Amendments
-The Amendments system provides a means of introducing new features to the decentralized Ripple consensus network without causing disruptions. The amendments system works by utilizing the core consensus process of the network to approve any changes by showing continuous support for two weeks before they go into effect.
+The Amendments system provides a means of introducing new features to the decentralized Ripple consensus network without causing disruptions. The amendments system works by utilizing the core consensus process of the network to approve any changes by showing continuous support before those changes go into effect. An amendment normally requires 80% support for two weeks before it can apply.
+When an Amendment has been enabled, it applies permanently to all ledger versions after the one that included it. You cannot disable an Amendment, unless you introduce a new Amendment to do so.
Background
-Any changes to transaction processing could cause servers to build a different ledger with the same set of transactions. This could cause anything from minor inconveniences (a minority of servers spend more time and bandwidth fetching the actual consensus ledger because they cannot rely on their own) to serious problems: consensus might halt from validating ledgers because servers are unable to reach a majority who agree on the same result.
-In theory, this could prompt a situation where the Ripple Consensus Ledger ceases to function because only a portion of validators have upgraded to a new version of the software.
-Amendments fix that problem while also providing advance notice of when any transaction processing changes will go into effect, so that any users and businesses who rely on the behavior of the Ripple Consensus Ledger have fair warning in advance. API changes that do not impact the Consensus process do not require Amendments.
-Amendment Lifecycle
-An amendment is a fully-functional feature or change, ready to apply as soon as a consensus of servers can handle it. A server that wants to use an amendment must have functional code for two modes: without the amendment (previous behavior) and with the amendment (new behavior). Every amendment has a unique identifying string, which should indicate who developed it, in order to avoid potential overlap.
-Every 256th ledger is called a "flag" ledger. The process of approving an amendment starts in the ledger version immediately before the flag ledger: at this time, rippled validator servers submit votes in favor of specific amendments alongside their validations for that ledger.
In the flag ledger itself, there is nothing unusual. However, during that time, the servers look at the votes of the validators they trust, and decide whether to insert an Amendment pseudo-transaction into the following ledger, with flags to indicate what it thinks happened:
Any changes to transaction processing could cause servers to build a different ledger with the same set of transactions. This could cause anything from minor inconveniences (a minority of servers spend more time and bandwidth fetching the actual consensus ledger because they cannot rely on their own) to serious problems: consensus might be unable to validate new ledger versions because servers are unable to reach a consensus who agree to the exact same result.
+In theory, this could prompt a situation where the Ripple Consensus Ledger cannot make progress because only a portion of validators have upgraded to a new version of the software. Amendments provide solution to this problem, so that new features can be enabled only when enough validators support those features.
+Users and businesses who rely on the Ripple Consensus Ledger can also use Amendments to provide advance notice of changes in transaction processing that might affect their business. However, API changes that do not impact transaction processing or the consensus process do not require Amendments.
+Amendment Process
+An amendment is a fully-functional feature or change, ready to apply when a consensus of servers can handle it. A rippled server that wants to use an amendment has business logic for two modes: without the amendment (previous behavior) and with the amendment (new behavior). Every amendment has a unique identifying hex value and a short name. The short name is for human use, and does not affect the status of the amendment.
Every 256th ledger is called a "flag" ledger. The process of approving an amendment starts in the ledger version immediately before the flag ledger: at this time, rippled validator servers submit votes in favor of specific amendments alongside their validations for that ledger. (Fee Voting also occurs around flag ledgers.)
In the flag ledger itself, there is nothing unusual. However, during that time, the servers look at the votes of the validators they trust, and decide whether to insert an EnableAmendment pseudo-transaction into the following ledger. The flags of an EnableAmendment pseudo-transaction indicate what the server thinks happened:
-
-
- The
tfGotMajorityflag means that support for a feature has increased across the threshold of 80% of trusted validators.
- - The
tfLostMajorityflag means that support for a feature has decreased across the threshold of 80% of trusted validators.
- - An Amendment pseudo-transaction with no flags means that support for a feature has been enabled. This is called the "Enabled" Amendment. +
- The
tfGotMajorityflag means that support for the amendment has increased to at least 80% of trusted validators.
+ - The
tfLostMajorityflag means that support for the amendment has decreased to less than 80% of trusted validators.
+ - An EnableAmendment pseudo-transaction with no flags means that support for the amendment has been enabled. (The change in transaction processing applies to every ledger after this one.)
A server only inserts the "Enabled" Amendment if there is a validated ledger which closed at least two weeks prior to the current flag ledger, with a Got-Majority Amendment psuedo-transaction, and no Lost-Majority Amendment psuedo-transactions for the same feature in the validated ledgers in between.
+A server only inserts the pseudo-transaction to enable an amendment if all of the following conditions are met:
+-
+
- There is a validated ledger which closed at least two weeks prior to the current flag ledger, which includes an EnableAmendment pseudo-transaction for this amendment with the
tfGotMajorityflag enabled.
+ - There are no EnableAmendment pseudo-transactions for this amendment with the
tfLostMajorityflag enabled in the validated ledgers between thetfGotMajoritypseudo-transaction and the current ledger.
+
It is theoretically possible (but extremely unlikely) that a tfLostMajority EnableAmendment pseudo-transaction could be included in the same ledger as the pseudo-transaction to enable an amendment. In this case, the pseudo-transaction with the tfLostMajority pseudo-transaction has no effect.
