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Troubleshooting IP Videoconferencing

VIEWS: 39 PAGES: 31

  • pg 1
									                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.                     1




                                                               Troubleshooting IP
                                                               Videoconferencing
                                                                                          Session VVT-330




                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.                     2




Copyright © 1998, Cisco Systems, Inc. All rights reserved. Printed in USA.
VVT-330                                                                                                         1
                          Goals Of This Session


                             • Give you an in-depth understanding of how
                               H.323 operates so you will know where to look
                               when diagnosing problems
                             • Look at several example problem scenarios and
                               how to resolve them
                             • Give you the tools you need to troubleshoot
                               Cisco IP/VC and MCM products



                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.   3




                          Recommended Prerequisites
                          For This Session

                              • An understanding of H.323 components,
                                protocols and message flows
                              • VVT-130, VVT-230 and VVT-213 sessions
                                recommended
                                         Our troubleshooting examples are based on the
                                         topologies illustrated in VVT -230
                                         QoS is covered in detail in VVT -213
                              • The information contained in this session will
                                apply generically to any H.323 product, and we
                                will indicate when covering any vendor-specific
                                features

                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.   4




Copyright © 1998, Cisco Systems, Inc. All rights reserved. Printed in USA.
VVT-330                                                                                       2
                             Session Outline—Agenda

                                    • Review components/functions of an
                                      H.323 network
                                    • Review H.323 sub-protocols/message flows,
                                      addressing schemes and bandwidth
                                      requirements
                                    • Identify typical/common error scenarios and how
                                      to systematically troubleshoot them
                                    • Identify what troubleshooting tools are available
                                      for H.323
                                    • Where to go for additional help and information

                     VVT–330
                     2918_05_2001_c1             © 2001, Cisco Systems, Inc. All rights reserved.               5




                             H.323 Components And Functions
                                                 • Gatekeepers
                                                          Call processing agent for H.323 networks, just like
                                                          CallManager is the call processing agent for IP
                                                          telephony networks
                                                          Direct vs. GKRCS
                                                 • Terminals
                         Collectively referred
                         Collectively referred
                         to as “Endpoints”
                         to as “Endpoints”




                                                 • Gateways
                                                          PSTN/H.323; H.320/H.323; H.323/H.323; other
                                                          protocols (e.g. SIP, MGCP, Skinny)
                                                 • MCU’s
                                                          MC vs. MP functionality

                     VVT–330
                     2918_05_2001_c1             © 2001, Cisco Systems, Inc. All rights reserved.               6




Copyright © 1998, Cisco Systems, Inc. All rights reserved. Printed in USA.
VVT-330                                                                                                             3
                          H.323 Protocol Review


                              • H.225 (RAS, Q.931)
                              • H.245 (capabilities negotiation/channel control)
                              • RTP/RTCP (media channels)
                              • Audio codecs (G.711, G.728, G.722, etc.)
                              • Video codecs (H.261, H.263, etc.)
                              • Data (T.120)



                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.           7




                          H.323 Protocol Review
                          H.225


                               • RAS (Registration, Admission and Status)
                                           Endpoint??gatekeeper communications
                               • GUP (Gatekeeper Update Protocol)
                                           Cisco proprietary protocol for Gatekeeper clustering
                               • Q.931
                                           Setup, proceeding, alerting, connect




                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.           8




Copyright © 1998, Cisco Systems, Inc. All rights reserved. Printed in USA.
VVT-330                                                                                               4
                          H.323 Protocol Review
                          H.225 RAS Definitions

                                   • GRQ (Gatekeeper Request)
                                   • RRQ (Registration Request)
                                   • ARQ (Admission Request)
                                                                                          Usage differs between
                                   • LRQ (Location Request)                               H.323v1 and H.323v2
                                   • RIP (Request In Progress)
                                   • BRQ (Bandwidth Request)
                                   • DRQ (Disengage Request)
                                   • RAI/RAC (Resource Availability Indication/Confirm)
                                   • IRQ/IRR (Information Request/Response)


                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.                           9




                          H.323 Protocol Review
                          H.245


                                              • Capabilities negotiation
                                                             Capabilities Set (advertisement)
                                                             Capabilities Ack (acknowledgement)
                                              • Open/close logical channels
                                                             OLC (open logical channel)
                                                             OLC Ack (acknowledgement)
                                              • H.245 control channel stays open for
                                                duration of call


