Digitus DN-80233, Руководство пользователя

Страница: 374 / 379

373
author, or other attributes of all or part of the message are as they appear to be. (
IBM Glossary of
Computing Terms
)
Management Information Base.
When SNMP devices send SNMP messages to the management
console (the device managing SNMP messages), it stores information in the MIB.
MBONE.
See “Multicast Backbone” on page 299.
MDC.
Management Data Clock.
MDI.
Management Data Interface.
MDIO.
Management Data Input/Output.
MDIX.
Management Dependent Interface Crossover.
MIB.
See “Management Information Base” on page 298.
MOSPF.
See “Multicast OSPF” on page 299.
MPLS.
See “Multi-Protocol Label Switching” on page 299.
Multicast Backbone.
The MBONE is a virtual network. It is layered on top of portions of the physical
Internet to support routing of IP multicast packets since that function has not yet been integrated into
many production routers. The network is composed of islands that can directly support IP multicast, such
as multicast LANs like Ethernet, linked by virtual point-to-point links called "tunnels". The tunnel endpoints
are typically workstation-class machines having operating system support for IP multicast and running the
"mouted" multicast routing daemon.
Multicasting.
To transmit a message to specific recipients across a network. A simple example of
multicasting is sending an e-mail message to a mailing list. Teleconferencing and videoconferencing also
use multicasting, but require more robust protocols and networks. Standards are being developed to
support multicasting over a TCP/IP network such as the Internet. These standards, IP Multicast and
Mbone, will allow users to easily join multicast groups. Note that multicasting refers to sending a message
to a select group whereas broadcasting refers to sending a message to everyone connected to a network.
The terms multicast and narrowcast are often used interchangeably, although narrowcast usually refers to
the business model whereas multicast refers to the actual technology used to transmit the data.
Multicast OSPF.
With a MOSPF specification, an IP Multicast packet is routed based both on the
packet's source and its multicast destination (commonly referred to as source/destination routing). As it is
routed, the multicast packet follows a shortest path to each multicast destination. During packet
forwarding, any commonality of paths is exploited; when multiple hosts belong to a single multicast group,
a multicast packet will be replicated only when the paths to the separate hosts diverge. See “OSPF” on
page 300 for more information.
Multiplexing.
A function within a layer that interleaves the information from multiple connections into
one connection.
Multi-Protocol Label Switching.
An initiative that integrates Layer 2 information about network links
(bandwidth, latency, utilization) into Layer 3 (IP) within a particular autonomous system—or ISP—in order
to simplify and improve IP-packet exchange. MPLS gives network operators a great deal of flexibility to
divert and route traffic around link failures, congestion, and bottlenecks. From a QoS standpoint, ISPs will
better be able to manage different kinds of data streams based on priority and service plan. For instance,
those who subscribe to a premium service plan, or those who receive a lot of streaming media or
high-bandwidth content can see minimal latency and packet loss. When packets enter into a MPLS-based
network, Label Edge Routers (LERs) give them a label (identifier). These labels not only contain
information based on the routing table entry (i.e., destination, bandwidth, delay, and other metrics), but
also refer to the IP header field (source IP address), Layer 4 socket number information, and
differentiated service. Once this classification is complete and mapped, different packets are assigned to
corresponding Labeled Switch Paths (LSPs), where Label Switch Routers (LSRs) place outgoing labels
on the packets. With these LSPs, network operators can divert and route traffic based on data-stream