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Routing Internet Engineering Task Force ForCES Protocol Extension Experience in implementing and deploying ForCES architecture has demonstrated need for a few small extensions both to ease programmability and to improve wire efficiency of some transactions. The ForCES protocol is extended with a table range operation and a new extension for error handling. This documents updates both RFC 5810 and RFC 7121 semantics to achieve that end goal.

Experience in implementing and deploying ForCES architecture has demonstrated need for a few small extensions both to ease programmability and to improve wire efficiency of some transactions. This document describes a few extensions to the ForCES Protocol Specification semantics to achieve that end goal. This document describes and justifies the need for 2 small extensions which are backward compatible. The document also clarifies details of how dumping of a large table residing on an FE (Forwarding Engine) is achieved. To summarize: A table range operation to allow a controller or control application to request an arbitrary range of table rows is introduced. Additional error codes returned to the controller (or control application) by an FE are introduced. Additionally a new extension to carry details on error codes is introduced. As a result the (FE Protocol Object) FEPO LFB is updated over the definition in . While already supported, an FE response to a GET request of a large table which does not fit in a single PL message is not described in . This document clarifies the details.

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in .

This document reiterates the terminology defined in several ForCES documents , , , and for the sake of contextual clarity. Control Engine (CE) Forwarding Engine (FE) FE Model LFB (Logical Functional Block) Class (or type) LFB Instance LFB Model LFB Metadata ForCES Component LFB Component ForCES Protocol Layer (ForCES PL) ForCES Protocol Transport Mapping Layer (ForCES TML)

In this section we present sample use cases to illustrate each challenge being addressed.

Consider, for the sake of illustration, an FE table with 1 million reasonably sized table rows which are sparsely populated. Assume, again for the sake of illustration, that there are 2000 table rows sparsely populated between the row indices 23-10023. Implementation experience has shown that existing approaches for retrieving or deleting a sizable number of table rows to be both programmatically tedious and inefficient on utilization of both compute and wire resources. By Definition, ForCES GET and DEL requests sent from a controller (or control app) are prepended with a path to a component and sent to the FE. In the case of indexed tables, the component path can either point to a table or a table row index. As an example, a control application attempting to retrieve the first 2000 table rows appearing between row indices 23 and 10023 can achieve its goal in one of: Dump the whole table and filter for the needed 2000 table rows. Send upto 10000 ForCES PL requests, incrementing the index by one each time, and stop when the needed 2000 entries are retrieved. If the application had knowledge of which table rows existed (not unreasonable given the controller is supposed to be aware of state within an NE), then the application could take advantage of ForCES batching to send fewer large messages (each with different path entries for a total of two thousand). As argued, while the above options exist, all are tedious.

has defined a generic set of error codes that are to be returned to the CE from an FE. Deployment experience has shown that it would be useful to have more fine grained error codes. As an example, the error code E_NOT_SUPPORTED could be mapped to many FE error source possibilities that need to be then interpreted by the caller based on some understanding of the nature of the sent request. This makes debugging more time consuming.

This section describes normative update to the ForCES protocol for issues discussed in .

We define a new TLV, TABLERANGE-TLV (type ID 0x117) that will be associated with the PATH-DATA TLV in the same manner the KEYINFO-TLV is.

shows how this new TLV is constructed.

