Project 3 Protocol Design v3.0

Transcription

1 Prject 3 Prtcl Design v3.0 Francisc J. Garcia-Ascani Prject 3 Prtcl Design v3.0 The fllwing assumptins are made: 1. At launch servers are able t cnnect t a well knwn multicast address and prt. 2. All messages sent, either multicast r unicast, are serialized XML bjects. 3. UA s aliases are appended with the parent s name (i.e. A.a., A.b, etc.). Cmmand Line Arguments 1. Server: servername mcip mcprt [-recver] 2. UA: serverip serverprt 3. User: useragentip useragentprt Server Discvery Initializatin When a server first launches, it multicasts a Server Hell message in rder t initiate the discvery prcess. If the initiating server receives at least ne Server Hell NAK, frm a pre-existing server, then there is a name cllisin. The initiating server must change its name thrugh user input; afterwards the Server Hell message is re-multicast. Once a pre-existing server receives a Server Hell message, it first checks if there is a name cllisin with itself and then with any f its neighbrs, by checking its lcal neighbr list. If there is a name cllisin with itself r with ne f its neighbrs a pre-existing server sends a Server Hell NAK t the initiating server. Nte that the initiating server may receive multiple NAKs fr the same name cllisin. The sending f multiple NAKs increases the prbability that the initiating server will receive at least ne NAK, in case f a lst message r link failure. If there is n name cllisin, then a pre-existing server must determine if a cnnectin ffer is t be made r nt. The prbability f making an ffer is 1 when a pre-existing server has yet t meet its minimum number f cnnectins. As cnnectins are made, this prbability decreases and appraches but never reaches 0 when its maximum number f cnnectins is reached. When a pre-existing server determines that a cnnectin is t be made, a Server Hell ACK is sent t the initiated server. Nte that this lad balance frmula will nly wrk if the minimum number f cnnectins is 2 r mre and the maximum number f cnnectins is always tw mre than the minimum number f cnnectins (i.e. Min Num = N, Max Num = N+2). Message Name Medium Channel Message Structure Server Hell Multicast Server t Server [Server Name] [Listening unicast address] [Listening unicast prt] Server Hell ACK Unicast Server t Server [Server Name] [Listening unicast address] [Listening unicast prt] Server Hell NAK Unicast Server t Server [Server Name that caused the cllisin] Neighbr Management When the initiating server receives a Server Hell ACK message it sends a Neighbr Cnnect message t the preexisting servers. As sn as a pre-existing server receives the Neighbr Cnnect message it adds the initiating server t its neighbr list and replies with a Neighbr Cnnect ACK message. After the initiating server receives a Neighbr Cnnect ACK the initiating server adds the pre-existing server t its neighbr list. After a successful cnnectin t its neighbrs the servers will backup their neighbr list and UA list t a nn-vlatile strage. In the rare event that the server receives a valid but delayed Server Hell NAK message, the server will frce a migratin upn its UAs t ne f its neighbrs. The server will then shutdwn. Message Name Medium Channel Message Structure Neighbr Cnnect Unicast Server t Server [Server Name] [Listening unicast IP] [Listening unicast prt] Neighbr Cnnect ACK Unicast Server t Server [Server Name] [Listening unicast IP] [Listening unicast prt]

