General Technology and IT Concepts

Routers often have multiple network interfaces (Ethernet, WiFi, fiber, etc.) and each type requires a different link-layer protocol. A single router can implement several link layers simultaneously to support different physical media and connection types.

Reliable delivery is the responsibility of the TRANSPORT layer (TCP), not the network layer. The network layer (IP) provides best-effort delivery without guarantees. Reliability, error correction, and flow control are higher-layer functions.

When you examine a packet on an Ethernet link, the headers appear in REVERSE order of encapsulation: Ethernet header (outermost), then IP header, then TCP header, then HTTP header (innermost). Each layer wraps the data from the layer above it.

Packet switching's key advantage is statistical multiplexing, sharing bandwidth among active users. This advantage is most pronounced for bursty traffic where resources can be dynamically allocated. Smooth traffic doesn't benefit as much since it doesn't have idle periods to exploit.

Traditional telephone networks (PSTN) use circuit switching, where a dedicated communication path is established for the duration of a call. This guarantees quality but wastes resources during silent periods. This contrasts with modern packet-switched VoIP networks.

Transmission delay depends on packet size because it's the time to push all bits onto the link (L/R where L is packet length). Propagation delay depends on distance and medium speed, not packet size. Processing and queueing delays are independent of packet length.

Datagram networks like IP are connectionless - routers treat each packet independently without maintaining connection state between end systems. Only virtual circuit networks (like ATM) track connections.

TTL is an IP header field used to prevent packets from looping indefinitely by decrementing at each router. It is NOT part of TCP - TCP operates at the transport layer while TTL is a network-layer mechanism.

ADSL is a point-to-point technology - each subscriber has a dedicated connection to the central office. It is NOT a shared medium like Ethernet or cable modem networks where multiple users share the same bandwidth.

HTML is a markup language for describing document structure and content, NOT a protocol. HTTP is the protocol for transferring web content. HTML itself has no protocol functionality.

Apache Struts is a web application framework for Java that facilitates developing web pages. It uses MVC (Model-View-Controller) architecture and extends the Java Servlet API. While it relates to web architecture, it's not specifically an EJB alternative (though it can work alongside or replace some EJB use cases) nor is it just a design pattern.

Apache Struts is an open-source web application framework hosted by the Apache Software Foundation. It follows the Model-View-Controller (MVC) pattern and is used for developing Java web applications.

Struts implements the Controller role in MVC architecture. It handles user requests, coordinates interaction between Model (data/business logic) and View (presentation), and manages the flow of the application.

Unlocking a report in Report Studio allows inserting objects (like text items or images) inside list columns, which is restricted in locked mode. The other actions (opening XML reports, applying conditional formatting, viewing Framework Manager-restricted data) do not require unlocking.

Package calculations appear on the Source tab in Report Studio, which displays all available data items from the package. The Functions tab contains built-in functions, Data Items tab shows report-specific data items, and Parameters tab is for query parameters.

Padding adds white space around text within a block by increasing internal spacing between the content and the block boundary. Margin adds external space outside elements, Positioning controls placement, and Size and Overflow manages dimensions and content spill behavior.

Global classes in Report Studio are modified through Page Explorer, which manages styles and classes that apply across all objects using that class. Query Explorer handles queries, Conditional Explorer manages conditional formatting, and Page Structure View shows the report hierarchy.

Report Studio is the Cognos tool designed for creating professional dashboard reports with visual components like gauges, lists, and graphs. It provides the flexibility to create executive-facing dashboards with multiple visualization types. Cognos Connection is for portal access, Cognos SDK is for development, and Metric Studio is for scorecard-style monitoring.

Analysis Studio is designed for interactive data exploration and analysis. It allows users to drill through data, discover patterns, and perform ad-hoc analysis that leads to new questions. Cognos Planning is for budgeting, TM1 is for financial modeling, and Query Studio is for simpler querying without deep analysis capabilities.