Just thought I'd throw this in since I have been in at least 3 customer
environments where forced 1000baseT without autoneg caused problems (be
it performance or link stability). Since a lot of us are using gigabit
ethernet as backup LAN, I thought it should be useful.
For reliable 1000Base-T operation AutoNeg is a reuirement, it says so
in the standard.
Excerpt from Sun Blueprint document "Auto negotiation best practices" :
--- cut here
The IEEE 802.3ab specification does not allow for forced mode 1000BASE-T with
autonegotiation disabled running at 1000 Mbps. As a result, many switch
vendors do
not support forced mode.
Clause 40 (1000BASE-T), subclause 40.5.1 of 802.3 states:
All 1000BASE-T PHYs shall provide support for Auto-Negotiation
(Clause 28) and shall be capable of operating as MASTER or SLAVE.
Auto-Negotiation is performed as part of the initial set-up of the link, and
allows the PHYs at each end to advertise their capabilities (speed, PHY
type, half or full duplex) and to automatically select the operating mode
for communication on the link. Auto-negotiation signaling is used for the
following two primary purposes for 1000BASE-T:
a) To negotiate that the PHY is capable of supporting 1000BASE-T half
duplex or full duplex transmission.
b) To determine the MASTER-SLAVE relationship between the PHYs at
each end of the link. 1000BASE-T MASTER PHY is c from a local source.
The SLAVE PHY uses loop timing where the clock is recovered from the
received data stream.
What this means is that although autonegotiation (Clauses 22 and 28) is
optional for
most variants of Ethernet and manual configuration (forced mode) is
allowed, this is
not the case for Gigabit copper (1000BASE-T). Per the IEEE 802.3u
specification, it
not possible to manually configure one link partner for 100 Mbps full
duplex and
still autonegotiate to full duplex with the other link partner. In all
cases, both ends
of the link must be set to the same value or the link may not connect or may
result in duplex mismatch as shown in following tables.
For CSMA/CD compatible devices that use the eight-pin modular connector
of ISO/
IEC 8877: 1992 and that also encompass multiple operational modes, if a
signaling
method is used to automatically configure the preferred mode of operation, the
autonegotiation function SHALL BE USED in compliance with Clause 28.
--- cut here
I have been in ONE environment where forced gigabit - no autoneg was
necessary, but this was due to an ancient Cisco firmware, after
upgrading the switches AutoNeg was necessary..
Ciao
Quoting Stan Horwitz <stan AT TEMPLE DOT EDU>:
On Mar 1, 2006, at 4:58 AM -- 3/1/06, Steffen wrote:
On Wed, 1 Mar 2006 10:20:24 +0100, Sebastian <seb AT OPEN2 DOT BE> wrote:
Maybe a dumb question, but 450GB in 15 hours looks like +- 100Mbps
network speed.
Hi Sebastian,
YES, was my 1st guess as well,
but all NICs are 1Gbps (NO autonegotiate)
and performance is much, much better using the NML on the same NIC.
Still looking on file system issues ant the like ...
Actually, with GB cards, auto-negotiation is recommended. Be that as
it may, its probably not your problem, esp. if you're not seeing
faulty TCP/IP packets going into your NetWorker box.
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