                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.                       10




Copyright © 1998, Cisco Systems, Inc. All rights reserved. Printed in USA.
VVT-330                                                                                                               5
                          H.323 Protocol Review
                          RTP/RTCP

                                 • Uses UDP for transport
                                 • RTCP timestamps are used to maintain
                                   lip-sync
                                              Endpoints need to support RTCP


                                       4 Bytes                     VER                    CC   M    Payload Type   Sequence Number

                                       4 Bytes                                                     RTP Timestamp

                                       4 Bytes                                            Synchronization Source (SSRC) ID


                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.                                              11




                          H.323 Protocol Review
                          Audio/Video Codecs


                                                                 • Audio codecs
                                                                                G.711 (8khz/64kbps)
                                                                                G.728 (8khz/16kbps)
                                                                                G.722 (16khz/64kbps)

                                                                 • Video codecs
                                                                                H.261, H.263 (H.263+, ++)


                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.                                              12




Copyright © 1998, Cisco Systems, Inc. All rights reserved. Printed in USA.
VVT-330                                                                                                                                   6
                          H.323 Protocol Review
                          Direct Mode Intrazone Call Example

                                                                                                   Gatekeeper
                                                         Admission Request
                                                         Admission Confirm
                                                                                                     Setup
                                                                                                 Call Proceeding
                                                                                                                              Admission Request
                                                                                                                               Admission Confirm
                                                                                                    Alerting
                                                                                                    Connect

                                                                                            Terminal Capabilities Set
                                                                                            Master Slave Termination

                                                                                          Terminal Capabilities Set Ack
                                                                                          Master Slave Termination Ack
                                                                                          Terminal Capabilities Set Ack
                                                                                           Master Slave Termination
                                                                                                 Open Logical
                                                                                                  Channel(s)
                                                                                                 Open Logical
                                                                                                Channel(s) ACK
                                                                                                 Open Logical
                                                                                                Channel(s) ACK
                                                                                                  RTP Media
                                                                                                  Stream(s)

                                                                                                                           RAS                             Q.931
                     VVT–330                                                                                              H.245                            RTP
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.                                                                            13




                          H.323 Protocol Review
                          GKRCS Intrazone Call Example

                                                                                                   Gatekeeper
                                                             Admission Request
                                                              Admission Confirm

                                                                      Setup
                                                                                                                                       Setup
                                                                Call Proceeding
                                                                                                                                   Call Proceeding

                                                                                                                                  Admission Request

                                                                                                                               Admission Confirm


                                                                                                                                      Alerting
                                                                    Alerting
                                                                                                                                      Connect
                                                                    Connect


                                                          Terminal Capabilities Set                                          Terminal Capabilities Set
                                                          Master Slave Termination                                           Master Slave Termination

                                                        Terminal Capabilities Set Ack                                      Terminal Capabilities Set Ack
                                                        Master Slave Termination Ack                                       Master Slave Termination Ack

                                                        Terminal Capabilities Set Ack
                                                        Master Slave Termination Ack                                       Terminal Capabilities Set Ack
                                                                                                                           Master Slave Termination Ack
                                                                 Open Logical
                                                                  Channel(s)                                                        Open Logical
                                                                                                                                     Channel(s)
                                                          Open Logical Channel(s)                                                  Open Logical
                                                                   ACK                                                            Channel(s) ACK
                                                          Open Logical Channel(s)
                                                                                                                                    Open Logical
                                                                   ACK                                                             Channel(s) ACK
                                                                                                 RTP Media
                                                                                                 Stream(s)
                                                                                                                           RAS                             Q.931
                     VVT–330                                                                                              H.245                            RTP
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.                                                                            14




Copyright © 1998, Cisco Systems, Inc. All rights reserved. Printed in USA.
VVT-330                                                                                                                                                                 7
                          H.323 Protocol Review
                          Direct Mode Interzone Call Example
                                                                                                       3-LRQ
                                                                                                       4-LCF

                                                       Gatekeeper                                                               Gatekeeper
                                 Q




                                                                                                    IP Network
                               AR




                                                                                                                                             9-
                                                                                                                                              8-
                                              P




