Weibin Zhao Henning Schulzrinne Department of Computer Science Columbia University

MDS 3/8/20012 * Directory Services l lookup/mapping: white page, yellow page l reverse lookup/mapping: DNS (domain name vs. IP) l attribute-based lookup/mapping: LDAP, SLP * Components l client l server l database l protocol Background

MDS 3/8/20013 MDS: Market-based Directory Services * Design Goals l survivability: adjust gracefully to service dynamic change and resource loss l dynamic update: price advertisement l scale to large systems * Some Critical Issues l data organization, distribution, replication l access control l scalability

MDS 3/8/20014 MDS Design * Approaches l use existing directory services as building block: SLP ílow-cost, widely accepted, reuse for other systems l enhance reliability and scalability * Out contributions l define scheme for interaction of SLP directory servers íMesh-enhanced Service Location Protocol (mSLP) l standalone and integrated implementation: Java l Internet draft being considered for RFC

MDS 3/8/20015 Architecture Application Service User AgentService Agent Directory Agent QueryRegistration Interaction

MDS 3/8/20016 Service Registration * Service Description l URL l attributes-value pairs: can be in different languages l service type: lpr, bank l service scope: Columbia-CS, Amazon * Service Registration l lifetime l full or incremental registration * Service Deregistration l deregister whole service or individual attributes

MDS 3/8/20017 Service Query * Query Service Type l list available service types in given scope * Query Service URL l given attribute description, find matched URLs * Query Attributes l list all or part attributes for given URL or service type

MDS 3/8/20018 Directory Agent (DA) Discovery * Active Discovery l multicast special service query íservice-type = directory-agent * Passive Discovery l listen to DA multicast advertisement * Other Methods l Static configuration l DHCP

MDS 3/8/20019 DA Interaction * Peering DA Architecture l peer DAs: share service scopes l more than one DA for each scope l peer DAs maintain same data for common scopes * Two Issues l group membership management l data exchange management

MDS 3/8/ DA Set Membership Management * Learning of New Peers l DA multicast, static configuration, DHCP l exchange common peer list (CPL) with peers l forward DA advertisement l send unsolicited DA advertisement to peer * Keeping Peer Relationship l keep-alive message * Removal of Peers l peer shut-down l keep-alive timeout (peer failure, network separation)

MDS 3/8/ Data Exchange Management * Initial Data Exchange l pull model: download data from new peers l optimize data download * Forward New Service Registration l push model l one-hop forwarding: full mesh connection DA1 (a,b)DA3 (a,c)DA2 (b,c) DA4 (a,b,c) (a,b)(c) (a,b)(a,c)(b,c) SA (a,c) (c) (a)

MDS 3/8/ Protocol Design * Mesh-Control Message (MeshCtrl) l peering connection notification (Pconn_Notification) l common peer notification (Cpeer_Notification) l get requested data (Get_Rdata) l requested data end (Rdata_End) l keep alive (Keep_Alive) * Mesh-Forwarding Extension (MeshFwd) l Action-ID: Rqst_Forward, No_Forward l SA registration timestamp

MDS 3/8/ Message Flows DA1DA2 (1) DAAdvert (2) create a peering connection (3) Pconn_Notification MeshCtrl (4) unsolicited DAAdvert (5) Cpeer_Notification MeshCtrl (5’) Cpeer_Notification MeshCtrl (6) Get_Rdata MeshCtrl (7) requested data in SrvReg(s) (8) Rdata_End MeshCtrl (6’) Get_Rdata MeshCtrl (7’) requested data in SrvReg(s) (8’) Rdata_End MeshCtrl (9) forward SrvReg/SrvDeReg(s) (9’) forward SrvReg/SrvDeReg(s) (10) Keep_Alive MeshCtrl(s) (10’) Keep_Alive MeshCtrl(s)

MDS 3/8/ Demo * Survivability in case of failure l DA crash l network separation l peer DAs handle DA failure (keep-alive timeout) l client (SA/UA) handle DA failure (response timeout) * Optimize data download scheme * Forward new service registration

MDS 3/8/ Conclusions * MDS l a robust distributed directory services l serve general purpose or customized applications l fully implemented in Java, open source software l submitted Internet draft to standardize protocol * Future work l advance mSLP to RFC * Thank you!