The Data Center IP Network

Together FIGURE 1-2 and FIGURE 1-3 provide a high-level overview of the various interconnected networks, collectively referred to as the Internet. These illustrations also show the relationship between the client-side and enterprise-side networks. They show two distinct networks that can be segregated based on business entities:

• The Internet Service Provider (ISP) that provides connectivity to the public Internet for both clients and enterprises

• The owners of the physical plant and communications equipment, which fall into one of the following categories:

  • The Incumbent Local Exchange Carrier (ILEC), which provides local access to subscribers in a local region

  • The Inter Exchange Carrier (IXC), which provides national and international access to subscribers

  • The Tier 2 ISP, which is usually a private company that leases lines and cage space at an ILEC facility, or it can be the ILEC or IXC itself.

Figure 1-2. High-Level Overview of Networks Spanning Clients, Data Center, Vendors, and Partners (a)

Figure 1-3. High-Level Overview of Networks Spanning Clients, Data Center, Vendors, and Partners (b)

The diagram shows Tier 2 ISPs as being relatively local ISPs, situated in the access networks, whereas Tier 1 ISPs have their own longhaul backbone and provide wider regional coverage, situated in the Core, or national backbone. Tier 1 often aggregates the traffic of many Tier 2 ISPs, in addition to providing services directly to individual subscribers. Large networks connect to each other through peering points, such as MAE-East/MAE-West, which are public peering points, or through Network Access Points (NAPs), such as SPRINTS NAP, which are private.

A client can be any software that initiates a request for a service. This means that a Web server itself can be a client. For example, when in the process of replying back to a client for a Web page, it needs to fetch images from an image server. FIGURE 1-2 and FIGURE 1-3 show remote dial-up clients as well as corporate clients. Depending on the distances between the client and the server hosting the Web service, data might need to traverse a variety of networks for end-to-end communication. The focus of this book is the network that interconnects the servers located in an enterprise data center or the data center of an ISP offering collocation services. We describe the features and functions of the networking equipment and servers in sufficient depth to help a network architect in the design of enterprise IP network architectures.

We take a layered approach, starting from the application layer down to the physical layer to describe the implications on the design of network architectures. We describe not only high-level architectural principles, but also key details such as tuning the transport layer for optimal working networks. We discuss in detail how the building blocks of the network architecture are constructed and work to make more informed design decisions. Finally, we present actual tested configurations, providing a baseline for customizing and extending these configurations to meet actual customer requirements.