Re: [Networker] Compare Netoworker to other backup products

Hey, I don't think network performance is at all off-topic on this
list..

And for my $0.02 worth. I agree with Oscar entirely about the
reliability of auto-neg... 

On my site there's about 200 people who deal with infrastructure, and
there are many differing opinions on the subject, and every week I end
up chasing down another lame server set up by someone who hasn't grasped
the concept, or its been plugged into a switch port that has old config
on it....

Purely from the issue of confusion over auto-neg I view Fast Ethernet as
a broken protocol, and only support gigabit on new installations... Of
course, inevitably, some people have tried to 'lock-down' gigabit... But
at least in these cases you can point at the IEEE standard which states
clearly that autoneg is not optional.

... And if anyone else wants a bit more light reading, here is Sun's
position on the subject...
http://www.sun.com/blueprints/0704/817-7526.pdf


-----Original Message-----
From: Legato NetWorker discussion [mailto:NETWORKER AT listserv.temple DOT edu]
On Behalf Of Oscar Olsson
Sent: Monday, 31 October 2005 9:50 AM
To: NETWORKER AT listserv.temple DOT edu
Subject: Re: [Networker] Compare Netoworker to other backup products

On Sat, 29 Oct 2005, Dag Nygren wrote:

DN> And here is a third one!
DN> I installed 10 -20 bigger Networker systems last year and saw about 
DN> 50% of these failing to negotiate decently under auto-negostiate.
DN> Usually they ended up with one end 100/half and the other 100/full.

And both ends were configured to auto-negotiate?

DN> So IMHO it is really stupid to trust the auto-stuff. And most of the

DN> times you dont't even nitice the poor performance until installing
Networker...
DN> 
DN> And it is REALLY hard to convince the network-guys that Their 
DN> Network has a flaw in it ;-)

True, since I'm the network guy as well, or at least one of them, at our
site. :)

Anyway, I feel like saying "You're probably all wrong, or you use crappy
switches, or fail to correctly set both ends to auto-negotiate or
possibly all of the above!". :) But I won't, since I'm such a nice guy.

Instead I'll include an URL on Cisco's website, that deals somewhat with
this topic:

http://www.cisco.com/en/US/tech/tk389/tk214/technologies_tech_note09186a
0080094781.shtml

One interesting part is:

"When to Use Ethernet 10/100Mb Auto-Negotiation

Auto-negotiation is an optional function of the IEEE 802.3u Fast
Ethernet standard that enables devices to automatically exchange
information over a link about speed and duplex abilities.

Auto-negotiation is targeted at ports which are allocated to areas where
transient users or devices connect to a network. For example, many
companies provide shared offices or cubes for Account Managers and
System Engineers to use when they are in the office rather than on the
road. Each office or cube will have an Ethernet port permanently
connected to the office's network. Because it may not be possible to
ensure that every user has either a 10Mb, a 100Mb Ethernet, or a
10/100Mb card in their laptop, the switch ports that handle these
connections must be able to negotiate their speed and duplex mode. The
alternative would be to provide both a 10Mb and a 100Mb port in each
office or cube and label them accordingly.

One of the most common causes of performance issues on 10/100Mb Ethernet
links is when one port on the link is operating at half-duplex while the
other port is operating at full-duplex. This occasionally happens when
one or both ports on a link are reset and the auto-negotiation process
doesn't result in both link partners having the same configuration. It
also happens when users reconfigure one side of a link and forget to
reconfigure the other side. Both sides of a link should have
auto-negotiation on, or both sides should have it off. Our current
recommendation is to leave auto-negotiation on for those devices
compliant with 802.3u.

Many performance-related support calls will be avoided by correctly
configuring auto-negotiation. Many Catalyst Ethernet switching modules
support 10/100Mb and half- or full-duplex. Exceptions include the
Ethernet Group switch modules. The show port capabilities {mod_num} |
{mod_num/port_num} command will show you if the module you are working
on supports 10/100Mb and half- or full-duplex. This document uses two
WS-X5530 Supervisor Engine IIIs, each with two optional uplink
10/100BaseTX Ethernet ports installed."

I would also like to recommend this document:
http://www.cisco.com/en/US/products/hw/switches/ps700/products_tech_note
09186a00800a7af0.shtml


And yes, I have seen several cases of where other network administrators
have claimed what has already been claimed about the suspected negative
effects of enabling auto negotiation. All of those cases ended up to be
related to the following errors:

* One end was configured for auto negotiation, or the two ends of the
link didn't match the speed/duplex setting.
* Some 3com cards were per default set, in windows, to use "hardware
default" instead of auto negotiate, which for some reason wasn't the
"hardware default" setting.

However, considering the number of reports, its also probable that some
low-end switches and/or NIC's haren't 100% compliant with the 802.3u
standard. But if one runs backups, I guess one wouldn't use that range
of equipment anyway? :) I can't think of an adapter based on Intel, 3com
or broadcom chipsets that has had any problem with this in at least five
years.

I understand that this thread has become somewhat offtopic, and
furthermore, I don't think I have much more to say about this issue, so
this will probably be my last post in this thread. But it would be
interesting for me to know as a network administrator what specific NICs
and switches are having problems with auto negotiation. Who knows, I
might bump into those combinations one day. Email me off-list.

//Oscar

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