BROCADE IP PRIMER

Chapter 1: Networking BasicsMB sound and the 100 bytes lost. In reality, it would be extremely difficult forthe human ear to perceive the difference. But this loss allowed you to be ableto stream the audio to your receiver in real time.Video streaming uses connectionless transport, too. Video uses even moredata to show its image (and sound). If we have any hope of streaming videoand audio (for, say, video conferencing), speed is much more important thanreliability.The most well-known Transport Layer protocols are Transmission Control Protocol(TCP), which is connection-oriented, and User Datagram Protocol (UDP),which is connectionless. Both of these protocols are part of the TCP/IP suite.The Network Layer (Layer 3)So, “we're off to see the wizard,” to quote Dorothy from The Wizard of Oz, butwe're still missing an important piece. How are we going to get there? If wewere in Oz, we could simply follow the yellow brick road. In the OSI ReferenceModel, we call it the Network Layer.The Network Layer's job is to decide how to get there. How does the data getfrom the sender to the receiver? That's the question that the Network Layerhas to resolve. It does this by using addressing, routing protocols, andnetworks.Addressing is simply assigning a number to every object you'd want to communicatewith. There are even objects called gateways or routers that will helpyou connect to remote addresses. These are Network Layer technologies.Routing protocols are used between routers to help them do their job. Mostrouting protocols will tell all of the other routers when a particular path is nolonger available (let's say someone tripped over a network cable). Some routingprotocols will tell other routers when paths become congested. The idea ofrouting protocols is that they are used by routers to help all of the other routersdo their job: get the data to where it needs to go.Networks, in this context, are groups of addresses. We'll dive much further intothis pool in the next chapter. For now, just know that addresses are groupedinto networks.Some people think of the Network Layer as the post office. The post officereceives mail, sorts it, labels it with a postal meter (which contains informationon where the letter is supposed to go, and how it will get there), and sends iton its way.The Network Layer is similar. It receives segments from the Transport Layer,and it adds its own little pieces of information (including addressing, and thepath it will take to get to its destination). This new creation is called a packet.Once the packet is created, it is sent to the Data Link Layer to continue theprocess.16 Brocade IP Primer