802.3X Flow Control For Gigabit Ethernet; Maximum Transmission Unit And Jumbo Frames - Nortel 8600 Configuration Manual

18 Ethernet module fundamentals
enable autonegotiation on one port in a multilink trunk, you must
enable autonegotiation on all ports in the multilink trunk and disable
SFFD.
SFFD detects faults for a single link between two devices. You can also
use Virtual Link Aggregation Control Protocol (VLACP) to detect link faults
end-to-end. For more information about VLACP, see Nortel Ethernet
Routing Switch 8600 Configuration — Link Aggregation, MLT, and SMLT
(NN46205-518).
For configuration examples and additional information about SFFD, see
the Single-Fiber Fault Detection Technical Configuration Guide on the
Nortel Technical Support Web site.
802.3x flow control for Gigabit Ethernet
Use flow control to protect against packet loss. Flow control prevents
Ethernet ports from receiving more data than they can process.
The 802.3x flow control mechanism is effective only at the Data Link Layer
(Layer 2). When packets are routed, flow control packets are ignored.
The Ethernet modules support IEEE 802.3x flow control in the following
ways:
•
generate 802.3x flow control PAUSE frames when they become
congested
•
respond to 802.3x PAUSE frames that enter from the other side of the
link
•
temporarily halt packet transmission when an 802.3x PAUSE frame
is received from the remote end
You can enable flow control only on 1 Gigabit Ethernet (GbE) and 10
Gbit/s ports. You cannot enable flow control for ports that run at less than
1 Gbit/s.
If you enable flow control, also configure the fc-pause-time parameter.
This parameter sets the timer value placed in the MAC flow control PAUSE
frame. This indicates to the link partner the length of time to pause
transmission.

Maximum transmission unit and jumbo frames

Jumbo frames are larger than the maximum Ethernet frame size
(maximum transmission unit, or MTU) specified in the IEEE 802.3
standard. For untagged frames, the maximum standard size is 1518 bytes.
For tagged frames, the maximum standard size increases by 4 bytes to
1522 bytes.
Nortel Ethernet Routing Switch 8600
Configuration — Ethernet Modules
NN46205-503 04.01 21 December 2009
Copyright © 2008-2009 Nortel Networks. All Rights Reserved.