2 Prject 3 Prtcl Design v3.0 Francisc J. Garcia-Ascani User Agent Management Servers ensure that their UA s maintain unique names by receiving a Set Alias message frm the UA. The server verifies that the name is unique by cmparing that name t its lcal UA list. If the name is unique the server sends a Set Alias ACK message, therwise the server sends a Set Alias NAK message. A UA shuld nt send any cmmands until its alias has been set by the user. Additinally, if a UA is in a chatrm the user shuld nt be able t change its alias; this check will be accmplished n the UA and nt by the server. Message Name Medium Channel Message Structure Set Alias Unicast UA t Server [Alias Name] Set Alias ACK Unicast Server t UA [Alias Name] Set Alias NAK Unicast Server t UA [Alias Name] [Message] Failure Recvery Detecting Failures A server shuld peridically send a Heartbeat message t its neighbrs. Every time a server receives a Heartbeat message it will update that neighbr s timestamp. The server will check its wn lcal neighbr list every N secnds, if an entry hasn t been updated in the last M checks that server is assumed t be dead, then it remves the server frm the lcal neighbr list and ntifies its UAs by sending an updated Backup Server List message. In the case that the server remves its dead neighbr and the server is nw rphaned the server will reinitiate the server discvery prtcl. A UA shuld als peridically ping its server t determine if it is alive by sending a Server Ping message. If the UA desn t receive a certain number f Server Png messages in the alltted time it determines that its server is dead and switches ver t ne f its backup servers. The server tracks the last time it received pings frm its UAs. If the server des nt receive a ping frm its UA in the alltted time the server assumes that the UA is dead and remves it frm its UA list. Message Name Medium Channel Message Structure Heartbeat Unicast Server t Server [Server Name] Server Ping Unicast UA t Server [UA Name] Server Png Unicast Server t UA N/A Switching Servers When a server initially cnnects t its neighbrs r when its neighbr s list is updated it sends an updated Backup Server List message t each f its cnnected UAs. If a UA detects that its server has failed the UA sends a Migrate message t the first backup server in its list. The backup server then respnds with a Migrate ACK upn receipt f a Migrate message. If the UA des nt receive a Migrate ACK message after an alltted time the UA attempts t cnnect t the next backup server in its list. When the UA receives the first Migrate ACK message it ignres any fllwing Migrate ACK messages. If a UA is nt able t cnnect t any f its back up server the UA must die. Once a UA has migrated, their backup server list is updated by their new parent. Nte that all UAs attempt t migrate t the same backup server. Therefre, chatrm services are nt interrupted as lng as all the UAs migrate t the same server. In the extreme case f chatrm fragmentatin (i.e. UAs belnging in the same chatrm but cnnected t different servers) user transparency is shattered. When the failed server recvers it reads its neighbr list and UA list frm the nn-vlatile strage, if it exists. The server then recnnects t its neighbrs, by issuing a Neighbr Cnnect message and in the case that the server is unable t cnnect t any f its neighbrs the server will reinitiate the server discvery prtcl. After cnnecting t at least ne f its neighbrs the server sends a Recnnect message directly t each ne f its UAs in its list. When a UA

3 Prject 3 Prtcl Design v3.0 Francisc J. Garcia-Ascani receives a Recnnect message it sends a Migrate message t its resurrected parent, awaits a Migrate ACK and then sends Recnnect ACK message infrming its riginal parent abut its current parent. When the riginal parent receives the Recnnect ACK message the parent sends a Recvered UA message t the UA s frmer parent. Upn receipt f a Recvered UA message the frmer parent remves the UA frm its lcal list. Message Name Medium Channel Message Structure [Backup Server Cllectin] Backup Server List Unicast Server t UA The backup server cllectin is cmpsed f: [Neighbr Name] [Listening unicast IP] [Listening unicast prt] [Migratin Inf] Migrate Unicast UA t Server The migratin inf is cmpsed f: [Server Name] [Chat rm name] [Chat rm multicast IP] [Chat rm multicast prt] [Chat rm seed] [UA Name] [UA listening unicast IP] [UA listening unicast prt] Migrate ACK Unicast Server t UA N/A Recnnect Unicast Server t UA [Server Name] [Listening unicast IP] [Listening unicast prt] Recnnect ACK Unicast UA t Server [Current Server Name] [Current Server Listening unicast IP] [Current Server Listening unicast prt] [Migratin Inf] Recvered UA Unicast Server t Server [UA Name] Querying fr Users When a user initiates a user search request, the User sends a Search message t its UA. The UA frwards this message t its server, appending its listening unicast IP and prt. The server first checks its wn UA list fr the desired user, and if fund, returns a User Fund message t the requesting UA. Regardless if a user is fund lcally r nt, the server then sends a Search message t its neighbrs. Therefre, the requesting user may receive delayed respnses depending n the size f the netwrk. Each server will maintain tw lists f searches. The first list maintains searches that riginated frm the server itself and is awaiting a respnse frm its neighbrs. The list als cntains the infrmatin f the UA that requested the search. The secnd list maintains searches that riginated frm neighbring servers and are awaiting a respnse frm the remaining neighbring servers. T prevent runaway searches each server checks the unique ID f the search against its lcal search lists. If a server receives a duplicate search request, it checks fr the desired user lcally and if a match is fund a Search Result ACK message is sent back t the requesting server; therwise a Search Result NAK message is sent back. Nte, that in either case the search is nt prpagated t its ther neighbrs. If a Search message reaches the end f the netwrk (i.e. a server with nly ne neighbr) and the server des nt cntain the desired user, the server then sends a Search Result NAK message t the neighbring server that requested the search. Nw nce a match is fund, a Search Result ACK message is sent back t the requesting server. When this message reaches the parent f the requesting UA, a User Fund message is sent t the UA. Additinally, each server will have a timeut perid f N, after which the server will respnd t its awaiting neighbrs with a Search Result NAK, if n users were fund. Message Name Medium Channel Message Structure Search Unicast Server t Server [Originating Server Name] [User name t search fr] [Unique Query ID] Search Unicast UA t Server [User name t search fr] [UA listening unicast IP] [UA listening unicast prt] Search Unicast User t UA [User name t search fr] Search Result ACK Unicast Server t Server [Originating Server Name] [User name t search fr] [Unique Query ID] [UA listening unicast IP] [UA listening unicast prt] Search Result NAK Unicast Server t Server [Originating Server Name] [User name t search fr] [Unique Query ID] User Fund Unicast Server t UA [UA name] [UA listening unicast IP] [UA listening unicast prt]

