ROHC-RTP-MIB

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Organization: IETF Robust Header Compression Working Group

Last Updated: 2004-06-03

Category: Header Compression, Telephony and VoIP

Description: Defines managed objects specific to the ROHC RTP, UDP, ESP, and Link Layer Assisted compression profiles.

IPNetwork Monitor uses several OIDs from this MIB in network discovery and polling the applicable devices. Start monitoring ROHC-RTP-MIB with a free 30-day trial of IPNetwork Monitor.

What Is ROHC-RTP-MIB?

ROHC-RTP-MIB is a vendor-neutral IETF standards-track MIB (RFC 3816) defining managed objects for RObust Header Compression (ROHC), a technique used on constrained/wireless links to compress RTP, UDP, ESP, and Link Layer Assisted protocol headers per RFC 3095 and RFC 3242. It exposes per-compression-context configuration and state, including context mode, padding behavior, packet size negotiation, and verification period, alongside runtime counters for acknowledgment traffic (ACKs, NACKs, and segment NACKs) exchanged between compressor and decompressor. Its monitoring value is centered on software-level compression-session health: tracking whether a ROHC context remains in a healthy state, whether negotiated packet sizes are being respected, and whether NACK/SNACK counts are rising (indicating decompression failures or context desynchronization) rather than any physical hardware sensor. It is explicitly defined against and dependent on RFC 3095 (ROHC framework) and RFC 3242 (LLA profile), which specify the compression profiles this MIB monitors. It is typically deployed on mobile/wireless gateway and router equipment (e.g., cellular access routers) that perform header compression to conserve bandwidth over radio links, consistent with the ROHC-RTP-MIB RFC (RFC 3816) it implements.

IPNetwork Monitor allows you to monitor SNMP objects defined in ROHC-RTP-MIB. Use the built-in SNMP Monitoring Browser to explore available variables, view their current values and descriptions, and select the objects you want to monitor. You can then create SNMP monitors, configure thresholds, and receive alerts when monitored values change.

Supported Devices

vendor-neutral, standards-based MIB, not tied to a specific manufacturer
cellular/mobile access router or gateway performing header compression

Monitoring Examples

An operator would poll rohcRtpContextTable entries -- rohcRtpContextState and rohcRtpContextMode -- to confirm a given compression context is operating normally, and watch rohcRtpContextNACKs and rohcRtpContextSNACKs for a rising count, which indicates the decompressor is repeatedly failing to reconstruct headers and requesting context updates. A high NACK rate combined with rohcRtpContextVerifyPeriod misalignment would point to a link-quality or configuration problem degrading the ROHC session's compression efficiency.

What Can Be Monitored

ROHC context state
context mode
negotiated/allowed packet sizes
ACK/NACK/SNACK counts
context verify period

Imported Objects

From ROHC-MIB

rohcChannelID	OBJECT-TYPE
rohcContextCID	OBJECT-TYPE

From SNMPv2-CONF

MODULE-COMPLIANCE
OBJECT-GROUP

From SNMPv2-SMI

Counter32
MODULE-IDENTITY
OBJECT-TYPE
Unsigned32
mib-2

From SNMPv2-TC

TruthValue

How to Use in IPNetwork Monitor

Example using rohcRtpContextACKs OID:

Select a device implementing ROHC-RTP-MIB as the target host to create a monitor — the SNMP service should be up and running on it. Click New Monitor, then check SNMP Custom on the Favorites tab, click Next, and confirm the host. On the next page, click Select... to open the built-in SNMP MIB Browser and type rohcRtpContextACKs into the Find box to locate it in the OID tree, selecting the specific row/instance you want to monitor since this is a table column, then select it and click OK. The number of all positive feedbacks (ACK) sent or received in this context, respectively. On the monitor's Main parameters page you can set the target's SNMP port (default 161), credentials, polling interval, and other settings — see the SNMP Monitor help for details. On the State conditions and Alerting tabs, configure when the monitor should change state and trigger an alert; since this is a Counter32-type OID, Value bounds is the most useful condition here — trigger an alert if the counter increases sharply between polls relative to its normal baseline, since an unexpected spike often reflects a real change in traffic or activity. Click Finish to create the monitor; you can adjust any parameter later.

