MBONE Deployment Working Group Dave Thaler
INTERNET-DRAFT University of Michigan
<draft-ietf-mboned-mdh-00.txt> Bernard Aboba
25 March 1997 Microsoft
Multicast Debugging Handbook
1. Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working docu-
ments of the Internet Engineering Task Force (IETF), its areas, and
its working groups. Note that other groups may also distribute work-
ing 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 mate-
rial or to cite them other than as ``work in progress.''
To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts Shadow
Directories on ds.internic.net (US East Coast), nic.nordu.net
(Europe), ftp.isi.edu (US West Coast), or munnari.oz.au (Pacific Rim).
The distribution of this memo is unlimited. It is filed as <draft-
ietf-mboned-mdh-00.txt>, and expires September 1, 1997. Please send
comments to the authors.
2. Abstract
This document serves as a handbook for the debugging of multicast con-
nectivity problems. In addition to reviewing commonly encountered
problems, the draft summarizes publicly distributable multicast diag-
nostic tools, and provides examples of their use, along with pointers
to source and binary distributions.
3. 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 prob-
lems. 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.
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4. Usage scenarios
Multicast diagnostic tools are typically employed in one of the fol-
lowing settings:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | |
| Customer service or | SDR |
| support | mtrace |
| | RTPmon |
| | Dr. Watson |
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | |
| | SDR |
| | mrinfo |
| Network or system | netstat |
| administrator | mconfig |
| | mstat |
| | mtrace |
| | RTPmon |
| | tcpdump |
| | Dr. Watson |
| | Duppkts |
| | mrouted.dump, mrouted.cache |
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | |
| | SDR |
| | mrtree |
| | map-mbone |
| Network Operations | MVIEW |
| Center | Multicast heartbeat |
| | mwatch and mcollect |
| | asn |
| | asname |
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4.1. Customer service and support
ISPs offering multicast services are likely to encounter the following
classes of customer questions:
Session announcement problems
Reception problems
Multicast router problems
Below we discuss how each of these types of problems may be diagnosed.
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4.1.1. 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 fol-
lowing procedure:
1. If only a specific session announcement is missing, check the ses-
sion 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 announce-
ments, 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 posi-
tion to receive, due to site or regional scoping. The loss may also
be the 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-neg-
ligible loss. These typically denote points of congestion (see sec-
tion 4.3.1). Note that if rate-limiting is installed on these con-
gested 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
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sources, and what is being announced.
4.1.2. 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 pro-
cedure:
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
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 sepa-
rating 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-neg-
ligible loss. These typically denote points of congestion (see sec-
tion 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.
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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 con-
necting 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 applica-
tions. 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 upgrad-
ing the user to an IGMP v2-capable stack.
IGMP-related questions are typically investigated by the following
procedure:
1. Obtain the vendor and version of the user's TCP/IP stack. Deter-
mine whether this stack is IGMP v2-enabled.
2. Ask the user to run Dr. Watson or a network sniffer and to indi-
cate whether IGMP queries are being seen, whether responses are being
sent, and if so, what version.
4.1.3. Multicast router problems
Multicast router questions are those which relate to the setup of a
multicast router. Sample complaints include:
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 follow-
ing 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
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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 vari-
ous 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 sub-
scribed 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.
4.2. 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 sup-
port to have performed the diagnostic tests described above, if this
has not been done, NOC personnel will need to perform the tests them-
selves 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:
1. Regularly generate summaries based on RTCP receiver and sender
reports, using RTP monitoring tools. Sample reports may include aver-
age 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.
4.3. Network or system administrator
The NOC will escalate network engineering problems to network engi-
neers 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
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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 condo-
lences).
Typical classes of problems encountered by network engineers and sys-
tem administrators include:
Congestion and rate-limiting problems
Multicast routing problems
4.3.1. 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.
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. Over-
loaded 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 indica-
tor 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 indi-
cation that the link's multicast rate limit should be raised or elimi-
nated entirely. Packet loss on a link without rate limiting is an
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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 sin-
gle 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).
4.3.2. 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
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 [10]. 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 num-
ber of unicast routes (25K+) into DVMRP. The problem may be investi-
gated via the following procedure:
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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 mul-
ticast 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. As described
in [11], non-pruning routers include mrouted versions prior to 3,
Cisco Systems IOS prior to version 11.0(3), and Bay Networks implemen-
tations prior to 9.0.
2. Confirm lack of pruning as follows. First, dump the multicast for-
warding 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 outgo-
ing interface list for every entry in the multicast forwarding table.
If so, it is likely that a non-pruner lies downstream in that direc-
tion.
4. You can confirm the existence of a non-pruner by creating a tempo-
rary, 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.
