The Internet Protocol is a fundamental part of the Internet’s success. It has also become the most popular Layer 3 protocol for general communication within LANs. Using the same protocol for LAN and WAN communication makes it possible to expand how we use networks. IP-based networks can carry messages of any type, from email to streaming media. Each type of traffic has its own requirements and provides its own challenges to the network. As more and more applications use IP-based networks to communicate, they use more and more of the available capacity. Newer standards and techniques are necessary to ensure networks are as efficient as possible.

Recall that Layer 3 protocols, including IP, route packets across networks. When a packet enters its destination network, the network stack needs to know the packet’s local destination. The Address Resolution Protocol (ARP) is the common protocol in IPv4 networks to provide local MAC addresses. IPv6 networks use the Neighbor Discovery Protocol (NDP) to provide a service similar to ARP. To find a local MAC address, the network device would first look up the supplied IPv4 address in its ARP table. A device’s ARP table contains the IPv4 address and the corresponding MAC address of known nodes. If the device finds no entry for the IPv4 address, it sends an ARP broadcast query to the network. In IPv6 networks, the NDP discovery request provides similar functionality. If the node is present in the network, it replies with its MAC address. The network device adds the newly discovered MAC address to the ARP table for IPv4 addresses or the neighbor table for IPv6 addresses and forwards the packet to its local destination.

ARP and NDP are important protocols for IP-based networks. They make it possible to use IP to transport traffic within local networks and between networks, including those connected to the Internet. Current networks are beginning to rely more on a combination of switching and routing to get packets to their destinations efficiently. Consider how organizations are using IP-based networks to implement UC solutions.

IP networks make it possible to efficiently exchange nearly any type of data between any two nodes on the network. This standard communication method supports many different types of traffic, including:

• Email messages
• Telephone calls
• Video conferencing
• Streaming audio and video
• Large file transfers
• Real-time data
• Instant messages

This list is only a representation of the many types of data IP networks can carry. Upper layer protocols carry much of the responsibility for handling different types of messages, but IP gets the packets that make up messages to their destinations. In the past, networks tended to be built for specific purposes; for example, the plain old telephone service (POTS) network was designed to support analog voice data, and it did that very well. The ability to use standard IP networks to transport multiple types of data makes networks valuable assets to any organization. Standard protocols such as IP make UC a reality.