Welcome!

Eclipse Authors: Pat Romanski, Elizabeth White, Liz McMillan, David H Deans, JP Morgenthal

Related Topics: Eclipse, Java IoT, Microservices Expo, Microsoft Cloud, Linux Containers, Machine Learning , Wearables

Eclipse: Article

P2P Explained: What Exactly is a Peer Network?

Peer networks are really just logical graphs of computers, or, in many cases, logical graphs of connected applications

Kevin Hoffman's Blog

This is the beginning of a series of blog posts that I plan on doing that will hopefully clear some of the fog surrounding peer networking. At this point in time, creating, consuming, and using peer networks has never been more simple, and there are more efforts on the horizon (topics of future posts) that will bring new meaning to peer networking. If you're as obsessed with networking as I am, this is an incredibly exciting time to be a programmer.

To start the series off, I want to talk about what a peer network really is, and what it means to smart client developers as well as mid-tier developers and even back-end service developers. Disclaimer: I've never been much for buzzwords or terminology, so I might call something by a different name here than you're used to - that's not intentional and its not me being stupid... I just am often out of the "buzzword" or "terminology" loop. I was using Model-View-Controller for months before realizing there was an actual name for that pattern ;)

What is a Peer Network?
Straining really hard to remember back in my days at college... mostly all I can remember are nights spent at the campus center (if you went to UMass, you know the place...) watching Beavis and Butthead and drinking beer... but every once in a while a glimpse of some basic computer science theory returns... like the concept of a fully connected graph. Remember? That's the one where you have a series of nodes and edges where each node has a 1-hop traversal path to every other node in the mesh. A partially connected graph is the same series of nodes, but the edges are more optimally arranged according to some weight or priority, often resulting in multi-hop traversals between any two nodes in the graph.

Peer networks are really just logical graphs of computers, or, in many cases, logical graphs of connected applications. The physical topology of the peer network, means of communication, and weighting of the edges are all implementation-specific details that differ from P2P network to P2P network, but all of them can be reduced down at some point to a drawing containing nodes and edges.

There are many different strategies for arranging peer networks, but the main differentiating factor involves the designation of state servers for central data storage within a peer network and the physical topology of the network. I'll discuss a few (but certainly not all!) of the common topologies of peer networks from an application network topology perspective as opposed to a hardware/physical topology. 

The Hybrid Peer Network
The hybrid peer network is probably the most common form of peer network. Usually it starts out where people have soaring ideals of creating a true serverless peer network and then they realize that such a thing is impractical for what they're doing. So, as a compromise, they stick a central server in the middle of the peer network. Nodes in the mesh still talk to each other as if they were peers when necessary, following the edges as hops and obeying other P2P rules, but when they need central information (which often includes information about who is in the peer network at the time, shared state, central registration, etc) then they talk to the central server. This creates a hybrid network - a network of peers that use traditional client/server patterns for talking to a central registration/state server. You see this kind of network in instant messaging networks all the time - peers talk to each other directly as peers, but the central server is responsible for authentication, authorization, registration, buddy list storage, etc.

Transient State Server Peer Network - Arbitrary / Simple Algorithm
To compensate for some of the issues that people have when building the peer network (such as the infrastructure needs of maintaining a central server and making its location public knowledge and securing it, etc) they often decide to make one of the peers the designated state server for some period of time. Using a simple algorithm, these peer networks often designate the most recently joined node in the mesh as the new state server. The problem with these networks is that the programmer needs to deal with fault tolerance manually - what do you do when the designated peer "server" leaves the mesh? You need to build logic into the system to be aware of that application leaving (either intentionally or through a crash) the mesh and then designating the next state server in line until another peer joins the mesh. 

Transient State Server Peer Network - Election / Complex Algorithm
To compensate for some of the downsides of the previous network arrangement, peer network programmers often create complex election algorithms where the peer itself essentially holds a vote to decide who gets to be the state server. Some advanced implementations do these votes periodically regardless of whether a new node has joined the mesh. This allows the state server to roam, building in a level of fault tolerance. In addition, this kind of topology can support multiple state servers where some are designated backup servers for failover. You can also build enterprise service bus (ESB) style networks where services sit on the peer mesh and respond (idempotently, of course) to requests. These are by far the most complex implementations, but, when implemented properly, these types of networks can become ridiculously powerful and are often the basis for many commercial third-party middleware implementations.

The "Pure" Serverless Peer Network
When I think of a peer network, the first thing that comes to mind is the pure implementation of a network. Peers are in the mesh or they aren't, they have no implicit or explicit ranking or relative importance above and beyond anyone else in the mesh. There is no central state server, the peers do not contain explicit logic to decide upon some node to be a transient state server. If there is shared state in the peer network, it is replicated simply throughout the entire network by pushing data through whatever connection pattern the peer network has already established. If one peer goes down, so what. If all peers go down, so what. The peer mesh can operate with one node or one thousand nodes or ten thousands nodes if necessary - the distributed partial connectivity of the whole thing allows the serverless peer network to scale to enormous sizes without negatively impacting the application using the network. 