OIDs

OID symbolic	OID numeric	Type	Access	Description
rohcRtpMIB	1.3.6.1.2.1.114			This MIB module defines a set of objects for monitoring and configuring RObust Header Compression (ROHC). The objects are specific to ROHC RTP (profile 0x0001), ROHC UDP (profile 0x0002), and ROHC ESP (profile 0x0003) defined in RFC 3095 and for the ROHC LLA profile (profile 0x0005) defined in RFC 3242. Copyright (C) The Internet Society (2004). The initial version of this MIB module was published in RFC 3816. For full legal notices see the RFC itself or see: http://www.ietf.org/copyrights/ianamib.html
rohcRtpObjects	1.3.6.1.2.1.114.1
rohcRtpContextTable	1.3.6.1.2.1.114.1.1		not-accessible	This table lists and describes RTP profile specific properties of compressor contexts and decompressor contexts. It extends the rohcContextTable of the ROHC-MIB module.
rohcRtpContextEntry	1.3.6.1.2.1.114.1.1.1		not-accessible	An entry describing a particular context.
INT rohcRtpContextState	1.3.6.1.2.1.114.1.1.1.3	INTEGER	read-only	State of the context as defined in RFC 3095. States initAndRefresh(1), firstOrder(2), and secondOrder(3) are states of compressor contexts, states noContext(4), staticContext(5) and fullContext(6) are states of decompressor contexts.
INT rohcRtpContextMode	1.3.6.1.2.1.114.1.1.1.4	INTEGER	read-only	Mode of the context.
T/F rohcRtpContextAlwaysPad	1.3.6.1.2.1.114.1.1.1.5	TruthValue	read-only	Boolean, only applicable to compressor contexts using the LLA profile. If its value is true, the compressor must pad every RHP packet with a minimum of one octet ROHC padding. The value of this object is only valid for LLA profiles, i.e., if the corresponding rohcProfile has a value of 0x0005. If the corresponding rohcProfile has a value other than 0x0005, then this object MUST NOT be instantiated.
T/F rohcRtpContextLargePktsAllowed	1.3.6.1.2.1.114.1.1.1.6	TruthValue	read-only	Boolean, only applicable to compressor contexts using the LLA profile. It specifies how to handle packets that do not fit any of the preferred packet sizes specified. If its value is true, the compressor must deliver the larger packet as-is and must not use segmentation. If it is set to false, the ROHC segmentation scheme must be used to split the packet into two or more segments, and each segment must further be padded to fit one of the preferred packet sizes. The value of this object is only valid for LLA profiles, i.e., if the corresponding rohcProfile has a value of 0x0005. If the corresponding rohcProfile has a value other than 0x0005, then this object MUST NOT be instantiated.
U32 rohcRtpContextVerifyPeriod	1.3.6.1.2.1.114.1.1.1.7	Unsigned32	read-only	This object is only applicable to compressor contexts using the LLA profile. It specifies the minimum frequency with which a packet validating the context must be sent. This tells the compressor that a packet containing a CRC field must be sent at least once every N packets, where N is the value of the object. A value of 0 indicates that periodical verifications are disabled. The value of this object is only valid for LLA profiles, i.e., if the corresponding rohcProfile has a value of 0x0005. If the corresponding rohcProfile has a value other than 0x0005, then this object MUST NOT be instantiated.
U32 rohcRtpContextSizesAllowed	1.3.6.1.2.1.114.1.1.1.8	Unsigned32	read-only	The value of this object is only valid for decompressor contexts, i.e., if rohcInstanceType of the corresponding rohcContextEntry has the value decompressor(2). For compressor contexts where rohcInstanceType has the value compressor(1), this object MUST NOT be instantiated. This object contains the number of different packet sizes that may be used in the context.
U32 rohcRtpContextSizesUsed	1.3.6.1.2.1.114.1.1.1.9	Unsigned32	read-only	The value of this object is only valid for decompressor contexts, i.e., if rohcInstanceType of the corresponding rohcContextEntry has the value decompressor(2). For compressor contexts where rohcInstanceType has the value compressor(1), this object MUST NOT be instantiated. This object contains the number of different packet sizes that are used in the context.
