networking - IP Fragmentation and Reassembly - Stack Overflow

QuarkChain - Future is here

QuarkChain
QuarkChain aims to build a user-friendly, decentralized and reliable blockchain that can ultimately handle millions of transactions per second.
Scalability has been integrated into the design of QuarkChain from the get-go and with this in mind they’ve set out to build a platform capable of supporting industries ranging from FinTech to gaming and social media.
The Problem There’s a saying in life that goes like this…
When you’re young you have time and energy, but no money.
When you’re an adult, you have money and energy, but no time.
When you’re retired, you have time and money, but no energy.
What a dilemma! Or should we say… trilemma?
Hmm, well is it really not possible to achieve all three? Of course it is!
A similar trilemma presents itself in blockchain however there has been no viable solution uncovered to date and this is exactly what QuarkChain along with many others in this space are attempting to solve.
The blockchain trilemma looks like this:
A permissioned (centralized) blockchain can provide scalability and security however loses all trace of decentralization. Permissioned blockchains are similar to centralized systems in the old world such as banks, Visa, as well as PayPal.
Opting for a permissionless (decentralized) blockchain such as Bitcoin or Ethereum provides security and a dispersed network however scalability is sacrificed, this was evident with the CryptoKitties dApp and excessive transaction fees when the demand on the Bitcoin network was high.
The real challenge therefore is figuring out how a blockchain can ACHIEVE ALL THREE:
Decentralization Scalability Security Whomever is able to solve this trilemma will likely score themselves “a one-way ticket to the moon”!
But before we leap towards thinking about getting onto the moon, let’s take a step back and consider exactly why it is that decentralization, security, and scalability are essential components for a blockchain…
BLOCKCHAIN SECURITY
The two primary components that ensure the security of a blockchain are:
Making sure only valid transactions are made; and That the network is safe and resistant to malicious attacks and users. Ensuring that only valid transactions are made allows users of cryptocurrency to maintain a strong level of trust and confidence in the value of the crypto.
If a user can easily send tokens they don’t own and make new ones out of thin air, this greatly undermines the value of the cryptocurrency.
This would be similar to printing money out of thin air, which has been a regular practice for many reserve banks around the world for several years. The more money is introduced into any economy this will drive inflation up causing the currency being printed to drop in value..
When this is taken to extremes hyperinflation can occur as was the case in Zimbabwe and this can cause all sorts of mayhem, strife, and havoc.
DECENTRALIZATION
As the term implies decentralization is the opposite of centralization and in the case of crypto an extreme level of centralization would be having a sole miner for a blockchain.
Anyone transacting on this blockchain would need to have a great deal of faith and trust that this sole miner won’t do anything dodgy as make up fake transactions.
Even if people trusted this miner, the network would still be at great risk as now anyone interested in taking down the blockchain has a single target to attack. They can launch a denial of service attack on the miner taking the whole network down or look to bribe, blackmail, or manipulate the miner into doing their bidding.
SCALABILITY
As written above, decentralization and security are essential for the ecosystem, they provide a reliable and costly efficient space to continue evolving into future tech. On the other hand, as shown on the next diagram, as security and decentralization grows, an enormous amount of data , requirements for storage and bandwidth needs grow with it, which intrinsically implies a diminution in the system´s scalability.
Solution As illustrated in the diagram below, there are three propositions to solving the problem of scalability:
Multi-blockchains → They may suffer from vulnerability issues, double-spending attacks, reverse transactions or strategic mining attacks. Lightning network→ BTC´s option to this problem seems to be inefficient. User’s transaction targets are random and happen sporadically. Sharding→ Omniledger´s solution to the problem, with the intricate consensus protocol. It may be limited by cross-shards transactions and single shard take overs. But partial solutions do not provide full efficiency especially in a time of exponential evolution. QuarkChain aims to fulfill the ultimate goal of any blockchain: Extending scalability far beyond current tech limits, while maintaining the balance for both security and decentralization.
QuarkChain’s bottom up approach to scalability begins by considering the two primary functions a blockchain serves as a public ledger which is:
Tracking the “state” of a ledger and all of the transactions that are made; and Ensuring only valid transactions are confirmed and recorded onto the ledger. 1. The “State” of a Ledger
If you’re not sure what a ledger is, you can think of it as the thing responsible for keeping track of and recording everything that occurs in your bank account.
Your account has a running list of debits (when money goes out of your account — boo!) and credits (when money goes into your account — woo!) which are recorded whenever money is sent or received into your account.
The “state” of the ledger then is simply a snapshot of what’s in your bank account at any point in time, which is otherwise known as your bank balance! When a friend sends $50 into your account that has $100 in it, the new “state” of your account will then be $150.
An ancient Papyrus ledger
  1. Confirmation of Transactions
If a transaction is made it doesn’t necessarily mean the transaction will go through and this is what confirming a transaction is all about.
Sending $100 to a friend with $50 in your account will see your transaction getting rejected! The transaction won’t be processed and confirmed as it is an invalid transaction due to insufficient funds in your account.
QuarkChain’s 2 Layered Blockchain System QuarkChain separates out these two primary functions with the use of a 2 layered system that allows for greater scalability:
The first layer consists of “elastic sharded” blockchains; and The second layer has a root blockchain.
The first layer with “elastic sharded” blockchains can be broken down as follows:
Elastic: the sharded (minor) blockchains on this layer are elastic because the amount can be increased or decreased as required. Sharded — each sharded minor-blockchain only processes a small subset of all the transactions that occur so they are considered “sharded” as they represent a small fragment of all the transactions occurring throughout the network. (This is what enables QuarkChain’s scalability.) Blockchains — the minor-blockchains keep track of the current state of the ledger by processing and recording relevant data such as user accounts and the transactions made between accounts The Second Layer and the Root Blockchain
