Network Working Group O. Nicklass, Ed. Request for Comments: 3896 RAD Data Communications, Ltd. Obsoletes: 2496 September 2004 Category: Standards Track Definitions of Managed Objects for the DS3/E3 Interface Type Status of this Memo This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited. Copyright Notice Copyright (C) The Internet Society (2004).
AbstractThis memo defines a portion of the Management Information Base (MIB) for use with network management protocols in the Internet community. In particular, it describes objects used for managing DS3 and E3 interfaces. This document is a companion to the documents that define Managed Objects for the DS0, DS1/E1/DS2/E2 and Synchronous Optical Network/Synchronous Digital Hierarchy (SONET/SDH) Interface Types. This document obsoletes RFC 2496. 1. The Internet Standard Management Framework. . . . . . . . . . 2 1.1. Changes from RFC 2496 . . . . . . . . . . . . . . . . . 2 1.2. Changes from RFC 1407 . . . . . . . . . . . . . . . . . 3 1.3. Companion Documents . . . . . . . . . . . . . . . . . . 4 2. Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.1. Use of ifTable for DS3 Layer . . . . . . . . . . . . . 4 2.2. Usage Guidelines. . . . . . . . . . . . . . . . . . . . 5 2.2.1. Usage of ifStackTable . . . . . . . . . . . . . 5 2.2.2. Usage of Channelization for DS3, DS1, DS0 . . . 7 2.2.3. Usage of Channelization for DS3, DS2, DS1 . . . 8 2.2.4. Usage of Loopbacks . . . . . . . . . . . . . . 9 2.3. Objectives of this MIB Module . . . . . . . . . . . . . 10 2.4. DS3/E3 Terminology . . . . . . . . . . . . . . . . . . 10 2.4.1. Error Events. . . . . . . . . . . . . . . . . . 10 2.4.2. Performance Parameters. . . . . . . . . . . . . 11 2.4.3. Performance Defects . . . . . . . . . . . . . . 14
2.4.4. Other Terms . . . . . . . . . . . . . . . . . . 16 3. Object Definitions . . . . . . . . . . . . . . . . . . . . . . 16 4. Appendix A - Use of the dsx3IfIndex and dsx3LineIndex. . . . . 54 5. Appendix B - The delay approach to Unavailable Seconds . . . . 56 6. Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . . 58 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 58 7.1. Normative References . . . . . . . . . . . . . . . . . . 58 7.2. Informative References . . . . . . . . . . . . . . . . . 59 8. Security Considerations. . . . . . . . . . . . . . . . . . . . 60 9. Author's Address . . . . . . . . . . . . . . . . . . . . . . . 62 10. Full Copyright Statement . . . . . . . . . . . . . . . . . . . 63 section 7 of RFC 3410 [RFC3410]. Managed objects are accessed via a virtual information store, termed the Management Information Base or MIB. MIB objects are generally accessed through the Simple Network Management Protocol (SNMP). Objects in the MIB are defined using the mechanisms defined in the Structure of Management Information (SMI). This memo specifies a MIB module that is compliant to the SMIv2, which is described in STD 58, RFC 2578 [RFC2578], STD 58, RFC 2579 [RFC2579] and STD 58, RFC 2580 [RFC2580]. RFC2496] are the following: (1) The dsx3FracIfIndex SYNTAX matches the description range. (2) Reference was added to Circuit Identifier object. (3) Usage of ifStackTable section was updated. (4) Align the DESCRIPTION clauses of few statistic objects with the near end definition, the far end definition and with [RFC3593]. (5) Add new value, dsx3M13, to dsx3LineType.
RFC 1407 are the following: (1) The Fractional Table has been deprecated. (2) This document uses SMIv2. (3) Values are given for ifTable and ifXTable. (4) Example usage of ifStackTable is included. (5) dsx3IfIndex has been deprecated. (6) The definition of valid intervals has been clarified for the case where the agent proxied for other devices. In particular, the treatment of missing intervals has been clarified. (7) An inward loopback has been added. (8) Additional lineStatus bits have been added for Near End in Unavailable Signal State, Carrier Equipment Out of Service. (9) A read-write line Length object has been added. (10) Added a lineStatus last change, trap and enabler. (11) Textual Conventions for statistics objects have been used. (12) A new object, dsx3LoopbackStatus, has been introduced to reflect the loopbacks established on a DS3/E3 interface and the source to the requests. dsx3LoopbackConfig continues to be the desired loopback state while dsx3LoopbackStatus reflects the actual state. (13) A dual loopback has been added to allow the setting of an inward loopback and a line loopback at the same time. (14) An object has been added to indicated whether or not this is a channelized DS3/E3. (15) A new object has been added to indicate which DS1 is to set for remote loopback.
