W4140 Network Laboratory Lecture 10 Nov 30 Fall 2006 Shlomo Hershkop Columbia University

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W4140 Network LaboratoryLecture 10Nov 30 -
Fall 2006Shlomo HershkopColumbia University
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Announcements

• Phase I due today
• I will get you feedback over the week
• Start to plan for phase II
• Thanksgiving
• No lab scheduled
• Lab 7 report due on Monday after break
• Please do reading
• Any issues ?

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Overview

• Next
• We will be running short labs on specific network
  devices
• This week
• Plan Phase II once you get feedback
• Review CISCO IOS docs
• Next week I will give you an in depth overview of
  CISCO routers from the ground up
• Next week
• Cisco router lab
• Following week
• Man in the middle attacks

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Cisco Lab Overview

• A) Select one router and one PC from a rack (PC1
  Router1 etc).
• B) Connect one of the PC cards with the router
  and setup the interfaces appropriately.
• C) Connect the one of the PC cards to a Hub and
  the Hub to the CS network. Make sure that the
  other teams working on the same rack use the same
  hub
• D) Get a DHCP address from the CS-network

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• E) Setup the vty's of the router to have a
  password that you know.
• F) After setting up the PC and the router try to
  connect to the router's VTY using ssh to the PC
  and then telnet to the IP address of the router.
• G) Now that you have access to the router do the
  following
• a) Setup a tftp server on the PC
• b) Save the startup router configuration to the
  tftp server
• c) Save the running configuration to the tftp
  server
• d) Upgrade the router's flash (ask me where to
  get the file).
• H) Modify the running-configuration to have a new
  enable password. Save the running configuration
  to a file. What do you notice about the password?

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• I) Load from the tftp server the running
  configuration that you had saved in step g.c to
  the running configuration of the server.
• J) Find the commands that display the router's
  memory and CPU utilization.
• - How do we find out if an interface is working
  properly?
• - How do we restrict access to the tftp server?

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• One of the reasons we are doing all this will be
  to get a feel for current technology and explore
  future tech
• Example unicast vs multicast
• Anycast BGP (another time)
• If you want to reach a single machine from
  anywhere
• Ping is your friend
• What happens ???

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Internet2Multicast WorkshopColumbia
University, New York, NYDecember 2005
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Acknowledgements

• Greg Shepherd
• Beau Williamson
• Marshall Eubanks
• Bill Nickless
• Caren Litvanyi
• Patrick Dorn
• Leonard Giuliano
• Alan Crosswell
• Debbie Fligor

Mitch Kutzko Matt Davy Yul Pyun Stig
Venaas University of Oregon Columbia
University NYSERNet Cisco Systems Juniper Networks
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Contents

• Overview
• Multicast on the LAN
• Source-Specific Multicast (SSM)
• Any-Source Multicast (ASM)
• Intra-domain ASM
• Inter-domain ASM
• Troubleshooting Methodology
• Best Current Practices Future of Multicast

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Overview
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The Basic Idea

• Instead of sending a separate copy of the data
  for each recipient, the source sends the data
  only once, and routers along the way to the
  destinations make copies as needed.
• Unicast does mass mailings multicast does chain
  letters.

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Unicast vs. Multicast
Unicast
Multicast
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The MBone

• The original multicast network was called the
  MBone. It used a simple routing protocol called
  DVMRP (Distance Vector Multicast Routing
  Protocol).
• As there were only isolated subnetworks that
  wanted to deal with DVMRP, the old MBone used
  tunnels to get multicast traffic between DVMRP
  subnetworks.
• i.e., the multicast traffic was hidden and sent
  between the subnetworks via unicast.
• This mechanism was simple, but required manual
  administration and absolutely could not scale to
  the entire Internet.
• Worse, DVMRP requires substantial routing traffic
  behind the scenes and this grew with the size of
  the MBone.
• Thus, the legend grew that multicast was a
  bandwidth hog.

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Multicast Grows Up

• Starting about 1997, the building blocks for a
  multicast-enabled Internet were put into place.
• An efficient modern multicast routing protocol,
  Protocol Independent Multicast - Sparse Mode
  (PIM-SM), was deployed. (PIM also has Dense and
  Sparse-Dense modes, but these are not widely
  used.)
• The mechanisms for multicast peering were
  established, using an extension to BGP called
  Multiprotocol BGP (MBGP), and peering became
  routine.
• The service model was split into
• a one-to-many (or broadcast) part a
  many-to-many part (e.g., for videoconferencing)
  Any-Source Multicast (ASM), and
• Source-Specific Multicast (SSM).
• By 2001, these had completely replaced the old
  MBone.

