MBone Working Group

MBone Euro-FAQ

Last modified: Sat Dec 13, 1997

The Mbone Euro-FAQ is written as an effort for the RIPE Mbone WG.

INTRODUCTION

This is the European edition of the Multicast Backbone (Mbone) Frequently Asked Questions (FAQ) and (most of) their answers.
This document contains numerous links to other documents available on the Internet.
The author is grateful to all maintainers of those documents for having them on-line.

There are several reasons for having a Euro-FAQ, besides the world-wide FAQ that is maintained. One of them being the fact that in Europe bandwidth is still expensive.
The RIPE community provides an ideal channel to coordinate efforts of ISPs, often complete countries that want to be connected to MBone and/or Internet.

DISCLAIMER: The FAQ comes without any warranty. The author can not guarantee the correctness and completeness of all information contained in this FAQ at any point in time. Since the Internet goes more and more commercial, please inform the author of any potential copyright violation.

Additions and corrections are welcome. Please send them to the author (address at the end of this document).

Section: GENERAL

G-01. What is Mbone?

Mbone is in general just an expression that describes an experimental part of the Internet which uses a special set of IP Addresses which are not Unicast (one to one) or
Broadcast (One to all), but rather something in between: Multicast (one to many). Most connections are Unicast. Your Web-browser gets this file from ONE Web-Server.
Broadcast is normally just used on LANs. If there are too many flying around, nobody can work anymore (-> Broadcast storms). Since the introduction of Switched-LANs, this pheonomenon is nearly history as well. (Token-Ring (even FDDI) networks still suffer from this fault sometimes).

G-02. Where can I find out more about Mbone?

First of all, since Mbone is not a full-fledged services, provided by all Internet Service Providers, documentation can sometimes be lacking. There are several nice starting points, though, listed here:

• Dan Mosedale's Quick and Dirty Guide to Getting Connected to the MBONE
• Don Brutzman's Paper on Mbone
• The Mbone FAQ maintained at AT&T Research's WWW server

G-03. I heard about the MICE Project, is that related to Mbone?

YES! The MICE Project uses the Mbone multicasting infrastructure.

Section: TECHNICAL

T-01. How is Mbone implemented?

Mbone is the overlay network, on top of the Internet, as a result of IETF developed technology. The Mbone is still (permanently?) under construction while new technologies are being introduced. The biggest obstacle is still that not all routers can natively speak multicast on backbone lines. Another reason might be that ISPs try to sell bandwidth and Mbone transmissions are until very soon not or not easy controllable in their bandwidth consumption.

T-02. What is an "mrouter"?

An mrouters is a multicast capable router using DVMRP as routing protocol. In today's Mbone most mrouters are workstations running the mroute-daemon (mrouted).

Mrouters maintain connections, called "tunnels" between each other. They encapsulate the Multicast packets into Unicast and transport it over the 'normal' Internet. Problem is of course not to lose too many packets. Packet drops in Multicast are directly affecting transmission quality.
Mrouters connecting to an ethernet also have the possibility of broadcasting the multicast packets over the ethernet. There are even special addresses reserved on Ethernet that permit the transmission of Multicast-pakets.

T-03. What is a "tunnel"?

A tunnel is a connection between two mrouters using "IP over IP".
A tunnel always has a source and a destination, but written as an IPv4 address.
A tunnel also has two parameters called "metric" and "threshold", defining the chraracteristics of the tunnel.

T-04. What is "metric" and "treshhold"?

The metric of a particular tunnel is used in calculating routing. The lowest value of the metric is 1. Each mrouter holds a routing table which has a next hop for each destination in the Mbone, with the metric being lowest.

T-05. What is PIM?

PIM is the 'newer' Multicast routing protocol (Protocol Independend Multicast) which has now become an RFC standard: (RFC2117).
There are major differences in the Routing protocols algorithms between DVMRP and PIM. A keyword of one function is 'pruning' which describes the act of telling the next 'upstream' mrouter not to send any unwanted traffic down the tree to us... This mechanism is called flood and prune and is responsible for most 'unwanted' or 'high' Mbone traffic. PIM has two modes. Sparse mode for wide-area networking which does not do flooding. And Dense-mode which basically is permitted to talk quite a lot in an LAN environment (i.e. Internet Exchange Point).