                                                                                                                                                AC
                            1-




                                                                                                                                                 AR
                                   RI

                                            F




                                                                                                                                                  F
                                          AC
                                 2-




                                                                                                                                                    Q
                                       5-




                                                                                                     6-Q.931 Setup
                                                                                                   7-Q.931 Proceeding
                                                                                                   10-Q.931 Alerting
                                                                                                   11-Q.931 Connect
                                                                                                 12-Q.931 Connect Ack
                                                                                                13-H.245 Capabilities Set
                                                                                                14-H.245 Capabilities Ack
                                                                                                15-H.245 Capabilities Ack
                                                                                             16-H.245 Open Logical channels
                                                                                           17-H.245 Open Logical Channels Ack
                                                                                           18-H.245 Open Logical Channels Ack
                                                                                           19-RTP Media Channels Established
                     VVT–330
                     2918_05_2001_c1    © 2001, Cisco Systems, Inc. All rights reserved.                                                                15




                          H.323 Protocol Review
                          Addressing Schemes


                                          • E.164 addresses
                                          • H.323-ID
                                                         Case sensitive
                                                         Requires DNS, sequential-LRQ or blast-LRQ
                                          • Zone Prefixes
                                                         Multiple wildcard mask options (e.g. * or…)
                                          • Service prefixes/technology prefixes


                     VVT–330
                     2918_05_2001_c1    © 2001, Cisco Systems, Inc. All rights reserved.                                                                16




Copyright © 1998, Cisco Systems, Inc. All rights reserved. Printed in USA.
VVT-330                                                                                                                                                      8
                          H.323 Protocol Review
                          Bandwidth Requirements


                            • H.225 RAS specifies that ARQ should indicate 2x
                              the requested bandwidth
                                       (e.g. 768kbps for a 384kbps call to account for
                                       duplex media)
                                       This is only used for gatekeeper bandwidth
                                       management
                                       Some endpoints have bugs, and ask for the wrong
                                       amount, which breaks the gatekeepers’ ability to
                                       properly track bandwidth utilization



                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.   17




                          H.323 Protocol Review
                          Bandwidth Requirements (Cont.)


                            • 13-15% overhead for RTP/UDP/IP headers
                              in addition to audio/video bitrate
                            • Voice, video and data combined should
                              never consume more than 75–80% of your
                              link capacity
                            • cRTP not recommended for video
                            • LFI not recommended for video


                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.   18




Copyright © 1998, Cisco Systems, Inc. All rights reserved. Printed in USA.
VVT-330                                                                                        9
                          H.323 Protocol Review
                          Bandwidth Requirements (Cont.)
                                                    Engineering The Network for Data, Voice, and Video



                                                                                          Voice/Video     Data   Routing
                                       Voice                       Video                                           etc
                                                                                            Control




                                             LLQ = 33%
                                                                  Sum of Traffic = 75%
                                                                                          Link Capacity

                        Link Capacity = (Min BW for Voice + Min BW for Video + Min BW for Data)/0.75
                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.                                    19




                          H.323 Protocol Review
                          Bandwidth Requirements (Cont.)

                           • Detailed example of 384kbps call over ATM:
                                       RTP data (audio/video samples) combined =
                                       approximately 384kbps
                                       Approximately 13% overhead for RTP/UDP/IP headers =
                                       approximately 434kbps
                                       ATM carries 48 bytes of payload per cell, so 434kbps
                                       requires approximately 1,130 cells per second
                                       Each ATM cell has an 8 byte header, so 1130cps * 8
                                       bytes/cell = approximately 72kbps, or 17%
                                       So 384kbps + 30% = approximately 500kbps of actual
                                       bandwidth required at layer-2


                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.                                    20




Copyright © 1998, Cisco Systems, Inc. All rights reserved. Printed in USA.
VVT-330                                                                                                                         10
                          Session Outline/Agenda

                            • Review components/functions of an
                              H.323 Network
                            • Review H.323 sub-protocols/message flows,
                              addressing schemes and bandwidth
                              requirements
                            • Identify typical/common error scenarios and how
                              to systematically troubleshoot them
                            • Identify what troubleshooting tools are available
                              for H.323
                            • Where to go for additional help and information

                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.   21




                          Common Error Scenarios


                             • Registration issues
                             • Call signaling/call setup issues
                             • H.320/H.323 gateway issues
                             • Misconfiguration of gateway/MCU services
                             • Codec negotiation issues (multi-vendor product
                               interaction)
                             • Poor video quality (packet loss, QoS, latency)


