消费级路由器中的组播支持状况如何
我正在设计一个系统，其中有多个小型嵌入式系统主机在局域网中进行通信。 UDP 多播非常适合我的目的。
但我担心普通路由器中的多播支持。我需要将系统部署到配备Wifi路由器的普通家庭，这样我就可以遇到任何类型的路由器。如果多播麻烦多于好处，我将使用 UDP 广播。
为了做出决定，我感谢当今普通路由器中有关多播支持的任何数据或经验：
- 今天销售的所有消费者路由器都合理地支持多播吗？ LAN 的限制对我来说不是问题，我不需要通过 Internet 进行多播。
- 旧路由器怎么样？
- 我需要注意常见的多播实现中是否存在任何大问题（例如数据包丢失、配置问题等）？
I am designing a system which has multiple small embedded systems hosts communicating in a LAN. UDP multicast fits nicely for my purpose.
But I am worried about multicast support in commonplace routers. I need to deploy the system to normal households equipped with a Wifi router, so I could encounter any kind of routers. I will use UDP broadcast if multicast will be more trouble than benefit.
To decide, I am thankful for any data or experience on multicast support in today's commonplace routers:
- Do all consumer routers sold today support multicast reasonably? Limitation to LAN is not an issue for me, I do not need multicast across the Internet.
- How about older routers?
- Are there any big issues in commonplace multicast implementations I need to be aware of (e.g. packet drops, configuration issues, etc.)?
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你说的是交换机还是路由器？在消费者环境中，我怀疑开关。我的经验是，它们都支持多播，尽管不是线速的。此外，便宜的设备往往会将任何多播流量广播到所有端口（无 IGMP 监听）。丢包绝对是您需要处理的问题，即使在“专业”网络设备上也可能并且将会发生。
编辑：只要您处于交换网络中，通常不需要配置任何内容。
Are you talking switches or routers? In a consumer setting I suspect switches. My experience is that they all support multicast, though not at wire speed. Also the cheap ones tend to broadcast any multicast traffic to all ports (no IGMP snooping). Packet loss is definitely something you need to deal with, it can and will happen even on 'professional' networking gear.
Edit: as long as you are in switched network, you typically don't need to configure anything.
在最坏的情况下，当路由器不允许多播流量时，我会将多播数据包封装到单播 IP 地址中。这样路由器就会将它们作为普通的单播数据进行处理。您可能需要检查 mrouted 。
祝你好运
In worst case scenarios, when the routers don't allow multicast traffic, I would encapsulate the multicast packets into a unicast IP address. This way the routers would handle them as normal unicast data. You might want to check mrouted .
Good luck
在许多情况下，设备要么不支持 IGMP 欺骗，要么默认处于关闭状态。有两个问题：
任何无线接口都可能因流量而饱和。
配置不当的单元可能会无意中将流量路由出默认网关，从而导致合法流量停滞。
无论哪种情况，您的设备都将被丢弃，因为调查成本几乎肯定会超过所获得的收益。
如果您的流量速率有限并且您不担心 WiFi 影响，则可以使用本地广播地址来确保传送到收件人，而不会影响路由通信。
您可以在节点中安装发现机制，可能值得实施单播覆盖以确保流量不会产生无意的影响。
拥有一些不合规设备的较大客户群请求支持将淹没与开发相关的任何成本或因未实现真正的多播而导致的额外流量。
In many scenarios the equipment either does not support IGMP spoofing, or it is off by default. There are two problems:
Any wireless interface can be saturated by the traffic.
Poorly configured units may inadvertently route traffic out the default gateway stalling legitimate traffic.
In either case, you will have your equipment discarded as the cost of investigation will almost certainly outweigh the benefit received.
If your traffic has a limited rate and you are not concerned about the WiFi impact, you could use the local broadcast address to ensure delivery to recipients, without impacting on the routed communications.
You could install a discovery mechanism into your nodes it may be worthwhile to implement a unicast overlay to ensure that traffic does not have inadvertent impact.
A single larger group of customers with some non-compliant devices requesting support will swamp any costs associated with development or additional traffic caused by not implementing true multicasting.