T-06. Is there a map of the European part of Mbone?

It is very hard to keep a graphical overview of a dynamically changing routing protocol topology.
But: There are a few maps that show the main links between the major providers and research networks in Europe.

T-07. Are there bandwidth requirements for 'being on the' Mbone?

Currently the MBone says that the upper limit to bandwidth are around 500kb/s. This sounds very high, but it's possible to run one concurrent MBone session (audio or video) with relatively good quality over one ISDN link (1 B channel = 64k). If it's possible to use 2 B-channels it is almost possible to receive a full audio+video conference session. (2B channels = 128k).

T-08. How does routing work in Mbone?

Bill or Axel? :-)

T-09. Where do I track new developments?

T-10. Which is the latest version of mrouted?

3.9b ?

T-11. What is the latest version of IOS for Cisco routers?

11.2(x)

T-12. What are the plans of other router/switch vendors w.r.t. multicasting?

T-13. How is Multicasting done in IPv6?

T-14. ?

Section: ORGANIZATIONAL

O-01. How can I connect to Mbone?

O-02. Which European service providers are connected to Mbone?

O-03. What do I do in case my service provider is not connected?

O-04. How are tunnels coordinated in Europe?

Ideally within the RIPE community, since they meet regularly anyway to discuss gerneral ISP problems in the greater European Internet scenario. The Working Group therefore would be at RIPE: http://www.ripe.net/ripe/wg/ mbone/index.html.

O-05. Can I multicast a conference on Mbone?

Yes, normally you can. A Multicast session is in most cases bi-directional. Every sink is also a potential source. Most tools permit reception as well transmission of the selected media.Other requirements might be that you have the necessary hardware (microphone or video camera) installed.
Please bare in mind that not everybody on Mbone might be interested in your transmission. Do not consume more bandwidth than stricktly needed, by make sure your thesholds are set right (refer to the technical section in case you are lost now).

O-06. How do I find out if my ISP offers Multicasting/MBone?

O-07. ?

Section: APPLICATIONS

A-01. What applications are in use on Mbone?

A-02. Where do I find all that software?

A-03. I am connected to Mbone, what's on tonight?

A-04. Does this software run on my system?

A-05. ?

Section: SECURITY

S-01. Are firewalls able to permit Mbone traffic?

Yes. It is possible to have Mbone traffic through a unicast firewall. What you need is that two protocols on top of IP are permitted through the firewall: - port 2 - port 4

This is an example for a Cisco router, where 192.1.1.1 is the remote Mbone router (somewhere in the Internet) and 192.2.2.2 is the local one, behind the unicast firewall on ethernet 0:

! Define the ethernet with the local Mbone router:
interface Ethernet 0
ip address 192.2.2.2 255.255.255.0
ip access-group 100
! Define the acces-list:
access-list 100 permit 2 192.1.1.1 0.0.0.0 192.2.2.2 0.0.0.0
access-list 100 permit 4 192.1.1.1 0.0.0.0 192.2.2.2 0.0.0.0

S-02. How do I separate my corporate IntraNet from Mbone, but still able to 'see' MBone-sessions?

S-03. How do I restrict my firewall to certain sessions/annoucements only?

Section: FINAL

F-01. Where to ask a question that is not answered in this FAQ?

First of all, try sending your question to your national mailing-list (see Q-99). In case this does not help and in case nobody is able to help you or point you to a location where help is available, try sending e-mail to the European Mbone list mentioned on the Mbone.com Info Page. In case this fails, try the worldwide list. Please use this order for things.

F-02. Who else contributed to this FAQ?

Many people helped in getting this FAQ into the stage in where it is now.
Thanks go to the following people (in alphabetical order):

• Magnus Danielson for starting this FAQ
• Havard Eindnes and Mark Handley for their previous contributions for this document