RFC2494], DS1/E1/DS2/E2 [RFC3895], and Synchronous Optical Network/Synchronous Digital Hierarchy (SONET/SDH) [RFC3592] Interface Types. ANSI-T1.102], ANSI T1.107-1988 [ANSI-T1.107], ANSI T1.107a-1990 [ANSI-T1.107a], and ANSI T1.404-1989 [ANSI-T1.404]. The E3 definitions contained herein are based on the E3 specifications in CCITT G.751 [CCITT-G.751] and ETSI T/NA(91)18 [ETSI-T/NA(91)18]. RFC2863] ifType ds3(30) ifSpeed Speed of line rate DS3 - 44736000 E3 - 34368000 ifPhysAddress The value of the Circuit Identifier. If no Circuit Identifier has been assigned this object should have an octet string with zero length. ifAdminStatus See interfaces MIB [RFC2863] ifOperStatus See interfaces MIB [RFC2863] ifLastChange See interfaces MIB [RFC2863]
ifName See interfaces MIB [RFC2863] ifLinkUpDownTrapEnable Set to enabled(1). ifHighSpeed Speed of line in Mega-bits per second (either 45 or 34) ifConnectorPresent Set to true(1) normally, except for cases such as DS3/E3 over AAL1/ATM where false(2) is appropriate Appendix A for informational purposes. The ifStackTable is used in the proxy case to represent the association between pairs of interfaces, e.g., this DS3 is attached to that DS3. This use is consistent with the use of the ifStackTable to show the association between various sub-layers of an interface. In both cases entire PDUs are exchanged between the interface pairs - in the case of a DS3, entire DS3 frames are exchanged; in the case of PPP and HDLC, entire HDLC frames are exchanged. This usage is not meant to suggest the use of the ifStackTable to represent Time Division Multiplexing (TDM) connections in general. External&Internal interface scenario: the SNMP Agent resides on a host external from the device supporting DS3/E3 interfaces (e.g., a router). The Agent represents both the host and the DS3/E3 device.
Example: A shelf full of CSUs connected to a Router. An SNMP Agent residing on the router proxies for itself and the CSU. The router has also an Ethernet interface: +-----+ | | | | | | +---------------------+ |E | | 44.736 MBPS | ds3 M13 Line#A | ds3 C-bit Parity |t | R |---------------+ - - - - - - - - - +------> |h | | | | |e | O | 44.736 MBPS | ds3 M13 Line#B | ds3 C-bit Parity |r | |---------------+ - - - - - - - - - - +------> |n | U | | | |e | | 44.736 MBPS | ds3 M13 Line#C | ds3 C-bit Parity |t | T |---------------+ - - - -- -- - - - - +------> | | | | | |-----| E | 44.736 MBPS | ds3 M13 Line#D | ds3 C-bit Parity | | |---------------+ - - - - -- - - - - +------> | | R | |_____________________| | | | | +-----+ The assignment of the index values could for example be: ifIndex Description 1 Ethernet 2 Line#A Router 3 Line#B Router 4 Line#C Router 5 Line#D Router 6 Line#A CSU Router 7 Line#B CSU Router 8 Line#C CSU Router 9 Line#D CSU Router 10 Line#A CSU Network 11 Line#B CSU Network 12 Line#C CSU Network 13 Line#D CSU Network
The ifStackTable is then used to show the relationships between the various DS3 interfaces. ifStackTable Entries HigherLayer LowerLayer 2 6 3 7 4 8 5 9 6 10 7 11 8 12 9 13 If the CSU shelf is managed by itself by a local SNMP Agent, the situation would be identical, except the Ethernet and the 4 router interfaces are deleted. Interfaces would also be numbered from 1 to 8. ifIndex Description 1 Line#A CSU Router 2 Line#B CSU Router 3 Line#C CSU Router 4 Line#D CSU Router 5 Line#A CSU Network 6 Line#B CSU Network 7 Line#C CSU Network 8 Line#D CSU Network ifStackTable Entries HigherLayer LowerLayer 1 5 2 6 3 7 4 8
