http://stupid.domain.name/ietf/

One document matched: draft-ietf-mboned-mdh-04.txt

Differences from draft-ietf-mboned-mdh-03.txt

MBONE Deployment Working Group Dave Thaler
INTERNET-DRAFT Microsoft
Category: Informational Bernard Aboba
<draft-ietf-mboned-mdh-04.txt> Microsoft
7 May 2000

Multicast Debugging Handbook

1. Status of this Memo

This document is an Internet-Draft and is in full conformance with all
provisions of Section 10 of RFC2026.

Internet-Drafts are working documents of the Internet Engineering Task
Force (IETF), its areas, and its working groups. Note that other groups
may also distribute working documents as Internet-Drafts. Internet-
Drafts are draft documents valid for a maximum of six months and may be
updated, replaced, or obsoleted by other documents at any time. It is
inappropriate to use Internet-Drafts as reference material or to cite
them other than as "work in progress."

The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.

To view the list Internet-Draft Shadow Directories, see
http://www.ietf.org/shadow.html.

2. Copyright Notice

3. Abstract

This document serves as a handbook for the debugging of multicast
connectivity problems. In addition to reviewing commonly encountered
problems, the draft summarizes publicly distributable multicast
diagnostic tools, and provides examples of their use, along with
pointers to source and binary distributions.

4. Introduction

In order to deploy multicast on a large scale, it is necessary for
Network Operations Centers, support personnel and customers to be able
to diagnose problems. Over the years a number of tools have been
developed that can assist in the diagnostic process. This document
serves as a handbook for the debugging of multicast connectivity
problems. In addition to reviewing commonly encountered problems, the
draft summarizes publicly distributable multicast diagnostic tools, and

Thaler & Aboba Informational [Page 1]

INTERNET-DRAFT Multicast Debugging Handbook 7 May 2000

provides examples of their use, along with pointers to source and binary
distributions.

5. Usage scenarios

Multicast diagnostic tools are typically employed in one of the
following settings:

5.1. Customer service and support

ISPs offering multicast services are likely to encounter the following
classes of customer questions:

Session announcement problems

Thaler & Aboba Informational [Page 2]

INTERNET-DRAFT Multicast Debugging Handbook 7 May 2000

Reception problems
Multicast router problems

Below we discuss how each of these types of problems may be diagnosed.

5.1.1. Session announcement problems

Session announcement questions are those which relate to the user's
session announcement software. Sample complaints include:

No conferences were visible in the session announcement tool
Conference X was not visible in the session announcement tool
I can see conferences when dialed into POPA, but not POPB
I can receive conferences listed in SDR, but sometimes when I join
conferences via a Web site, I cannot receive them.

Session announcement questions are typically investigated via the
following procedure:

1. If only a specific session announcement is missing, check the
session announcement from somewhere where it is being received, and find
the group(s) and ports that the session utilizes, as well as the source
IP addresses. If the problem is with all session announcements, find
the information on any current session announcement which should be seen
by the user.

2. Find out the user's IP address, if known, and the POP dialed into or
router connected to. One way to determine the user's router given their
IP address is to mtrace or traceroute to their address.

3. Do an mtrace between the session announcement's origin and the
receiver on the sap.mcast.net group. If the mtrace succeeds, note any
hops showing loss.

4. If the mtrace never gets past the receiver itself, check the NASes
or routers with mstat -l to see if the relevant group has been joined.
If not, the problem is probably with the receiver's host. Ask the user
to check with Dr. Watson or a sniffer to see if the router is sending
IGMP membership queries, and if the host is responding with membership
reports and if so, what versions are being used.

5. If the sap.mcast.net group has been joined, but the mtrace failed,
the problem is likely a multicast routing problem (see section 4.1.3).

6. If the mtrace succeeded, and one hop shows 100% loss, compare the
output with the TTL of the session announcement. Users may download
session descriptions from Web sites that they may not be in the position
to receive, due to site or regional scoping. The loss may also be the

Thaler & Aboba Informational [Page 3]

INTERNET-DRAFT Multicast Debugging Handbook 7 May 2000

result of a scoped boundary separating the originator and the receiver,
which will also be indicated as such by mtrace.

7. Otherwise, if the mtrace succeeded, look for hops showing non-
negligible loss. These typically denote points of congestion (see
section 4.3.1). Note that if rate-limiting is installed on these
congested links, session announcements are often lost since SAP traffic
is given lower priority.

8. If all else fails, request a network sniff from the user, and check
whether it shows traffic to sap.mcast.net, and if so, from what sources,
and what is being announced.

5.1.2. Reception problems

Reception questions are those where the user has successfully received
the session announcement, but was unable to receive one or more media
streams for the session joined. Sample complaints include:

I joined conference X, but nothing happened
I joined conference X, got video but no audio
I joined conference X, and got intermittent audio
I can't see source X, but source X can see me (or vice versa)

Reception questions are typically investigated via the following
procedure:

1. Check the session announcement, find the group(s) and ports that the
session utilizes, as well as the source IP addresses.

2. Find out the user's IP address, if known, and the POP dialed into or
router connected to. One way to determine the user's router given their
IP address is to mtrace or traceroute to their address.

3. Check if the user is sending RTCP reports with RTPmon, and if so,
what the loss rate is.

4. Do an mtrace between the source and the receiver on the relevant
group. If the mtrace succeeds, note any hops showing loss.

5. If the mtrace never gets past the receiver itself, check the NASes
or routers with mstat -l to see if the relevant group has been joined.
If not, the problem is probably with the receiver's host. Check with
Dr. Watson to see if the router is sending IGMP membership queries, and
if the host is responding with membership reports and if so, what
versions are being used.

6. If the relevant group has been joined, but the mtrace failed, the

Thaler & Aboba Informational [Page 4]

INTERNET-DRAFT Multicast Debugging Handbook 7 May 2000

problem is likely a multicast routing problem (see section 4.1.3).

7. If the mtrace succeeded, and one hop shows 100% loss, compare the
output with the TTL of the session announcement. The user may not be in
a position to receive data from the source, due to site or regional
scoping. The loss may also be the result of a scoped boundary
separating the source and the receiver, which will also be indicated as
such by mtrace.

8. Otherwise, if the mtrace succeeded, look for hops showing non-
negligible loss. These typically denote points of congestion (see
section 4.3.1).

9. If all else fails, request a network sniff from the user, and check
whether it shows traffic to the relevant group, and if so, from what
sources.

Other reception complaints include:
When I join my first conference, it works great. But then when I quit
that and join another one, it doesn't work anymore.

Why is my modem light is still flashing even after I've quit SDR and
VIC?

Such problems are often IGMP-related problems observed by a user
connecting to the network using a host which is running a TCP/IP stack
implementing IGMP v1. Such users will experience long leave latencies,
with resulting poor reception and/or performance of other applications.
Such problems can be distinguished from ordinary reception problems in
that they typically do not occur for the first session joined, only for
subsequent sessions. The solution consists of upgrading the user to an
IGMP v2-capable stack. IGMP is described in [2].

