Thomas Schmidt haw-hamburg.de. The RTP MIB. > Design of the RTP MIB > Application: Remote Multicast Monitoring

Transcription

1 The RTP MIB > Design of the RTP MIB > Application: Remote Multicast Monitoring

2 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 2

3 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 3

4 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 4

5 RTP MIB Tree Root ISO Org DoD 1. SessionNewIndex MIB 1 & 2 MIB 1 Mgmt Internet Private 87. RTP 1. MIBObjects 2. SessionInverseTable 3. SessionTable 4. SenderInverseTable 5. SenderTable 6. RcvrInverseTable 7. RcvrTable MIB 2 2. Conformance 1. Groups 2. Compliances 5

6 RTP MIB management applications. Rows created by management operations are deleted by management operations by setting rtpsessionrowstatus 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 6

7 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 7

8 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. 8

9 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) 9

10 RTP Monitoring 10

11 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 11

12 RTT Probe Application for Cisco 12

13 Documents RFC 2959 Real-Time Transport Protocol Management Information Base J. Chesterfield, B. Fenner, L. Breslau: Remote Multicast Monitoring using RTP MIB, online: 13