Assume that a DS3 (with ifIndex 1) is Channelized into DS1s (without DS2s). The object dsx3Channelization is set to enabledDs1. When this object is set to enabledDS1, 28 ifEntries of type DS1 will be created by the agent. If dsx3Channelization is set to disabled, then the DS1s are destroyed. Assume the entries in the ifTable for the DS1s are created in channel order and the ifIndex values are 2 through 29. In the DS1 MIB, there will be an entry in the dsx1ChanMappingTable for each ds1. The entries will be as follows: dsx1ChanMappingTable Entries ifIndex dsx1Ds1ChannelNumber dsx1ChanMappedIfIndex 1 1 2 1 2 3 ...... 1 28 29 In addition, the DS1s are channelized into DS0s. The object dsx1Channelization is set to enabledDS0 for each DS1. There will be 24 DS0s in the ifTable for each DS1. Assume the entries in the ifTable are created in channel order and the ifIndex values for the DS0s in the first DS1 are 30 through 53. In the DS0 MIB [RFC2494], there will be an entry in the dsx0ChanMappingTable for each DS0. The entries will be as follows: dsx0ChanMappingTable Entries ifIndex dsx0Ds0ChannelNumber dsx0ChanMappedIfIndex 2 1 30 2 2 31 ...... 2 24 53 RFC3895], there will be an entry in the dsx1ChanMappingTable for each DS2. The entries will be as follows:
dsx1ChanMappingTable Entries ifIndex dsx1Ds1ChannelNumber dsx1ChanMappedIfIndex 1 1 2 1 2 3 ...... 1 7 8 In addition, the DS2s are channelized into DS1s. The object dsx1Channelization is set to enabledDS1 for each DS2. There will be 4 DS1s in the ifTable for each DS2. Assume the entries in the ifTable are created in channel order and the ifIndex values for the DS1s in the first DS2 are 9 through 12, then 13 through 16 for the second DS2, and so on. In the DS1 MIB, there will be an entry in the dsx1ChanMappingTable for each DS1. The entries will be as follows: dsx1ChanMappingTable Entries ifIndex dsx1Ds1ChannelNumber dsx1ChanMappedIfIndex 2 1 9 2 2 10 2 3 11 2 4 12 3 1 13 3 2 14 ... 8 4 36
To model the current state of loopbacks on a DS3 interface, the object dsx3LoopbackStatus defines which loopback is currently applied to an interface. This object, which is a bitmap, will have bits turned on which reflect the currently active loopbacks on the interface as well as the source of those loopbacks. The following restrictions/rules apply to loopbacks: The far end cannot undo loopbacks set by a manager. A manager can undo loopbacks set by the far end. Both a line loopback and an inward loopback can be set at the same time. Only these two loopbacks can co-exist and either one may be set by the manager or the far end. A LineLoopback request from the far end is incremental to an existing Inward loopback established by a manager. When a NoLoopback is received from the far end in this case, the InwardLoopback remains in place. ANSI- T1.231]. If the definition in this document does not match the definition in the ANSI T1.231 document, the implementer should follow the definition described in this document.
Excessive Zeros (EXZ) Error Event An EXZ is the occurrence of any zero string length equal to or greater than 3 for B3ZS, or greater than 4 for HDB3 (See T1.231 section 220.127.116.11.2). Line Coding Violation (LCV) Error Event This parameter is a count of both BPVs and EXZs occurring over the accumulation period. An EXZ increments the LCV by one regardless of the length of the zero string. (Also known as CV-L. See T1.231 section 18.104.22.168.) P-bit Coding Violation (PCV) Error Event For all DS3 applications, a coding violation error event is a P-bit Parity Error event. A P-bit Parity Error event is the occurrence of a received P-bit code on the DS3 M-frame that is not identical to the corresponding locally-calculated code (See T1.231 section 22.214.171.124.1). C-bit Coding Violation (CCV) Error Event For C-bit Parity and SYNTRAN DS3 applications, this is the count of coding violations reported via the C-bits. For C-bit Parity, it is a count of CP-bit parity errors occurring in the accumulation interval. For SYNTRAN, it is a count of CRC-9 errors occurring in the accumulation interval (See T1.231 section 126.96.36.199.2).