IGMP-related questions are typically investigated by the following
procedure:

1. Obtain the vendor and version of the user's TCP/IP stack. Determine
whether this stack is IGMP v2-enabled.

2. Ask the user to run Dr. Watson or a network sniffer and to indicate
whether IGMP queries are being seen, whether responses are being sent,
and if so, what version.

5.1.3. Multicast router problems

Multicast router questions are those which relate to the setup of a
multicast router. Sample complaints include:

Thaler & Aboba Informational [Page 5]

INTERNET-DRAFT Multicast Debugging Handbook 7 May 2000

I can get video and audio when online with ISDN, but not with a
modem, or vice versa.

I can't bring up a DVMRP tunnel to my site. Why not?

My router works great. Why can't I get multicast?

Why can't I source multicast?

Multicast routing questions are typically investigated via the following
procedure:

1. Ask the user what the router vendor is, and what software version
they have running. Attempt to verify this information using mrinfo or
mstat.

2. Check whether this vendor and version supports multicast routing, and
whether an upgrade to a later version is recommended.

3. Ask for a copy of the router configuration file.

4. Check whether the user has NAT enabled; this is incompatible with
most multicast routing protocols, and so should be switched off.

5. Find out the user's IP address(es), or if not known, the POP dialed
into or router connected to.

6. Check the loss rate and connectivity by doing an mtrace from various
sources to the user's IP address.

7. Check the user's router with mstat -l to see if it has joined any
multicast groups, and check upstream routers to see if they are
subscribed to any groups.

8. When all else fails, request a network sniff and examine it to
determine what multicast routing protocols are being run, if any.

5.2. Network Operations Center

A Network Operations Center (NOC) will typically receive a complaint
after it has been investigated by customer support and determined to be
a network-related issue. Although it is desirable for customer support
to have performed the diagnostic tests described above, if this has not
been done, NOC personnel will need to perform the tests themselves to
isolate the cause of the problem. If the proper systems have been
installed, in most cases, the NOC will already have been alerted to the
problem prior to receiving referrals from customer support. The
following diagnostic procedures are recommended:

Thaler & Aboba Informational [Page 6]

INTERNET-DRAFT Multicast Debugging Handbook 7 May 2000

1. Regularly generate summaries based on RTCP receiver and sender
reports, using RTP monitoring tools. Sample reports may include average
loss rates experienced during sessions, or users whose loss rates exceed
a particular threshold.

2. Determine the source of the problems by doing mtraces between the
sources and the receivers.

3. On a network monitoring station, keep track of the functioning of
multicast-enabled hardware, either by doing periodic mtraces, or by
using a heartbeat monitor to receive SNMP traps from equipment losing
the heartbeat.

4. In order to keep track of group topologies, use mapping tools such as
map-mbone, MVIEW, or mrtree, along with autonomous system mapping tools
such as asn and asname.

5.3. Network or system administrator

The NOC will escalate network engineering problems to network engineers
and system administrators if their intervention is required. In order to
understand the origin of the problem and repair it, it is necessary to
diagnose the operations of individual systems and routers using router
and system diagnostics such as netstat, mrinfo, mstat, mconfig, RTPmon,
and mtrace, as well as network analysis tools such as tcpdump or Dr.
Watson.

In smaller installations the network engineer or system administrator
often doubles as customer support and network operations guru, in which
case problems may be escalated without any triage (our condolences).

Typical classes of problems encountered by network engineers and system
administrators include:

Congestion and rate-limiting problems
Multicast routing problems

5.3.1. Congestion and rate limiting problems

Congestion and rate limiting problems result in high packet loss with
subsequent loss of session announcements and decrease in quality of
audio and video. These problems may be investigated via the following
procedure:

1. Use RTPmon to check for receivers experiencing packet loss.

2. Do an mtrace from the source to the receiver on the relevant group in
order to locate the problematic hops.

Thaler & Aboba Informational [Page 7]

INTERNET-DRAFT Multicast Debugging Handbook 7 May 2000

3. Do an mtrace in the opposite direction to help distinguish whether
the problem is with the router or the link at that hop.

4. If the reverse mtrace shows similar loss at an hop adjacent to the
lossy hop in the forward mtrace, odds are that the intermediate router
is overloaded. Use mrinfo to check the fanout on the router.
Overloaded routers are often the result of having too many tunnels.

5. If the reverse mtrace shows no problems near that hop, indicating
that loss is one-way, then check the router on the upstream end of the
link with mstat -nv to see if it has a rate-limit set on the link, and
if the link traffic is near that limit.

6. If the reverse mtrace shows loss over the same link, the problem is
likely to be link congestion. Use mstat -nv to see how much bandwidth
is being used by multicast traffic. (If mstat fails, running an mtrace
with the -T option may help to confirm link congestion, although the
statistics can be misleading.)

7. If a congested link is suspected, but mstat failed, another indicator
can be obtained by doing an mtrace from the session announcer to the
destination on other groups joined by the receiver, such as the SAP
group, and comparing loss statistics.

8. Check for unicast packet loss over the link using ping. Multicast
(but not unicast) packet loss on a link with a rate limit is an
indication that the link's multicast rate limit should be raised or
eliminated entirely. Packet loss on a link without rate limiting is an
indication of congestion. On such links it may be desirable to add a
rate limit. Since DVMRP prunes are currently not retransmitted by most
routers, prunes may be lost if no rate limit exists, which may further
worsen the congestion problem.

9. Use mstat -gR to see whether a single group is using an inordinate
amount of the link bandwidth. If so, use mstat to see whether a single
source to that group is using an inordinate amount of the link
bandwidth. If so, attempt to contact the source (contact information
may be available in the session announcement).

5.3.2. Multicast routing problems

Multicast routing problems include:

Duplicate packets
Injection of bogus routes (typically into DVMRP)
Redistribution of unicast routes (via BGP or an IGP) into DVMRP
Non-pruning routers

Thaler & Aboba Informational [Page 8]

INTERNET-DRAFT Multicast Debugging Handbook 7 May 2000

Duplicate packets are a symptom of routing loops. This problem may be
investigated via the following procedure:

1. Use a program such as Duppkts to detect duplicate packets.

2. Use a network monitor or RTPmon to find the sources and receivers on
the group.

3. Do an mtrace from the source(s) to the receivers in order to find
the loop. Duplicates will also show up in mtrace output as hops with
negative loss.

Bogus route injection problems may be investigated via the following
procedure:

1. Dump the DVMRP routing table. The routing table may be examined
remotely via mstat using the -r options, or locally (for mrouted) by
sending the USR1 signal to mrouted, generating the /var/tmp/mrouted.dump
file.

2. Check the table for bogus routes (known as "martians"). Bogus routes
include addresses reserved for use by private internets, as described in
[9]. These routes include 10/8, 172.16/12, or 192.168/16, or more
specific routes within these regions. Injecting a default route into
the DVMRP backbone is also considered to be a bogus route.

3. Locate the origin of the bogus routes by doing an mtrace to an IP
address in the bogus range.

Symptoms of unicast route redistribution are injection of a large number
of unicast routes (25K+) into DVMRP. The problem may be investigated via
the following procedure:

1. Examine the routing table. The DVMRP routing table may be examined
remotely via mstat -r, or locally (for mrouted) by sending the USR1
signal to mrouted, generating the /var/tmp/mrouted.dump file. For
protocol independent multicast routing protocols (such as Sparse-Mode
PIM), examine the unicast routing table.

