Multicast básico

Multicast básico

1. como multimidia trabalha?

2. tipos de trafego

   • unicast
   • multicast
   • anycast
   • broadcast

3. protocolo de camada transporte usado

   • UDP - best effort
   • congestion-avoidance mechanisms such as weighted random early detection (WRED), which causes TCP flows to go into TCP slow start, are not effective for multicast.

4. beneficios

   • With IP multicast, the source server sends only one copy of each packet, and packets are sent only to intended recipients.

5. caracteristicas e beneficios

   • suporta varios data stream para um simples IP
   • envio de varios hosts usando menos BW
   • + eficiente uso da BW pois multiplos stream são substituidos por só 1
   • support para cisco apps

6. classe IP usada

   • 224.0.0.0 to 224.0.0.255 (Reserved link-local addresses) 224.0.1.0 to 238.255.255.255 (Globally scoped addresses) 232.0.0.0 to 232.255.255.255 (Source-specific multicast addresses) 233.0.0.0 to 233.255.255.255 (GLOP addresses) 239.0.0.0 to 239.255.255.255 (Administratively scoped addresses)

7. problemas

   • potential for duplicate packets received and the potential for packets to arrive out of order.
     • Usa Reverse Path Forwarding (RPF) para combater isso
       • check to determine whether a multicast packet enters a router on the correct interface
       • If the incoming multicast packet is using that interface, the RPF check passes, and the packet is forwarded. If the multicast packet comes in a different interface, the RPF check fails, and the packet is discarded.
   • best-effort - ocasinal drops
   • inviavel para apps real-time para retransmissão
   • congestion

8. host se unindo e saindo de um grupo

9. response supression

10. formato cabeçalho IGMPv1 e v2

11. mensagens IGMPv1 e v2

12. eleição do multicast query

13. mantendo um grupo no IGMPv1 e v2

14. formas de otimizar a transmissão multicast na LAN - SWITCHES

    • IGMP snooping
      • switch LAN aprende as portas que devem ser enviados o trafego multicast
      • Used on higher-end switches
    • CGMP
      • o router após receber uma mensagem IGMP report de uma estação solicitando participação num grupo mult. envia mensagem CGMP para o switch informando o MAC das estações que devem receber o trafego multicast
      • o router diz ao switch qual de suas interfaces tem grupos multicasts
      • Used on low-end switches
    • GARP Multicast Registration Protocol (GMRP)
    • Router-Port Group Management Protocol (RGMP):

15. principio basico roteamento multicast

16. tecnicas de construção de arvores

    • Multicast traffic flows from a source to a destination over a distribution tree, which is a loop-free path. The two types of distribution trees
      • Source distribution tree:
        • path between each source router and each last-hop router (that is, a router connected to a receiver)
        • Source distributions trees place (S, G) states in a router’s multicast routing table to indicate the address of the source (S) and the address of the group (G)
        • PIM-DM
      • Shared distribution tree
        • Creates a tree from a central rendezvous point (RP) router to all last-hop routers, with source distribution trees created from all sources to the RP, at the expense of increased delay.
        • Shared distribution trees place (*, G) states in a router’s multicast routing table to indicate that any device could be the source (that is, using the wildcard [*] character) for the group (G).
        • PIM-SM
        • Rendezvous Points
          • In a PIM-SM network, one or more routers need to be designated as RPs.
          • These routers are the central point to which multicast servers send traffic to be dispersed to clients who want to receive it.
          • automatically configuring an RP
            • Auto-RP
            • Bootstrap Router (BSR)
      • PIM é usado para criar as arvores

17. protocolo usado entre PC e router para deixar este ciente de qual de suas interfaces tem multiplos recebedores multicast

    • IGMPv1
      • Para se juntar ao grupo multicast um PC envia pro router uma mensagem - Report message (often called a Join message)
      • a cada 60s o router confirma com o PC se ele ainda quer fazer parte do grupo - IGMP Query message
      • 3 minutos sem resposta o router entende que saiu
      • The destination address of this router query is 224.0.0.1, which addresses all IP multicast hosts.
    • IGMPv2
      • idem anterior exceto por alguns detalhes
      • can send queries to a specific group
      • Leave message is supported - PC pode proativamente enviar uma mensagem pedindo para sair do grupo
    • IGMPv3
      • uso do Source-Specific Multicast (SSM)
        • aplicação de filtro

18. comandos

    • show ip igmp interface [interface-id] - ver qual router é o QUERIER
    • show ip igmp group - display IP multicast groups that a router is aware
    • enabled for multicast routing - Router(config)#ip multicast-routing
    • Router(config-if)#ip pim {dense-mode | sparse-mode | sparse-dense-mode}
    • Router#show ip mroute

19. ROUTERS - multicast fowarding prot - Campus

    • PIM sparse mode
      • Typically, sparse mode multicast is used when a small number of receiving hosts are on a subnet and especially if they spread over a number of networks.
      • Router(config-int)# ip pim sparse-mode
    • PIM Bidirecional
    • PIM Dense Mode
      • PIM Dense mode operates using the concepts of source distribution trees
      • It is used when the majority of the hosts on a network are interested in receiving the multicast stream
      • Router(config-int)# ip pim dense-mode

20. Interdominio

    • MBGP
    • MSDP com PIM-SM
    • PIM-SSM

21. utilidades

    • video conference
    • broadbans app
    • IP telephone
    • Digital television
    • corp communication
    • audio digital
    • PDA devices