4 Prject 3 Prtcl Design v3.0 Francisc J. Garcia-Ascani XML Message Frmat Using a XML frmat t represent the message structure decuples the need t specify data types fr the messages. In rder t sustain interperability f different implementatins all the teams must use the same XML message frmats when sending messages. Each message is sent as a string that cntains the XML structure. Teams can either create their wn XML parsers r use the fllwing package t serialize/de-serialize their bjects t XML and back again. User Messages Alias Used t defined named alias (Prject 1) <Cmmand>UserAlias</Cmmand> <AliasName>sand</AliasName> <IP>sand.cise.ufl.edu</IP> Create Rm Creates a chatrm and names that chatrm (Prject 2) <Cmmand>UserCreateRm</Cmmand> <Rm> <AliasName>COP5615</AliasName> </Rm> Jin Rm Allws user t jin a chatrm (Prject 2) <Cmmand>UserJinRm</Cmmand> <Rm> <AliasName>COP5615</AliasName>

5 Prject 3 Prtcl Design v3.0 Francisc J. Garcia-Ascani </Rm> Leave Rm Allws user t leave a chatrm (Prject 2) <Cmmand>UserLeaveRm</Cmmand> <Rm> <AliasName>COP5615</AliasName> </Rm> List Users (Frmerly ulist ) Lists all the users that are in the chatrm (Prject 2) <Cmmand>UserListUsers</Cmmand> <Rm> <AliasName>COP5615</AliasName> </Rm> Set Alias Used t set ne s alias name (Prject 1) <Cmmand>UserSetAlias</Cmmand> Remve Alias Used t remve an existing alias (Prject 1)

6 Prject 3 Prtcl Design v3.0 Francisc J. Garcia-Ascani <Cmmand>UserRemveAlias</Cmmand> CSend Sends a message t current chatrm multicast address (Prject 2) <Cmmand>UserCSend</Cmmand> <ChatMessage>Hell</ChatMessage> Search Refer t Prject 3 <Cmmand>UserSearch</Cmmand> List Rms List all existing chatrm names (Prject 2) <Cmmand>UserListRms</Cmmand> Exit Used t terminate the system (Prject 1)