illustrates a GET request for a range of rows 11 to 23 of a table with component path of "1/6". Path flag of F_SELTABRANGE (0x2 i.e bit 1, where bit 0 is F_SELKEY as defined in RFC 5810) MUST be set to indicate the presence of the TABLERANGE-TLV. The pathflag bit F_SELTABRANGE can only be used in a GET or DEL and is mutually exclusive with F_SELKEY. The FE MUST enforce the path flag constraints and ensure that the selected path belongs to a defined indexed table component. Any violation of these constraints MUST be rejected with an error code of E_INVALID_TFLAGS with a description of what the problem is when using extended error reporting (refer to ). It should be noted that there are combination of path selection mechanisms that should not appear together for the sake of simplicity of operations. These include: TABLERANGE-TLV and KEYINFO-TLV as well as multiple nested TABLERANGE-TLVs. The TABLERANGE-TLV contents constitute: A 32 bit start index. An index of 0 implies the beginning of the table row. A 32 bit end index. A value of 0xFFFFFFFF implies the last entry. The response for a table range query will either be: The requested table data returned (when at least one referenced row is available); in such a case, a response with a path pointing to the table and whose data content contains the row(s) will be sent to the CE. The data content MUST be encapsulated in sparsedata TLV. The sparse data TLV content will have the "I" (in ILV) for each table row indicating the table indices. An EXTENDEDRESULT-TLV (refer to ) when: Response is to a range delete request. The Result will either be: A success if any of the requested-for rows is deleted A proper error code if none of the requested for rows can be deleted data is absent where the result code of E_EMPTY with an optional content string describing the nature of the error (refer to ). When both a path key and path table range are reflected on the the pathflags, an error code of E_INVALID_TFLAGS with an optional content string describing the nature of the error (refer to ). other standard ForCES errors (such as ACL constraints trying to retrieve contents of an unreadable table), accessing unknown components etc.

We define several things: A new set of error codes. Allocating some reserved codes for private use. A new TLV, EXTENDEDRESULT-TLV (0x118) that will carry a code (which will be a superset of what is currently specified in ) but also an optional cause content. This is illustrated in .

EXTENDEDRESULT-TLV Result Value is 32 bits and is a superset of RFC 5810 Result TLV Result Value. The new version code space is 32 bits as opposed to the RFC 5810 code size of 8 bits. The first 8 bit values(256 codes) are common to both code spaces. Code Mnemonic Details 0x18 E_TIMED_OUTA time out occured while processing the message 0x19 E_INVALID_TFLAGSInvalid table flags 0x1A E_INVALID_OPRequested operation is invalid 0x1B E_CONGEST_NTNode Congestion notification 0x1C E_COMPONENT_NOT_A_TABLEComponent not a table 0x1D E_PERMOperation not permitted 0x1E E_BUSYSystem is Busy 0x1F E_EMPTYTable is empty 0x20 E_UNKNOWNA generic catch all error code. Carries a string to further extrapolate what the error implies.

Codes 0x100-0x200 are reserved for use as private codes. Since these are freely available it is expected that the FE and CE side implementations will both understand/interpret the semantics of any used codes and avoid any conflicts.

Like all other ForCES TLVs, the EXTENDEDRESULT-TLV is expected to be 32 bit aligned. The EXTENDEDRESULT-TLV Result Value derives and extends from the same current namespace that is used by RESULT-TLV Result Value as specified in RFC 5810, section 7.1.7. The main difference is that we now have a 32 bit result value (as opposed to old 8 bit). The optional result content is defined to further disambiguate the result value. It is expected UTF-8 string values to be used. The content result value is intended to be consumed by the (human) operator and implementations may choose to specify different contents for the same error code. Additionally, future codes may specify cause contents to be of types other than string. It is recommended that the maximum size of the cause string should not exceed 32 bytes. The cause string is not standardized by this document.

To support backward compatibility, we update and the FEPO LFB (in ) version to 1.2. We also add a new component ID 16 (named EResultAdmin) and a capability Component ID 32 (named EResultCapab). An FE will advertise its capability to support extended TLVs via the EResultCapab table. When an FE is capable of responding with both extended results and older result TLVs, it will have two table rows one for each supported value. By default an FE capable of supporting both modes will assume the lowest common denominator i.e EResultAdmin will be EResultNotSupported; and will issue responses using RESULT-TLVs. It should be noted an FE advertising FEPO version 1.2 MUST support EXTENDEDRESULT-TLVs at minimum. On an FE which supports both RESULT-TLVs and EXTENDEDRESULT-TLVs, a master CE can turn on support for extended results by setting the EResultAdmin value to 2 in which case the FE MUST switch over to sending only EXTENDEDRESULT-TLVs. Likewise a master CE can turn off extended result responses by writing a 1 to the EResultAdmin. An FE that does not support one mode or other MUST reject setting of EResultAdmin to a value it does not support by responding with an error code of E_NOT_SUPPORTED. It is expected that all CEs participating in a high availability(HA) mode be capable of supporting FEPO version 1.2 whenever EResultAdmin is set to strict support of EXTENDEDRESULT-TLVs. The consensus between CEs in an HA setup to set strict support of EXTENDEDRESULT-TLVs is out of scope for this document.