The second layer serves the function of confirming the transactions that take place throughout the network. This is done by sending the block headers of the minor blockchains that contain all the transactions to the root blockchain, the root blockchain then confirms these transactions by creating a new block with all of the block headers.
QuarkChain’s 2nd layer system offers a higher amount of transactions per second whilst accounting for bottlenecks that occur from increased throughput such as computing power, data storage, and internet bandwidth.
Structure of QuarkChain’s 2nd Layered Blockchain
Are We Decentralized Yet?
QuarkChain incorporates several features to ensure decentralization of the network:
Collaborative mining driven by game-theoretic incentives to ensure when miners mine for their own selfish benefit that this behavior aligns with what is best for the overall system. Mining difficulty algorithms are designed so that hash power is evenly distributed among sharded minor-blockchains and the root blockchain. Each blockchain offers different rewards and difficulty levels so that weak miners can achieve similar levels of expected returns by mining solo when compared to joining a mining pool. This lessens the need for mining pools and results in less centralization. Main Features — Tech Overview Smart Contracts
QuarkChain supports smart contracts with the use of Ethereum Virtual Machine (EVM), sharded blockchains therefore run their own smart contracts local to their blockchain via EVM.
Sharded blockchains can be thought of as mini-Ethereum’s or clones of Ethereum running simultaneously and parallel to one another with unique individual wallets associated to them.
So for sharded blockchain 1, you will also have wallet 1, and on sharded blockchain 2 there is wallet 2, and so forth… As you can imagine it would be a hassle to keep track of these wallets, especially if there are a hundred or even thousands of these sharded blockchains, which is why QuarkChain offers the following two features:
Simple Account Management Smart Wallet In QuarkChain users are able to use a single “Primary Account” where the majority of the user’s funds will be parked for them to manage all other wallets. When a user wants to send funds to a different sharded blockchain the user simply sends it from their Primary Account.
Primary account sending transactions to wallets located in other sharded blockchains
The Primary Account is combined with a “Smart Wallet” to automatically handle “cross”-shard transactions, these “cross”-shared transactions can be made anytime and are confirmed within minutes.
(A cross-shard transaction is a transaction that is made from one sharded blockchain to another sharded blockchain, e.g. sending funds from Wallet 1 to Wallet 2 would constitute a cross-shard transaction, whereas a transaction made from one wallet to another wallet within the same shard, e.g. Shard 1, is considered an “in-shard” transaction.)
Roadmap
Q1 2018 — White paper and developing verification code 0.1 proof of concept Q2 2018 — Release verification code 0.2 and implement Testnet 0.1 with Wallet 0.1. Testnet 0.1 supports basic transactions including both in-shard and cross-shard transactions Q3 2018 — Release Testnet 0.2 and Wallet 0.2. Testnet 0.2 supports further features such as smart contracts, reshard, etc. Q4 2018 — Release of QuarkChain Core 1.0, Mainnet 1.0, together with Smart Wallet 1.0 Core 1.0 will provide basic functionality and basic optimization (e.g. GPU support) for QuarkChain. Q2 2019 — Release of QuarkChain Core 2.0, Mainnet 2.0, together with Smart Wallet 2.0 Code 2.0 further optimizez Core 1.0 and enables clustering feature for mini-nodes to form a cluster and run as a full node. Token Economics Token Name : QKC Hard Cap : 20 Million USD The QuarkChain token (QKC) will be an ERC-20 token until Mainnet 1.0 launches Q4 2018, the QKC (ERC-20) will then be converted to QuarkChain’s mainnet tokens. Crowdsale intended for end of May or start of June 2 year vesting period for the team with an extended vesting period for QuarkChain’s Foundation QKC will be used to pay for transaction fees and to reward community contributors that help improve QuarkChain’s system A significant amount of QKC will be dedicated to incentivizing developers to build dApps on QuarkChain’s platform
Development Team
Qi Zhou — Founder
Qi Zhou achieved 10M tps as a member of the real time infrastructure team at Facebook Expert in scalability and was a key developer in achieving 10m IOPS with clustering for EMC 5+ years as a software engineer. Short stints with key roles at Facebook (1 year), Dell EMC (2.5 years), Google (9 months) and Ratrix Technologies (10 months). PHD from Georgia institute of Technology
Zhaoguang Wang — Software Engineer
Zhaouang has 6+ years experience as a system backend engineer working on large complex distributed systems Key roles at Facebook (1 year), Instagram (4 months), Google (5 years) PHD and Masters degree in Computer Science and Engineering, University of Michigan
Xiaoli Ma — Research Scientist
Professor at Georgia Institute of Technology (Combined 7 years, 10 months) Previously CTO and Co Founder of Ratrix Technologies (6 years, 5 months)
Yaodong Yang — Research Scientist
Vice Chairman in Education at Xi’an Jiaotong University, Frontier Institute of Science and Technology Co-founder of Demo++ (Tech Incubator) Yaodong has authorized 50+ papers in peer reviewed journals and has over 600 citations in his name.
Wencen Wu — Research Scientist
Wencen has been a Assistant Professor at Rensselaer Polytechnic Institute (4 years and 6 months). Has a MSC and PHD in Electrical and Computer Engineering Operations Team
Anturine Xiang — Marketing and Community
Anturine has 6+ years experience within finance and technology at Wall Street and Silicon Valley Key Roles as Lead Platform Analytics at Wish, Business Development and Marketing at Beepi, Consumer Marketing and Analytics at LinkedIn Partners and Investors
Arun G. Phadke
Arun is a University Distinguished Professor emeritus in the Department of Electrical Engineering at Virginia Tech Fellow of National Academy of Engineering, USA
Bill Moore
Managing Director of Walden International (Global venture capital firm) Previously Chief Engineer Sun Microsystems who co-led the ZFS team, also Former President of DSSD/EMC (Dell)
Mike Miller
Mike is a PhD Physicist with 100+ publications Founder of Cloundant which was acquired by IBM in 2014
Kevin Hsu
Kevin is a serial investor in blockchain companies
Leo Wang
Leo is a recognised cryptocurrency fund manager who invested in blockchain projects. He is an Angel investor in NEO with over 17 years of field experience in mobile internet in China
Zhiyun Qian
Cybersecurity expert who discovered serious vulnerabilities in Linux, Android and TCP/IP Assistant Professor at University of California Riverside
submitted by xnxkillswitch to QuarkChain [link] [comments]

