WAAS Integration with Application Performance Management (APM) Solutions
Cisco WAAS is a software component that is resident on a hardware device deployed at each location with users and servers. This hardware device, which can be deployed as a router–integrated network module for the Integrated Services Router (ISR) or as an appliance, is named either Cisco Wide–Area Application Engine (WAE) or Cisco Wide–Area Virtualization Engine (WAVE). The distinction between the two is that a WAVE device, available only as an appliance, can also provide branch office virtualization services in conjunction with WAN optimization and application acceleration. WAE devices provide only WAN optimization and application acceleration and do not provide virtualization.
This article provides an introduction to the Cisco WAAS hardware family, along with an in–depth examination of the hardware and software architecture. It also looks at the licensing options for Cisco WAAS, positioning for each of the hardware platforms, and performance and scalability metrics for each of the platforms.
Cisco WAAS Product Architecture
The Cisco WAAS product family consists of a series of appliances and router-integrated network modules that are based on an Intel x86 hardware architecture. The product–family scales from 512 MB of memory to 24 GB of memory, utilizing single–processor subsystems up to dual quad–core processor subsystems. Each Cisco WAAS device, regardless of form factor, is configured with some amount of hard disk storage and a compact flash card. The compact flash card is used for boot–time operation and configuration files, whereas the hard disk storage is used for optimization data (including object cache and Data Redundancy Elimination [DRE]), swap space, software image storage repository, and guest operating system storage in the case of WAVE devices. Having a compact flash card enables the device to remain accessible on the network should the device suffer hard drive subsystem failure for troubleshooting and diagnostics purposes (in such a scenario, optimization and virtualization services would not be operational). Also, by using the compact flash card in this way, a WAAS device can successfully boot and become accessible on the network if no disks are available to the device.
The foundational layer of the Cisco WAAS software is the underlying Cisco Linux platform. The Cisco Linux platform is hardened to ensure that rogue services are not installed and secured such that third–party software or other changes cannot be made. The Cisco Linux platform hosts a command–line interface (CLI) shell similar to that of Cisco IOS Software, which, along with the Central Manager and other interfaces, form the primary means of configuring, managing, and troubleshooting a device or system. All relevant configuration, management, monitoring, and troubleshooting subsystems are made accessible directly through this CLI as opposed to exposing the Linux shell..
The Cisco Linux platform hosts a variety of services for WAAS run–time operation. These include disk encryption, Central Management Subsystem (CMS), interface–manager, reporting facilities, network interception and bypass, application traffic policy (ATP) engine, and kernel–integrated virtualization services, as shown in Figure 1.
Figure 1 Cisco WAAS Hardware and Software Architecture
The following sections examine each of the Cisco WAAS architecture items.
Cisco WAAS devices can be configured to encrypt the data, swap, and spool partitions on the hard disk drives using encryption keys that are stored on and retrieved from the Central Manager. The disk encryption feature uses AES–256 encryption, the strongest commercially available encryption, and keys are stored only in the WAAS device memory after they have been retrieved from the Central Manager during the device boot process. Should a WAAS device be physically compromised or a disk stolen, power is removed from the device, which destroys the copy of the key in memory (memory is not persistent). When the hard disks are encrypted, loss of the key renders data on the disk unusable and scrambled. Keys are stored in the Central Manager database (which can be encrypted) and synchronized among all Central Manager devices for high availability. If a WAAS device is not able to retrieve its key from the Central Manager during boot time, it remains in pass–through mode until connectivity is restored or disk encryption is administratively bypassed. Additionally, the fetching of the key from the Central Manager is done over the Secure Sockets Layer (SSL)–encrypted session that is used for message exchanges between the WAAS devices and the Central Manager devices.
Central Management Subsystem
CMS is a process that runs on each WAAS device, including accelerators and Central Managers. This process manages the configuration and monitoring components of a WAAS device and ensures that each WAAS device is synchronized with the Central Manager based on a scheduler known as the Local Central Manager (LCM) cycle. The LCM cycle is responsible for synchronizing the Central Manager CMS process with the remote WAAS device CMS process to exchange configuration data, fetch health and status information, and gather monitoring and reporting data. The CMS process is tied to a management interface configured on the WAAS device known as the primary interface, which is configured on the WAAS device CLI prior to registration to the Central Manager. Any communication that occurs between WAAS devices for CMS purposes is done using SSL–encrypted connections for security.
The Cisco WAAS device interface manager manages the physical and logical interfaces that are available on the WAAS device. Each WAAS device includes two integrated Gigabit Ethernet interfaces (including the network modules, one interface is internal and shares connectivity to a peer interface in the router through the router backplane, the other is external and can be cabled to a LAN switch, similar to an appliance). Each WAAS appliance has expansion slots to support one or more additional feature cards, such as the inline bypass adapter, which has two two–port fail–to–wire pairs. The interface manager also provides management over logical interfaces that can be configured over physical interfaces. Logical interfaces include active/standby interfaces, where one physical interface is used as a primary interface and a second interface is used as a backup in the event the primary interface fails. Another logical interface is the PortChannel interface, which can be used to team WAAS device interfaces together for the purposes of high availability and load balancing. It should be noted that active/standby interfaces are used when WAAS device interfaces connect to separate switches, whereas PortChannel interfaces are used when the WAAS device interfaces connect to the same switch.
Monitoring Facilities and Alarms
Cisco Linux provides an interface for the Cisco WAAS software to use for purposes of monitoring and generating alarms. Cisco WAAS supports the Simple Network Management Protocol (SNMP) versions 1, 2c, and 3, and a host of Management Information Bases (MIB) that provide complete coverage over the health of each individual WAAS device. Cisco WAAS also supports the definition of up to four syslog servers, which can be used as alarm recipients when syslog messages are generated. The WAAS Central Manager also has an alarm dashboard, which is described in Chapter 7, "System and Device Management." The Central Manager makes an application programming–interface (API) available for third–party visibility systems, which is also discussed in Chapter 7, Chapter 8, "Configuring WAN Optimization," and Chapter 9, "Configuring Application Acceleration." Transaction logs can be configured to be stored on each of the accelerator devices in the network for persistent retention of connection statistics, which might be useful for troubleshooting, debugging, or analytics purposes. Transaction logs are not covered in this book, but a full reference on their usage can be found in the Cisco WAAS documentation.
Note: The alarm book (which covers syslog messages, SNMP traps, and Central Manager dashboard alarms), error book (which covers console messages), and product documentation can be downloaded from Cisco.com at http://www.cisco.com/cgi-bin/tablebuild.pl/waas41.
About the Author: