[MUD-Dev] MMORPG/MMOG Server design

J C Lawrence claw at kanga.nu
Fri Feb 21 13:26:42 New Zealand Daylight Time 2003


On Fri, 21 Feb 2003 14:27:27 -0000 
Daniel Harman <Daniel.Harman at barclayscapital.com> wrote:

> Whilst this is attractive in its simplicity, it adds an extra hop
> which doesn't strike me as ideal. Furthermore if the login server
> goes down, you lose all active connections too. EQ for instance
> has a login server, but only talks to it for initial auth, thus
> you don't have such a major single point of failure.

Two concerns:

  1) Extra-hop induced latency

  2) Single point of failure

Given a reasonably fast system with a faster back-haul the injected
latency from a connection proxy should be in the realm of very low
double digit milliseconds or less.  Not a concern or problem.  This
is well known non-rocket science space.

SPOF I suspect is also not terribly interesting (tho building fault
tolerant systems is always a fascinating process):

  -- How many 9's are really needed for a connection proxy?  

  -- How many of those 9's can be transparently made up for by
  adding either a fault-redirector in front of your proxy and/or
  extending your client to cycle across your pool of connection
  proxies upon TCP RESET?

    -- What is the real impact if a connection proxy burps, drops
    its connections, and the players see a lag/burp in their game
    experience but otherwise continue on unaffected?  (You'd have to
    add some similar logic to the back-haul response lines, or do
    transaction rollbacks/re-synchronisation but neither is a hugely
    horrible space).

While its nice when connection proxies have five 9's, I really doubt
its necessary, especially given that some very minor slight of hand
can make even three 9's look damned close to five subjectively.

--
J C Lawrence                
---------(*)                Satan, oscillate my metallic sonatas. 
claw at kanga.nu               He lived as a devil, eh?		  
http://www.kanga.nu/~claw/  Evil is a name of a foeman, as I live.

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