2. Check if a single site is the predominant route injector. This site
is likely to be the problem. One way to check this is to mtrace to
addresses in a number of "suspect" prefixes.

3. If your router supports it, set a route limit on the DVMRP tunnel
interface. A limit of 7000 routes is currently recommended. You may also
wish to set "route-hog notification" at 5000 routes.

Non-pruning DVMRP routers are those which maintain groups in the

Thaler & Aboba Informational [Page 9]

INTERNET-DRAFT Multicast Debugging Handbook 7 May 2000

multicast routing table although there are no downstream subscribers.
The problem can be solved via the following procedure:

1. Check the router version number using mstat or mrinfo. Non-pruning
routers include mrouted versions prior to 3, Cisco Systems IOS prior to
version 11.0(3), and Bay Networks implementations prior to 9.0.

2. Confirm lack of pruning as follows. First, dump the multicast
forwarding table. This can be done remotely with mstat -N, or locally
(for mrouted) by sending the USR2 signal to mrouted, generating the
/var/tmp/mrouted.cache file.

3. Check the forwarding table to see if an interface is in the outgoing
interface list for every entry in the multicast forwarding table. If
so, it is likely that a non-pruner lies downstream in that direction.

4. You can confirm the existence of a non-pruner by creating a
temporary, unadvertised, session and sending (preferably with a low data
rate) data to that group. After a few moments, dump the forwarding
table again. If any interfaces appear in the outgoing interface list of
the entry for your test stream, then non-pruners lie in those
directions.

5. If a non-pruner exists downstream, use mrtree to follow the path of
the data downstream to the non-pruning router(s).

6. If your router supports it, enable the reject non-pruners option. If
not, and the unpruned interface is a tunnel, consider disabling the
tunnel.

Thaler & Aboba Informational [Page 10]

INTERNET-DRAFT Multicast Debugging Handbook 7 May 2000

6. Appendix - Multicast Diagnostic Tools

6.1. Types of tools

Multicast diagnostic tools typically fall into the following categories:

RTP monitoring tools are used to monitor the transmission quality and

Thaler & Aboba Informational [Page 11]

INTERNET-DRAFT Multicast Debugging Handbook 7 May 2000

popularity of individual sessions. Multicast router diagnostics are used
to obtain information on the configuration and state of multicast
routers. MBONE mapping tools are used to map out the topology for a
particular group. These tools can show the topology at the level of
individual systems, or at the level of autonomous system connections.
Multicast traceroute tools are used to trace the path between a source
and destination. Network Operations Center tools are used to monitor the
state of network devices within an autonomous system. Network analysis
tools (such as tcpdump and Dr. Watson) are used to analyze traffic on
the network.

Thaler & Aboba Informational [Page 12]

INTERNET-DRAFT Multicast Debugging Handbook 7 May 2000

6.2. Facilities utilized

Multicast diagnostic tools typically rely on one or more of the
following facilities:

Tools using RTCP reports analyze RTCP source and receiver reports,
providing information on packet loss, inter-arrival jitter, bandwidth

Thaler & Aboba Informational [Page 13]

INTERNET-DRAFT Multicast Debugging Handbook 7 May 2000

availability, or listenership. These tools therefore will only work with
RTP implementations which support RTCP reporting. Tools using SNMP MIBs
perform queries for variables in the IGMP, multicast routing, DVMRP, and
PIM MIBs. As a result, these tools depend on implementation of the
relevant SNMP MIBs in the network devices that are being monitored.
Tools based IGMP ASK_NEIGHBORS messages use these messages to map
portions of the MBONE, and thus will only work with routers implementing
DVMRP. Tools based on IGMP tracing perform a multicast traceroute. These
tools are typically only useful in cases where multicast routers along
the path have a route back to the source.

Diagnostic tools may use more than one of these facilities. For example,
mstat makes use of SNMP MIBs, as well as the IGMP ASK_NEIGHBORS
facility.

6.3. RTP monitoring tools

This class of tools provides information required to monitor the
performance of RTP-based applications.

6.3.1. RTPmon

Authors

David Bacher, Andrew Swan, and Lawrence A. Rowe
{drbacher,aswan,rowe}@cs.berkeley.edu
Computer Science Division - EECS
University of California
Berkeley, CA 94720-1776

Description

RTPmon allows network administrators or support personnel to monitor
listenership as well as session quality experienced by subscribers.
The tool also facilitates tracing the cause of problems resulting in
quality degradation. To accomplish this task, RTPmon summarizes and
analyzes information provided by RTCP source and receiver reports.

Receivers are displayed for a given sender in the form of a
spreadsheet, with cells being filled in with metrics such as packet
loss rate or jitter. Clicking on a cell displays a stripchart of
statistics on packet loss rate, smoothed packet loss rate and jitter.
From the stripchart it is possible to launch an mtrace between the
sender and the receiver, a convenient way of diagnosing network
problems along the multicast distribution path. Clicking on a
receiver or sender displays summary information.

For groups with large memberships, the display may be limited to

Thaler & Aboba Informational [Page 14]

INTERNET-DRAFT Multicast Debugging Handbook 7 May 2000

members surpassing a given threshold in packet loss rate or jitter.
Using RTPmon it is possible to sort receivers for a given sender
according to maximum or average loss.

Further information is available in the RTPmon man page.

Example

For examples and further information, see the rtpmon man page, or:
http://bmrc.berkeley.edu/~drbacher/projects/mm96-demo/

Facilities used

RTCP source and receiver reports
IGMP multicast trace (if installed)

Availability

RTPmon is available for UNIX and may be obtained from:
ftp://mm-ftp.cs.berkeley.edu/pub/rtpmon/

Bug reports and suggestions should be sent to:
rtpmon@bmrc.berkeley.edu.

6.3.2. RTPcast/RTPlisten, RTPquality, Duppkts, RTPdump, RTPtools,
Msessmon, Mpoll

Author
Mpoll: Andrew Patrick <andrew@calvin.dgbt.doc.ca>

Description

RTPcast listens to RTCP receiver reports and forwards data to another
multicast group; RTPlisten then listens to that group. RTPdump
listens for, and dumps RTP and RTCP packets. Duppkts listens on a
multicast group and port, and reports the number of packets received
and lost, as well as the number of duplicates. RTPquality listens to
RTCP receiver reports and writes data on packet loss, as well as late
and non-sequenced packets. RTPtools allows recording and playback of
RTP sessions. Msessmon provides a routemap of participants in RTP
conferences as well as stripcharts of statistics on RTP packet loss
and jitter. Mpoll is a survey collection tool that can be used to
collect quality ratings during multicast sessions.