                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.   22




Copyright © 1998, Cisco Systems, Inc. All rights reserved. Printed in USA.
VVT-330                                                                                        11
                          Common Error Scenarios
                          Registration Issues


                            • E.164 address/H.323-ID conflicts
                                       Can conflict with other terminals, or with
                                       service/technology prefixes
                                               Example: Gateway service prefix = 9; terminal E.164
                                               address = 9165551212
                                       Can conflict with a previous uncleared registration if IP
                                       address changes and original registration is still there.
                                               12.1(5)XM offers a new “endpoint-ttl” command to
                                               help alleviate this issue



                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.              23




                          Common Error Scenarios
                          Registration Issues (Cont.)

                              • Gatekeeper failover/re-registration issues
                                           HSRP—Cisco gatekeeper operates per the standard,
                                           but some endpoints don’t respond correctly
                                           Alternate Gatekeeper—Cisco gatekeeper supports it,
                                           but no H.323 videoconferencing endpoints
                                           support it yet
                              • Multicast gatekeeper discovery
                                           Endpoints could end up on the wrong gatekeeper
                                           Either route this multicast address to the correct
                                           gatekeeper or don’t use it


                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.              24




Copyright © 1998, Cisco Systems, Inc. All rights reserved. Printed in USA.
VVT-330                                                                                                   12
                          Common Error Scenarios
                          Registration Issues (Cont.)

                                         • AAA Authentication (Cisco gatekeeper
                                           specific feature)
                                                        Endpoints E.164-ID/H.323-ID must match the
                                                        username/password in AAA server
                                                        Cisco gateways and MCU’s use unique
                                                        E.164/H.323-ID’s
                                                                3540 MCU example:
                                                                               E164-ID: 776785023218
                                                                               H323-ID: RV-MCU-023218




                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.                 25




                          Common Error Scenarios
                          Call Signaling Issues

                             • Intrazone H.323 call failures
                                        Wrong E.164-ID dialed or endpoint not registered
                                        (destination not found)
                                        E.164-ID conflicts with service/technology prefix
                                                Example: Gateway service prefix = 9; terminal E.164
                                                address = 9165551212
                                        E.164-ID conflicts with remote zone prefix
                                                Example 1: directory gatekeeper zone prefix = *
                                                Example 2: E.164 address dialed = 9161234, remote
                                                zone prefix = 916*
                                        Intrazone or session bandwidth exceeded

                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.                 26




Copyright © 1998, Cisco Systems, Inc. All rights reserved. Printed in USA.
VVT-330                                                                                                      13
                          Common Error Scenarios
                          Call Signaling Issues (Cont.)


                             • Interzone H.323 call failures
                                        Wrong E.164-ID dialed, no zone prefix match
                                        Remote gatekeeper sends LRJ (destination not found)
                                        LRQ timers/TTL issues with sequential/
                                        blast-LRQ methods
                                        Called number not found or routed to the wrong
                                        destination due to parsing order issues (see examples
                                        on previous slide)
                                        Interzone or remote bandwidth exceeded



                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.                               27




                          Common Error Scenarios
                          Call Signaling Issues (Cont.)

                              • Proxy usage misconfigured
                                          Default setting on Cisco gatekeeper is to “use -proxy”
                                          inbound-to/ outbound-from terminal

                                          PROXY USAGE CONFIGURATION :
                                               Inbound Calls from all other zones :
                                                    to terminals in local zone sj -13-vsc -gk : use proxy
                                                    to gateways in local zone sj-13-vsc-gk     : do not use proxy
                                               Outbound Calls to all other zones :
                                                    from terminals in local zone sj -13-vsc-gk : use proxy
                                                    from gateways in local zone sj-13-vsc-gk     : do not use proxy




                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.                               28




Copyright © 1998, Cisco Systems, Inc. All rights reserved. Printed in USA.
VVT-330                                                                                                                    14
                          Common Error Scenarios
                          Call Signaling Issues (Cont.)