Amendment Voting
+Operators of rippled validators can choose which amendments to support or reject using the feature command. This decides which amendments the validator votes for in the amendment process. By default, rippled votes in favor of every amendment it knows about.
The operator of a rippled validator can "veto" an amendment using the feature command. In this case, that validator never sends a vote in favor of the amendment. If enough trusted validators veto an amendment, then the amendment does not apply.
As with all aspects of the consensus process, amendment votes are only taken into account by servers that trust the validators sending those votes. Currently, Ripple recommends only trusting the 5 default validators that Ripple (the company) operates. For now, trusting only those validators is sufficient to coordinate with Ripple on releasing new features.
+Known Amendments
+The following is a comprehensive list of all known amendments and their status on the production Ripple Consensus Ledger:
+| Name | +Introduced | +Enabled | +
|---|---|---|
| Tickets | +v0.31.0 | +TBD | +
| SusPay | +v0.31.0 | +TBD | +
| TrustSetAuth | +v0.30.0 | +TBD | +
| MultiSign | +v0.31.0 | +Expected 2016-04-18 | +
| FeeEscalation | +v0.31.0 | +Expected 2016-04-11 | +
FeeEscalation
+| Amendment ID | +
|---|
| 42426C4D4F1009EE67080A9B7965B44656D7714D104A72F9B4369F97ABF044EE | +
Changes the way the transaction cost applies to proposed transactions. Modifies the consensus process to prioritize transactions that pay a higher transaction cost.
+This amendment introduces a fixed-size transaction queue for transactions that were not able to be included in the previous consensus round. If the rippled servers in the consensus network are under heavy load, they queue the transactions with the lowest transaction cost for later ledgers. Each consensus round prioritizes transactions from the queue with the largest transaction cost (Fee value), and includes as many transactions as the consensus network can process. If the transaction queue is full, transactions drop from the queue entirely, starting with the ones that have the lowest transaction cost.
While the consensus network is under heavy load, legitimate users can pay a higher transaction cost to make sure their transactions get processed. The situation persists until the entire backlog of cheap transactions is processed or discarded.
+A transaction remains in the queue until one of the following happens:
+-
+
- It gets applied to a validated ledger (regardless of success or failure) +
- It becomes invalid (for example, the
LastLedgerSequencecauses it to expire)
+ - It gets dropped because there are too many transactions in the queue with a higher transaction cost. +
MultiSign
+| Amendment ID | +
|---|
| 4C97EBA926031A7CF7D7B36FDE3ED66DDA5421192D63DE53FFB46E43B9DC8373 | +
Introduces simple multi-signing as a way to authorize transactions. Creates the SignerList ledger node type and the SignerListSet transaction type. Adds the optional Signers field to all transaction types. Modifies some transaction result codes.
This amendment allows addresses to have a list of signers who can authorize transactions from that address in a multi-signature. The list has a quorum and 1 to 8 weighted signers. This allows various configurations, such as "any 3-of-5" or "signature from A plus any other two signatures."
+Signers can be funded or unfunded addresses. Funded addresses in a signer list can sign using a regular key (if defined) or master key (unless disabled). Unfunded addresses can sign with a master key. This amendment does not allow second-level multi-signing (signers using multi-signatures to contribute to multi-signatures). Multi-signed transactions have the same permissions as transactions signed with a regular key.
+An address with a SignerList can disable the master key even without a regular key, or remove a regular key even if the master key is disabled. Therefore, the tecMASTER_DISABLED transaction result code is renamed tecNO_ALTERNATIVE_KEY. The tecNO_REGULAR_KEY transaction result is retired and replaced with tecNO_ALTERNATIVE_KEY. Additionally, this amendment adds the following new transaction result codes:
-
+
temBAD_SIGNER
+temBAD_QUORUM
+temBAD_WEIGHT
+tefBAD_SIGNATURE
+tefBAD_QUORUM
+tefNOT_MULTI_SIGNING
+tefBAD_AUTH_MASTER
+
SusPay
+| Amendment ID | +
|---|
| DA1BD556B42D85EA9C84066D028D355B52416734D3283F85E216EA5DA6DB7E13 | +
Provides "Suspended Payments" for XRP as a means of escrow within the Ripple Consensus Ledger. Creates the SuspendedPayment ledger node type and the new transaction types SuspendedPaymentCreate, SuspendedPaymentFinish, and SuspendedPaymentCancel.
This amendment is still in development. The current version is enabled on the Ripple Test Net.
+TrustSetAuth
+| Amendment ID | +
|---|
| 6781F8368C4771B83E8B821D88F580202BCB4228075297B19E4FDC5233F1EFDC | +
Allows pre-authorization of accounting relationships (zero-balance trust lines) when using Authorized Accounts.
+With this amendment enabled, a TrustSet transaction with tfSetfAuth enabled can create a new RippleState ledger node even if it keeps all the other values of the RippleState node in their default state. The new RippleState node has the lsfLowAuth or lsfHighAuth flag enabled accordingly. The sender of the transaction must have lsfRequireAuth enabled.
Tickets
+| Amendment ID | +
|---|
| C1B8D934087225F509BEB5A8EC24447854713EE447D277F69545ABFA0E0FD490 | +
Introduces Tickets as a way to reserve a transaction sequence number for later execution. Creates the Ticket ledger node type and the transaction types TicketCreate and TicketCancel.
This amendment is still in development.