Example

Information on these tools is available from:

Thaler & Aboba Informational [Page 15]

INTERNET-DRAFT Multicast Debugging Handbook 7 May 2000

http://sauce.mmlab.uninett.no/mice-nsc/tools.html

Facilities used

RTCP source and receiver reports

Availability

Binaries for RTPcast/RTPlisten are available from:
ftp://sauce.uio.no/mice-nsc/util/rtp

Source code for RTPquality is available from:
ftp://sauce.uio.no/mice-nsc/util/rtp/rtpqual.c

Source code for RTPdump is available at:
ftp://sauce.uio.no/mice-nsc/util/rtpdump-1.0.tar.gz

Source code for RTPtools is available at:
ftp://sauce.uio.no/mice-nsc/util/rtptools/rtptools-1.9.tar.gz

Source and binaries for Msessmon is available at:
ftp://sauce.uio.no/mice-nsc/util/msessmon/

Source and binaries for Mpoll is available at:
ftp://sauce.uio.no/mice-nsc/util/mpoll/

6.4. Multicast router diagnostics

This class of tools facilitates monitoring and management of multicast
routers.

6.4.1. mrouted.dump, mrouted.cache

Author

Bill Fenner, fenner@research.att.com

Description

Sending the USR1 signal to mrouted dumps the internal routing table
to /var/tmp/mrouted.dump; sending the USR2 signal dumps the
forwarding cache to /var/tmp/mrouted.cache.

Further information on mrouted and the mrouted.dump and mrouted.cache
file formats is available in the mrouted man page.

Example

Thaler & Aboba Informational [Page 16]

INTERNET-DRAFT Multicast Debugging Handbook 7 May 2000

% cat mrouted.dump
vifs_with_neighbors = 2

Virtual Interface Table
Vif Name Local-Address M Thr Rate Flags
0 ed0 128.31.107.1 subnet: 128.31.107/24 1 1 0 querier
peers: 128.31.107.249 (3.8) (0xe)
groups: 239.109.100.200
224.0.0.2
224.0.0.4
pkts in : 4075
pkts out: 0

1 ed0 128.31.107.1 tunnel: 204.67.107.11 1 32 500
peers: 204.67.107.11 (11.2) (0x1a)
pkts in : 0
pkts out: 2359

Multicast Routing Table (3801 entries)
Origin-Subnet From-Gateway Metric Tmr In-Vif Out-Vifs
207.10.165.51/32 128.31.107.249 10 20 0 1
207.10.165.50/32 128.31.107.249 10 20 0 1
206.172.195.32/32 128.31.107.249 9 20 0 1
172/8 128.31.107.249 10 20 0 1
...

% cat mrouted.cache
Multicast Routing Cache Table (198 entries)
Origin Mcast-group CTmr Age Ptmr IVif Forwvifs
131.107.2.139/32 224.0.12.0 58s 7m - -1
>131.107.2.139
143.107.103.0/27 224.0.1.1 3m 2m 3m 0P
>143.107.103.5
128.232/16 224.0.1.1 4m 7m 4m 0P
>128.232.2.209
157.161/16 224.0.1.1 67s 6m - 0 1
>157.161.114.2
206.152.163/24 224.0.1.15 74s 7m - 0 1
>206.152.163.21
4.0.0.34/32 224.0.1.32 56s 4m 25s 0P 1p
>4.0.0.34
137.39.2.254/32 224.0.1.32 3m 5m - 0 1
>137.39.2.254
137.39.43.32/30 224.0.1.32 38s 5m - 0 1
>137.39.43.34
...

Thaler & Aboba Informational [Page 17]

INTERNET-DRAFT Multicast Debugging Handbook 7 May 2000

Facilities used

Internal facilities (forwarding cache and routing table)

Availability

The SNMP-capable mrouted distribution is available at:
ftp://ftp.merit.edu/net-research/mbone/mirrors/mrouted/

6.4.2. mrinfo

Author

Van Jacobson, van@ee.lbl.gov

Description

mrinfo displays information about a multicast router; to do this, it
uses the IGMP ASK_NEIGHBORS message to discover the router's physical
and virtual interfaces. Routers are also queried for their version
number, and if this query is successful, for their metrics,
thresholds, and flags. Results are printed in an indented list format
similar to that for map-mbone.

Example

% mrinfo 192.80.214.199
192.80.214.199 (collegepk-mbone1.bbnplanet.net) [version 11.2,prune,mtrace,snmp]:
128.167.252.196 -> 0.0.0.0 (local) [1/0/pim/querier/leaf]
192.80.214.199 -> 0.0.0.0 (local) [1/0/pim/querier/leaf]
192.41.177.196 -> 0.0.0.0 (local) [1/0/pim/querier/down/leaf]
128.167.252.196 -> 128.167.254.165 (devo.sura.net) [1/32/tunnel/querier/down/leaf]
128.167.252.196 -> 131.119.0.197 (paloalto-mbone1.bbnplanet.net)
[1/64/tunnel/pim/querier]
128.167.252.196 -> 199.94.207.2 (cambridge1-mbone1.bbnplanet.net)
[1/32/tunnel/pim/querier]
128.167.252.196 -> 137.39.43.34 (MBONE1.UU.NET) [1/32/tunnel/querier]
128.167.252.196 -> 192.41.177.199 (wtn-ms2.bbnplanet.net) [1/16/tunnel/querier]
128.167.252.196 -> 128.244.93.3 (sage.jhuapl.edu) [1/32/tunnel/querier]
128.167.252.196 -> 192.221.34.22 (cdrn.bbnplanet.net) [1/32/tunnel/querier]
128.167.252.196 -> 128.167.1.197 (cpk-ms1.ser.bbnplanet.com) [1/16/tunnel/querier]
128.167.252.196 -> 134.205.93.150 (dilbert.sam.pentagon.mil) [1/32/tunnel/querier]
128.167.252.196 -> 192.221.48.234 (atlanta3-mbone1.bbnplanet.net)
[1/64/tunnel/pim/querier]
128.167.252.196 -> 204.167.201.38 (dallas2-mbone1.bbnplanet.net)
[1/64/tunnel/pim/querier]
128.167.252.196 -> 205.130.85.3 (philipii.nap.edu) [1/32/tunnel/querier/down/leaf]
128.167.252.196 -> 128.175.13.36 (pfet.nss.udel.edu) [1/32/tunnel/querier/down/leaf]

Thaler & Aboba Informational [Page 18]

INTERNET-DRAFT Multicast Debugging Handbook 7 May 2000

128.167.252.196 -> 192.41.177.197 (wtn-ms1.bbnplanet.net) [1/32/tunnel/querier]
128.167.252.196 -> 204.148.62.28 (mbone-e.ans.net) [1/32/tunnel/querier]
128.167.252.196 -> 205.128.246.2 (usnrctc.bbnplanet.net) [1/32/tunnel/pim/querier]

Facilities used

IGMP ASK_NEIGHBORS message (DVMRP)

Availability

mrinfo is available for UNIX and is included in the SNMP-capable
mrouted distribution, available at:
ftp://ftp.merit.edu/net-research/mbone/mirrors/mrouted/

mrinfo is also available in the MVIEW distribution, available at:
ftp://ftp.merit.edu/net-research/mbone/mview/

6.4.3. netstat

Author

Unknown

Description

On multicast-enabled systems, netstat is typically extended so as to
provide information on virtual interfaces and the multicast
forwarding cache (-g option), as well as multicast routing statistics
(-gs option), and igmp behavior (-s option).