                              • ILS/GAB call failures
                                          Gatekeeper may reject terminating ARQ
                                                  Some do—ours used to but no longer does
                                                  as of 12.1(5)T
                                          Bypasses gatekeeper by dialing IP address
                                          directly; gatekeeper will be incapable of
                                          tracking bandwidth usage, and CAC
                                          mechanism will break down


                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.     29




                          Common Error Scenarios
                          H.320/H.323 Gateway Issues


                              • ISDN provisioning is the #1 issue in TAC cases
                                          Must be provisioned for “voice and data”
                                                  Bonding must be enabled
                                                  Error message on gateway debug will be
                                                  “incompatible destination”
                                          NPI/TOA settings on certain IXC’s circuits
                                                  Translating from “unknown/unknown” to
                                                  circuit-specific messaging format
                                          PRI line-buildout (i.e. LBO) on 3525 gateways


                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.     30




Copyright © 1998, Cisco Systems, Inc. All rights reserved. Printed in USA.
VVT-330                                                                                          15
                          Common Error Scenarios
                          H.320/H.323 Gateway Issues (Cont.)


                            • Inbound H.320/H.323 call failures
                                       Bonding/line-hunting issues
                                                Gateway may not have enough B-channels available
                                                to complete the call
                                       DID vs. IVR/TCS4
                                                DID number must match the E.164 address
                                                Look at the gateway debug log to see how many
                                                digits the telco is passing



                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.                                                          31




                          Common Error Scenarios
                          H.320/H.323 Gateway Issues (Cont.)
                                           • DID inbound call failure example
                                                                                                        Gateway queries
                                                                                                      gatekeeper for “5551212”      Gatekeeper
                                                                             Telco passes “5551212”
                                                                                    to gateway
                                                  12”
                                               512
                                            855
                                         “40
                                     als
                                 r di
                              Use
                                                                      ISDN (PSTN)

                                                                                              IP/VC 3525 Gateway
                                                         RI                                   Did Range = (408) 555-1000
                                                  3xB                                         through (408) 555-1999


                                                                                                                                 E.164 = 51212


                                           Get the Telco to pass the correct number of
                                            digits, or change your internal dial plan
                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.                                                          32




Copyright © 1998, Cisco Systems, Inc. All rights reserved. Printed in USA.
VVT-330                                                                                                                                               16
                          Common Error Scenarios
                          H.320/H.323 Gateway Issues (Cont.)


                           • Outbound H.323/H.320 call failures
                                       Dialing the wrong speed/prefix
                                              Example: service prefix 9 is provisioned for 384kbps;
                                              user dials 914085551212 at 128kbps
                                       RAI/RAC and line-hunting (Direct vs. GKRCS)
                                              Even with RAI/RAC, gateway could still be busy or
                                              lack sufficient resources; choose your RAI
                                              threshold carefully



                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.               33




                          Common Error Scenarios
                          H.320/H.323 Gateway Issues (Cont.)


                           • H.261 versus H.263
                                       H.263 requires additional resources on IP/VC
                                       gateways
                                       3525 can do three 384kbps calls using H.261,
                                       but only two when H.263 is used
                                              Future Cisco gateway offerings will eliminate
                                              this



                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.               34




Copyright © 1998, Cisco Systems, Inc. All rights reserved. Printed in USA.
VVT-330                                                                                                    17
                          Common Error Scenarios
                          H.320/H.323 Gateway Issues (Cont.)
                                                      • Audio transcoding issues
                                                                                                                  User at 128\kbps uses G.728,
                                                                                                                  User at 128\kbps uses G.728,
                                                                                                                  gateway transcodes to G.711
                                                                                                                  gateway transcodes to G.711
                           MCU does G.711
                           MCU does G.711
                                                                                                                ISDN (PSTN)
                                                                                                                               1xBR
                                                                                                                                      I
                                                                                           IP/VC 3525 Gateway




                                       IP/VC 3540 MCU                                                           ISDN (PSTN)
                                                                                                                              3xB
                                                                                                                                 RI
                                                                                           IP/VC 3525 Gateway

                           • Version 2.2 resolves this via flow-control messages
                           • Pre-2.2; make sure all gateways are set to the same
                             transcoding priority
                           • Future audio transcoding module in MCU will resolve this as well
                     VVT–330
                     2918_05_2001_c1    © 2001, Cisco Systems, Inc. All rights reserved.                                                   35