Imagine a GET request to a path that is a table i.e a table dump. Such a request is sent to the FE with a specific correlator, say X. Imagine this table to have a large number of entries at the FE. For the sake of illustration, lets say millions of rows. This requires that the FE delivers the response over multiple messages, all using the same correlator X. The protocol document does not adequately describe how a large multi-part GET response message is delivered. The text in this section clarifies. We limit the discussion to a table object only. Implementation experience of dumping large tables indicates we can use the transaction flags to indicate that a GET response is the beginning, middle or end of a multi-part message. In other words we mirror the effect of an atomic transaction sent by a CE to an FE.

| | correlator = X | | | | (1) Query-Response, SOT,AT, OP=GET-RESPONSE, DATA | |<-----------------------------------------------------| | correlator = X | | DATA TLV (SPARSE/FULL) | | | | (2) Query-Response, MOT,AT, OP=GET-RESPONSE, DATA | |<-----------------------------------------------------| | correlator = X | | DATA TLV (SPARSE/FULL) | | | | (3) Query-Response, MOT,AT, OP=GET-RESPONSE, DATA | |<-----------------------------------------------------| | correlator = X | | DATA TLV (SPARSE/FULL) | . . . . . . . . | | | (N) Query-Response, MOT,AT, OP=GET-RESPONSE, DATA | |<-----------------------------------------------------| | correlator = X | | DATA TLV (SPARSE/FULL) | | | | (N) Query-Response, EOT,AT, OP=GET-RESPONSE | |<-----------------------------------------------------| | correlator = X | | RESULT TLV (SUCCESS) | | | ]]>

The last message to go to the CE, which carries the EOT flag, MUST NOT carry any data. This allows us to mirror ForCES 2PC messaging where the last message is an empty commit message. GET response will carry a result code TLV in such a case.

The author would like to thank Evangelos Haleplidis and Joel Halpern for discussions that made this document better. Adrian Farrel did an excellent AD review of the document which improved the quality of this document. Tobias Gondrom did the Security Directorate review. Brian Carpenter did the Gen-ART review. Nevil Brownlee performed the Operations Directorate review. S Moonesamy(SM) worked hard to review our publication process. Pearl Liang caught issues in the IANA specification. The author would like to thank the following IESG members who reviewed and improved this document: Alia Atlas, Barry Leiba, Brian Haberman, Kathleen Moriarty, Richard Barnes, and Spencer Dawkins.

This document registers two new top Level TLVs and two new path flags and updates an IANA registered FE Protocol object Logical Functional Block (LFB). The defines an update to the FE Protocol Object LFB to version 1.2. The IANA registry https://www.iana.org/assignments/forces sub-registy "Logical Functional Block (LFB) Class Names and Class Identifiers" will need to be append for FE Protocol Object LFB version 1.2 and this document reflected in the reference column. Updates are required to the "TLV types" subregistry for the TLVs below. The following new TLVs are defined: TABLERANGE-TLV (type ID 0x117) EXTENDEDRESULT-TLV (type ID 0x118) subregistry "RESULT-TLV Result Values" is affected by the entries below. The Defined RESULT-TLV Result Values are changed: codes 0x21-0xFE are unassigned. codes 0x18-0x20 are defined by this document in . codes 0x100-0x200 are reserved for private use. A new sub-registry for EXTENDEDRESULT-TLV Result Values needs to be created. The codes 0x00-0xff are mirrored from the RESULT-TLV Result Values sub-registry. Any new allocations of this code range (in the range 0x21-0xfe) must happen only within the new sub-registry and not in RESULT-TLV Result Values sub-registry. The codes 0x100-0x200 are reserved for private use as described earlier and the code ranges 0x21-0xfe and 0x201-0xffffffff should be marked as Unassigned with the IANA allocation policy of Specification Required . The Designated Expert (DE) needs to ensure existing deployments are not broken by any specified request. The DE should post a given code request to the ForCES WG mailing list (or a successor designated by the Area Director) for any comment and review. The DE should then either approve or deny the registration request, publish a notice of the decision to the ForCES WG mailing list or its successor, and inform IANA of his/her decision. A denial notice must be justified by an explanation and, in the cases where it is possible, concrete suggestions on how the request can be modified so as to become acceptable.