Example

%netstat -g

Virtual Interface Table
Vif Thresh Rate Local-Address Remote-Address Pkts-In Pkts-Out
0 1 0 128.15.2.120 16323 385
1 32 512 128.15.2.120 202.34.126.2 2 0

Multicast Forwarding Cache
Origin Group Packets In-Vif Out-Vifs:Ttls
128.15.2.120 224.2.195.166 281 0
128.15.1.110 239.100.101.223 1660 0
128.15.1.135 238.27.27.1 1660 0
128.15.1.110 239.111.111.235 1660 0
...

%netstat -gs

Thaler & Aboba Informational [Page 19]

INTERNET-DRAFT Multicast Debugging Handbook 7 May 2000

multicast forwarding:
182880 multicast forwarding cache lookups
8237 multicast forwarding cache misses
6736 upcalls to mrouted
193 upcall queue overflows
5567 upcalls dropped due to full socket buffer
177 cache cleanups
7234 datagrams with no route for origin
0 datagrams arrived with bad tunneling
0 datagrams could not be tunneled
954 datagrams arrived on wrong interface
0 datagrams selectively dropped
0 datagrams dropped due to queue overflow
0 datagrams dropped for being too large

%netstat -s
ip:
3807182 total packets received
0 bad header checksums
...
icmp:
40 calls to icmp_error
0 errors not generated 'cuz old message was icmp
...
igmp:
18504 messages received
0 messages received with too few bytes
48 messages received with bad checksum
2478 membership queries received
0 membership queries received with invalid field(s)
194 membership reports received
0 membership reports received with invalid field(s)
0 membership reports received for groups to which we belong
8510 membership reports sent
tcp:
10705 packets sent
5536 data packets (1532081 bytes)
...
udp:
3104045 datagrams received
0 with incomplete header
...

Facilities used

Netstat accesses system internal data structures in order to carry
out its function.

Thaler & Aboba Informational [Page 20]

INTERNET-DRAFT Multicast Debugging Handbook 7 May 2000

Availability

netstat is included with a variety of operating systems, including
UNIX, OS/2, and Windows. For further information, please consult the
netstat man page or documentation.

6.4.4. mstat

Author

Dave Thaler, dthaler@microsoft.com

Description

mstat is a general purpose tool for obtaining router configuration
and status information. In order to perform its task, mstat utilizes
SNMP MIBs (such as the IGMP, multicast routing, PIM, and DVMRP MIBs),
as well as ASK_NEIGHBORS IGMP messages. mstat displays the contents
of various MBONE-related data structures in various formats,
depending on the options selected. Options include:

-G Show the PIM group table
-I Show the PIM interface table.
-K Show the cached IP multicast route table; works for
all SNMP-capable routers.
-N Show the IP Multicast Next Hop Table.
-P Show the PIM neighbor table.
-a Show the alternate subnet table.
-b Show the scoped boundary table.
-d Show the DVMRP neighbor table.
-g Show the Group Summary table.
-i Show the DVMRP interface table; similar to an
mrinfo report.
-l Show the IGMP local group table.
-r Show the DVMRP routing table; similar to a portion of
the mrouted.dump file.
-t Show the DVMRP routing next hop table; similar to
another portion of the mrouted.dump file.
-v Show statistics corresponding to the DVMRP interface table.

Examples

% mstat
IP Multicast Route Table for bigco.com
Mcast-group Origin-Subnet InIf UpTime Tmr Pkts Bytes RpF Proto
NTP.MCAST.NET 0.0.0.0/32 0 245341 179 0 0 0 pim
NTP.MCAST.NET 128.232.0.49/32 7 206403 418 3056 293376 17 dvmrp
NTP.MCAST.NET 128.232.2.209/32 7 206403 417 3027 290592 19 dvmrp

Thaler & Aboba Informational [Page 21]

INTERNET-DRAFT Multicast Debugging Handbook 7 May 2000

NTP.MCAST.NET 143.107.103.5/32 7 592 218 3 228 3 dvmrp
NTP.MCAST.NET 157.161.114.2/32 7 27703 517 411 31236 11 dvmrp
IETF-2-VIDEO.MC 0.0.0.0/32 0 245349 175 0 0 0 pim
IETF-2-VIDEO.MC 206.152.163.21/32 7 242567 244 46887 4149336 3388 dvmrp
MTRACE.MCAST.NE 0.0.0.0/32 0 1690 177 0 0 0 pim
MTRACE.MCAST.NE 194.104.0.25/32 7 405 483 2 792 0 dvmrp
MTRACE.MCAST.NE 206.54.224.150/32 7 456 569 4 1072 4 dvmrp
CISCO-RP-DISCOV 0.0.0.0/32 0 245534 0 0 0 0 pim
224.0.14.1 203.15.123.99/32 4 17 161 0 0 0 dvmrp
224.0.92.3 171.68.201.39/32 4 174 4 0 0 0 dvmrp
224.2.0.1 13.2.116.11/32 4 150 26 0 0 0 dvmrp
224.2.0.1 128.32.38.218/32 4 147 30 0 0 0 dvmrp
224.2.2.1 205.226.8.183/32 4 146 30 0 0 0 dvmrp
224.2.20.165 13.2.116.11/32 4 55 119 0 0 0 dvmrp
224.2.100.100 13.2.116.11/32 4 87 91 0 0 0 dvmrp
SAP.MCAST.NET 164.67.63.7/32 4 114 64 1 855 0 dvmrp
SAP.MCAST.NET 193.61.212.130/32 4 153 23 1 868 0 dvmrp
SAP.MCAST.NET 199.94.220.184/32 4 26 152 1 416 0 dvmrp
SAP.MCAST.NET 206.154.213.242/32 4 156 19 1 360 0 dvmrp
...

Examples of the many other options are provided in the mstat man pages.

Facilities used

PIM, DVMRP, IGMP, and multicast routing MIBs
IGMP ASK_NEIGHBORS message (DVMRP)

Availability

mstat is included in the SNMP-capable mrouted distribution,
available at:
ftp://ftp.merit.edu/net-research/mbone/mirrors/mrouted/

mstat is also available in the MVIEW distribution, available at:
ftp://ftp.merit.edu/net-research/mbone/mview/

6.4.5. mconfig

Author

Dave Thaler, dthaler@microsoft.com

Description

mconfig allows the user to display and (if the community string is
known) to modify the configuration of a multicast router implementing
the DVMRP MIB.

Thaler & Aboba Informational [Page 22]

INTERNET-DRAFT Multicast Debugging Handbook 7 May 2000

Example

For more information on mconfig, please see the man page.

Facilities used

DVMRP MIB

Availability

mconfig is available for UNIX and is included in the SNMP-capable
mrouted distribution, available at: ftp://ftp.merit.edu/net-
research/mbone/mirrors/mrouted/

6.5. Multicast traceroute

6.5.1. mtrace

Author

Bill Fenner, fenner@research.att.com

Description

mtrace provides a facility by which to trace the path between a
sender and a receiver of a particular group. This is particularly
useful when used alongside a facility such as RTPmon, which allows
you to identify problem source-receiver pairs.