                          Common Error Scenarios
                          Misconfiguration of Services

                                • How to properly configure service settings on
                                  the MCU’s and gateways is the second most
                                  common issue in TAC cases
                                             MCU bandwidth = video bit rate only
                                                      Example: 320k for a 384kbps call
                                                      (64k left for G.711 audio)
                                             Continuous presence bandwidth can be calculated
                                             two ways
                                                      High bandwidth example: 320k in/1280k out
                                                      Low bandwidth example: 80k in/320k out


                     VVT–330
                     2918_05_2001_c1    © 2001, Cisco Systems, Inc. All rights reserved.                                                   36




Copyright © 1998, Cisco Systems, Inc. All rights reserved. Printed in USA.
VVT-330                                                                                                                                          18
                          Common Error Scenarios
                          Codec Negotiation Issues


                             • Few examples of codecs failing to negotiate;
                               this all works quite well in general; the problem
                               is that you have to know what each endpoint is
                               capable of
                                        Example: MCU set to H.263, but VCON 4.01 and below
                                        only does H.261; VCON 4.4 and above supports
                                        H.263 now
                                        In a mixed endpoint environment, you have to know
                                        what everyone’s capabilities are, and plan accordingly



                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.             37




                          Common Error Scenarios
                          Poor Video Quality


                                                    • Four primary sources of poor
                                                      video quality:
                                                                   Ethernet port settings
                                                                   Lack of QoS
                                                                   End-to-end latency
                                                                   Endpoint encoding capabilities



                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.             38




Copyright © 1998, Cisco Systems, Inc. All rights reserved. Printed in USA.
VVT-330                                                                                                  19
                          Common Error Scenarios
                          Poor Video Quality (Cont.)

                            • The most common cause of packet loss is Ethernet
                              port negotiation issues
                                       3510 is 10/half, and you have to set the switch port to 10/half,
                                       not auto, or you will see errors on the switch port
                                       3540 is 100/full but you have to set the switch port to auto,
                                       not 100/full, or you will see errors on the switch port
                                       Polycom FX is 100/full
                                       Other Polycom models are 10/half
                                       PC-based (NIC cards) have there own unique issues
                                       Bottom line = you need to experiment (using “show port” or
                                       “show interface” commands) with each device/port settings
                                       to get it to 0% errors; then the video will look great


                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.                   39




                          Common Error Scenarios
                          Poor Video Quality (Cont.)

                           • The second most common cause of packet loss
                             is the lack of QoS
                                       You must protect video from data, and voice from video
                                       Video packets are large (up to 1500Bytes/
                                       packet or MTU)
                                       Do not use LFI with video.
                                       Multiple QoS methods available
                                              Proxy with LLQ
                                              ACL with LLQ
                                              RSVP (currently have H.323/RSVP sync problem;
                                              future version of proxy may resolve this)

                         *Reference: VVT-230, VVT -213 and AVVID QoS Design Guide
                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.                   40




Copyright © 1998, Cisco Systems, Inc. All rights reserved. Printed in USA.
VVT-330                                                                                                        20
                          Common Error Scenarios
                          Poor Video Quality (Cont.)

                                                “I”                                                             “I”
                                              Frame                                                           Frame
                                             1024-1518                                                       1024-1518
                                               Bytes                                                           Bytes
                                                                                                                           600Kpbs

                        30pps


                                                                               “P” and “B” Frames
                                                                                 128-256 Bytes
                        15pps

                                                                                                                           32Kpbs

                               • “I” frame is a full sample of the video
                               • “P” and “B” frames use quantization via motion vectors and
                                 prediction algorithms
                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.                                         41




                          Common Error Scenarios
                          Poor Video Quality (Cont.)


                            Video Conferencing Traffic Packet Size Breakdown

                                                                                                                 65–128 Bytes
                                                                                     1025–1518
                                                                                       Bytes

                                                                                                   129–256
                                                                         513–1024                   Bytes
                                                                           Bytes

                                                                                          65–128
                                                                                           Bytes



                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.                                         42




Copyright © 1998, Cisco Systems, Inc. All rights reserved. Printed in USA.
VVT-330                                                                                                                              21
                          Common Error Scenarios
                          Poor Video Quality (Cont.)

