[e2e] why does pppoe connection has session timeout ?

Detlef Bosau detlef.bosau at web.de
Thu May 30 04:43:13 PDT 2013

Am 30.05.2013 11:21, schrieb Jing Shen:
> hi,
> maybe this is not a right place to ask this question,  if intrusive accept my applogy please.
> Doing with those access network ,   there is always a max session timeout  for each pppoe or dial-up link.
> According to document of broadband access server, a default max session timeout value is designed.
> In radius protocol document, there is also max session timeout attribute.
> To my experience, no matter how we do  dialup connection (  ppp over fiber or ppp over telephone network)
> internet connection will has a max session time.   no matter how we do , after that time  ppp connection will be
> cut by access server.
> so why  does protocol designer set this parameter ?
> Jing

Either a pppoe server will keep any pppoe conversation he has ever 
started, more precisely: answered to, or you'll find a way to shut down 
a pppoe conversation which is no longer needed.

Neither Ethernet nor an Internet is "reliable", so a "shut down request" 
by the client may be lost. Therefore you introduce a time out.

What you, however, may mix up is the time out for a ppp connection 
(don't ask me how it is called, I would have to look it up), i.e. the 
time until a server would shut down a connection if no packets from the 
peer arived, or the maximum connection time used by some German 
providers to discrimiate dial up connections from permanent ones.  The 
first has technical reasons the latter has economical ones.
> ' spamcontrol'

Detlef Bosau
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