Implementing IBM System Networking 10Gb Ethernet Switches

Chapter 2. IBM System Networking Switch 10Gb Ethernet switch features 67

Forming BGP peer routers

Two BGP routers become peers or neighbors after you establish a TCP connection between

them. For each new route, if a peer is interested in that route (if a peer would like to receive

your static routes and the new route is static), an update message is sent to the peer that

contains the new route. For each route removed from the route table, if the route has already

been sent to a peer, an update message that contains the route to withdraw is sent to

that peer.

For each Internet host, you must be able to send a packet to that host, and that host must

have a path back to you. This setup means that whoever provides Internet connectivity to that

host must have a path to you. Ultimately, this means that they must “hear a route” that covers

the section of the IPv4 space you are using; otherwise, you do not have connectivity to the

host in question.

2.4 IP multicast

IP multicast represents a one-to-many communications scheme with one host that sends a

stream and a number of hosts that receive it.

IPv4 multicast always uses UDP as a transport layer protocol with class D

(224.0.0.0 - 239.255.255.255) IP addresses as the Layer 3 destination address.

There are two major protocol types used in a multicast network:

򐂰 Internet Group Management Protocol (IGMP): Used for hosts that signal a router that they

are interested in receiving multicast traffic destined for the particular group (or multicast

address). IGMP is a “host-to-router” multicast protocol.

򐂰 Protocol Independent Multicast (PIM): For providing loop-free multicast traffic delivery in a

network. PIM is considered a “router-to-router” multicast protocol.

For more information, see IP Multicast Protocol Configuration, REDP-4777.

2.4.1 Internet Group Management Protocol

Internet Group Management Protocol (IGMP) is used by IPv4 Multicast routers to learn about

the existence of host group members on their directly attached subnet (for more information,

see RFC 2236 at http://www.ietf.org/rfc/rfc2236.txt). The IPv4 Multicast routers get

this information by broadcasting IGMP membership queries and listening for IPv4 hosts

reporting their host group memberships. This process is used to set up a client/server

relationship between an IPv4 Multicast router that provides the data streams on behalf of the

multicast sender and the clients that want to receive the data.

IBM System Networking switches can perform IGMP Snooping, and connect to static

multicast routers (Mrouters). They can act asan IGMPQuerier, and participate in the IGMP

Querier election process.

IBM System Networking switches support IGMP versions 1, 2, and 3.

IGMP Snooping

IGMP Snooping allows the switch to forward multicast traffic only to those ports that request

it. IGMP Snooping prevents multicast traffic from being flooded to all ports. The switch learns

which server hosts are interested in receiving multicast traffic, and forwards it only to ports

connected to those servers.