Note that the utility of mtrace is often limited by the multicast
topology. Where multicast and unicast topologies are not aligned (as
is the case in many multicast-enabled networks) mtrace may not
function.

For information on the details of the protocol, see reference [8].

Example

% mtrace 131.243.73.36 128.15.1.250 224.2.195.166
Mtrace from 131.243.73.36 to 128.15.1.250 via group 224.2.195.166
Querying full reverse path... * switching to hop-by-hop:
0 bigman.bigco.com (128.15.1.250)
-1 * * littleman.bigco.com (128.15.1.249) DVMRP thresh^ 1
-2 * * * seamr1-gw.nwnet.net (192.35.180.201) DVMRP thresh^ 32
-3 * * seamr2-gw.nwnet.net (192.220.238.130) DVMRP thresh^ 0
-4 * * mcast.cac.washington.edu (140.142.116.1) DVMRP thresh^ 32
-5 * * * * dec3800-1-fddi-0.Sacramento.mci.net (204.70.164.29) didn't respond

Thaler & Aboba Informational [Page 23]

INTERNET-DRAFT Multicast Debugging Handbook 7 May 2000

-6 * * *
-7 * *
Resuming...
-5 dec3800-1-fddi-0.Sacramento.mci.net (204.70.164.29) DVMRP thresh^ 64
-6 dec3800-2-fddi-0.SanFrancisco.mci.net (204.70.158.61) DVMRP thresh^ 1
-7 mbone.nsi.nasa.gov (192.203.230.241) DVMRP thresh^ 64
-8 * * llnl-mr2.es.net (134.55.12.229) DVMRP thresh^ 64
-9 * * lbl-mr1.es.net (134.55.12.101) DVMRP thresh^ 8
-10 * * mr1.lbl.gov (131.243.64.184) DVMRP thresh^ 32
-11 * * ir40gw.lbl.gov (131.243.64.1) DVMRP thresh^ 0
-12 * * irals.lbl.gov (131.243.128.6) PIM thresh^ 0
-13 bl7-36.als.lbl.gov (131.243.73.36)
Round trip time 74 ms; total ttl of 72 required.

Waiting to accumulate statistics... Results after 10 seconds:

Source Response Dest Overall Packet Statistics For Traffic From
131.243.73.36 128.15.1.250 Packet 131.243.73.36 To 224.2.195.166
v __/ rtt 77 ms Rate Lost/Sent = Pct Rate
131.243.73.1
131.243.128.6 irals.lbl.gov
v ^ ttl 1 6 pps 0/60 = 0% 6 pps
131.243.128.40
131.243.64.1 ir40gw.lbl.gov
v ^ ttl 2 13 pps 0/60 = 0% 6 pps
131.243.64.184 mr1.lbl.gov
v ^ ttl 35 9 pps 0/60 = 0% 6 pps
198.128.16.13
134.55.12.101 lbl-mr1.es.net
v ^ ttl 35 0 pps 0/60 = 0% 0 pps
134.55.12.229 llnl-mr2.es.net
v ^ ttl 69 0 pps 1/60 = 2% 0 pps
192.203.230.241 mbone.nsi.nasa.gov
v ^ ttl 70 0 pps 0/59 = 0% 0 pps
204.70.158.61 dec3800-2-fddi-0.SanFrancisco.mci.net
v ^ ttl 70 0 pps 0/59 = 0% 0 pps
204.70.164.29 dec3800-1-fddi-0.Sacramento.mci.net
v ^ ttl 72 0 pps 0/59 = 0% 0 pps
140.142.116.1 mcast.cac.washington.edu
v ^ ttl 72 0 pps 0/59 = 0% 0 pps
192.220.249.66
192.220.238.130 seamr2-gw.nwnet.net
v ^ ttl 72 0 pps 0/59 = 0% 0 pps
192.220.238.129
192.35.180.201 seamr1-gw.nwnet.net
v ^ ttl 72 0 pps 0/59 = 0% 0 pps
128.15.1.249 littleman.bigco.com
v __ ttl 72 0 pps ?/59 0 pps

Thaler & Aboba Informational [Page 24]

INTERNET-DRAFT Multicast Debugging Handbook 7 May 2000

128.15.1.250 128.15.1.250
Receiver Query Source

Facilities used

IGMP multicast trace facility

Availability

mtrace is now distributed independently of mrouted.
Source code is available from:
ftp://ftp.parc.xerox.com/pub/net-research/ipmulti/mtrace5.1.tar.Z

Binaries:
ftp://ftp.parc.xerox.com/pub/net-research/ipmulti/mtrace5.1-sparc-sunos41x.tar.Z
ftp://ftp.parc.xerox.com/pub/net-research/ipmulti/mtrace5.1-sparc-solaris2.tar.Z
ftp://ftp.parc.xerox.com/pub/net-research/ipmulti/mtrace5.1-alpha-osf1.tar.Z
ftp://ftp.parc.xerox.com/pub/net-research/ipmulti/mtrace5.1-sgi-irix.tar.Z

6.6. MBONE mapping tools

6.6.1. mrtree

Author

Dave Thaler, dthaler@microsoft.com
Andy Adams, ala@merit.edu

Description

mrtree uses a combination of IGMP and SNMP queries to discover the
actual and potential multicast (sub)trees for a given source and
group, rooted at a given router. An actual tree, discovered using the
multicast routing MIB, consists of routers which are currently
forwarding multicast traffic to a group from a given source. A
potential tree, discovered using the DVMRP MIB, is one which would
exist if every host were a member of the group.

Example

% mrtree mbone.merit.edu 224.2.143.24 204.62.246.73
Actual distribution tree rooted at mbone.merit.edu for group 224.2.143.24
and source 204.62.246.73...
0 mbone.merit.edu (198.108.2.20) [ver 3.8,prune,genid,mtrace],
247390 pkts
1 cujo.merit.edu (198.108.60.97) [ver 3.6,prune,genid,mtrace], 333448
6 pkts (1347%)

Thaler & Aboba Informational [Page 25]

INTERNET-DRAFT Multicast Debugging Handbook 7 May 2000

2 subnet: 198.108.60/24
2 shockwave.merit.edu (198.108.60.69) [ver 3.8,prune,genid,mtrace,snmp],
1239130 pkts (500%)
1 tibia.cic.net (192.217.65.100) [ver 3.8,prune,genid,mtrace]
... (No response from tibia.cic.net)
2 fibula.cic.net (192.217.65.101) [ver 3.8,prune,genid,mtrace] ?
2 dcl2.gw.uiuc.edu (192.17.2.8) [ver 1.0] ?
2 goober.mci.net (204.70.104.45) [ver 3.6,prune,genid,mtrace] ?
... (goober.mci.net did not respond to DVMRP 'NEIGHBORS' msg)
1 a-wing.jvnc.net (130.94.40.6) [ver 3.3]
... (a-wing.jvnc.net does not support SNMP)
2 liberty-eth0/0.jvnc.net (130.94.40.1) [ver 10.2] ?
2 noc.hpc.org (192.187.8.2) [ver 3.8,prune,genid,mtrace] ?
2 liberty.jvnc.net (130.94.40.201) [ver 10.2] ?
2 dstest.ds.internic.net (198.49.45.4) [ver 3.8,prune,genid,mtrace] ?
2 cybercast.cc.nus.sg (137.132.9.70) [ver 3.6,prune,genid,mtrace] ?
... (cybercast.cc.nus.sg did not respond to DVMRP 'NEIGHBORS' msg)