                                                     Video Conferencing Traffic Packets
                                                          Per Second Breakdown
                                               120                                                             Low PPS
                                                                                                               High PPS
                                               100

                                                 80

                                                 60

                                                 40

                                                 20

                                                    0
                                                                   128K                   384K   512K   768K
                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.                                   43




                          Common Error Scenarios
                          Poor Video Quality (Cont.)
                            • The third most common cause of poor video quality
                              is end-to-end latency
                                       ITU-TG.114 (one-way transmission time) recommends >=150ms as
                                       the maximum desired one-way latency to achieve high-quality voice
                                       (http://www.protocols.com/voip/testing.htm)
                                       Video codecs alone introduce 100-300ms
                                       MCU’s and gateways add 100-500ms
                                       IP/VC MCU’s add some latency (~100ms); but some other vendors
                                       add significantly more (200-300ms) due to de-coding/re-encoding
                                       processes
                                       Non-terrestrial links add up to 1000ms
                                       Serialization and queuing delays as utilization approaches 100%
                                       Bottom line = The videoconferencing industry has some work to do
                                       to improve these delay figures, but the network should not add
                                       significant latency

                         *Reference: VVT-230, VVT -213 and AVVID QoS Design Guide
                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.                                   44




Copyright © 1998, Cisco Systems, Inc. All rights reserved. Printed in USA.
VVT-330                                                                                                                        22
                          Common Error Scenarios
                          Poor Video Quality (Cont.)

                             • The fourth most common cause of poor video
                               quality is the endpoints encoding capabilities
                                        NetMeeting can only do 15FPS; we always
                                        recommend a hardware-based codec for
                                        enterprise quality video
                                        Polycom ViaVideo’s and VCON ViGO’s are dependant
                                        on PC’s speed/power
                                        Even many high-end desktop endpoints can only do
                                        15fps encode/30fps decode; be sure to check the
                                        endpoint specs to understand what each is capable of
                                        IP/VC MCU only does 15fps in continuous-presence
                                        mode (but so do others when you look at the receive
                                        frame rate)

                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.        45




                          Session Outline/Agenda

                            • Review components/functions of an
                              H.323 network
                            • Review H.323 sub-protocols/message flows,
                              addressing schemes and bandwidth
                              requirements
                            • Identify typical/common error scenarios and how
                              to systematically troubleshoot them
                            • Identify what troubleshooting tools are available
                              for H.323
                            • Where to go for additional help and information

                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.        46




Copyright © 1998, Cisco Systems, Inc. All rights reserved. Printed in USA.
VVT-330                                                                                             23
                          Troubleshooting Tools



                                 • Gatekeeper debug options
                                 • Gateway debug options
                                 • MCU debug options
                                 • Endpoint debug options
                                 • Using a Packet Analyzer (i.e. “Sniffer”)


                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.                47




                          Troubleshooting Tools
                          Gatekeeper Debug Options

                                          • H.225 ASN1—RAS, Q.931
                                          • H.245 ASN1—if proxy is used for call
                                          • SNMP MIBS in Cisco MCM Gatekeeper
                                                         Can be used to trap all RAS messages
                                          • Cisco IOS® debug commands available
                                                         debug                 RAS
                                                         debug                 h225 asn1
                                                         debug                 h245 asn1
                                                         debug                 gatekeeper main 10
                                                         debug                 proxy h323 statistics



                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.                48




Copyright © 1998, Cisco Systems, Inc. All rights reserved. Printed in USA.
VVT-330                                                                                                     24
                          Troubleshooting Tools
                          Gateway Debug Options


                              • Q.931 and capabilities negotiation process
                                          Cisco IP/VC gateways debug screen can be accessed
                                          via telnet
                                          No CLI commands on current products; debug
                                          messages will print to the screen by default
                              • SNMP
                                          Currently no specific MIB’s available, but you can at
                                          least monitor uptime



                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.             49




                          Troubleshooting Tools
                          MCU Debug Options

                               • Q.931, conference creation and capabilities
                                 negotiation process
                                            Cisco IP/VC MCU’s debug screen can be accessed
                                            via telnet
                                            No CLI commands on current products; debug
                                            messages will print to the screen by default
                               • SNMP
                                            Currently no specific MIB’s available, but you can at
                                            least monitor uptime




                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.             50




Copyright © 1998, Cisco Systems, Inc. All rights reserved. Printed in USA.
VVT-330                                                                                                  25
                          Troubleshooting Tools
                          Endpoint Debug Options