CN_Unit_4_Lec_1_IP_Header_Fragmentation - YouTube 4.4.1 - IP Datagram Format and Fragmentation  FHU ... Fragmentation-3  Fragmentation of IP datagram  Fragmentation of fragment Fragmentation dans les réseaux IP  Slimane Bah IP Header and Fragmentation-Network Layer - YouTube

RFC 8900: IP Fragmentation Considered Fragile. Date de publication du RFC : Septembre 2020 Auteur(s) du RFC : R. Bonica (Juniper Networks), F. Baker, G. Huston (APNIC), R. Hinden (Check Point Software), O. Troan (Cisco), F. Gont (SI6 Networks) Réalisé dans le cadre du groupe de travail IETF intarea Première rédaction de cet article le 12 septembre 2020 You are still very confused about how fragmentation works. With an original payload of 4500 octets passing through a router to a network with an MTU of 2600 you would get: 20 octet IPv4 header and 2576 octet payload; 20 octet IPv4 header and 1924 octet payload; When those fragments pass through another router to a network with an MTU of 1400 ... I have an IP packet of header length of 20 Bytes and data length of 4096 Bytes. The maximum transfer unit of the network is only 1500 Bytes. As I understand fragmentation, the fragmented packet will ... networking ip ip-fragmentation. asked Mar 11 '12 at 22:57. liv2hak. 263 2 2 gold badges 12 12 silver badges 25 25 bronze badges. 3. votes. 2answers 195 views seeing remote MTUs of 250 and 68 ... While IP network rely on variable length packets, ATM, in order to facilitate faster switching speeds, and in order to interoperate better with the many different Time Division Multiplexing (TDM) physical layers, specified fixed length cells. IPv4, in particular not only provides for a variable length packet, but fragmentation in flight. The ... Thus length of the packet is 20 ( IP Header ) + 1020 ( payload ) = 1040 . Ans 2: The offset is the address or the locator from where the data starts with reference to the original data payload. For IP the data payload comprises all the data thats after the IP header and Options header. Thus the system/router takes the payload and divides it into smaller parts and keeps the track of the offset ...

[index] [33270] [45355] [29712] [9776] [10016] [1131] [35430] [10485] [18861] [27911]

CN_Unit_4_Lec_1_IP_Header_Fragmentation - YouTube

Video Covers, IP header in brief with clear explanation of each header field. It clarify the minimum header length, maximum header size and also fields like:... An overview of the format of IP datagrams and the IP fragmentation algorithm. The slides are adapted from Kurose and Ross, Computer Networks 5th edition and ... Cette leçon porte sur la fragmentation dans les réseaux IP. Intervenant: Slimane BAH. Editeur: El Mahdi EL MHAMDI. IP v4 Header Format ,Fragmentation and Reassembly in IPv4 Fragmentation-4 Fragmentation of IP datagram Fragmentation and reassembling - Duration: ... IPv4 Packet Header Format Part 2 IIT Lecture Series Computer Netowrks - Duration: 10:34. CSE ...

#