Simple Module Chord

Package: oversim.overlay.chord
File: src/overlay/chord/Chord.ned

The main module of the Chord implementation

Author: Ingmar Baumgart, Markus Mauch

Usage diagram:

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Inheritance diagram:

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Extends:

Name	Type	Description
BaseOverlay	simple module	Base class for overlay implementations

Used in compound modules:

Name	Type	Description
ChordModules	compound module	Implementation of the Chord KBR overlay as described in "Chord: A Scalable Peer-to-Peer Lookup Protocol for Internet(1,2) Applications" by I. Stoica et al. published in Transactions on Networking.

Parameters:

Name	Type	Description
rpcUdpTimeout	double	default timeout value for direct RPCs
rpcKeyTimeout	double	default timeout value for routed RPCs
optimizeTimeouts	bool	calculate timeouts from measured RTTs and network coordinates
rpcExponentialBackoff	bool	if true, doubles the timeout for every retransmission
localPort	int	UDP port for overlay messages
overlayId	int	identifies the overlay this node belongs to (used for multiple overlays)
debugOutput	bool	enable debug output
keyLength	int	overlay key length in bits
nodeId	string	optional nodeId as string in hexadecimal notation
useCommonAPIforward	bool	enable CommonAPI forward() calls
drawOverlayTopology	bool	draw arrow to successor node?
hopCountMax	int	maximum number of overlay hops
recNumRedundantNodes	int	numRedundantNodes for recursive routing
joinOnApplicationRequest	bool	only join the overlay on application request
collectPerHopDelay	bool	delay statistics for single hops
routeMsgAcks	bool	use RPCs for route messages
lookupRedundantNodes	int	number of next hops in each step
lookupParallelPaths	int	number of parallel paths
lookupParallelRpcs	int	number of nodes to ask in parallel
lookupVerifySiblings	bool	true, if siblings need to be authenticated with a ping
lookupMajoritySiblings	bool	true, if sibling candidates are selected by a majority decision if using parallel paths
lookupMerge	bool	true, if parallel Rpc results should be merged
lookupFailedNodeRpcs	bool	communicate failed nodes
lookupStrictParallelRpcs	bool	limited the number of concurrent rpcs to parameter parallelRpcs
lookupUseAllParallelResponses	bool	merge all parallel responses from earlier steps
lookupNewRpcOnEveryTimeout	bool	send a new RPC immediately after an RPC timeouts
lookupNewRpcOnEveryResponse	bool	send a new RPC after every response, even if there was no progress
lookupFinishOnFirstUnchanged	bool	finish lookup, if the last pending RPC returned without progress
lookupVisitOnlyOnce	bool	if true, the same node is never asked twice during a single lookup
lookupAcceptLateSiblings	bool	if true, a FindNodeResponse with sibling flag set is always accepted, even if it is from a previous lookup step
routingType	string	default routing mode (iterative, semi-recursive,...)
rejoinOnFailure	bool	rejoin after loosing connection to the overlay?
sendRpcResponseToLastHop	bool	needed by KBR protocols for NAT support
recordRoute	bool	record visited hops on route
dropFindNodeAttack	bool	if node is malicious, it tries a findNode attack
isSiblingAttack	bool	if node is malicious, it tries a isSibling attack
invalidNodesAttack	bool	if node is malicious, it tries a invalidNode attack
dropRouteMessageAttack	bool	if node is malicious, it drops all received BaseRouteMessages
measureAuthBlock	bool	if true, measure the overhead of signatures in rpc messages
restoreContext	bool	if true, a node rejoins with its old nodeId and malicious state
successorListSize	int	max number of successors in the SuccessorList
joinRetry	int	after joinRetry unsuccessful join requests, we fetch a need bootstrap node from the GlobalNodeList
stabilizeRetry	int	retries before a successor is considered failed
joinDelay	double	delay between join retries (sec)
stabilizeDelay	double	stabilize interval (sec)
fixfingersDelay	double	fix_fingers interval (sec)
aggressiveJoinMode	bool	use modified (faster) JOIN protocol
checkPredecessorDelay	double	checkPredecessor interval (sec)
extendedFingerTable	bool	use the extended finger table?
numFingerCandidates	int	number of fingers when using extended finger table
proximityRouting	bool	use proximity routing
memorizeFailedSuccessor	bool	do not use failed sucessor again and inform new successor
mergeOptimizationL1	bool	enable merge optimization OPL1
mergeOptimizationL2	bool	activate merge optimization OPL2
mergeOptimizationL3	bool	activate merge optimization OPL3
mergeOptimizationL4	bool	activate merge optimization OPL4

Properties:

Name	Value	Description
class	Chord
display	i=block/circle

Gates:

Name	Direction	Description
udpIn	input	gate from the UDP layer
udpOut	output	gate to the UDP layer
tcpIn	input	gate from the TCP layer
tcpOut	output	gate to the TCP layer
appIn	input	gate from the application
appOut	output	gate to the application
direct_in	input	gate for sendDirect

Source code:

//
// The main module of the Chord implementation
//
// @author Ingmar Baumgart, Markus Mauch
//
simple Chord extends BaseOverlay
{
    parameters:
        @class(Chord);
        volatile int successorListSize; // max number of successors in the SuccessorList
        // after joinRetry unsuccessful join requests, we fetch
        // a need bootstrap node from the GlobalNodeList
        int joinRetry;
        int stabilizeRetry; // retries before a successor is considered failed
        double joinDelay @unit(s); // delay between join retries (sec)
        double stabilizeDelay @unit(s); // stabilize interval (sec)
        double fixfingersDelay @unit(s); // fix_fingers interval (sec)
        bool aggressiveJoinMode; // use modified (faster) JOIN protocol
        double checkPredecessorDelay @unit(s); // checkPredecessor interval (sec)
        bool extendedFingerTable; // use the extended finger table?        
        int numFingerCandidates; // number of fingers when using extended finger table
        bool proximityRouting;    // use proximity routing
        // do not use failed sucessor again and inform new successor
        bool memorizeFailedSuccessor;
        bool mergeOptimizationL1; // enable merge optimization OPL1
        bool mergeOptimizationL2; // activate merge optimization OPL2
        bool mergeOptimizationL3; // activate merge optimization OPL3
        bool mergeOptimizationL4; // activate merge optimization OPL4
}