rfc2127.txt
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signaling channel whose address is not TEI=127. ifOutNUcastPkts Deprecated. Return the number of frames transmitted on this signaling channel with TEI=127. ifOutMulticastPkts Return zero. ifOutBroadcastPkts Return the number of frames transmitted on this signaling channel with TEI=127.Roeck Standards Track [Page 13] RFC 2127 ISDN MIB March 1997 ifOutDiscards The total number of outbound frames which were discarded. Possible reasons are: buffer shortage. ifOutErrors The number of frames which could not be transmitted due to errors. ifOutQlen Deprecated. Return zero. ifSpecific Deprecated. Return {0 0}.3.3. Relationship to other MIBs3.3.1. Relationship to the DS1/E1 MIB Implementation of the DS1/E1 MIB [12] is not required for supporting this MIB. It is however recommended to implement the DS1/E1 MIB on entities supporting Primary Rate interfaces.3.3.2. Relationship to the DS0 and DS0Bundle MIBs Implementation of the DS0 MIB [13] is optional. Implementation of the DS0Bundle MIB [13] may be required only if hyperchannels are to be supported, depending on the multiplexing scheme used in a given implementation. See chapter 3.4.2 for details on how to implement hyperchannels.3.3.3. Relationship to the Dial Control MIB Implementation of the Dial Control MIB [15] is required.3.4. ISDN interface specific information and implementation hints3.4.1. ISDN leased lines ISDN leased lines can be specified on a per-B-channel basis. To do so, the value of isdnBearerChannelType has to be set to leased(2). There is no signaling protocol support for leased line B channels, since there is no signaling protocol action for these kinds of interfaces.Roeck Standards Track [Page 14] RFC 2127 ISDN MIB March 1997 If there is no signaling support available for an ISDN interface, this must be specified in the appropriate interface specific table. For Basic Rate interfaces, isdnBasicRateSignalMode of isdnBasicRateTable must be set to inactive(2). For Primary Rate interfaces, dsx1SignalMode of dsx1ConfigTable in DS1/E1 MIB [12] must be set to none(1). There are no isdnLapdTable or isdnSignalingTable entries for such interfaces. Depending on the leased line type and the service provider, the D channel can be used for data transfer. If this is the case the D channel interface type is ds0(81) instead of lapd(77) and its usage is identical to B channel usage if there is no signaling channel available. For a Primary Rate interface which is entirely used as a leased line, there is no ISDN specific information available or required. Such leased lines can entirely be handled by the DS1/E1 MIB.3.4.2. Hyperchannels The active switch protocol defines if hyperchannels are supported, and the actual support is implementation dependent. Hyperchannel connections will be requested by the interface user at call setup time, e.g. by the peer connection handling procedures. In the ISDN MIB, the isdnBearerMultirate object of isdnBearerTable can be used to check if hyperchannels are being used for an active call. If hyperchannels are being used, multiplexing between the encapsulation layer and the B channels is required, since there is one encapsulation layer interface connected to several B channel interfaces. This can be accomplished in two ways. o The DS0Bundle MIB [13] can be used to provide the multiplexing. See the DS0Bundle MIB document for details. o The ifStackTable can be used to provide the multiplexing. In this case, there are several ifStackTable entries with the same value of HigherLayer, and different values of LowerLayer. It is up to the implementor to decide which multiplexing scheme to use. Each hyperchannel call is treated as one call in the isdnSignalingStatsTable, independent of the number of B channels involved.Roeck Standards Track [Page 15] RFC 2127 ISDN MIB March 1997 For a hyperchannel call, all objects in the isdnBearerTable entries related to this call (i.e., all isdnBearerTable entries associated to B channels used by the hyperchannel) have identical values. The related objects in the isdnBearerTable are: isdnBearerPeerAddress isdnBearerPeerSubAddress isdnBearerCallOrigin isdnBearerInfoType isdnBearerMultirate isdnBearerCallSetupTime isdnBearerCallConnectTime isdnBearerChargedUnits3.4.3. D channel backup and NFAS trunks D channel backup is defined in Q.931 [8], Annex F. It describes Non- Associated signaling and its use and functionality is basically identical to Non Facility Associated Signaling (NFAS) trunks. Non Facility Accociated Signaling (NFAS) basically means that a D channel on a PRI interface is used to manage calls on other PRI trunks. This is required in North America for H11 channels, since all 24 time slots are being used for B channels. According to Q.931, Annex F, the D channel backup feature can be provided on a subscription basis and is network dependent. The D channel backup procedure is described in detail in Q.931. For D channel backup, the controlling isdnSignalingTable entry is layered on top of all attached LAPD interfaces. This layering is done using the ifStack table. There is only one active LAPD interface, however. Inactive LAPD interfaces have an ifOperStatus of dormant(5). NFAS trunks are also handled using the ifStack table. In this case, a signaling channel is layered on top of a LAPD interface as well as on top of all physical interfaces which are controlled by the signaling channel, but do not supply a D channel.3.4.4. X.25 based packet-mode service in B and D channels X.25 based packet mode service over B channels can be handled using the Dial Control MIB by creating an appropriate peer entry. The peer entry ifType can then be x25(5), thus providing access to X.25 service.Roeck Standards Track [Page 16] RFC 2127 ISDN MIB March 1997 X.25 based packet mode service over D channels can be handled by creating an ifEndpointTable entry with an isdnEndpointIfType of x25ple(40). The upper protocol layers can then be attached to this interface using the ifStack table.3.4.5. SPID handling Service Profile IDentifiers (SPIDs) are defined for BRI interfaces only, and being used in North America. SPIDs are required for DMS- 100, NI-1 and NI-2, and are optional for 5ESS. A switch can define up to 8 SPIDs per BRI. Each Terminal Endpoint has a SPID