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What capabilities does IP Multicast provide ?

• Cost-efficient distribution of data
• Timely distribution of data
• Robust distribution of data
• Data here could be
• Files
• Streamed Audio or Video

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Cost Efficient Data Distribution

• This is the core of the streaming case.
• Unicast streaming is just too expensive.
• This is true either on the commodity Internet or
  on the Intranet.
• Multicast is especially compelling for video.

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Timely Distribution of Data

• This is the argument for multicast in financial
  services.
• In unicast, it takes time to send packets
  separately to each receiver.
• Even if cost is not a problem, time may be.
• Example A DS3 would take 2 days to distribute a
  100 megabyte file to 10,000 desktops. With
  multicast, this would take 18 seconds.
• Multicasting is compelling here if timely
  distribution is important.

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Robust Distribution of Data

• In some streaming or data distribution cases, the
  problem is handling sudden large increases in
  load.
• Multicast was designed to handle sudden large
  increases in load.

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Case Study 9/11/2001

• Internet News Melt-downWeb Site Performance
  900 AM to 1000 AM
• Site Users able to access
• ABCNews.com 0
• CNN.com 0
• NYTimes.com 0
• USAToday.com 18
• MSNBC.com 22
• (source Keynotes Business Performance /
  Interactive Week 9/17/2001)

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Internet News Performance on 9/11/2001

• Of course, the melt-down was caused by the
  incredible demand for news after the attacks.
• Unicast streaming web sites suffered similar
  problems, at least from anecdotal evidence
• By contrast, multicast performed well
• Large increase in traffic
• Roughly 1 Gigabit per second saved at peak
• Over time, the multicast peering mesh degraded,
  but this was NOT due to increased traffic

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Eyewitness Accounts

• We had a large plasma screen in the iLabs at
  NetworldInterop intended to demonstrate high
  rate HDTV over I2. We came in Tuesday morning and
  were preparing for the first day of the show when
  word came in about the initial plane crash into
  the towers. Our I2 Lead, Roy Hockett was able to
  switch the stream to a CNN broadcast from UMich.
  We began attracting exhibitors to the display
  even before the showfloor opened. Once the
  attendees were on the floor, the crowd had grown
  to well over a hundred.
• By this point, three things had happened. The
  crowds around the one display had grown so large
  as to constitute a fire hazard, all the major
  news web sites had completely melted down, and
  CNN was being multicast from several sources. We
  then started loading multicast tools on every PC
  in the NOC, from the one driving the large video
  wall to people's individual laptops. By 1030
  (about half an hour after the floor opened) we
  had at least 3 large displays as well as a number
  of normal monitors turned out towards the
  plexiglass walls.
• Soon after, we had a good number of exhibitors
  come and ask how to get "the CNN viewer
  software.
• 
  Jim Martin, ltjrm_at_nortelnetworks
  .comgt
• More than 1,000 copies of StreamPlayerII, our
  multicast MPEG viewer, were downloaded or handed
  out on disk between 9/11 and 9/12. We normally
  average 20 to 100 per day.
• 
  Rich Mavrogeanes
  ltrmavro_at_vbrick.comgt

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Viewership

• Sudden increase in Multicast traffic of at least
  1000 group members
• Mostly viewing VBricks television broadcast
• Measured viewership gt830
• But each measured point could have many
  individual viewers since they multicast locally
• BANDWIDTH SAVED in excess of 1 Gbps vs. unicast

Crowds viewing the 9/11 multicasts at
NetworldInterop
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How is Multicast Being Used Today?

• Network Video!
• Netcast Events, TV over IP, Distance Learning,
  Collaboration
• See https//mail.internet2.edu/wws/arc/bigvideo/
• Other applications
• Some examples follow...

