How are the clusters connected in different regions in a distributed system? - cluster-computing

Question

A newbie here trying to understand distributed architecture. I understand that the nodes in clusters are interconnected via LAN. How are the clusters connected in different regions, lets say different continents? Are there any frameworks or patterns I can read on this?

Answer 1

In general, it is achieved using fully redundant undersea cables (fiber network cables). The cables have very thin threads(glass fiber) that transfer data using fiber-optic technology almost at the speed of light in ocean between the continents. Once the data is received at the other continent, it shall be processed by connecting with an existing network via edge networks that is closest to it which in turn takes it to other endpoints/gateways as applicable.
The routing in such scenario depends on the underlying routing protocol and the endpoints. In general, there are Border Gateway Protocol (BGP) enabled gateways that will automatically learn routes to other sites and carry the data accordingly.
Cloud providers such as AWS has components such as AWS region extended with AWS Local Zones and AWS wavelength that in turn work along with internet service providers and meet the performance requirement of the application . This is achieved by having the AWS infrastructure (have AWS compute and storage services within ISP datacenters ) configured closer to the user or at the edge of the 5G network such that the application traffic from the particular set of 5G devices can reach the servers in wavelength zones with minimal latency without opting through normal internet which would have introduced latency in reaching the server.
The exact pattern/architecture depends on the software requirement/design and the software components and hardware components in use.
A typical pattern that can be taken for example is Geode pattern as depicted below. This has set of geographical nodes with backend services deployed such that they can service any request for any client in any region. By distributing request processing around the globe, this pattern brings in improvement in latency and improves availability.
Typically, the geo-distributed datastores should also be co-located with the compute resources that process the data if the data is geo-distributed across a far-flung user base. The geode pattern brings the compute to the data. It is a kind deploying service in the form satellite deployments that are spread around the globe where each of this is termed as geode.
This pattern relies on features(routing protocols) of Azure that routes traffic to nearby geode via the shortest path which in-turn brings improvement in latency and performance. The pattern is deployed such that there is global load balancer and the geode is behind it. It uses a geo-replicated read-write service like Azure Cosmos DB for the data plane, that brings in data consistency in cross-geode via Data replication services such that all geodes can serve all requests.
There is also the deployment-stamp pattern that can be used if there are Multi-region applications where each tenant's data and traffic should be directed to a specific region.
This relies on Azure Front Door for directing traffic to the closest instance or it can utilize API Management deployed across multiple regions ​for enabling geo-distribution of requests and geo-redundancy of the traffic routing service. As shown in below diagram, the Azure Front Door can be configured with a backend pool, enabling requests to be directed to the closest available API Management instance. The global distribution features of Cosmos DB can be used to keep the mapping information updated across each region.
Azure Front door is often referred as "Scalable and secure entry point for fast delivery of your global applications". As shown below, the Front Door operates at Layer 7 (HTTP/HTTPS layer) using anycast protocol with split TCP and Microsoft's global network for improved latency, global connectivity. Based on the routing method the Front Door will route the client requests to the fastest and most available application backend(Internet-facing service hosted inside or outside of Azure).
The equivalent of Azure FrontDoor in Google Cloud Platform is the Google Cloud CDN which is termed as "Low-latency, low-cost content delivery using Google's global network" and it leverages Google's globally distributed edge caches to accelerate content delivery for websites and applications served out of Google Compute Engine.
Similarly, Amazon has Amazon CloudFront . This is as a CDN service that securely delivers data, videos, applications, and APIs to customers globally with low latency, high transfer speeds, all within a developer-friendly environment. The AWS backbone is also a private network built on a global, fully redundant, fiber network linked via trans-oceanic cables across various oceans. Amazon CloudFront automatically maps network conditions and intelligently routes the traffic to the most performant AWS edge location to serve up cached or dynamic content.
Here is a reference for AWS and a use case describing between different continents using AWS global backbone. for users need access to the applications running in one data center as well as the core systems running in their another data center with the different sites interconnected by a global WAN. Traffic using inter-region Transit Gateway peering is always encrypted, stays on the AWS global network, and never traverses the public Internet. Transit Gateway peering enables international, in this case intercontinental, communication. Once the traffic arrives at the particular continent/region’s Transit Gateway, the customer routes the traffic over an AWS Direct Connect (or VPN) to the central data center, where core systems are hosted.