THE AWS CERTIFIED ADVANCED NETWORKING – SPECIALTY EXAM OBJECTIVES COVERED IN THIS CHAPTER MAY INCLUDE, BUT ARE NOT LIMITED TO, THE FOLLOWING:
Objective 1.5: Design a routing strategy and connectivity architecture between on-premises networks and the AWS Cloud.
Objective 1.6: Design a routing strategy and connectivity architecture that include multiple AWS accounts, AWS Regions, and VPCs to support different connectivity patterns.
In this chapter, you will review the lower two layers of the OSI model, which will help you to understand how the AWS network interconnects to the outside world. We will learn the fundamentals of interconnecting your on-premises network to the AWS cloud using Direct Connect and site-to-site VPN interconnects. A network that interconnects AWS with an on-premises data center is defined as a hybrid network and is the focus of this chapter and Chapter 7, “Connecting On-Premises Networks.”
We will begin this chapter with a basic overview of the lower OSI networking layers of physical and data link are covered, and their implementation options when connecting to AWS are covered.
Next we discuss routing with a look at static and dynamic routing. You will learn about the different methods used to interconnect VPCs.
Since BGP is the primary routing protocol used to connect with AWS, a primer on how BGP operates is covered in this chapter to give you a base understanding of the protocol needed for AWS hybrid networking.
In the past, companies either hosted their compute resources in private enterprise data centers or leased space at a collocation facility. Now, with cloud computing, compute resources are migrating to AWS and other cloud providers, which then require connectivity from the corporate facilities into the cloud. Since it is common for many computer systems and applications to remain behind or distributed across many data centers and different cloud providers at many different locations, a knowledge of hybrid networking is required to interconnect these data centers.
The Open System Interconnect model, as shown in Figure 6.1, defines a framework for networking that allows manufacturers to design products that can work with products from other manufacturers that also follow the specifications. This allows for competition and innovation in the networking industry. An understanding of the OSI model greatly assists you in understanding networking. This topic is out of scope for the AWS Advanced Networking exam and is taught in more fundamental networking studies. However, if you are not deeply familiar with the OSI model, taking the time to study and learn the concepts will make understanding networking much less challenging.
The exam blueprint does, however, specify that knowledge of layer 1 and 2 technologies as they relate to AWS may appear on the exam. So, in this section, we will cover what specifically applies to AWS networking deployments with a focus on the Direct Connect service.
OSI layer 1 is the physical layer, or PHY, and defines both the electrical/optical and physical specifications for devices. The physical layer standardizes the relationship between a device and a transmission medium, which is most often either copper, optical, or radio waves. The physical layer also includes the layout of pins, voltages, cable specifications, networking hubs, repeaters, adapters, and host bus adapters (used in storage networks), to name the most common specifications.
This layer is responsible for the actual physical connection between the devices and contains information in the form of bits, or ones and zeros. It’s responsible for transmitting individual bits from one endpoint to the next. When receiving data, this layer will demodulate the signal back into zeros and ones and then send it up to the data link layer, which puts the data frame back together, and the flow continues up the OSI stack.
The primary tasks performed at the physical layer include synchronization of the bits by providing a clock. This clock controls both the sender and receiver providing synchronization at the bit level. The physical layer also defines the transmission rate, i.e., the number of bits sent per second. Physical topologies specify the way in which the different device endpoints and nodes are arranged in a network. Examples of this include bus, star, and mesh topologies. The transmission mode defines the way in which the data flows between the two connected devices, such as simplex, half-duplex, or full duplex.
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