assigned. It is normally built from the party number (calling address for outgoing calls) with a number of digits prepended and appended. Since each network appears to be different, both the calling address and the SPID have to be stored. The SPID identifies the particular services that have been provisioned for a terminal. If there are two B channels on a BRI, there can be two SPIDs, one for each of the two B channels. There can also be a single SPID, providing access to both B channels. The SPID gets registered with the switch after link establishment. There is one data link for each SPID. As part of terminal registration, an EID (Endpoint IDentifier) is defined by the switch. On incoming calls, the switch may provide the EID, a called party number, or both, depending on the ISDN code implemented in the switch. The EID has two bytes: USID (User Service IDentifier) and TID (Terminal IDentifier). These are later used by some of the software versions running on the switch side (e.g. compliant with NI-1, 5ESS custom) to broadcast SETUP messages with these included, so the correct endpoint would accept the call. Other switch software versions identify the endpoint with the Called Party Number. In the ISDN MIB, the SPID can be entered using the isdnEndpointSpid object of isdnEndpointTable. The isdnSignalingCallingAddress, already being used to specify the calling number, cannot be used to record the SPID since the values of the SPID and the Calling Address may differ and both may be required to be present.3.4.6. Closed User Groups Closed User Groups (CUG), as defined in I.255.1 [14], are supported for circuit mode calls by ETSI (ETS 300 138) and 1TR6. In these networks, an ISDN address can have one or more Closed User GroupsRoeck Standards Track [Page 17] RFC 2127 ISDN MIB March 1997 assigned. If there is more than one Closed User Group assigned to a given address, one of those is the preferred Closed User Group. For such addresses, only calls from assigned Closed User Groups are accepted by the network. Thus, Closed User Groups are a parameter for peer entries and are defined in the Dial Control MIB. A peer entry attached to a Closed User Group has to point to an ISDN interface which is attached to the Closed User Group in question.3.4.7. Provision of point-to-point line topology In the ISDN standards, there are two different meanings for the term "point-to-point". In ISDN standards, the term point-to-point are usually used for data link connections, i.e. layer 2 connections, where each layer 2 connection from the TE to the network is a single point-to-point connection. Multiple connections of this kind may exist on one physical (layer 1) connection, however, and in case of Basic Rate interfaces there may be several TE's connected to one physical line to the network. The second meaning of "point-to-point" refers to the line topology, i.e. to layer 1 connections. For Primary Rate interfaces, the line topology is always point-to-point. For Basic Rate interfaces, layer 1 point-to- point connections do exist in several countries, usually being used for connecting PBX systems to the network. The second meaning (layer 1 connections) is what will be referred to as "point-to-point" connection throughout this document. For Basic Rate interfaces, the isdnBasicRateTable object isdnBasicRateLineTopology can be used to select the line topology.3.4.8. Speech and audio bearer capability information elements The objects speech(2), audio31(6) and audio7(7), as being used in isdnBearerInfoType, refer to the Speech, 3.1 kHz Audio and old 7 kHz Audio (now Multi-use) bearer capabilities for ISDN, as defined in Q.931 [8], chapter 4.5.5, octet 3 of bearer capability information element. These capabilities are signaling artifices that allow networks to do certain things with the call. It is up to the network to decide what to do.Roeck Standards Track [Page 18] RFC 2127 ISDN MIB March 1997 The Speech Bearer Capability means that speech is being carried over the channel, as in two people talking. This would be POTS-type speech. The network may compress this, encrypt it or whatever it wants with it as long as it delivers POTS quality speech to the other end. In other words, a modem is not guaranteed to work over this connection. The 3.1 kHz Audio capability indicates that the network carries the 3.1 kHz bandwidth across the network. This would (theoretically) allow modem signals to be carried across the network. In the US, the network automatically enters a capability of 3.1 kHz Audio on calls coming into the ISDN from a POTS network. This capability restricts the network from interfering with the data channel in a way that would corrupt the 3.1 kHz VoiceBand data. 7 kHz Audio was meant to signal the use of a higher quality audio connection (e.g., music from radio). It was changed to Multi-Use capability to allow it to be used for video-conferencing with fall back to audio. In some cases, the Speech or 3.1 kHz Bearer Capability provides a 56 kbit/s data path through the network. Therefore, some people are setting up calls with the Speech or 3.1 kHz BC and transmitting 56 kbit/s data over the connection. This is usually to take advantage of favorable tariffs for Speech as opposed to Data. On the incoming side, the equipment is usually configured to ignore the Bearer Capability and either answer all Speech calls as 56 kbit/s data or to use one Directory Number for real speech and another for data.3.4.9. Attaching incoming calls to router ports In ISDN, there are several ways to identify an incoming call and to attach a router port to this call. o The call can be identified and attached to a router port using the ISDN Calling Address, that is, the peer ISDN address. Since the peer address is defined in a Dial Control MIB configuration entry for this peer, this would be the most natural way to attach an incoming call to a router port. In this configuration, only a single isdnSignalingTable entry is required for each physical ISDN interface. Unfortunately, the ISDN Calling Address is not available in all countries and/or switch protocols. Therefore, other means for attaching incoming calls to router ports must be provided.Roeck Standards Track [Page 19] RFC 2127 ISDN MIB March 1997⌨️ 快捷键说明
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