed: 1000mbps, BPDU Error:
      None,
      MAC-REWRITE Error: None, Loopback: Disabled,
       Source filtering: Disabled, Flow control: Enabled, Auto-negotiation:
      Disabled, Remote fault: Online
       Device flags   : Present Running
       Interface flags: SNMP-Traps Internal: 0x4000
       Link flags     : None
       CoS queues     : 8 supported, 8 maximum usable queues
       Current address: b0:c6:9a:87:35:36, Hardware address:
      b0:c6:9a:87:35:36
       Last flapped   : 2010-09-27 02:32:24 UTC (4d 02:29 ago)
       Input rate     : 0 bps (0 pps)
       Output rate    : 0 bps (0 pps)
       Active alarms  : None
       Active defects : None

      show interfaces ge-3/0/0
      speed 1g;
      mtu 9192;
      link-mode full-duplex;
      gigether-options {
         no-auto-negotiation;
      }
      unit 0 {
         family inet {
             address xxx.xxx.xxx.253/30;
         }
      }

      run show interfaces ge-3/0/0
      Physical interface: ge-3/0/0, Enabled, Physical link is Up
       Interface index: 152, SNMP ifIndex: 184
       Link-level type: Ethernet, MTU: 1514, Speed: 1000mbps, BPDU Error:
      None,
      MAC-REWRITE Error: None, Loopback: Disabled,
       Source filtering: Disabled, Flow control: Enabled, Auto-negotiation:
      Disabled, Remote fault: Online
       Device flags   : Present Running
       Interface flags: SNMP-Traps Internal: 0x4000
       Link flags     : None
       CoS queues     : 8 supported, 8 maximum usable queues
       Current address: b0:c6:9a:87:35:36, Hardware address:
      b0:c6:9a:87:35:36
       Last flapped   : 2010-09-27 02:32:24 UTC (4d 02:35 ago)
       Input rate     : 0 bps (0 pps)
       Output rate    : 1192 bps (2 pps)
       Active alarms  : None
       Active defects : None


      Thanks
      Harris
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