                             • Many endpoints now have HTML, SNMP
                               and telnet interfaces
                                         Example: Polycom sends SNMP traps to GMS
                                         when problems are detected

                             • Many offer packet loss, latency and bit-
                               rate statistics


                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.   51




                          Troubleshooting Tools
                          Using a Packet Analyzer


                            • A sniffer can show you things that the
                              gatekeeper debugs won’t show you
                                       Direct-mode gatekeeper only shows you H.225
                                       RAS information. Q.931, H.245 and RTP traffic
                                       is directly between the endpoints unless proxy
                                       is involved
                                       Make sure your sniffer can decode H.323



                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.   52




Copyright © 1998, Cisco Systems, Inc. All rights reserved. Printed in USA.
VVT-330                                                                                        26
                          Session Outline/Agenda

                            • Review components/functions of an
                              H.323 network
                            • Review H.323 sub-protocols/message flows,
                              addressing schemes and bandwidth
                              requirements
                            • Identify typical/common error scenarios and how
                              to systematically troubleshoot them
                            • Identify what troubleshooting tools are available
                              for H.323
                            • Where to go for additional help and information

                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.                    53




                          Where to Get More Information
                          Online Documentation
                            • MCM configuration guide
                                       http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/1
                                       21cgcr/multi_c/mcprt1/mcdmcm.htm
                            • IP/VC users guides
                                       http://www.cisco.com/univercd/cc/td/doc/product/ipvc/index.htm
                            • Design guides and white papers
                                       http://www.cisco.com/go/ese
                            • QoS design guide
                                       http://www.cisco.com/tac/iptelsolguide
                            • H.323 protocol information
                                       http://www.packetizer.com
                                       http://www.protocols.com
                                       http://www.itu.int
                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.                    54




Copyright © 1998, Cisco Systems, Inc. All rights reserved. Printed in USA.
VVT-330                                                                                                         27
                                            Networking Professionals
                                                  Connection



                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.                                     55




                          Where to Get More Information
                          Networking Professionals Connection



                                                                                                      New
                                                                                                      E-Mail Subscriptions
                                                                                                      Discussion Forums

                                                                                                      Live, Online
                                                                                                      Presentations
                                                                                                      Message Board
                                                                                                      Discussions with
                                                                                                      Cisco Experts

                                                                                                      Biweekly Newsletter
                                                                                                      (6500+ Subscribers)

                                                                                                      Calendar of Events

                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.
                                                                                          http://www.cisco.com/go/netpro    56




Copyright © 1998, Cisco Systems, Inc. All rights reserved. Printed in USA.
VVT-330                                                                                                                          28
                          Where to Get More Information
                          Networking Professionals Connection


                          Join a
                          Conversation
                              VPN
                              Voice and Video
                              More to Come

                          Participate
                          in Polls

                          Links to
                          Relevant
                          Information




                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.              57




                          Where to Get More Information
                          Networking Professionals Connection


                                          • Access to
                                                         A “community” of professional peers
                                                         Timely, relevant information
                                          • Opportunity to
                                                         Share expertise
                                                         Learn from more experienced professionals
                                                         Ask Cisco experts for answers



                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.              58




Copyright © 1998, Cisco Systems, Inc. All rights reserved. Printed in USA.
VVT-330                                                                                                   29
                          Where to Get More Information
                          Field Support



                             • Ask your Systems Engineer for assistance!
                                         Your SE has access to BU resources such as Product
                                         Managers, Technical Marketing and Developers
                                         They can escalate questions and problems when
                                         additional assistance is needed
                                         Many SE’s and CSE’s have specialized training on the
                                         video products (i.e. Convergence Virtual Team)




                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.                     59




                                                               Troubleshooting IP
                                                               Videoconferencing
                                                                                          Session VVT-330




                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.                     60




Copyright © 1998, Cisco Systems, Inc. All rights reserved. Printed in USA.
VVT-330                                                                                                          30
                                                      Please Complete Your
                                                         Evaluation Form
                                                                                          Session VVT-330




                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.                     61




                     VVT–330
                     2918_05_2001_c1   © 2001, Cisco Systems, Inc. All rights reserved.                     62




Copyright © 1998, Cisco Systems, Inc. All rights reserved. Printed in USA.
VVT-330                                                                                                          31

								
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