Protocol Support; Performance - Broadcom NetXtreme BCM57 Series User Manual

NetXtreme User Guide Broadcom Gigabit Ethernet Teaming Services

Protocol Support

ARP and IP/TCP/UDP flows are load balanced. If the packet is an IP protocol only, such as ICMP or IGMP, then
all data flowing to a particular IP address will go out through the same physical adapter. If the packet uses TCP
or UDP for the L4 protocol, then the port number is added to the hashing algorithm, so two separate L4 flows
can go out through two separate physical adapters to the same IP address.
For example, assume the client has an IP address of 10.0.0.1. All IGMP and ICMP traffic will go out the same
physical adapter because only the IP address is used for the hash. The flow would look something like this:
IGMP ------> PhysAdapter1 ------> 10.0.0.1
ICMP ------> PhysAdapter1 ------> 10.0.0.1
If the server also sends an TCP and UDP flow to the same 10.0.0.1 address, they can be on the same physical
adapter as IGMP and ICMP, or on completely different physical adapters from ICMP and IGMP. The stream may
look like this:
IGMP ------> PhysAdapter1 ------> 10.0.0.1
ICMP ------> PhysAdapter1 ------> 10.0.0.1
TCP------> PhysAdapter1 ------> 10.0.0.1
UDP------> PhysAdatper1 ------> 10.0.0.1
Or the streams may look like this:
IGMP ------> PhysAdapter1 ------> 10.0.0.1
ICMP ------> PhysAdapter1 ------> 10.0.0.1
TCP------> PhysAdapter2 ------> 10.0.0.1
UDP------> PhysAdatper3 ------> 10.0.0.1
The actual assignment between adapters may change over time, but any protocol that is not TCP/UDP based
goes over the same physical adapter because only the IP address is used in the hash.

Performance

Modern network interface cards provide many hardware features that reduce CPU utilization by offloading
certain CPU intensive operations (see Teaming and Other Advanced Networking Properties). In contrast, the
BASP intermediate driver is a purely software function that must examine every packet received from the
protocol stacks and react to its contents before sending it out through a particular physical interface. Though the
BASP driver can process each outgoing packet in near constant time, some applications that may already be
CPU bound may suffer if operated over a teamed interface. Such an application may be better suited to take
advantage of the failover capabilities of the intermediate driver rather than the load balancing features, or it may
operate more efficiently over a single physical adapter that provides a particular hardware feature such as Large
Send Offload.
Broadcom ®
April 2017 • 2CS57XX-CDUM514-R Page 115