5. Appendix - Multicast Diagnostic Tools
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5.1. Types of tools
Multicast diagnostic tools typically fall into the following cate-
gories:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | |
| RTP monitoring tools | RTPmon |
| | Msessmon |
| | RTPquality |
| | RTPdump |
| | RTPcast/RTPlisten |
| | Duppkts |
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | |
| | mrinfo |
| Multicast router | netstat |
| diagnostics | mconfig |
| | mstat |
| | mrouted.dump, mrouted.cache |
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | |
| Multicast traceroute | mtrace |
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | |
| | mrtree |
| | map-mbone |
| MBONE mapping tools | asn |
| | asname |
| | mcollect & mwatch |
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | |
| NOC tools | MVIEW |
| | Multicast heartbeat |
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | |
| Network analysis | tcpdump |
| tools | Dr. Watson |
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
RTP monitoring tools are used to monitor the transmission quality and
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
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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.
5.2. Facilities utilized
Multicast diagnostic tools typically rely on one or more of the fol-
lowing facilities:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | |
| RTCP source and | RTPmon |
| receiver reports | Msessmon |
| | RTPquality |
| | RTPdump |
| | RTPcast/RTPlisten |
| | Duppkts |
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | |
| | multicast heartbeat |
| SNMP MIBs | mconfig |
| | mstat |
| | MVIEW |
| | mrtree |
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | |
| IGMP trace facility | mtrace |
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | |
| | mrinfo |
| | mrtree |
| IGMP ASK_NEIGHBORS | map-mbone |
| message (DVMRP) | |
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | |
| Routing arbiter and | asn |
| WHOIS Databases | asname |
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | |
| Internal structures | tcpdump |
| | netstat |
| | mrouted.dump, mrouted.cache |
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Tools using RTCP reports analyze RTCP source and receiver reports,
providing information on packet loss, inter-arrival jitter, bandwidth
availability, or listenership. These tools therefore will only work
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with RTP implementations which support RTCP reporting. Tools using
SNMP MIBs perform queries for variables in the IGMP, multicast rout-
ing, DVMRP, and PIM MIBs. As a result, these tools depend on implemen-
tation 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 mul-
ticast routers along the path have a route back to the source.
Diagnostic tools may use more than one of these facilities. For exam-
ple, mstat makes use of SNMP MIBs, as well as the IGMP ASK_NEIGHBORS
facility.
5.3. RTP monitoring tools
This class of tools provides information required to monitor the per-
formance of RTP-based applications.
5.3.1. 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 moni-
tor listenership as well as session quality experienced by sub-
scribers. 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 spread-
sheet, with cells being filled in with metrics such as packet loss
rate or jitter. Clicking on a cell displays a stripchart of statis-
tics 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
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.
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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/ or
Facilities used
RTCP source and receiver reports
IGMP multicast trace (if installed)
Availability
RTPmon is available for UNIX and may be obtained from:
ftp://bmrc.berkeley.edu/pub/rtpmon/
Bug reports and suggestions should be sent to:
rtpmon@bmrc.berkeley.edu.
5.3.2. RTPcast/RTPlisten, RTPquality, Duppkts, RTPdump, RTPtools,
Msessmon
Author
Description
RTPcast listens to RTCP receiver reports and forwards data to
another multicast group; RTPlisten then listens to that group. RTP-
dump 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 par-
ticipants in RTP conferences as well as stripcharts of statistics
on RTP packet loss and jitter.
Example
Information on these tools is available from:
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
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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-1.6.tar.gz
Source and binaries for Msessmon is available at:
ftp://sauce.uio.no/mice-nsc/util/msessmon/
5.4. Multicast router diagnostics
This class of tools facilitates monitoring and management of multicast
routers.
5.4.1. mrouted.dump, mrouted.cache
Author
Bill Fenner, fenner@parc.xerox.com
Description
Sending the USR1 signal to mrouted dumps the internal routing table
to /var/tmp/mrouted.dump; sending the USR2 signal dumps the for-
warding 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
% 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
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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
...
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/
5.4.2. 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 for-
mat similar to that for map-mbone.
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INTERNET-DRAFT 25 March 1997
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]
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/
5.4.3. netstat
Author
Unknown
Description
On multicast-enabled systems, netstat is typically extended so as
to provide information on virtual interfaces and the multicast for-
warding cache (-g option), as well as multicast routing statistics
(-gs option), and igmp behavior (-s option).
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INTERNET-DRAFT 25 March 1997
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
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
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INTERNET-DRAFT 25 March 1997
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.
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.
5.4.4. mstat
Author
Dave Thaler, thalerd@eecs.umich.edu
Description
mstat is a general purpose tool for obtaining router configuration
and status information. In order to perform its task, mstat uti-
lizes 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.
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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
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/
5.4.5. mconfig
Author
Dave Thaler, thalerd@eecs.umich.edu
Description
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INTERNET-DRAFT 25 March 1997
mconfig allows the user to display and (if the community string is
known) to modify the configuration of a multicast router implement-
ing the DVMRP MIB.
