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Gary Kaiser

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Top Stories by Gary Kaiser

Transaction-Centric NPM: Enabling IT/Business Collaboration One of the consequences of digital disruption is that IT is propelled much closer to users, who expect applications and services to be available and to perform well anytime, anywhere, on any device. Communicating with the business now more than ever requires communicating with these users, and effective communication requires a clear understanding of their experience with the application services you deliver. But how well do you understand end-user experience? To answer that question, let's first define end-user experience as the transaction response time a user receives from an application service; click to glass seems to be the term in vogue. Alternatively, you can look at the question from a different perspective: How is the quality of your application services measured? Are you driven primarily by infr... (more)

Understanding Application Performance on the Network | Part 6

In Part V, we discussed processing delays caused by "slow" client and server nodes. In Part VI, we'll discuss the Nagle algorithm, a behavior that can have a devastating impact on performance and, in many ways, appear to be a processing delay. Common TCP ACK Timing Beyond being important for (reasonably) accurate packet flow diagrams, understanding "normal" TCP ACK timing can help in the effective diagnosis of certain types of performance problems. These include those introduced by the Nagle algorithm, which we will discuss here, and application windowing, to be discussed in Par... (more)

Understanding Application Performance on the Network | Part 4

We know that losing packets is not a good thing; retransmissions cause delays. We also know that TCP ensures reliable data delivery, masking the impact of packet loss. So why are some applications seemingly unaffected by the same packet loss rate that seems to cripple others? From a performance analysis perspective, how do you understand the relevance of packet loss and avoid chasing red herrings? In Part II, we examined two closely related constraints - bandwidth and congestion. In Part III, we discussed TCP slow-start and introduced the Congestion Window (CWD). In Part IV, we'... (more)

Understanding Application Performance on the Network | Part 5

In Part IV, we wrapped up our discussions on bandwidth, congestion and packet loss. In Part V, we examine the four types of processing delays visible on the network, using the request/reply paradigm we outlined in Part I. Server Processing (Between Flows) From the network's perspective, we allocate the time period between the end of a request flow and the beginning of the corresponding reply flow to server processing. Generally speaking, the server doesn't begin processing a request until it has received the entire flow, i.e., the last packet in the request message; similarly, th... (more)

Understanding APM on the Network

In Part 6, we dove into the Nagle algorithm - perhaps (or hopefully) something you'll never see. In Part VII, we get back to "pure" network and TCP roots as we examine how the TCP receive window interacts with WAN links. TCP Window Size Each node participating in a TCP connection advertises its available buffer space using the TCP window size field. This value identifies the maximum amount of data a sender can transmit without receiving a window update via a TCP acknowledgement; in other words, this is the maximum number of "bytes in flight" - bytes that have been sent, are traver... (more)