repo-ng

Repo Command

============

For insertion, deletion and other operations of repo, these commands are encoded in the form of [[ndn-cxx:SignedInterest|Signed Interests]]:

    /<repo-prefix>/<command-verb>/................./.........................................

                                  \______  _______/ \__________________  ___________________/

                                         \/                            \/

                                 RepoCommandParameter   Signed Interest additional components

The semantics of repo command interest is as follows:

The name semantics is defined to have following components:

* ``<repo prefix>`` refers to specific prefix repo is listening

* ``<command verb>`` refers to the name of command

* ``<RepoCommandParameter>`` refers to parameters of repo command

The following components are components of singed interest for access control:

* ``<timestamp>``

* ``<random-value>``

* ``<SignatureInfo>``

* ``<SignatureValue>``

For prefix of repo /ucla/cs/repo/, the command will be defined as this:

    /ucla/cs/repo/<command verb>/<RepoCommandParameter>/<timestamp>/<random-value>/<SignatureInfo>/<SignatureValue>

### RepoCommandParameter

    RepoCommandParameter ::= REPOCOMMANDPARAMETER-TYPE TLV-LENGTH

                               Name?

                               StartBlockId?

                               EndBlockId?

                               ProcessId?

                               InterestLifetime?

                               ForwardingHint?

    Name                  ::= NAME-TYPE TLV-LENGTH NameComponent*

    NameComponent         ::= NAME-COMPONENT-TYPE TLV-LENGTH BYTE+

    StartBlockId          ::= STARTBLOCKID-TYPE TLV-LENGTH

                               NonNegativeInteger

    EndBlockId            ::= ENDBLOCKID-TYPE TLV-LENGTH

                               NonNegativeInteger

    ProcessId             ::= PROCESSID-TYPE TLV-LENGTH

                               NonNegativeInteger

    InterestLifetime      ::= INTEREST-LIFETIME-TYPE TLV-LENGTH

                               NonNegativeInteger

    ForwardingHint       ::= FORWARDING-HINT-TYPE TLV-LENGTH

                               Delegation+

#### StartBlockId, EndBlockId

StartBlockId and EndBlockId are used to process segmented data. StartBlockId indicate the first segment number and EndBlockId indicate the last segment number. Repo will process segment data whose segment id between StartBlockId and EndBlockId. If StartBlockId is missing, the first segment id the repo process is 0; If EndBlockId is missing, this scenario is described in specific process in Repo Insertion Command section and Repo Deletion Command section.

#### Conflict of Selectors and StartBlockId, EndBlockId

Repo cannot process command with both selectors and StartBlockId, EndBlockId in RepoCommandParameter. If the RepoCommandParameter carries both, repo will ignore this command interest and return with error code of 405.

#### ProcessId

ProcessId is used by insertion and deletion check command to indicate specific insertion and deletion process. The ProcessId is fetched by repo command response of insertion and deletion command.

#### InterestLifetime

InterestLifetime is the maximum latency between interest sent and data received. If no data received after the InterestLifetime, the interest will time out. InterestLifetime is optional and a default value will be set if it is not specified.

#### ForwardingHint

The ForwardingHint element contains a list of name delegations, as defined in Link Object section. Each delegation implies that the requested Data packet can be retrieved by forwarding the Interest along the delegation path. Specifics of the forwarding logic for Interests with ForwardingHint will be defined in a separated document.

## Repo Command Response

Repo command response is the response data packet of repo command interest. The response contains statuscode to indicate the status of command process and other information. A TLV-encoded block called ``RepoCommandResponse`` is encoded in content of the data packet.

    RepoCommandResponse   ::= INSERTSTATUS-TYPE TLV-LENGTH

                               ProcessId?

                               StatusCode

                               StartBlockId?

                               EndBlockId?

                               InsertNum?

                               DeleteNum?

    ProcessId            ::= PROCESSID-TYPE TLV-LENGTH

                                NonNegativeInteger 

    StatusCode            ::= STATUSCODE-TYPE TLV-LENGTH

                                NonNegativeInteger    

    StartBlockId          ::= STARTBLOCKID-TYPE TLV-LENGTH

                                NonNegativeInteger

    EndBlockId            ::= ENDBLOCKID-TYPE TLV-LENGTH

                                NonNegativeInteger

    InsertNum             ::= INSERTNUM-TYPE TLV-LENGTH

                                NonNegativeInteger

    DeleteNum             ::= DELETENUM-TYPE TLV-LENGTH

                                NonNegativeInteger

### Name

Name indicates the Name in repocommandparameter of repo command

### ProcessId

ProcessId is a random number generated by repo to indicate the number of the command process. Client could use this ProcessId to check the status of specific command.

### StatusCode

StatusCode indicates the status of repo command process. The statuscodes of insert and deletion command are described in following insertion and deletion specification.

### StartBlockId, EndBlockId

StartBlockId and EndBlockId are the same as those of RepoCommandParameter. If either of those in RepoCommandParameter is missing, repo will set them as the Id known for now. For example, if StartBlockId is missing in RepoCommandParameter, StartBlockId in response will be set 0. If EndBlockId is missing in RepoCommandParameter, EndBlockId will be set null untill Repo get FinalBlockId in data packet. If FinalBlockId in returned data packet is less than EndBlockId, the EndBlockId will be set FinalBlockId.

### InsertNum, DeleteNum

InsertNum is used in reponse of insertion status check to indicate how many data packets have been successfully inserted into the repo. DeleteNum is used in response of deletion command and deletion check command. DeleteNum indicates how many data packets have been successfully deleted from repo.

## Repo TLV Type Encoding Number

Type                  | Number

----------------------| -------

RepoCommandParameter  | 201

StartBlockId          | 204

EndBlockId            | 205

ProcessId             | 206

RepoCommandResponse   | 207

StatusCode            | 208

InsertNum             | 209

DeleteNum             | 210

InterestLifetime      | 214

## Repo Trust Model

The trust model of repo depends on people who deploy the repo service, such as PKI. Repo can specify their own verification policies, and data consumers can specify their own trust anchors. The NDN [FAQ](http://named-data.net/project/faq/#How_does_NDN8217s_8220trust_management8221_work) shows how NDN trust managment works.