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Video Netcast Events

• Technical events
• IETF, NANOG see videolab.uoregon.edu
• Joint Techs http//jointtechs.es.net/vancouver200
  5/netcast.html
• Scientific events
• Undersea exploration with Robert Ballard
  www.explorethesea.com
• Performance events
• Digital Video Transport Service
  (http//apps.internet2.edu/dvts.html) provides
  relatively cheap painless high-quality network
  video, and is increasingly popular for a wide
  variety of uses.
• DVTS over multicast is ideal for netcasting
  performance events.
• DancingQ performance event http//arts.internet2.
  edu/dancingq.html http//people.internet2.edu/7E
  bdr/CometDVIP/DanceQ.html

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Video TV over IP

• DV Guide http//db.arts.usf.edu/dvguide/
• ResearchChannel www.researchchannel.org/projects/
  i2wg/prj_multi.asp
• Northwestern University
• Cable TV via campus networks http//www.tss.nort
  hwestern.edu/nutv/helpguide/
• C-SPAN over Abilene http//www.i2-multicast.nort
  hwestern.edu/
• Several other campuses (Cornell, Columbia,
  Duke...) have TV-over-IP projects, or are
  considering them
• Open Student Television Network
• www.ostn.tv
• "a national initiative of student television
  stations working together to build a digital
  channel of student television shows"

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Video TV over IP

• Set-top boxes are available from several vendors,
  e.g.
• www.vbrick.com/products/EtherneTV-stb.asp
• www.aminocom.com
• www.i3micro.com
• www.2wire.com
• www.bastinc.com
• Some corporations, particularly in the financial
  sector, pay big bucks to have cable news
  multicast on their intranets.

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Video Distance Learning

• University of Hawaii uses multicast in its Hawaii
  Interactive Television Service
• http//www.hawaii.edu/dl/general/
• Two-way interactive video and audio to all UH
  campuses and education centers
• Each classroom can view and converse with at
  least two other sites, and listen to additional
  sites
• Each campus can receive and transmit multiple
  classes simultaneously

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Video Distance Learning

• U. of HawaiiInteractive TV Locations and
  Staff Sites

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Video Collaboration

• Access Grid
• www.accessgrid.org "The Access Grid is an
  ensemble of resources...used to support
  group-to-group interactions across the Grid."
• survey of AG multicast issueswww.andrewpatrick.c
  a/multicast-survey/
• Access Grid via VRVShttp//www.vrvs.org/Document
  ation/VAG/

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Other Applications

• While it seems clear that the killer app for
  multicast will involve video, there are other
  things you can do with it...
• radio www.onthei.com, www.kexp.org
• file distribution (a popular intranet ASM
  application)
• NNTP
• Please keep us informed about your current and
  planned applications!
• See https//mail.internet2.edu/wws/arc/wg-multicas
  t

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Essential Multicast Terminology
IP source IP unicast addr Ethernet source MAC
addr IP destination IP multicast addr Ethernet
dest MAC addr
receivers
source
Multicast stream

• source origin of multicast stream
• multicast address an IP address in the Class D
  range (224.0.0.0 239.255.255.255), used to
  refer to multiple recipients. A multicast address
  is also called a multicast group or channel.
• multicast stream stream of IP packets with
  multicast address for IP destination address. All
  multicast uses UDP packets.
• receiver(s) recipient(s) of multicast stream
• tree the path taken by multicast data. Routing
  loops are not allowed, so there is always a
  unique series of branches between the root of the
  tree and the receivers.

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(S,G) notation

• For every multicast source there must be two
  pieces of information the source IP address, S,
  and the group address, G.
• These correspond to the sender and receiver
  addresses in unicast.
• This is generally expressed as (S,G).
• Also commonly used is (,G) - every source for a
  particular group.

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Multicast Building Blocks

• The SENDERS send without worrying about receivers
• Packets are sent to a multicast address (RFC
  1700)
• This is in the class D range (224.0.0.0 -
  239.255.255.255)
• The RECEIVERS inform the routers what they want
  to receive
• done via Internet Group Management Protocol
  (IGMP), version 2 (RFC 2236) or later
• The routers make sure the STREAMS make it to the
  correct receiving networks.
• Multicast routing protocol PIM-SM

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Multicast Protocol Summary

• Essential Protocols
• PIM-SM - Protocol Independent Multicast - Sparse
  Mode is used to propagate forwarding state
  between routers.
• IGMP - Internet Group Management Protocol is used
  by hosts and routers to tell each other about
  group membership.
• Other Protocols (much more on these later in the
  workshop)
• MBGP - Multiprotocol Border Gateway Protocol is
  used to exchange routing information for
  inter-domain reverse-path forwarding (RPF)
  checking.
• MSDP - Multicast Source Discovery Protocol is
  used to exchange active-source information.

