Networking

For decades, IT security has relied on the “castle-and-moat” model: a strong perimeter designed to keep threats out, assuming everything inside is trusted. This perimeter-focused strategy is familiar and relatively convinient, but in an era where a single compromised workload can unravel an entire infrastructure, it’s a catastrophic negligence. The core issue is that this model is blind to the modern battlefield. A workload, broadly defined as the resources and processes needed to run an application, such as hosts, virtual machines, and containers, drives the majority of communication in today’s data centers. According to industry analysis, east-west traffic now accounts for over 80% of data center communication. This internal traffic is invisible to perimeter defenses, creating a vast, unprotected space where attackers can move laterally after a single breach. Microsegmentation is the modern approach designed to secure this internal territory. Here are four impactful truths about this transformative technology. ...

What if a simple packet(s) could bring down the internet? In the world of TCP/IP, vulnerabilities like SYN flood attacks have threatened network stability for decades. This deep dive explores the ingenious mitigation known as TCP SYN cookies, from the basics of TCP state management to its pragmatic trade-offs and lessons for modern engineering. Transmission Control Block The Transmission Control Block (TCB) is a critical data structure created when a TCP entity opens a TCP connection. A TCB contains the whole state of the connection and must maintain all information required to send and receive segments. ...

In today’s fast paced digital word, miliseconds count. The traditional way that TCP connections are established, known as the three-way handshake (3WHS), introduces a significant latency cost: at least one full Round-Trip Time (RTT) before any actual data can be exchanged. For applications like web browsing, where many connections are short-lived or frequently re-established, this delay can severely impact user experience. This is where TCP Fast Open (TFO) comes in. Documented in RFC 7413, TFO is an experimental TCP mechanism designed to save up to one full RTT by allowing data to be carried in the initial SYN and SYN-ACK packets of a TCP connection, enabling the receiving end to consume it during the handshake itself. ...

In modern data center networks, Virtual Extensible LAN (VXLAN) and Virtual Port Channels (vPC) are foundational technologies, offering enhanced scalability, flexibility, and redundancy. When combined, they create a robust and highly available network infrastructure. However, understanding how IP addresses are handled in a vPC VXLAN environment, particularly the roles of Virtual IP (VIP) and Primary IP (PIP) addresses, is crucial for ensuring optimal traffic flow and preventing common pitfalls like black-holing. ...

Multicast is a powerful communication method in computer networks that allows a single sender to efficiently deliver data to multiple interested recipients simultaneously. Unlike unicast (one-to-one) or broadcast (one-to-all on a segment), multicast conserves network bandwidth and processing resources by minimizing duplicate transmissions, replicating packets only when necessary. At the heart of this efficiency are multicast trees, which are fundamental to how multicast protocols like Protocol Independent Multicast (PIM) build loop-free forwarding topologies. ...