Line Errored Seconds (LES) A Line Errored Second is a second in which one or more CV occurred OR one or more LOS defects. (Also known as ES-L. See T1.231 section 188.8.131.52.) P-bit Errored Seconds (PES) An PES is a second with one or more PCVs OR one or more Out of Frame defects OR a detected incoming AIS. This gauge is not incremented when UASs are counted. (Also known as ESP-P. See T1.231 section 184.108.40.206.) P-bit Severely Errored Seconds (PSES) A PSES is a second with 44 or more PCVs OR one or more Out of Frame defects OR a detected incoming AIS. This gauge is not incremented when UASs are counted. (Also known as SESP-P. See T1.231 section 220.127.116.11.) C-bit Errored Seconds (CES) An CES is a second with one or more CCVs OR one or more Out of Frame defects OR a detected incoming AIS. This count is only for the SYNTRAN and C-bit Parity DS3 applications. This gauge is not incremented when UASs are counted. (Also known as ESCP-P. See T1.231 section 18.104.22.168.) C-bit Severely Errored Seconds (CSES) A CSES is a second with 44 or more CCVs OR one or more Out of Frame defects OR a detected incoming AIS. This count is only for the SYNTRAN and C-bit Parity DS3 applications. This gauge is not incremented when UASs are counted. (Also known as SESCP-P. See T1.231 section 22.214.171.124.) Severely Errored Framing Seconds (SEFS) A SEFS is a second with one or more Out of Frame defects OR a detected incoming AIS. This item is not incremented during unavailable seconds. (Also known as SAS-P. See T1.231 section 126.96.36.199.) Unavailable Seconds (UAS) UAS are calculated by counting the number of seconds that the interface is unavailable. The DS3 interface is said to be unavailable from the onset of 10 contiguous PSESs, or the onset of the condition leading to a failure (see Failure States). If the condition leading to the failure was immediately preceded by one or more contiguous PSESs, then the DS3 interface unavailability starts from the onset of these PSESs. Once unavailable, and if no failure is present, the DS3 interface becomes available at the onset of 10 contiguous seconds with no PSESs. Once unavailable, and if a
failure is present, the DS3 interface becomes available at the onset of 10 contiguous seconds with no PSESs, if the failure clearing time is less than or equal to 10 seconds. If the failure clearing time is more than 10 seconds, the DS3 interface becomes available at the onset of 10 contiguous seconds with no PSESs, or the onset period leading to the successful clearing condition, whichever occurs later. With respect to the DS3 error counts, all counters are incremented while the DS3 interface is deemed available. While the interface is deemed unavailable, the only count that is incremented is UASs. Note that this definition implies that the agent cannot determine until after a ten second interval has passed whether a given one-second interval belongs to available or unavailable time. If the agent chooses to update the various performance statistics in real time then it must be prepared to retroactively reduce the PES, PSES, CES, and CSES counts by 10 and increase the UAS count by 10 when it determines that available time has been entered. It must also be prepared to adjust the PCV, CCV, and SEFS count as necessary since these parameters are not accumulated during unavailable time. Similarly, it must be prepared to retroactively decrease the UAS count by 10 and increase the PES, CES, PCV, and CCV counts as necessary upon entering available time. A special case exists when the 10 second period leading to available or unavailable time crosses a 900 second statistics window boundary, as the foregoing description implies that the PCV, CCV, PES, CES, PSES, CSEC, SEFS, and UAS counts for the PREVIOUS interval must be adjusted. In this case successive GETs of the affected dsx3IntervalPSESs and dsx3IntervalUASs objects will return differing values if the first GET occurs during the first few seconds of the window. The agent may instead choose to delay updates to the various statistics by 10 seconds in order to avoid retroactive adjustments to the counters. A way to do this is sketched in Appendix B. In any case, a linkDown trap shall be sent only after the agent has determined for certain that the unavailable state has been entered, but the time on the trap will be that of the first UAS (i.e., 10 seconds earlier). A linkUp trap shall be handled similarly. According to [ANSI-T1.231] unavailable time begins at the _onset_ of 10 contiguous severely errored seconds -- that is, unavailable time starts with the _first_ of the 10 contiguous SESs. Also, while an interface is deemed unavailable all counters for that interface are