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/
5.5. Multicast traceroute
5.5.1. mtrace
Author
Bill Fenner, fenner@parc.xerox.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
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INTERNET-DRAFT 25 March 1997
-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
128.15.1.250 128.15.1.250
Receiver Query Source
Facilities used
IGMP multicast trace facility
Thaler & Aboba [Page 21]
INTERNET-DRAFT 25 March 1997
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
5.6. MBONE mapping tools
5.6.1. mrtree
Author
Dave Thaler, thalerd@eecs.umich.edu
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%)
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)
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INTERNET-DRAFT 25 March 1997
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/
5.6.2. 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 (flood-
ing) 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 exces-
sive load on multicast routers.
If a starting router is specified but the -f option is not used,
then the search terminates after the first hop routers are discov-
ered, the output of map-mbone is very similar to that for mrinfo.
Routers discovered by map-mbone are queried for their version num-
bers, and if this query is successful, for their metrics, thresh-
olds, 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]
Thaler & Aboba [Page 23]
INTERNET-DRAFT 25 March 1997
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/
5.6.3. asn
Author
Dave Thaler, thalerd@eecs.umich.edu
Description
asn gives the AS number of a given IP address by querying the rout-
ing arbiter database.
Example
% asn 141.213.10.41
AS237
Facilities used
Routing arbiter database
Availability
Thaler & Aboba [Page 24]
INTERNET-DRAFT 25 March 1997
asn is included in the MVIEW distribution, available at:
ftp://ftp.merit.edu/net-research/mbone/mview/
5.6.4. asname
Author
Dave Thaler, thalerd@eecs.umich.edu
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:
ftp://ftp.merit.edu/net-research/mbone/mview/
5.7. Network Operations Center tools
These tools are suitable for use in a Network Operations Center.
5.7.1. MVIEW
Authors
Dave Thaler, thalerd@eecs.umich.edu
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
Thaler & Aboba [Page 25]
INTERNET-DRAFT 25 March 1997
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/
5.7.2. Multicast heartbeat
Author
Many and various
Description
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 heart-
beat generator be located close to the RP or core nodes, so as that
loss of the heartbeat will correlate closely with loss of connec-
tivity 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 the SNTP heartbeat, consult references
[1] and [9].
Facilities used
SNTP (for time-based heartbeats)
SAP (for session announcement heartbeats)
SNMP traps (for alerts)
Availability
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5.8. Network analysis tools
5.8.1. 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 mul-
ticast 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.
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 Win-95 and is free. (Source is not pro-
vided.) See http://www.cavebear.com/dwtnda/ for various documents
and download information.
5.8.2. 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 cap-
tured, 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
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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 subnet-
work, 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.
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
6. Acknowledgments
Thanks to Karl Auerbach for the description of the Dr. Watson tool,
and to Michael Stanton for the description of the Mtap tool.
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7. References
[1] D. Mills. "Simple Network Time Protocol (SNTP) Version 4 for
IPv4, IPv6 and OSI." RFC 2030, University of Delaware, October, 1996.
[2] S.E. Deering. "Host Extensions for IP Multicasting." RFC 1112,
Stanford University, August, 1989.
[3] K. McCloghrie, D. Farinacci, D. Thaler. "Internet Group Manage-
ment Protocol MIB." draft-ietf-idmr-igmp-mib-04.txt, cisco Systems,
University of Michigan, November 1996.
[4] M. Handley. "SAP: Session Announcement Protocol (Version 1)."
draft-ietf-mmusic-sap-02.ps, UCL, December, 1996.
[5] K. McCloghrie, D. Farinacci, D. Thaler. "IP Multicast Routing
MIB." draft-ietf-idmr-multicast-routmib-04.txt, cisco Systems, Univer-
sity of Michigan, November 1996.
[6] K. McCloghrie, D. Farinacci, D. Thaler. "Protocol Independent
Multicast MIB." draft-ietf-idmr-pim-mib-02.txt, cisco Systems, Univer-
sity of Michigan, June 1996.
[7] D. Thaler. "Distance Vector Multicasting Routing Protocol MIB."
draft-ietf-idmr-dvmrp-mib-03.txt, University of Michigan, June 1996.
[8] W. Fenner, S. Casner. "A "traceroute" facility for IP Multi-
cast." draft-ietf-idmr-traceroute-ipm-01.txt, Xerox PARC, Precept
Software, November 1996.
[9] B. Aboba, T. Pfenning. "The Use of SNTP as a Multicast Heart-
beat." draft-ietf-mboned-sntp-heart-02.txt, Microsoft, December, 1996
[10] Y. Rekhter, et al. "Address Allocation for Private Internets."
RFC 1918, Cisco Systems, February, 1996
[11] J. Hawkinson. "Multicast Pruning a Necessity." draft-ietf-
mboned-pruning-01.txt, September, 1996
8. Authors' Addresses
Dave Thaler
EECS Department
University of Michigan
Ann Arbor, MI 48109
Phone: 313-763-5243
EMail: thalerd@eecs.umich.edu
Bernard Aboba
Microsoft Corporation
One Microsoft Way
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Redmond, WA 98052
Phone: 206-936-6605
EMail: bernarda@microsoft.com
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