7 Prject 3 Prtcl Design v3.0 Francisc J. Garcia-Ascani <Cmmand>UserExit</Cmmand> List List all the current existing aliases (Prject 1) <Cmmand>UserList</Cmmand> Send Used t send a message t named alias (Prject 1) <Cmmand>UserSend</Cmmand> <ChatMessage>Hi</ChatMessage> User Agent Messages Send Used t send a message t named alias (Prject 1) <Cmmand>UASend</Cmmand> <ChatMessage>Hi</ChatMessage> CSend Sends a message t current chatrm multicast address (Prject 2) <Cmmand>UACSend</Cmmand> <Seed>seed</seed>

8 Prject 3 Prtcl Design v3.0 Francisc J. Garcia-Ascani <ChatMessage>Hi</ChatMessage> List Rms List all existing chatrm names (Prject 2) <Cmmand>UAListRms</Cmmand> Create Rm Creates a chatrm and names that chatrm (Prject 2) <Cmmand>UACreateRm</Cmmand> <Rm> <AliasName>COP5615</AliasName> </Rm> Jin Rm Allws user t jin a chatrm (Prject 2) <Cmmand>UAJinRm</Cmmand> <Rm> <AliasName>COP5615</AliasName> </Rm> Leave Rm Allws user t leave a chatrm (Prject 2)

9 Prject 3 Prtcl Design v3.0 Francisc J. Garcia-Ascani <Cmmand>UALeaveRm</Cmmand> <Rm> <AliasName>COP5615</AliasName> </Rm> Search Refer t Prject 3 <Cmmand>UASearch</Cmmand> List Users (Frmerly ulist ) Lists all the users that are in the chatrm (Prject 2) <Cmmand>UAListUsers</Cmmand> <Rm> <AliasName>COP5615</AliasName> </Rm> Server Ping Refer t Prject 3 <Cmmand>UAServerPing</Cmmand> Migrate Refer t Prject 3

10 Prject 3 Prtcl Design v3.0 Francisc J. Garcia-Ascani <Cmmand>UAMigrate</Cmmand> <MigratinInf> <Server> <AliasName>server</AliasName> </Server> <Rm> <AliasName>COP5615</AliasName> <IP> </IP> <Seed>seed</Seed> </Rm> </MigratinInf> Recnnect Acknwledgement Refer t Prject 3 <Cmmand>UARecnnectAck</Cmmand> <Server> <AliasName>sand</AliasName> <IP>sand.cise.ufl.edu</IP> </Server> <MigratinInf> <Server> <AliasName>server</AliasName> </Server> <Rm> <AliasName>COP5615</AliasName> <IP> </IP> <Seed>seed</Seed> </Rm> </MigratinInf> Set Alias Refer t Prject 3

11 Prject 3 Prtcl Design v3.0 Francisc J. Garcia-Ascani <Cmmand>UASetAlias</Cmmand> Server Messages Server Create Rm Acknwledgement ACK sent t UA (Prject 2) <Cmmand>ServerCreateRmAck</Cmmand> <Rm> <AliasName>bbsRm</AliasName> <IP> </IP> <Seed>seed</Seed> </Rm> Server Create Rm Negative Acknwledgement NAK sent t UA (Prject 2) <Cmmand>ServerCreateRmNak</Cmmand> <Rm> <AliasName>bbsrm</AliasName> </Rm> <StatusMessage>Rm culd nt be created.</statusmessage> Server Jin Rm Acknwledgement ACK sent t UA (Prject 2)

12 Prject 3 Prtcl Design v3.0 Francisc J. Garcia-Ascani <Cmmand>ServerJinRmAck</Cmmand> <Rm> <AliasName>bbsRm</AliasName> <IP> </IP> <Seed>seed</Seed> </Rm> <StatusMessage>Jined rm successfully.</statusmessage> Server Jin Rm Negative Acknwledgement NAK sent t UA (Prject 2) <Cmmand>ServerJinRmNak</Cmmand> <Rm> <AliasName>bbsrm</AliasName> </Rm> <StatusMessage>Culd nt jin rm.</statusmessage> Server Leave Rm Acknwledgement ACK sent t UA (Prject 2) <Cmmand>ServerLeaveRmAck</Cmmand> <StatusMessage>Left rm successfully.</statusmessage> <Rm> <AliasName>bbsrm</AliasName> </Rm> Server Leave Rm Negative Acknwledgement NAK sent t UA (Prject 2)

