Face Management Protocol
The Face Management Protocol provides a method for an entity such as ccndc to control the faces maintained by ccnd, which are subsequently used in the Registration Protocol.
The FMP supports "newface", "destroyface", and "queryface" operations.
A request operation is represented as a CCNx Interest with a CCNx ContentObject encoding the majority of the request parameters embedded as a component of the Interest name. A response is represented as a ContentObject for which the name matches the Interest, and the content encodes any necessary response data.
For the Face Management Protocol, the CCNx ContentObject encoding the request and reply is the FaceInstance.
To create a new face ccndc signs a content object NFBLOB whose Content is a ccnb-encoded FaceInstance containing
other fields necessary to set up a socket (at least IPProto, Host, and Port).
ccndc then expresses an interest in /ccnx/CCNDID/newface/NFBLOB
CCNDID is the pubid of the local ccnd
NFBLOB is the signed content object
The verb, "newface" occurs redundantly in both the interest prefix and in the NFBLOB. Its presence in the prefix is for dispatching the request. It is also in the NFBLOB, so that it is signed.
ccnd creates the new face and answers with a FaceInstance containing at least the PublisherPublicKeyDigest and FaceID.
FaceInstance ::= Action? PublisherPublicKeyDigest? FaceID? IPProto? Host? Port? MulticastInterface? MulticastTTL? FreshnessSeconds? Action ::= ("newface" | "destroyface" | "queryface") PublisherPublicKeyDigest ::= SHA-256 digest FaceID ::= nonNegativeInteger IPProto ::= nonNegativeInteger [IANA protocol number; 6=TCP, 17=UDP] Host ::= textual representation of numeric IPv4 or IPv6 address Port ::= nonNegativeInteger [1..65535] MulticastInterface ::= textual representation of numeric IPv4 or IPv6 address MulticastTTL ::= nonNegativeInteger [1..255] FreshnessSeconds ::= nonNegativeInteger
When FaceInstance is used as a request, the Action must be specified. It will not be present in a response.
newface - If a face matching the parameters does not already exist, an attempt is made to create it. Then if the face exists (whether new or old) the full description is returned as a FaceInstance.
destroyface - at least the FaceID must be present. If permitted, the face is destroyed.
queryface - specification TBD
Identifies the ccnd that the information is relevant for. PublisherPublicKeyDigest is not necessary for self-registration, but indicates the ccnd to which the request is directed, if present. PublisherPublicKeyDigest is always present in a response.
FaceID is not present in a newface request, but must be specified in a destroyface or queryface request. FaceID is always present in a response.
Identifies the IPv4 or IPv6 numeric address of the remote ccnd for this FaceInstance.
Port identifies the port on the remote ccnd, or the port for the multicast group.
If the Host is a multicast address, and there are multiple interfaces present, MulticastInterface will identify the unicast numeric address of the interface to which the multicast address will be attached.
Specifies the TTL to be used for multicast operations. The default value is 1.
FreshnessSeconds is optional in a request, but is treated as a hint by ccnd. In a response, FreshnessSeconds specifies the remaining lifetime of the face.
Prefix Registration Protocol
The prefix registration protocol uses the ForwardingEntry element type to represent both requests and responses.
ForwardingEntry ::= Action? Name? PublisherPublicKeyDigest? FaceID? ForwardingFlags? FreshnessSeconds? Action ::= ("prefixreg" | "selfreg" | "unreg") Name ::= the name prefix to be registered PublisherPublicKeyDigest ::= SHA-256 digest of the ccnd's public key (CCNDID) FaceID ::= nonNegativeInteger ForwardingFlags ::= nonNegativeInteger FreshnessSeconds ::= nonNegativeInteger
When ForwardingEntry is used as a request, the Action must be specified. It will not be present in a response.
prefixreg - Register (or re-register) the prefix on the specified face.
selfreg - Register (or re-register) the prefix on the current face; the FaceID need not be present in the request, but if present it must match the current face.
unreg - Remove the prefix registration for the specified face.
Identifies the ccnd that the information is relevant for. It is optional in a request (the name in the requesting interest has already addressed the appropriate node). PublisherPublicKeyDigest is always present in a response.
FaceID is required in prefixreg and unreg requests. FaceID is always present in a response.
This is the name prefix to be acted on.
This integer holds the inclusive OR of the following bit fields:
CCN_FORW_ACTIVE 1 CCN_FORW_CHILD_INHERIT 2 CCN_FORW_ADVERTISE 4 CCN_FORW_LAST 8 CCN_FORW_CAPTURE 16 CCN_FORW_LOCAL 32 CCN_FORW_TAP 64 CCN_FORW_CAPTURE_OK 128
The CCN_FORW_ACTIVE bit indicates that the entry is active; interests will not be sent for inactive entries (but see note below).
CCN_FORW_CHILD_INHERIT says that this entry may be used even if there is a longer match available. In the absence of this bit, the presence of a longer matching prefix that has an active entry will prevent this entry from being used.
CCN_FORW_ADVERTISE says that the prefix may be advertised to other nodes.
CCN_FORW_LAST indicates that this entry should be used last, if nothing else worked. This is intended to be used by ccndc and similar programs to monitor unanswered interests. The presence of this flag on any entry causes the associated face to be considered non-local, as far as interest forwarding is concerned. Thus it will not receive interests with Scope=1, nor will it receive interests in namespaces that are marked local. However, the ability of the face to change prefix registrations is not affected.
CCN_FORW_CAPTURE says that no shorter prefix may be used, overriding child-inherit bits that would otherwise make the shorter entries usable. For a child-inherit bit to be overridden, the CCN_FORW_CAPTURE_OK must be set in the same forwarding entry that has CCN_FORW_CHILD_INHERIT set. Note that this means that using CCN_FORW_CAPTURE will have no effect if the CCN_FORW_CAPTURE_OK flag is not used.
CCN_FORW_LOCAL restricts the namespace to use by applications on the local machine.
CCN_FORW_TAP causes the entry to be used right away. This is intended for debugging and monitoring purposes. It is likely that there will be no response as a result, so no intentional delay is added before any further forwarding of this interest.
‘CCN_FORW_CAPTURE_OK’ used in conjunction with CCN_FORW_CHILD_INHERIT allows a CCN_FORW_CAPTURE flag on a longer prefix to override the effect of the child-inherit bit.
The flags CCN_FORW_ADVERTISE, CCN_FORW_CAPTURE and CCN_FORW_LOCAL affect the prefix as a whole, rather than the individual registrations. Their effects take place whether or not the CCN_FORW_ACTIVE bit is set.
FreshnessSeconds is optional in a request, but is treated as a hint by ccnd. In a response, FreshnessSeconds specifies the remaining lifetime of the registration.