Meshes and Mesh Network Optimization
Hopefully you don't have to worry about this. If you are writing an application that takes advantage of a peer network/peer mesh, the details of optimizing the connections between nodes should be abstracted and hidden from you. If you're operating at this low level, you might want to consider using a different peer networking API because you should be concerned with making your application communicate with other instances of itself across a peer network, not about optimizing graph traversal patterns.

What's Next?
In upcoming posts on peer networking, I am going to go into detail about various implementations, including Windows Communication Foundation (WCF)'s Peer Channel, PNRP and its managed API, the differences between what those APIs do and sample applications. I will also eventually end up at a sample application that uses both WCF and PNRP in what I think is an example of a really powerful, really scalable Internet-scoped peer application. 

tags:          
links: digg this  del.icio.us  technorati  reddit

[This blog appeared originally here and is republished in full with the kind permission of the author, who retains copyright.]

More Stories By Kevin Hoffman

Kevin Hoffman, editor-in-chief of SYS-CON's iPhone Developer's Journal, has been programming since he was 10 and has written everything from DOS shareware to n-tier, enterprise web applications in VB, C++, Delphi, and C. Hoffman is coauthor of Professional .NET Framework (Wrox Press) and co-author with Robert Foster of Microsoft SharePoint 2007 Development Unleashed. He authors The .NET Addict's Blog at .NET Developer's Journal.

Comments (3) View Comments

Share your thoughts on this story.

Add your comment
You must be signed in to add a comment. Sign-in | Register

In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.


Most Recent Comments
Anonymous 05/23/08 09:57:32 AM EDT

Kevin,

One of the key pieces of information that a peer node needs to join the mesh, is the address of SOME peer node that is already in the network. You didn't really explain how the different variations on the P2P theme deal with that, except for the hybrid model with the static central node, which can be advertised out-of-band and expected to be always on. Can you say more about how that problem is solved?

Daniella 04/30/08 04:31:23 PM EDT

I liked the post :) interesting!

SH 04/29/08 10:57:44 AM EDT

Great post! But why the term "logical graphs" instead of just "graphs"? You simply mean "nodes and edges", I believe, and not [http://en.wikipedia.org/wiki/Logical_graph Logical Graph]. Picky, I know, but it goes even a step further in avoiding buzzwords.