13 Prject 3 Prtcl Design v3.0 Francisc J. Garcia-Ascani <Cmmand>ServerLeaveRmNak</Cmmand> <StatusMessage>Culd nt leave rm.</statusmessage> <Rm> <AliasName>bbsRm</AliasName> <IP> </IP> <Seed>seed</Seed> </Rm> Server List Rms Acknwledgement ACK sent t UA (Prject 2) <Cmmand>ServerListRmsAck</Cmmand> <RmList> <Rm> <AliasName>bbsrm</AliasName> </Rm> <Rm> <AliasName>janesrm</AliasName> </Rm> </RmList> Server List Rms Negative Acknwledgement NAK sent t UA (Prject 2) <Cmmand>ServerListRmsNak</Cmmand> <StatusMessage>Culd nt list rms r n rms present.</statusmessage> Server List Users Acknwledgement ACK sent t UA (Prject 2)

14 Prject 3 Prtcl Design v3.0 Francisc J. Garcia-Ascani <Cmmand>ServerListUsersAck</Cmmand> <Rm> <AliasName>bbsrm</AliasName> </Rm> <UserList> <IP>sand.cise.ufl.edu</IP> <AliasName>rainy</AliasName> <IP>rain.cise.ufl.edu</IP> </UserList> Server List Users Negative Acknwledgement NAK sent t UA (Prject 2) <Cmmand>ServerListUsersNak</Cmmand> <StatusMessage>Culd nt list users. Rm des nt exist.</statusmessage> Server Update Rm Acknwledgement ACK sent t UA (Prject 2) <Cmmand>ServerUpdateRmAck</Cmmand> <Rm> <AliasName>bbsRm</AliasName> <IP> </IP> <Seed>seed</Seed> </Rm> Server Hell Refer t Prject 3

15 Prject 3 Prtcl Design v3.0 Francisc J. Garcia-Ascani <Cmmand>ServerHell</Cmmand> Server Hell Acknwledgement Refer t Prject 3 <Cmmand>ServerHellAck</Cmmand> Server Hell Negative Acknwledgement Refer t Prject 3 <Cmmand>ServerHellNak</Cmmand> <StatusMessage>Errr message</statusmessage> Server Neighbr Cnnect Refer t Prject 3 <Cmmand>ServerNeighbrCnnect</Cmmand> Server Neighbr Cnnect Ack Refer t Prject 3 <Cmmand>ServerNeighbrCnnectAck</Cmmand> Server Heartbeat Refer t Prject 3

16 Prject 3 Prtcl Design v3.0 Francisc J. Garcia-Ascani <Cmmand>ServerHeartbeat</Cmmand> Server Png (t UA) Refer t Prject 3 <Cmmand>ServerServerPng</Cmmand> Server Backup Server List (t UA) Refer t Prject 3 <Cmmand>ServerBackupServerList</Cmmand> <AliasList> <AliasName>sand</AliasName> <IP>sand.cise.ufl.edu</IP> <AliasName>rain</AliasName> <IP>rain.cise.ufl.edu</IP> </AliasList> Server Migrate Acknwledgement Refer t Prject 3 <Cmmand>ServerMigrateAck</Cmmand> Server Recnnect Refer t Prject 3

17 Prject 3 Prtcl Design v3.0 Francisc J. Garcia-Ascani <Cmmand>ServerRecnnect</Cmmand> Recvered UA Refer t Prject 3 <Cmmand>ServerRecveredUA</Cmmand> <IP>sand.cise.ufl.edu</IP> Server Search Refer t Prject 3 <Cmmand>ServerSearch</Cmmand> <QueryID>1</QueryID> Server Search Results Acknwledgement Refer t Prject 3 <Cmmand>ServerSearchResultsAck</Cmmand> <QueryID>1</QueryID>

