[ClusterLabs] Antw: Re: Antw: Re: EL6, cman, rrp, unicast and iptables

Ulrich Windl Ulrich.Windl at rz.uni-regensburg.de
Mon Sep 14 09:33:34 EDT 2015

>>> Noel Kuntze <noel at familie-kuntze.de> schrieb am 14.09.2015 um 13:55 in
Nachricht <55F6B5B5.8020107 at familie-kuntze.de>:

> Hash: SHA256
> Hello Ullrich,
>> Actually I don't understand that claim: If packets are delivered in order
>>(mostly), any TOTEM packet has the same change to arrive than any other 

s/change/chance/ # typing error, maybe lack of coffeine in the morning

> packet.
>> While all other communication protocols can actually deal with Ethernet and

> the
>> Internet, TOTEM is the only protocol that can fail even in a switched LAN.
>> haven't benn convinced yet that it's not an implementation issue of TOTEM.
>> Instead of telling people to fiddle with their network configuration, I'd
>> prefer putting more efforts into fixing TOTEM.
> I assume with "change to arrive", you mean delay? Or do you mean the 
> ordering of
> the packets?
> Totem behaves like it does because it needs to detect a failed node, afaik.

What totem does it detect network problems when there are none:

# grep ringid.*FAULTY /var/log/messages |wc -l

> This is something that no other protocol you encounter on the internet/LAN 
> is supposed to do.

Definitely not: 0 interface errors on any interface, not communication

> All of those protocols are either for error reporting (ICMP) or for 
> transceiving of
> data (udp/tcp). UDP obviously has no congestion algorithm, but TCP does.

Even NFS over UDP is much smarter than TOTEM is.

>> The main problem with priorities is who decides what is most important,
>> especially if a medium is shered by many different software stacks and

s/shered/shared/  #se above

>> applications.
> Obviously some type of prioritzation has to be done, or at least should be 
> done,
> because some things *are* more important than others. The only thing that 
> can
> control congestion centrally in a computer system is the interface that 
> controls
> access to it, so it's either the NIC or the software that controls access to

> it, so the network stack
> of the operating system. The problem is a different one when the LAN is 
> bridged, rather then switched, because then
> the transmission of other hosts affects the transmission of one host.

If you have a central authority that can decide on each eand every priority
you are right. I was talking from practical experience...

> - -- 
> Mit freundlichen Grüßen/Kind Regards,
> Noel Kuntze
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