Facilities used

DVMRP and multicast routing MIBs
IGMP ASK_NEIGHBORS message (DVMRP)

Availability

mrtree is available for UNIX and is included in the
SNMP-capable mrouted distribution, available at:
ftp://ftp.merit.edu/net-research/mbone/mirrors/mrouted/

mrtree is also available in the MVIEW distribution, available at:
ftp://ftp.merit.edu/net-research/mbone/mview/

6.6.2. map-mbone

Author

Pavel Curtis, pavel@parc.xerox.com

Description

map-mbone is useful for discovering the topology within a DVMRP
routing domain; to do this, it uses the IGMP ASK_NEIGHBORS message to
discover the neighbors of the starting router. If the -f (flooding)
option is enabled (this is the default if no starting router is
specified), then once these neighbors are discovered, they too are
queried. This continues until the leaf routers are reached. This
option should be used with care since it can result in excessive load
on multicast routers.

Thaler & Aboba Informational [Page 26]

INTERNET-DRAFT Multicast Debugging Handbook 7 May 2000

If a starting router is specified but the -f option is not used, then
the search terminates after the first hop routers are discovered, the
output of map-mbone is very similar to that for mrinfo. Routers
discovered by map-mbone are queried for their version numbers, and if
this query is successful, for their metrics, thresholds, and flags,
and the results are presented in an indented list format.

Example

% map-mbone 192.80.214.199
192.41.177.196: alias for 128.167.252.196

128.167.252.196 (collegepk-mbone1.bbnplanet.net): <v11.2>
192.41.177.196: 192.41.177.196 [1/0/querier/down]
192.80.214.199: 192.80.214.199 (collegepk-mbone1.bbnplanet.net) [1/0/querier]
128.167.252.196: 205.128.246.2 (usnrctc.bbnplanet.net) [1/32/tunnel/querier]
204.148.62.28 (mbone-e.ans.net) [1/32/tunnel/querier]
192.41.177.197 (wtn-ms1.bbnplanet.net) [1/32/tunnel/querier]
128.175.13.36 (pfet.nss.udel.edu) [1/32/tunnel/querier/down]
205.130.85.3 (philipii.nap.edu) [1/32/tunnel/querier/down]
204.167.201.38 (dallas2-mbone1.bbnplanet.net) [1/64/tunnel/querier]
192.221.48.234 (atlanta3-mbone1.bbnplanet.net) [1/64/tunnel/querier]
134.205.93.150 (dilbert.sam.pentagon.mil) [1/32/tunnel/querier]
128.167.1.197 (cpk-ms1.ser.bbnplanet.com) [1/16/tunnel/querier]
192.221.34.22 (cdrn.bbnplanet.net) [1/32/tunnel/querier]
128.244.93.3 (sage.jhuapl.edu) [1/32/tunnel/querier]
192.41.177.199 (wtn-ms2.bbnplanet.net) [1/16/tunnel/querier]
137.39.43.34 (MBONE1.UU.NET) [1/32/tunnel/querier]
199.94.207.2 (cambridge1-mbone1.bbnplanet.net) [1/32/tunnel/querier]
131.119.0.197 (paloalto-mbone1.bbnplanet.net) [1/64/tunnel/querier]
128.167.254.165 (devo.sura.net) [1/32/tunnel/querier/down]
128.167.252.196 (collegepk-mbone1.bbnplanet.net) [1/0/querier]

192.80.214.199 (collegepk-mbone1.bbnplanet.net): alias for 128.167.252.196

Facilities used

IGMP ASK_NEIGHBORS message (DVMRP)

Availability

map-mbone is available for UNIX, and the software and manual pages are included
in the SNMP-capable mrouted distribution, available at:
ftp://ftp.merit.edu/net-research/mbone/mirrors/mrouted/

Thaler & Aboba Informational [Page 27]

INTERNET-DRAFT Multicast Debugging Handbook 7 May 2000

6.6.3. asn

Author

Dave Thaler, dthaler@microsoft.com

Description

asn gives the AS number of a given IP address by querying the routing
arbiter database.

Example

% asn 141.213.10.41
AS237

Facilities used

Routing arbiter database

Availability

asn is included in the MVIEW distribution, available at:
ftp://ftp.merit.edu/net-research/mbone/mview/

6.6.4. asname

Author

Dave Thaler, dthaler@microsoft.com

Description

asname gets the name of an AS, given the AS number by querying the
WHOIS database.

Example

% asname 237
NSFNETTEST14-AS

Facilities used

WHOIS database

Availability

asname is included in the MVIEW distribution, available at:

Thaler & Aboba Informational [Page 28]

INTERNET-DRAFT Multicast Debugging Handbook 7 May 2000

ftp://ftp.merit.edu/net-research/mbone/mview/

6.7. Network Operations Center tools

These tools are suitable for use in a Network Operations Center.

6.7.1. MVIEW

Authors

Dave Thaler, dthaler@microsoft.com
Andy Adams, ala@merit.edu

Description

MVIEW uses utilities such as mstat, mtrace, mrtree, asn and asname in
order to produce a graphical depiction of the multicast network
topology and the actual and potential multicast trees for a given
group and source.

Example

Further information on MVIEW as well as examples are available from:
http://www.merit.edu/net-research/mbone/mviewdoc/Welcome.html

Facilities used

PIM, DVMRP, IGMP, and multicast routing MIBs (mstat)
IGMP ASK_NEIGHBORS message (mrinfo)
Routing arbiter database (asn)
WHOIS database (asname)

Availability

MVIEW is available for UNIX, and can be obtained from:
ftp://ftp.merit.edu/net-research/mbone/mview/

Documentation is available as:
ftp://ftp.merit.edu/net-research/mbone/mviewdoc/

6.7.2. Multicast heartbeat

Author

Many and various

Description

Thaler & Aboba Informational [Page 29]

INTERNET-DRAFT Multicast Debugging Handbook 7 May 2000

Devices implementing the multicast heartbeat listen on a designated
group. If traffic is not observed on the group for a specified amount
of time, an SNMP trap is generated. This allows multicast monitoring
to be easily integrated into existing SNMP consoles. In situations
where a shared-tree multicast routing protocol is used (such as
sparse-mode PIM or CBT), it is recommended that the heartbeat
generator be located close to the RP or core nodes, so as that loss
of the heartbeat will correlate closely with loss of connectivity to
the RP or core. Suitable heartbeat mechanisms include SNTP, which
uses the group 224.0.1.1 (ntp.mcast.net) and UDP port 123; and SAP,
which uses the group 224.2.127.254 (sap.mcast.net) and UDP port 9875.

Example

For further information on SNTP, consult [1].

