Routers & 'jumbo frame'

By i8DRM
Dec 22, 2013
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  1. If one has a NIC with 'jumbo frame' capability, how important is it to pick a router having this capability on its gigabit WAN? I've no interest in LAN, as I will never have more than one PC, so this question is entirely focused on gigabit WAN and jumbo frames. Thanks.
  2. ITLogicSystems

    ITLogicSystems TS Enthusiast

    More than likely you would not be able to see a difference in Jumbo frames on a local LAN/WAN vs. standard packet encapsulation. Unless you are moving a crazy amount of data back & forth between a fileserver, NAS device, your PC & the WAN connection. However, to utilize a jumbo frame encapsulation you would need a router or a switch that supports it.

    Here is a few links to learn more about Jumbo Frames & Packet Encapsulation:

    Hope this helps!!
  3. jobeard

    jobeard TS Ambassador Posts: 8,945   +584

    Jumbo frames seems like a great idea - - until you consider fragmentation and reassembly issues. It has been shown that the reassembly can be made to fail and induce stack overflows, which lead to failures and elevation of privileges - - ie you get hacked.

    In addition, if there's an error in transmission and there needs to be a retry, reassembly gets to be nasty.

    If you're trying to get good performance,
    • set the MTU to 1492 (to stop fragmentation)
    • set the SACKOpts option on the NIC
    Best Wishes
  4. tipstir

    tipstir TS Ambassador Posts: 2,383   +105

    Router that support jumbo frames works more ideally with NIC that support Jumbo frames. Example all gig systems with jumbo frame option are set to 9K. Data transfer to these system is more faster with Jumbo frames enabled. Your only got to see this feature better on LAN to LAN then WAN to LAN or LAN to WAN.

    MTU is set to 1500 on all systems. I haven't seen any degrade.
  5. jobeard

    jobeard TS Ambassador Posts: 8,945   +584

    Limiting MTU is not contrary to Jumbo Frames. The TCP3123 option = 3 uses timestamps to dynamically alter the FRAME size according to the existing performance

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