frozen except for the UAS count. It follows that an implementation which strictly complies with this standard must _not_ increment any counters other than the UAS count -- even temporarily -- as a result of anything that happens during those 10 seconds. Since changes in the signal state lag the data to which they apply by 10 seconds, an ANSI-compliant implementation must pass the one-second statistics through a 10-second delay line prior to updating any counters. That can be done by performing the following steps at the end of each one second interval. i) Read near/far end CV counter and alarm status flags from the hardware. ii) Accumulate the CV counts for the preceding second and compare them to the ES and SES threshold for the layer in question. Update the signal state and shift the one-second CV counts and ES/SES flags into the 10-element delay line. Note that far-end one-second statistics are to be flagged as "absent" during any second in which there is an incoming defect at the layer in question or at any lower layer. iii) Update the current interval statistics using the signal state from the _previous_ update cycle and the one-second CV counts and ES/SES flags shifted out of the 10-element delay line. This approach is further described in Appendix B. ANSI- T1.107a]. The Remote Alarm Indication failure, in C-bit Parity DS3 applications, is declared as soon as the presence of either one or two alarm signals are detected on the Far End Alarm Channel. See [ANSI-T1.107]. The Remote Alarm Indication failure may also be declared after detecting the far-end SEF/AIS defect (aka yellow). The Remote Alarm Indication failure is cleared as soon as the presence of the any of the above alarms are removed. Also, the incoming failure state is declared when a defect persists for at least 2-10 seconds. The defects are the following: Loss of Signal (LOS), an Out of Frame (OOF) or an incoming Alarm Indication Signal (AIS). The Failure State is cleared when the defect is absent for less than or equal to 20 seconds.
Far End SEF/AIS defect (aka yellow) A Far End SEF/AIS defect is the occurrence of the two X-bits in a M-frame set to zero. The Far End SEF/AIS defect is terminated when the two X-bits in a M-frame are set to one. (Also known as SASCP-PFE. See T1.231 section 188.8.131.52.6) Out of Frame (OOF) defect A DS3 OOF defect is detected when any three or more errors in sixteen or fewer consecutive F-bits occur within a DS3 M- frame. An OOF defect may also be called a Severely Errored Frame (SEF) defect. An OOF defect is cleared when reframe occurs. A DS3 Loss of Frame (LOF) failure is declared when the DS3 OOF defect is consistent for 2 to 10 seconds. The DS3 OOF defect ends when reframe occurs. The DS3 LOF failure is cleared when the DS3 OOF defect is absent for 10 to 20 seconds. (See T1.231 section 184.108.40.206.1) An E3 OOF defect is detected when four consecutive frame alignment signals have been incorrectly received in there predicted positions in an E3 signal. E3 frame alignment occurs when the presence of three consecutive frame alignment signals have been detected. Loss of Signal (LOS) defect The DS3 LOS defect is declared upon observing 175 +/- 75 contiguous pulse positions with no pulses of either positive or negative polarity. The DS3 LOS defect is terminated upon observing an average pulse density of at least 33% over a period of 175 +/- 75 contiguous pulse positions starting with the receipt of a pulse. (See T1.231 section 220.127.116.11.1) Alarm Indication Signal (AIS) defect The DS3 AIS is framed with "stuck stuffing." This implies that it has a valid M-subframe alignments bits, M-frame alignment bits, and P bits. The information bits are set to a 1010... sequence, starting with a one (1) after each M- subframe alignment bit, M-frame alignment bit, X bit, P bit, and C bit. The C bits are all set to zero giving what is called "stuck stuffing." The X bits are set to one. The DS3 AIS defect is declared after DS3 AIS is present in contiguous M-frames for a time equal to or greater than T, where 0.2 ms <= T <= 100 ms. The DS3 AIS defect is terminated after AIS is absent in contiguous M-frames for a time equal to or greater than T. (See T1.231 section 18.104.22.168.3)
The E3 binary content of the AIS is nominally a continuous stream of ones. AIS detection and the application of consequent actions, should be completed within a time limit of 1 ms. ITU-T-M.1400] for additional information). Proxy In this document, the word proxy is meant to indicate an application which receives SNMP messages and replies to them on behalf of the devices which implement the actual DS3/E3 interfaces. The proxy may have already collected the information about the DS3/E3 interfaces into its local database and may not necessarily forward the requests to the actual DS3/E3 interface. It is expected in such an application that there are periods of time where the proxy is not communicating with the DS3/E3 interfaces. In these instances the proxy will not necessarily have up-to-date configuration information and will most likely have missed the collection of some statistics data. Missed statistics data collection will result in invalid data in the interval table.