Does bridging cause any packet latency?

Discussion in 'Networking Issues' started by Cisco-GEEK J., Oct 20, 2006.

  1. Cisco-GEEK J.

    Cisco-GEEK J. LI Guru Member

    Should modem-routers be bridged to a more efficient router like the BEFSR41 or should a network connection be used only through the modem-router for lower latency between end nodes and greater throughput (that's what I believe)?

    I would like to also know what's the difference in the DMZ option in any Linksys Router compared to high class modem-routers that support NAT Passthrough as DMZ?
  2. eric_stewart

    eric_stewart Super Moderator Staff Member Member

    I'm sure that somewhere there are some more scientific tests than what I would offer, but I *can* say that I have tested my router behind my DSL modem-router with the modem-router in router mode and bridged mode and could detect 0 difference in speed.

    FWIW, my download speed averaged exactly the same, 4107 kbps download and 631 kbps upload over a series of 100 tests.

    The WRT-series Linksys boxes work like most other vendors' software-only where the router simply exposes an inside host to the outside world and still NAT the inside host. I can't see any performance advantages relative to the kind of throughput you would see on a typical home network in any case. I suppose that theoretically, because you don't need to examine inbound packets before forwarding them to the inside host, there might be some difference in performance. However, unless the SPI firewall's connection table is saturated it shouldn't be noticeably faster.

  3. ifican

    ifican Network Guru Member

    Whos to say that the modem-router is less efficient that a linksys or any other router? Any device that a packet travels through whether bridged or routed is going to induce some delay? On high end equipment it can range from several hundred nano seconds to a couple miliseconds, on over taxed devices it can run up to several hundred miliseconds. The Soho devices that most of us use often run right around 1-2 ms delay per device. That being said I would bridge the modem and let the firewall / router do the nating.

    As for your DMZ question, nat passthru is not a dmz, its just as it states nat passthru. The significance between the modem nat and the router nat is the router nat is going to still somewhat (firewall) protect the traffic. The implementation on most soho routers is a software dmz that still ultimately sits behind the firewall. The firewall inspects the traffic for known attacks and then simply forwards the unsolicited non attack packets to the dmz host identified on the dmz page. Hope that helps the understanding.
  4. Cisco-GEEK J.

    Cisco-GEEK J. LI Guru Member

    I took the interest in reading some articles about how NAT works and found out that DMZ only reserves a private IP for dynamic NAT mapping and all firewall and filter applications are exclusive for that IP.

    True DMZ or otherwise known as NAT/IP Passtrhough does the same thing except all inbound traffic is forwarded to the reserved IP address without consent, a static public IP address is used and NAT isn't being used.
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