WAN Optimization

ACK Message Each exchange of data between two connected peers involves a 32-bit sequence number (coordinating position within the data stream and identifying which data has been previously sent) and, if the ACK flag is set, an acknowledgment number (defining which ... [full story]

Application and Protocol Barriers to Application Performance The performance of an application is constantly impacted by the barriers and limitations of the protocols that support the given application and the network that resides between the communicating nodes. Just because an application ... [full story]

Application Protocols Network latency is generally measured in milliseconds and is the delta between the time a packet leaves an originating node and the time the recipient begins to receive the packet. Several components exist that have a negative impact on ... [full story]

Architecture of Accelerator Services All accelerator devices (and acceleration technology in general) have some posture to services deployed in the network. These network services include any action that can be performed against network packets and flows, including network visibility, monitoring, end-to-end ... [full story]

Bandwidth Bandwidth is the amount of data that can be passed along a communications channel in a given period of time. Specifically, each message that is exchanged between two nodes communicating on a network requires that some network capacity, or bandwidth, ... [full story]

Business Continuance and Disaster Recovery Business continuance and disaster recovery planning are becoming commonplace in today's enterprise, driven particularly by both compliance (as mentioned in the previous section) and the overarching threats presented by malicious attackers (inside and outside), natural disaster, ... [full story]

Cache Capacity Layer 2 and Layer 3 caches reside in the processor chip. These caches accelerate the processor's ability to receive data. Processors today support caches that range in size from 1 MB to 24 MB or larger. Typically, the larger ... [full story]

Central Processing Unit There are several factors to take into consideration when selecting a processor. As the CPU speed war continues, competition will only benefit your applications and their performance. The continual evolution of processors will make selecting the correct processor ... [full story]

Changing the Application Business Model In light of the challenges discussed in this chapter so far, IT organizations have begun turning to new ways of solving complex infrastructure, productivity, and performance issues. A new class of networking technologies called application acceleration ... [full story]

Checksum Verification Each exchange of data between two connected peers involves a 16-bit checksum number. The recipient uses the checksum to verify that the data received is identical to the data sent by the originating node. If the checksum verification fails, ... [full story]

CIFS CIFS sessions between a client and file server can be used for many functions, including remote drive mapping, simple file copy operations, or interactive file access. CIFS operations perform very well in a LAN environment. However, given that CIFS was ... [full story]

Compliance, Data Protection, Business Continuity, and Disaster Recovery Compliance, data protection, business continuity, and disaster recovery have become priorities for IT organizations in the last decade, in particular due to acts of war, natural disasters, scandalous employee behavior (financial, security, and ... [full story]

Consolidating and Protecting Servers in the New IT Operational Model Already burdened with the challenges of providing access to content, applications, and services for the growing geographically dispersed workforce, IT organizations are also faced with a conflicting challenge: controlling capital and ... [full story]

Data Reordering As each segment is received, the sequence number is examined and the data is placed in the correct order relative to the other segments. In this way, data can be received out of order, and TCP will reorder the ... [full story]

Differentiated Services DiffServ is more commonly used than IntServ and is referred to as soft QoS due to its reliance on per-hop behaviors at each node in the network, dictated largely by a common understanding and configuration of how to handle ... [full story]

Disk Storage The spinning disk is inevitably going to be the choke point for application performance in many server environments, as information is exchanged between the server bus and magnetized areas on a spinning platter. Typical storage deployments have changed radically ... [full story]

Dual-Core Support A dual-core processor is simply a single processor chip that contains two processors that can work in parallel. A common benefit of a dual-core processor is that the individual processors will each have their own primary cache, or Level ... [full story]

Employing Quality of Service The previous section presented two means of examining the network to gather a fundamental understanding of how the network is being used. This information forms the foundation from which you can make decisions about how to align ... [full story]

Establishing a Redundancy Plan One of the most important factors in network stability is the redundancy plan. Redundancy planning and implementation can be leveraged at any place within the network, ranging from the data center application servers to the remote branch ... [full story]

Facing the Unavoidable WAN Nearly all remote locations today have some form of network connection that connects the location to the data center or an intermediate location such as a regional office. This connection, commonly a WAN connection in the case ... [full story]

Fiber Channel Fiber Channel (FC) attached storage is commonly connected to the server via Lucent connectors (LCs) embedded within a small form-factor pluggable (SFP) optical adapter, such as a PCI host bus adapter (HBA). HBAs have throughput ratings of up to ... [full story]

File System Considerations A file system facilitates the storage needs of an application, housing any data that the application or server itself cannot hold in physical RAM. A file system is a creation of its parent, the operating system. File systems ... [full story]

Flow Control Flow control is the process of ensuring that data is sent at a rate that the recipient and the network are able to sustain. From the perspective of an end node participating in a conversation, flow control consists of ... [full story]

Forwarding Delays Forwarding delays are the amount of time spent determining where to forward a piece of data. With modern routers and switches that leverage dedicated hardware for forwarding, a piece of data may move through the device in under 1 ... [full story]

Front Side Bus Speed The front side bus is a significant factor in the server's ability to move data about the server. The numerical rating of a server's front side bus designates at what speed the processor can transfer data to ... [full story]

FTP Many network administrators consider the FTP a "necessary evil." Legacy applications and logging hosts commonly use FTP for simple, authenticated file transfers. FTP is viewed as a simple solution but with a potential for a major impact. Everything from the ... [full story]

Hewlett-Packard Hewlett-Packard (http://www.hp.com) offers several different server platform product lines and a proprietary operating system called HP-UX. In addition to supporting HP-UX, the Hewlett-Packard server platforms support other operating systems, such as Microsoft Windows Server 2003, Novell Corporation's NetWare, Red Hat ... [full story]

HTTP For Internet traffic that uses HTTP as a transfer mechanism, several factors contribute to latency and the perception of latency, including the following: Throughput of the connection between the client and server The speed of the client and server hosts themselves The complexity ... [full story]

Hyper-Threading Hyper-threading and Super-threading are offerings that are specific to processors manufactured by Intel Corporation. Hyper-threading allows a single processor to appear as if two separate processors exist. Super-threading allows a thread, or thread of execution, to be shared with a ... [full story]

IBM IBM (http://www.ibm.com) offers a broad array of 32-bit and 64-bit servers. These servers support operating systems offered by vendors such as Microsoft and Red Hat. Select servers include the POWER5 series processor that is designed to specifically support operating systems such ... [full story]

Identifying Network Components Understanding network infrastructure and network management is the first step in venturing to assess and manage application performance over the network. If you do not know how your network is designed and implemented, you will not be in ... [full story]

Identifying Non-Network Components Similarly, become familiar with each of the non-network components that have an impact on application performance, including these: The make and model of client laptops, desktops, and servers The version of operating system and the licensed features that are in ... [full story]