18 Prject 3 Prtcl Design v3.0 Francisc J. Garcia-Ascani Server Search Results Negative Acknwledgement Refer t Prject 3 <Cmmand>ServerSearchResultsNak</Cmmand> <QueryID>1</QueryID> User Fund Refer t Prject 3 <Cmmand>ServerUserFund</Cmmand> <IP>sand.cise.ufl.edu</IP> Set Alias Acknwledgement Refer t Prject 3 <Cmmand>ServerSetAliasAck</Cmmand> Set Alias Negative Acknwledgement Refer t Prject 3

19 <Cmmand>ServerSetAliasNak</Cmmand> <StatusMessage>Unable t set alias name.</statusmessage> Prject 3 Prtcl Design v3.0 Francisc J. Garcia-Ascani

20 Prject 3 Prtcl Design v3.0 Francisc J. Garcia-Ascani Revisins V3.0 v2.9 v2.8 v2.7 v2.6 v2.5 v2.4 v2.3 v2.2 v2.1 v2.0 Added missing Alias tag in ServerSearchResultsACK and ServerSearchResultsNAK Updated ServerSetAliasNAK: mved StatusMessage field ut frm Alias Added missing infrmatin in UARecnnectAck. Added new sectin: User Agent Management Added the fllwing messages: UASetAlias, ServerSetAliasAck, ServerSetAliasNak Mdified the fllwing messages: ServerSearch Made XML mre cmpliant with W3 XML specificatin. Revised UserListUsers, UserCSend, UserCreateRm, UserLeaveRm, and UserListUsers cmmands. Cmpletely restructured XML Added migratin infrmatin t Recnnect ACK Additin f a "-recver" cmmand line ptin as an argument t the server. Cmplete verhaul f search functinality Mre granularity within csend messages Eliminatin f ne message frm the server recvery phase Eliminatin f the neighbr list message Eliminatin f the neighbr png message Added the fllwing XML message frmat in the UA sectin: Send and CSend Renamed the fllwing messages: Search Results t Search Results Ack Mdified the fllwing messages: Search (Server t Server) Added the fllwing messages: Search Results Nak Added XML Message Frmat sectin. Specified a range fr the number f neighbr cnnectins Remved the fllwing messages: List Neighbrs, Neighbr Discnnect, Neighbr Discnnect ACK, Neighbr Dead Changed the name f the Migrate Request t Recnnect Added the fllwing messages: Current Server, Recnnect ACK, Remve UA Initial prtcl

21 Prject 3 Prtcl Design v3.0 Francisc J. Garcia-Ascani FAQ Nte: This FAQ was generated based n peer review. 1. User shuld nt cntrl netwrk tplgy. As prpsed in class users may have the ptin t discnnect frm its existing neighbr(s). After careful cnsideratin allwing users this ability vilates user transparency. Therefre, cmmands allwing the user t cntrl netwrk tplgy have been remved. 2. Neighbr's user list is maintained at each server which is unnecessary as discussed in class. Maintaining a neighbr s user list is necessary when searching fr a user as it reduces netwrk traffic. 3. Server recvery is nt described and children recvery is nt discussed. Read frm the prtcl: When the failed server recvers it reads its neighbr list and UA list frm the nnvlatile strage, if it exists. The server then recnnects t its neighbrs, by issuing Neighbr Cnnect message and then sends a Migrate Request message t each ne f its UAs. 4. Chatrm wnership nt described. Refer t the Switching Servers sectin. 5. N mentin f data types and semantics. Frm Wiki: A prtcl can be defined as the rules gverning the syntax, semantics, and synchrnizatin f cmmunicatin. 6. Hw are different messages differentiated n different threads n a server? Defining what threads spawn each message is beynd the scpe f this dcument. 7. Hw ften t check whether a server is alive? If nt ften, then the tw message passes are gd. If peridically, t many messages are passed. This is left t each grup t determine. 8. Necessary t determine if yur chatrm is alive? Chatrms stay alive even if servers fail. Refer t the Switching Servers sectin. 9. "Neighbr Discnnect" message is nt required as status f neighbring servers is taken care by peridic server ping. Refer t questin #1.