User guide

HP Virtual Connect for Cisco Network Administrators (version 4.x)
Document Number: C01386629 Date: January 2014
page 25
(see Appendix A for a description of the elements in the above diagram)
Note:
Port channels can only form when VC uplink ports on the same physical VC Ethernet module are
connected to the same external switch. VC does not support port channels that span across
different VC Ethernet modules.
Port Channeling (802.3ad) Load Balancing Algorithm
VC-Enet’s implementation of port channeling, or EtherChannel, uses a load balancing algorithm
for the purpose of distributing frames across the physical ports that make up the port channel.
The biggest concern in distributing frames across multiple physical ports is “frame ordering”.
For any particular conversation between two network devices (e.g. FTP transfer, telnet session,
etc.), it is optimal that the network infrastructure deliver the frames in the order in which
the transmitter transmitted them. This minimizes frame reordering on the receivers end. Also,
while TCP provides header information for putting frames back into the correct order, other
protocols, such as UDP, do not. Therefore, frame ordering is critical. This means that any load
balancing algorithm used by port channeling must load balance frames but also maintain frame
ordering. This is accomplished by using an algorithm that makes the same load balancing
decision for frames from the same conversation.
Typical EtherChannel Load Balancing Algorithms (from worst to best):
•
• Source MAC address
Identifies all conversations coming from the same MAC address and load balances them all down a
single link in the port channel
• Destination MAC address
Identifies all conversations destined for the same MAC address and load balances them all down a