@ThingsExpo Stories
"Space Monkey by Vivent Smart Home is a product that is a distributed cloud-based edge storage network. Vivent Smart Home, our parent company, is a smart home provider that places a lot of hard drives across homes in North America," explained JT Olds, Director of Engineering, and Brandon Crowfeather, Product Manager, at Vivint Smart Home, in this SYS-CON.tv interview at @ThingsExpo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
Coca-Cola’s Google powered digital signage system lays the groundwork for a more valuable connection between Coke and its customers. Digital signs pair software with high-resolution displays so that a message can be changed instantly based on what the operator wants to communicate or sell. In their Day 3 Keynote at 21st Cloud Expo, Greg Chambers, Global Group Director, Digital Innovation, Coca-Cola, and Vidya Nagarajan, a Senior Product Manager at Google, discussed how from store operations and ...
"Cloud Academy is an enterprise training platform for the cloud, specifically public clouds. We offer guided learning experiences on AWS, Azure, Google Cloud and all the surrounding methodologies and technologies that you need to know and your teams need to know in order to leverage the full benefits of the cloud," explained Alex Brower, VP of Marketing at Cloud Academy, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clar...
In his session at 21st Cloud Expo, Carl J. Levine, Senior Technical Evangelist for NS1, will objectively discuss how DNS is used to solve Digital Transformation challenges in large SaaS applications, CDNs, AdTech platforms, and other demanding use cases. Carl J. Levine is the Senior Technical Evangelist for NS1. A veteran of the Internet Infrastructure space, he has over a decade of experience with startups, networking protocols and Internet infrastructure, combined with the unique ability to it...
"Akvelon is a software development company and we also provide consultancy services to folks who are looking to scale or accelerate their engineering roadmaps," explained Jeremiah Mothersell, Marketing Manager at Akvelon, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
It is of utmost importance for the future success of WebRTC to ensure that interoperability is operational between web browsers and any WebRTC-compliant client. To be guaranteed as operational and effective, interoperability must be tested extensively by establishing WebRTC data and media connections between different web browsers running on different devices and operating systems. In his session at WebRTC Summit at @ThingsExpo, Dr. Alex Gouaillard, CEO and Founder of CoSMo Software, presented ...
"There's plenty of bandwidth out there but it's never in the right place. So what Cedexis does is uses data to work out the best pathways to get data from the origin to the person who wants to get it," explained Simon Jones, Evangelist and Head of Marketing at Cedexis, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
WebRTC is great technology to build your own communication tools. It will be even more exciting experience it with advanced devices, such as a 360 Camera, 360 microphone, and a depth sensor camera. In his session at @ThingsExpo, Masashi Ganeko, a manager at INFOCOM Corporation, introduced two experimental projects from his team and what they learned from them. "Shotoku Tamago" uses the robot audition software HARK to track speakers in 360 video of a remote party. "Virtual Teleport" uses a multip...
"IBM is really all in on blockchain. We take a look at sort of the history of blockchain ledger technologies. It started out with bitcoin, Ethereum, and IBM evaluated these particular blockchain technologies and found they were anonymous and permissionless and that many companies were looking for permissioned blockchain," stated René Bostic, Technical VP of the IBM Cloud Unit in North America, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Conventi...
Gemini is Yahoo’s native and search advertising platform. To ensure the quality of a complex distributed system that spans multiple products and components and across various desktop websites and mobile app and web experiences – both Yahoo owned and operated and third-party syndication (supply), with complex interaction with more than a billion users and numerous advertisers globally (demand) – it becomes imperative to automate a set of end-to-end tests 24x7 to detect bugs and regression. In th...
SYS-CON Events announced today that Telecom Reseller has been named “Media Sponsor” of SYS-CON's 22nd International Cloud Expo, which will take place on June 5-7, 2018, at the Javits Center in New York, NY. Telecom Reseller reports on Unified Communications, UCaaS, BPaaS for enterprise and SMBs. They report extensively on both customer premises based solutions such as IP-PBX as well as cloud based and hosted platforms.
SYS-CON Events announced today that CrowdReviews.com has been named “Media Sponsor” of SYS-CON's 22nd International Cloud Expo, which will take place on June 5–7, 2018, at the Javits Center in New York City, NY. CrowdReviews.com is a transparent online platform for determining which products and services are the best based on the opinion of the crowd. The crowd consists of Internet users that have experienced products and services first-hand and have an interest in letting other potential buye...
"MobiDev is a software development company and we do complex, custom software development for everybody from entrepreneurs to large enterprises," explained Alan Winters, U.S. Head of Business Development at MobiDev, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
A strange thing is happening along the way to the Internet of Things, namely far too many devices to work with and manage. It has become clear that we'll need much higher efficiency user experiences that can allow us to more easily and scalably work with the thousands of devices that will soon be in each of our lives. Enter the conversational interface revolution, combining bots we can literally talk with, gesture to, and even direct with our thoughts, with embedded artificial intelligence, whic...
SYS-CON Events announced today that Evatronix will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Evatronix SA offers comprehensive solutions in the design and implementation of electronic systems, in CAD / CAM deployment, and also is a designer and manufacturer of advanced 3D scanners for professional applications.
Leading companies, from the Global Fortune 500 to the smallest companies, are adopting hybrid cloud as the path to business advantage. Hybrid cloud depends on cloud services and on-premises infrastructure working in unison. Successful implementations require new levels of data mobility, enabled by an automated and seamless flow across on-premises and cloud resources. In his general session at 21st Cloud Expo, Greg Tevis, an IBM Storage Software Technical Strategist and Customer Solution Architec...
To get the most out of their data, successful companies are not focusing on queries and data lakes, they are actively integrating analytics into their operations with a data-first application development approach. Real-time adjustments to improve revenues, reduce costs, or mitigate risk rely on applications that minimize latency on a variety of data sources. In his session at @BigDataExpo, Jack Norris, Senior Vice President, Data and Applications at MapR Technologies, reviewed best practices to ...
An increasing number of companies are creating products that combine data with analytical capabilities. Running interactive queries on Big Data requires complex architectures to store and query data effectively, typically involving data streams, an choosing efficient file format/database and multiple independent systems that are tied together through custom-engineered pipelines. In his session at @BigDataExpo at @ThingsExpo, Tomer Levi, a senior software engineer at Intel’s Advanced Analytics gr...
When talking IoT we often focus on the devices, the sensors, the hardware itself. The new smart appliances, the new smart or self-driving cars (which are amalgamations of many ‘things’). When we are looking at the world of IoT, we should take a step back, look at the big picture. What value are these devices providing? IoT is not about the devices, it’s about the data consumed and generated. The devices are tools, mechanisms, conduits. In his session at Internet of Things at Cloud Expo | DXWor...
Everything run by electricity will eventually be connected to the Internet. Get ahead of the Internet of Things revolution. In his session at @ThingsExpo, Akvelon expert and IoT industry leader Sergey Grebnov provided an educational dive into the world of managing your home, workplace and all the devices they contain with the power of machine-based AI and intelligent Bot services for a completely streamlined experience.