C32 rohcRtpContextACKsEx	1.3.6.1.2.1.114.1.1.1.10	Counter32	read-only	The number of all positive feedbacks (ACK) sent or received in this context, respectively. Discontinuities in the value of this counter can occur at re-initialization of the management system, and at other times as indicated by the value of ifCounterDiscontinuityTime. For checking ifCounterDiscontinuityTime, the interface index is required. It can be determined by reading the rohcChannelTable of the ROHC-MIB.
C32 rohcRtpContextNACKs	1.3.6.1.2.1.114.1.1.1.11	Counter32	read-only	The number of all dynamic negative feedbacks (ACK) sent or received in this context, respectively. Discontinuities in the value of this counter can occur at re-initialization of the management system, and at other times as indicated by the value of ifCounterDiscontinuityTime. For checking ifCounterDiscontinuityTime, the interface index is required. It can be determined by reading the rohcChannelTable of the ROHC-MIB.
C32 rohcRtpContextSNACKs	1.3.6.1.2.1.114.1.1.1.12	Counter32	read-only	The number of all static negative feedbacks (ACK) sent or received in this context, respectively. Discontinuities in the value of this counter can occur at re-initialization of the management system, and at other times as indicated by the value of ifCounterDiscontinuityTime. For checking ifCounterDiscontinuityTime, the interface index is required. It can be determined by reading the rohcChannelTable of the ROHC-MIB.
C32 rohcRtpContextNHPs	1.3.6.1.2.1.114.1.1.1.13	Counter32	read-only	This object is only applicable to contexts using the LLA profile. It contains the number of all no-header packets (NHP) sent or received in this context, respectively. Discontinuities in the value of this counter can occur at re-initialization of the management system, and at other times as indicated by the value of ifCounterDiscontinuityTime. For checking ifCounterDiscontinuityTime, the interface index is required. It can be determined by reading the rohcChannelTable of the ROHC-MIB. The value of this object is only valid for LLA profiles, i.e., if the corresponding rohcProfile has a value of 0x0005. If the corresponding rohcProfile has a value other than 0x0005, then this object MUST NOT be instantiated.
C32 rohcRtpContextCSPs	1.3.6.1.2.1.114.1.1.1.14	Counter32	read-only	This object is only applicable to contexts using the LLA profile. It contains the number of all context synchronization packets (CSP) sent or received in this context, respectively. Discontinuities in the value of this counter can occur at re-initialization of the management system, and at other times as indicated by the value of ifCounterDiscontinuityTime. For checking ifCounterDiscontinuityTime, the interface index is required. It can be determined by reading the rohcChannelTable of the ROHC-MIB. The value of this object is only valid for LLA profiles, i.e., if the corresponding rohcProfile has a value of 0x0005. If the corresponding rohcProfile has a value other than 0x0005, then this object MUST NOT be instantiated.
C32 rohcRtpContextCCPs	1.3.6.1.2.1.114.1.1.1.15	Counter32	read-only	This object is only applicable to contexts using the LLA profile. It contains the number of all context check packets (CCP) sent or received in this context, respectively. Discontinuities in the value of this counter can occur at re-initialization of the management system, and at other times as indicated by the value of ifCounterDiscontinuityTime. For checking ifCounterDiscontinuityTime, the interface index is required. It can be determined by reading the rohcChannelTable of the ROHC-MIB. The value of this object is only valid for LLA profiles, i.e., if the corresponding rohcProfile has a value of 0x0005. If the corresponding rohcProfile has a value other than 0x0005, then this object MUST NOT be instantiated.
C32 rohcRtpContextPktsLostPhysical	1.3.6.1.2.1.114.1.1.1.16	Counter32	read-only	This object is only applicable to decompressor contexts using the LLA profile. It contains the number of physical packet losses on the link between compressor and decompressor, that have been indicated to the decompressor. Discontinuities in the value of this counter can occur at re-initialization of the management system, and at other times as indicated by the value of ifCounterDiscontinuityTime. For checking ifCounterDiscontinuityTime, the interface index is required. It can be determined by reading the rohcChannelTable of the ROHC-MIB. The value of this object is only valid for LLA profiles, i.e., if the corresponding rohcProfile has a value of 0x0005. If the corresponding rohcProfile has a value other than 0x0005, then this object MUST NOT be instantiated.
