Networking Topologies Overview

Networking Topologies

• Topology refers to the layout of how devices are arranged in a network, both physically and logically.

• Two main types of networks: Underlay (real network with routers, switches) and Overlay (logical connections like GRE or IPsec tunnels).

  Overlay networks are virtual networks built on top of physical network infrastructure. They are commonly used to address specific networking challenges or to provide additional functionality. Here are some circumstances that involve overlay networks:

  1. Virtual Private Networks (VPNs): VPNs use overlays to create secure connections over the internet. They encapsulate data packets and often use encryption to ensure privacy, allowing remote users to access an organization's internal network safely.

  2. Software-Defined Networking (SDN): In SDN, overlay networks can be used to abstract the underlying hardware, enabling more flexible network management. This approach allows for easier network configuration and automated control through centralized controllers.

  3. Cloud Networking: Cloud service providers often use overlay networks to interconnect their data centers and to provide seamless connectivity to customers. These overlays can provide features like traffic isolation, enhanced security, and efficient resource allocation.

  4. Network Function Virtualization (NFV): NFV can use overlays to deploy network services like firewalls and load balancers as virtual functions on a shared hardware platform. This enables dynamic scaling and a reduction in capital expenses by decoupling hardware and software.

  5. Data Center Networks: In data centers, overlays are used to interconnect different network segments or tenant environments, often implemented through technologies such as VXLAN or NVGRE, which help extend Layer 2 networks over a Layer 3 infrastructure.

  6. Internet of Things (IoT): Overlay networks support IoT by providing a unified networking layer that can handle diverse communication protocols and technologies. They help manage device interconnectivity, data traffic, and scaling challenges in IoT ecosystems.

  7. Streaming and Content Distribution: Content delivery networks (CDNs) utilize overlays to efficiently distribute streaming media and other resources across geographically distributed servers to enhance user experience and reduce latency.

  8. Peer-to-Peer (P2P) Networks: Overlays are fundamental in P2P systems, where network participants create logical links over the internet to share files or resources. This structure allows efficient data distribution without relying on centralized servers.

  9. Blockchain and Distributed Ledgers: Overlay networks facilitate communication and consensus within blockchain networks by allowing participants to propagate transactions and blocks across nodes spread over the internet.

  These scenarios show how overlay networks are used to provide enhanced functionality, flexibility, and scalability across various networking environments.

Historical Context

• Early networking used coaxial cables, known as 10Base2, allowing data transfer speeds of 10 megabits per second over shared segments of nearly 200 meters.
• The bus topology connected multiple devices on a single medium, leading to potential signal collisions when two devices transmitted simultaneously.

Bus Topology

• Characterized as one collision domain (only one device can communicate at a time) and one broadcast domain (all devices receive broadcast messages).

  A collision domain is a network segment where data packets can collide with each other when being sent over a shared communication medium. This typically happens in networks using a hub or a repeater, where multiple devices share the same bandwidth. In a collision domain, only one device can successfully transmit data at any given time. If two or more devices attempt to send data simultaneously, a collision occurs, causing the devices to stop, wait for a random backoff period, and then attempt to retransmit. This can lead to network inefficiencies and increased latency, especially as more devices are added to the network. Collision domains are reduced or eliminated by using network switches, which provide each connected device with its own dedicated bandwidth, allowing multiple devices to communicate simultaneously without interference.

• If a single cable segment failed, the entire network would go down.

Hubs and Layer 1 Devices

• Hubs function as multi-port repeaters, creating a logical bus topology where all devices share the same communication channel, leading to a single collision and broadcast domain.
• Transitioned to using unshielded twisted pairs (10BaseT) instead of coax cables.

Star vs. Logical Bus

• A hub creates a physical star topology connecting devices, yet logically maintains a bus topology due to shared communication channels.
• This setup can lead to difficulties in communication when many devices attempt to transmit simultaneously.

Layer 2 Switches

• Switches operate at Layer 2 of the OSI model and learn device addresses, allowing communication between devices without interference.
• Each port on a switch represents an individual collision domain, reducing the chances of collisions compared to hubs.

Ring Topology

• Devices can be arranged in a ring, allowing a token passing system to control communication (e.g., token ring).
• In token ring systems, a central Multi-station Access Unit (MAU) creates a physical star while logically forming a ring.

Wide Area Networks (WAN)

• WANs connect geographically dispersed sites, requiring separate connectivity methods (cloud, firewalls, routers).
• Common WAN topologies include hub-and-spoke and full mesh setups.

Hub-and-Spoke vs. Full Mesh

• Hub-and-spoke topology features a central hub that connects to multiple sites, simplifying connectivity.
• Full mesh topology enables direct connections between every site but can become complex and impractical as the number of sites increases.

Partial Mesh

• A hybrid topology that includes some direct connections between sites while maintaining central hub links, offering flexibility and fault tolerance.

Network Design Considerations

• Underlay provides the foundational connectivity for networks, while overlay allows for logical structuring and functionality based on the underlying physical network.
• Each type of network serves distinct purposes and requires tailored design strategies.

This quiz explores the concept of networking topologies, focusing on how networks are structured both in the underlay and overlay systems. Understanding these designs is crucial for optimizing network connectivity and efficiency.