Facilities used

SNTP (for time-based heartbeats)
SAP (for session announcement heartbeats)
SNMP traps (for alerts)

Availability

6.8. Network analysis tools

6.8.1. Dr. Watson, the Network Detective's Assistant (DWTNDA)

Author

Karl Auerbach, karl@cavebear.com

Description

DWTNDA is a general purpose troubleshooting tool with some IP
multicast tools (in addition to a fair number of non-multicast
tools). For example it can watch IGMP "join" activity on a LAN and
put up a real-time display in tabular format. It can generate some
test packets, like IGMPv2 Leaves or Group Membership Requests. It can
generate and respond to multicast pings (icmp, udp, or snmp based.)
It will eventually acquire more sophisticated multicast facilities.

Example

See http://www.cavebear.com/dwtnda/ for examples.

Thaler & Aboba Informational [Page 30]

INTERNET-DRAFT Multicast Debugging Handbook 7 May 2000

Facilities used

This is a troubleshooting tool, so it will typically respond to
packets that, strictly speaking, ought to go unanswered.

Availability

DWTNDA runs on MS-DOS and Windows 95/98 and is free. Source is not
provided. See http://www.cavebear.com/dwtnda/ for various documents
and download information.

6.8.2. Mtap

Author

Luis Fernando da Silva Barra, barra@ax.apc.org
Michael Stanton, michael@omega.lncc.br

Description

MTap is a tool for observing IP multicast packet traffic crossing a
subnet, normally an Ethernet.

Each packet sent to an IP multicast group address (class D) is
captured, and information is extracted concerning its origin, its
size, and so forth. This information is summarized, permitting the
determination of the current network load resulting from multicast
traffic. Apart from global summaries, traffic information is
summarized by group and by source, permitting the determination of
the contribution of each group and each individual sender to global
traffic. The data recorded are as follows: number of multicast
packets and total multicast bytes passing through the network, load
level, and date and time of the last packet received.

As well as processing packets sent to a multicast address, MTap also
records separately multicast packets encapsulated in point-to-point
packets. Thus we can also deal with traffic in DVMRP tunnels between
multicast routers, and tunnel traffic data are recorded in the same
way as for a group.

As well as recording the data. MTap also permits that individual
packet data be exhibited in dump format at capture time, both for
multicast packets and for tunneled packets.

In order to evaluate the impact which a group imposes on a
subnetwork, MTap can enter or leave a multicast group, using the IGMP
protocol. Thus traffic can be observed for a group which has no other
members on the subnetwork.

Thaler & Aboba Informational [Page 31]

INTERNET-DRAFT Multicast Debugging Handbook 7 May 2000

In addition to passively observing and recording multicast traffic,
MTap has a notification mechanism, which sets off an alarm whenever
user-specified load levels are exceeded, either globally, by group or
by tunnel. Notifications are also logged in a dedicated window.

Example

Further information on Mtap will be available from:
http://www.inf.puc-rio.br/~michael/GERENTE/tools

Facilities used

Berkeley Packet Filter (BPF)

Availability

MTap uses a window-based user interface, developed using Tcl/Tk, and
captures packets through the Berkeley Packet Filter (BPF). It can
thus be ported to different platforms.

Mtap, which is still under development, has been ported to Linux and
Solaris; minor problems related to packet capture have still to be
resolved for the Solaris version. When it is released, it will be
available from:
http://www.inf.puc-rio.br/~michael/GERENTE/tools

7. References

[1] Mills, D., "Simple Network Time Protocol (SNTP) Version 4 for IPv4,
IPv6 and OSI", RFC 2030, October 1996.

[2] Fenner, W., "Internet Group Management Protocol, Version 2", RFC
2236, November 1997.

[3] McCloghrie, K., Farinacci, D., Thaler, D., "Internet Group
Management Protocol MIB", Internet draft (work in progress), draft-
ietf-idmr-igmp-mib-10.txt, June 1999.

[4] Handley, M., Jacobson, V., "SDP: Session Descripton Protocol
(Version 1)", RFC 2327, April 1998.

[5] McCloghrie, K., Farinacci, D., Thaler D., "IP Multicast Routing
MIB", Internet draft (work in progress), draft-ietf-idmr-multicast-
routmib-10.txt, July 1999.

[6] McCloghrie, K., Farinacci, D., Thaler, D., "Protocol Independent
Multicast MIB", Internet draft (work in progress), draft-ietf-idmr-

Thaler & Aboba Informational [Page 32]

INTERNET-DRAFT Multicast Debugging Handbook 7 May 2000

pim-mib-07.txt, July 1999.

[7] Thaler, D., "Distance Vector Multicasting Routing Protocol MIB",
Internet draft (work in progress), draft-thaler-dvmrp-mib-09.txt,
May 1998.

[8] Fenner, W., Casner, S., "A "traceroute" facility for IP Multicast",
Internet draft (work in progress), draft-ietf-idmr-traceroute-
ipm-05.txt, June 1999.

[9] Rekhter, Y. et al., "Address Allocation for Private Internets", RFC
1918, February, 1996.

8. Security Considerations

SNMP-based monitoring tools require that the manager be provided access
to the relevant MIBs. In order to limit security risks, such access will
typically be provided on a selective basis. For example, the
authentication and access control facilities in SNMP v3 can be used to
limit access to authorized users.

MBONE-mapping tools such as map-mbone should be used with care since in
flooding mode they can result in excessive load on multicast routers.

Through use of RTP monitoring tools, it may be possible to obtain
sensitive information on user viewing habits. In order to protect
against this, encryption technologies such as IPSEC can be used to
provide confidentiality.

9. Acknowledgments

Thanks to Karl Auerbach for the description of the Dr. Watson tool, and
to Michael Stanton for the description of the Mtap tool.

10. Authors' Addresses

Dave Thaler
Microsoft Corporation
One Microsoft Way
Redmond, WA 98052

Phone: 425-703-8835
EMail: dthaler@microsoft.com

Bernard Aboba
Microsoft Corporation
One Microsoft Way
Redmond, WA 98052

Thaler & Aboba Informational [Page 33]

INTERNET-DRAFT Multicast Debugging Handbook 7 May 2000

Phone: 425-936-6605
EMail: bernarda@microsoft.com

11. Full Copyright Statement

Copyright (C) The Internet Society (1999). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it or
assist in its implmentation may be prepared, copied, published and
distributed, in whole or in part, without restriction of any kind,
provided that the above copyright notice and this paragraph are included
on all such copies and derivative works. However, this document itself
may not be modified in any way, such as by removing the copyright notice
or references to the Internet Society or other Internet organizations,
except as needed for the purpose of developing Internet standards in
which case the procedures for copyrights defined in the Internet
Standards process must be followed, or as required to translate it into
languages other than English. The limited permissions granted above are
perpetual and will not be revoked by the Internet Society or its
successors or assigns. This document and the information contained
herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE
INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF

12. Expiration Date

This memo is filed as <draft-ietf-mboned-mdh-04.txt>, and expires
December 1, 2000.

Thaler & Aboba Informational [Page 34]

PAFTECH AB 2003-2026

2026-04-23 11:30:13