Users Guide

11–Marvell Teaming Services
Executive Summary
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Network Addressing
To understand how teaming works, it is important to understand how node
communications work in an Ethernet network. This document is based on the
assumption that the reader is familiar with the basics of IP and Ethernet network
communications.
The following information provides a high-level overview of the concepts of
network addressing used in an Ethernet network. Every Ethernet network
interface in a host platform, such as a computer system, requires a globally
unique Layer 2 address and at least one globally unique Layer 3 address. Layer 2
is the data link layer, and Layer 3 is the network layer as defined in the OSI model.
The Layer 2 address is assigned to the hardware and is often referred to as the
MAC address or physical address. This address is pre-programmed at the factory
and stored in NVRAM on a network interface card or on the system motherboard
for an embedded LAN interface. The Layer 3 addresses are referred to as the
protocol or logical address assigned to the software stack. IP and IPX are
examples of Layer 3 protocols. In addition, Layer 4 (Transport Layer) uses port
numbers for each network upper level protocol such as Telnet or FTP. These port
numbers are used to differentiate traffic flows across applications. Layer 4
protocols such as TCP or UDP are most commonly used in today’s networks. The
combination of the IP address and the TCP port number is called a socket.
Ethernet devices communicate with other Ethernet devices using the MAC
address, not the IP address. However, most applications work with a host name
that is translated to an IP address by a naming service such as Windows Internet
Name Service (WINS) and DNS. Therefore, a method of identifying the MAC
address assigned to the IP address is required. The address resolution protocol
for an IP network provides this mechanism. For IPX, the MAC address is part of
the network address and ARP is not required. ARP is implemented using an ARP
Request and ARP Reply frame. ARP Requests are typically sent to a broadcast
address while the ARP Reply is typically sent as unicast traffic. A unicast address
corresponds to a single MAC address or a single IP address. A broadcast address
is sent to all devices on a network.