The security considerations that have been described in the ForCES protocol apply to this document as well.

&RFC2119; &RFC5810; &RFC5811; &RFC5812; &RFC7121; &RFC5226; &RFC3746;

This version of FEPO updates the earlier one given in RFC 7121. The xml has been validated against the schema defined in .

CEHBPolicyValues The possible values of CE heartbeat policy uchar CEHBPolicy0 The CE will send heartbeats to the FE every CEHDI timeout if no other messages have been sent since. CEHBPolicy1 The CE will not send heartbeats to the FE FEHBPolicyValues The possible values of FE heartbeat policy uchar FEHBPolicy0 The FE will not generate any heartbeats to the CE FEHBPolicy1 The FE generates heartbeats to the CE every FEHI if no other messages have been sent to the CE. FERestartPolicyValues The possible values of FE restart policy uchar FERestartPolicy0 The FE restarts its state from scratch HAModeValues The possible values of HA modes uchar NoHA The FE is not running in HA mode ColdStandby The FE is running in HA mode cold Standby HotStandby The FE is running in HA mode hot Standby CEFailoverPolicyValues The possible values of CE failover policy uchar CEFailoverPolicy0 The FE should stop functioning immediate and transition to the FE OperDisable state CEFailoverPolicy1 The FE should continue forwarding even without an associated CE for CEFTI. The FE goes to FE OperDisable when the CEFTI expires and no association. Requires graceful restart support. FEHACapab The supported HA features uchar GracefullRestart The FE supports Graceful Restart HA The FE supports HA CEStatusType Status values. Status for each CE uchar Disconnected No connection attempt with the CE yet Connected The FE connection with the CE at the TML has been completed Associated The FE has associated with the CE IsMaster The CE is the master (and associated) LostConnection The FE was associated with the CE but lost the connection Unreachable The CE is deemed as unreachable by the FE StatisticsType Statistics Definition RecvPackets Packets Received uint64 RecvErrPackets Packets Received from CE with errors uint64 RecvBytes Bytes Received from CE uint64 RecvErrBytes Bytes Received from CE in Error uint64 TxmitPackets Packets Transmitted to CE uint64 TxmitErrPackets Packets Transmitted to CE that incurred errors uint64 TxmitBytes Bytes Transmitted to CE uint64 TxmitErrBytes Bytes Transmitted to CE incurring errors uint64 AllCEType Table Type for AllCE component CEID ID of the CE uint32 Statistics Statistics per CE StatisticsType CEStatus Status of the CE CEStatusType ExtendedResultType Possible extended result support uchar EResultNotSupported Extended Results are not supported EResultSupported Extended Results are supported FEPO The FE Protocol Object, with EXtended Result control 1.2 CurrentRunningVersion Currently running ForCES version uchar FEID Unicast FEID uint32 MulticastFEIDs the table of all multicast IDs uint32 CEHBPolicy The CE Heartbeat Policy CEHBPolicyValues CEHDI The CE Heartbeat Dead Interval in millisecs uint32 FEHBPolicy The FE Heartbeat Policy FEHBPolicyValues FEHI The FE Heartbeat Interval in millisecs uint32 CEID The Primary CE this FE is associated with uint32 BackupCEs The table of all backup CEs other than the primary uint32 CEFailoverPolicy The CE Failover Policy CEFailoverPolicyValues CEFTI The CE Failover Timeout Interval in millisecs uint32 FERestartPolicy The FE Restart Policy FERestartPolicyValues LastCEID The Primary CE this FE was last associated with uint32 HAMode The HA mode used HAModeValues AllCEs The table of all CEs AllCEType EResultAdmin Turn Extended results off or on. default to off ExtendedResultType 1 SupportableVersions the table of ForCES versions that FE supports uchar HACapabilities the table of HA capabilities the FE supports FEHACapab EResultCapab the table of supported result capabilities ExtendedResultType PrimaryCEDown The primary CE has changed LastCEID LastCEID PrimaryCEChanged A New primary CE has been selected CEID CEID ]]>