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Thomas [email protected]
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The RTP MIB
> Design of the RTP MIB> Application: Remote Multicast Monitoring
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Thomas [email protected]
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Management Information Base for Real-Time Transport
> Defined in RFC 2959 for RTPv1 (RFC 1889)> Represents RTP/RTCP information for Hosts (end systems)
and RTP Monitors – Translators & Mixers are excluded> Structured around the abstract concepts of
– Session: association between participants, using the same destination RTP address (network address + RTP/RTCP ports)
– Sender: source of an RTP session identified by SSRC– Receiver: unicast or multicast sink of RTP stream with unique
SSRC
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Basic Use of RTP Management
> RTP host systems may use RTP MIB to collect session & stream data from its sending & receiving
> RTP monitors may use RTP MIB to collect session & stream statistical data (from RTCP) for surveying network performance and QoS values
> RTP host monitors may survey endpoints receiving its streams – using session & sender data for its own sending, but receiver data from its peers
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Structure of RTP MIB
> Essentially three tables– rtpSessionTable describes active sessions at the host or
monitor– rtpSenderTable contains information about senders to RTP
session– rtpRcvrTable contains information about RTP receivers
> Three corresponding inverse tables– reverse lookup tables to easily identify rows in tables without
search – used for group identification
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RTP MIB Tree
Root
ISO OrgDoD
InternetMgmt
MIB 1 & 287. RTP
MIB 1
MIB 2
Private
1. SessionNewIndex
1. Groups
7. RcvrTable
6. RcvrInverseTable
5. SenderTable
4. SenderInverseTable3. SessionTable2. SessionInverseTable
2. Compliances
1. MIBObjects
2. Conformance
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RTP MIBmanagement applications. Rows created by management operations
are deleted by management operations by settingrtpSessionRowStatus to 'destroy(6)'."
INDEX { rtpSessionIndex }::= { rtpSessionTable 1 }
RtpSessionEntry ::= SEQUENCE {rtpSessionIndex Integer32,rtpSessionDomain TDomain,rtpSessionRemAddr TAddress,rtpSessionLocAddr TAddress,rtpSessionIfIndex InterfaceIndex,rtpSessionSenderJoins Counter32,rtpSessionReceiverJoins Counter32,rtpSessionByes Counter32,rtpSessionStartTime TimeStamp,rtpSessionMonitor TruthValue,rtpSessionRowStatus RowStatus}
RTP MIB
http://www.informatik.haw-hamburg.de/~schmidt/nmm/RTP.my
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Remote Multicast Monitoring
Problem: Multicast traffic is intended for real-time distribution, but difficult to monitor:– Multicast distribution follows non-local transmission along a
(shared) routing tree– Mcast membership as well as the distribution tree are
dynamic and may change during its lifetime – Multicast (router) states are not present until traffic flows
Background: RTP/RTCP and the MIB are designed to cope with multicast distribution
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Basic Credentials
1. RTCP receiver reports are transmitted to session’s multicast address
2. By creating an entry for a multicast group in the session table and setting it active and to monitor, the agent is caused to join that multicast group.
3. Thereby the agent becomes a passive monitor.
Problem: Active injection into the group ….
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Passive Monitoring
RTP MIB is a QoS Watchdog> RTCP Data for Senders, Receivers and Sessions
– Reports on activities, delay, jitter, loss …
> Management for Hosts and Monitors– RTCP on Hosts and Monitors reports to group– Agent capable of sorting out data
> Typical Point of Application: Gateway (e.g. AudioCodes Card)
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RTP Monitoring
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Active Monitoring
RTT Mon observes QoS flaws before users> Proactively Implant QoS Probes
– Exchange and evaluate RT probe packets– Supported by several vendors, e.g. Cisco Routers
> Preconfigure Relevant Traversals– Have probes ready for critical paths of your network
> Run on Suspicion or on Schedule– Preconfigure alarms/actions for automation
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RTT Probe Application for Cisco
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Documents
RFC 2959 Real-Time Transport Protocol Management Information Base
J. Chesterfield, B. Fenner, L. Breslau: Remote Multicast Monitoring using RTP MIB, 2002.online: http://www.cl.cam.ac.uk/users/jac90/MMNS02.pdf
http://www.cl.cam.ac.uk/users/jac90/MMNS02.pdf
The RTP MIBManagement Information Base for Real-Time TransportBasic Use of RTP ManagementStructure of RTP MIBRTP MIB TreeRTP MIBRemote Multicast MonitoringBasic CredentialsPassive MonitoringRTP MonitoringActive MonitoringRTT Probe Application for CiscoDocuments