局域网中的多播与广播 [英] Multicast vs Broadcast in LAN

问题描述

使用多播组发送消息而不是仅将消息广播到特定端口是否有任何优势?我了解到，在广播时，其他不希望收到消息的计算机也收到了消息，但这对性能/流量有多大影响?不在乎的计算机不会立即转储邮件吗?

Is there any advantage to using a multicast group to send messages rather than just broadcasting them to a specific port? I understand that when broadcasting, other computers that don't want the messages receive them too, but how much does it affect performance/traffic? Don't the computers that don't care just dump the message immediately?

作为附带的问题，LAN外部的多播功能是否可以正常工作?

As a side question, does multicast outside the LAN work at all?

推荐答案

我假设您正在谈论IP流量.当您说LAN时，我将假设您的意思是办公大楼内的以太网拓扑(我将在下面更具体地讨论拓扑).

I will assume you're talking about IP traffic. When you say LAN, I will assume you mean an ethernet topology inside an office building (I will be more specific about topologies below).

当广播效果不佳时，应使用多播.听起来像是个贪吃蛇，但实际上，这是回答问题的最好方法...人们为什么要多播而不是广播是有很多原因的.

Multicast should be used when broadcasting isn't good enough. That sounds like a snark, but in reality it's the best way to answer the question... there are many reasons why people might want multicast instead of broadcast...

• 不需要时，多播不会消耗CPU和带宽资源.根据您发送的广播数量，这可能对相关各方没有意义.但是，广播流量将始终消耗VLAN中每个设备的带宽
• 可以在单个交换式以太网内修剪多播流量 VLAN /广播域，通过-广播不能在广播域中删除定义.
• 中型和大型办公楼局域网通常有5到10个 VLAN ，可容纳300人. Vlan 是一种定义广播域边界的方法.可以设计多播流量和拓扑，以使该流量可靠地穿越以太网广播域.在多个广播域之间转发任何实际的广播流量不是一个好主意.您经常在办公楼中(最多可容纳40人)找到多个 VLAN 或广播域.
• 与以上几点密切相关，可以通过广域网发送IP多播流量.
• 如果支付您薪水的客户对广播一无所知，则应使用多播而不是广播流量

• Multicast doesn't consume CPU and bandwidth resources when it isn't required. Depending on how much broadcast you send, that may or may not be meaningful to the parties involved. However, broadcast traffic will always consume bandwidth for every device in a Vlan
• Multicast traffic can be pruned inside a single switched ethernet Vlan / broadcast domain, broadcasts by-definition can't be pruned within a broadcast domain.
• Medium and large office building LANs usually have maybe 5 or 10 Vlans for perhaps 300 people. A Vlan is a way of defining a boundary on broadcast domains. Multicast traffic and topologies can be designed so this traffic reliably crosses ethernet broadcast domains; it's not a good idea to forward any real volume of broadcast traffic across multiple broadcast domains. You often find multiple Vlans or broadcast domains in office buildings with as few as 40 people.
• Closely related to the point above, IP multicast traffic can be sent across a Wide Area Network.
• Multicast should be used instead of broadcast traffic if the customers who pay your salary are dogmatic about it

出于多种原因，您可能想使用广播流量而不是多播流量 ...

There are several reasons you might want to use Broadcast traffic instead of multicast traffic...

• 您的应用程序的流量非常低，并且限制为单个Vlan
• 您认为目标受众的价格太便宜，无法支付增加的人员和IT基础架构以正确进行多播(IP多播要求比简单的IP单播/广播流量要详细得多)
• 如果未正确配置基础结构，则(作为一般规则)IP多播将被视为广播流量.组播要求会在任何应用程序部署时间表上增加时间/成本
• 否则，软件开发人员不希望花费时间和精力来解决各种主机OS IGMP堆栈和其他多播基础结构复杂问题

这篇关于局域网中的多播与广播的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！