Gary Kaiser

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Top Stories by Gary Kaiser

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'll focus on packet loss, continuing the concepts from these two previous entries. TCP Reliability TCP ensures reliable delivery of data through its sliding window approach to managing byte sequences and acknowledgements; among other things, this sequencing allows a receiver to inform the send... (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)

IT Operations and Digital Disruption | @DevOps Summit #APM #DevOps

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 experie... (more)

Understanding Application Performance on the Network | Part 1

As a network professional, one of your newer roles is likely troubleshooting poor application performance. For most of us, our jobs have advanced beyond network "health," towards sharing - if not owning - responsibility for application delivery. There are many reasons for this more justifiable than the adage that the network is first to be blamed for performance problems. (Your application and system peers feel they are first to be blamed as well.) Two related influencing trends come to mind: Increased globalization, coupled with (in fact facilitated by) inexpensive bandwidth me... (more)

Understanding Application Performance on the Network | Part 3

In Part II, we discussed performance constraints caused by both bandwidth and congestion. Purposely omitted was a discussion about packet loss - which is often an inevitable result of heavy network congestion. I'll use this blog entry on TCP slow-start to introduce the Congestion Window (CWD), which is fundamental for Part IV's in-depth review of Packet Loss. TCP Slow-Start TCP uses a slow-start algorithm as it tries to understand the characteristics (bandwidth, latency, congestion) of the path supporting a new TCP connection. In most cases, TCP has no inherent understanding of th... (more)