C32 rohcRtpContextPktsLostPreLink	1.3.6.1.2.1.114.1.1.1.17	Counter32	read-only	This object is only applicable to decompressor contexts using the LLA profile. It contains the number of pre-link packet losses on the link between compressor and decompressor, that have been indicated to the decompressor. Discontinuities in the value of this counter can occur at re-initialization of the management system, and at other times as indicated by the value of ifCounterDiscontinuityTime. For checking ifCounterDiscontinuityTime, the interface index is required. It can be determined by reading the rohcChannelTable of the ROHC-MIB. The value of this object is only valid for LLA profiles, i.e., if the corresponding rohcProfile has a value of 0x0005. If the corresponding rohcProfile has a value other than 0x0005, then this object MUST NOT be instantiated.
rohcRtpPacketSizeTable	1.3.6.1.2.1.114.1.2		not-accessible	This table lists all allowed, preferred, and used packet sizes per compressor context and channel. Note, that the sizes table represents implementation parameters that are suggested by RFC 3095 and/or RFC 3242, but that are not mandatory.
rohcRtpPacketSizeEntry	1.3.6.1.2.1.114.1.2.1		not-accessible	An entry of a particular packet size.
U32 rohcRtpPacketSize	1.3.6.1.2.1.114.1.2.1.3	Unsigned32	not-accessible	A packet size used as index.
T/F rohcRtpPacketSizePreferred	1.3.6.1.2.1.114.1.2.1.4	TruthValue	read-only	This object is only applicable to compressor contexts using the LLA profile. When retrieved, it will have the value true(1) if the packet size is preferred. Otherwise, its value will be false(2). The value of this object is only valid for LLA profiles, i.e., if the corresponding rohcProfile has a value of 0x0005. If the corresponding rohcProfile has a value other than 0x0005, then this object MUST NOT be instantiated.
T/F rohcRtpPacketSizeUsed	1.3.6.1.2.1.114.1.2.1.5	TruthValue	read-only	This object is only applicable to compressor contexts using the UDP, RTP, or ESP profile. When retrieved, it will have the value true(1) if the packet size is used. Otherwise, its value will be false(2). The value of this object is only valid for UDP, RTP, and ESP profiles, i.e., if the corresponding rohcProfile has a value of either 0x0001, 0x0002 or 0x0003. If the corresponding rohcProfile has a value other than 0x0001, 0x0002 or 0x0003, then this object MUST NOT be instantiated.
INT rohcRtpPacketSizeRestrictedType	1.3.6.1.2.1.114.1.2.1.6	INTEGER	read-only	This object is only applicable to preferred packet sizes of compressor contexts using the LLA profile. When retrieved, it will indicate whether the packet size is preferred for NHP only, for RHP only, or for both of them. The value of this object is only valid for LLA profiles, i.e., if the corresponding rohcProfile has a value of 0x0005. If the corresponding rohcProfile has a value other than 0x0005, then this object MUST NOT be instantiated.
rohcRtpConformance	1.3.6.1.2.1.114.2
rohcRtpCompliances	1.3.6.1.2.1.114.2.1
rohcRtpCompliance	1.3.6.1.2.1.114.2.1.1			The compliance statement for SNMP entities that implement the ROHC-RTP-MIB. Note that compliance with this compliance statement requires compliance with the rohcCompliance MODULE-COMPLIANCE statement of the ROHC-MIB and with the ifCompliance3 MODULE-COMPLIANCE statement of the IF-MIB (RFC2863).
rohcRtpGroups	1.3.6.1.2.1.114.2.2
rohcRtpContextGroup	1.3.6.1.2.1.114.2.2.1			A collection of objects providing information about ROHC RTP compressors and decompressors.
rohcRtpPacketSizesGroup	1.3.6.1.2.1.114.2.2.2			A collection of objects providing information about allowed and used packet sizes at a ROHC RTP compressor.
rohcRtpStatisticsGroup	1.3.6.1.2.1.114.2.2.3			A collection of objects providing ROHC compressor and decompressor statistics.

RFC description

Monitors RObust Header Compression (ROHC) contexts for RTP, UDP, ESP, and LLA profiles in RFC 3095 and RFC 3242.

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