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Multicast Addressing

• IPv4 Multicast Group Addresses
• 224.0.0.0239.255.255.255
• Class D Address Space
• High order bits of 1st Octet 1110
• Source sends to group address
• Receivers receive traffic sent to group address

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CIDR Address Notation

• The multicast address block is 224.0.0.0 to
  239.255.255.255
• It is cumbersome to refer to address blocks in
  the above fashion. Address blocks are usually
  described using CIDR notation
• This specifies the start of a block, and the
  number of bits THAT ARE FIXED.
• In this shorthand, the multicast address space
  can be described as 224.0.0.0/4 or, even more
  simply, as 224/4. The fixed part of the address
  is referred to as the prefix, and this block
  would be pronounced "two twenty four slash four."
• Note that the LARGER the number after the slash,
  the LONGER the prefix and the SMALLER the address
  block.

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Multicast Addressing

• RFC 3171
• http//www.iana.org/assignments/multicast-addresse
  s
• Examples
• 224.0.0.0 - 224.0.0.255 (224.0.0/24) - reserved
  not forwarded
• 224.0.0.1 - All local hosts
• 224.0.0.2 - All local routers
• 224.0.0.4 - DVMRP
• 224.0.0.5 - OSPF
• 224.0.0.6 - Designated Router OSPF
• 224.0.0.9 - RIP2
• 224.0.0.13 - PIM
• 224.0.0.18 - VRRP
• 224.0.0.22 IGMP
• 232.0.0.0 - 232.255.255.255 (232/8) - SSM
• 239.0.0.0 - 239.255.255.255 (239/8) -
  Administrative Scoping
• Ordinary multicasts dont have to request a
  multicast address from IANA.

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Scoping

• TTL value defines scope and limits distribution
• IP multicast packet must have TTL gt interface TTL
  or it is discarded
• No longer recommended as a reliable scoping
  mechanism
• Administratively Scoped Addresses RFC 2365
• 239.0.0.0239.255.255.255
• Private address space
• Similar to RFC 1918 unicast addresses
• Not used for global Internet traffic
• Used to limit scope of multicast traffic
• Same addresses may be in used in different
  sub-networks for different multicast sessions
• Examples
• Site-local scope 239.253.0.0/16
• Organization-local scope 239.192.0.0/14

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Multicast Address Allocation

• For a long time, this was a sore spot. There was
  no way to claim or register a Multicast Class D
  address like unicast address blocks can be
  registered.
• For temporary teleconferences, this is not such a
  problem, but it does not fit well into a
  broadcast model.
• Now, there are two solutions
• For SSM, addresses dont matter, as the broadcast
  address is really unique as long as the (S,G)
  pair is unique.
• For ASM, there is GLOP.

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Multicast Addressing

• GLOP addresses
• Provides globally available private Class D space
• 233.x.x/24 per AS number
• RFC 2770
• How?
• Insert the 16-bit AS number into the middle two
  octets of the 233/8
• Online GLOP calculatorwww.shepfarm.com/multicast
  /glop.html
• If you have an AS, you have multicast addresses.

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Expanding MulticastAddress Assignment

• GLOP based address assignment has worked well.
• Every organization gets the same amount of space,
  a /24.
• What if you need more?
• There is an (as yet unused) mechanism for
  requesting more GLOP space RFC 3138.
• Is this unused because of lack of demand, or
  because the mechanism is not fully implemented?

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Prefix-based Multicast Address Assignment

• Dave Thaler of Microsoft has proposed
  prefix-based assignment.
• draft-ietf-mboned-ipv4-uni-based-mcast-02.txt
• The idea is that every unicast address assignment
  you have is mapped into a multicast address
  range.
• Take one of the unused multicast /8's
• For a /N unicast assignment, the multicast
  address block becomes
• /8 /N24 - N bits of available addresses
• So, a /24 provides a /32 a /16 provides a /24 a
  /8 provides a /16
• This would complement GLOP by giving larger
  organizations more addresses.