CODEWITHSUNDEEP
network-programming
Richard
Richard

Reputation: 15562

Can NIC send n network messages(to n destinations), simultaneously?

Can a machine send n network messages/packets (to n destinations), simultaneously? Is there a upper bound on level of parallelism and what affects network's parallelism.

More specific, say there are 2 packets and four event, s1, r1 and s2, r2 denotes send/receive packet 1 and send/receive packet 2. When we send asynchronously (like s1, s2...r1,r2) and synchronously (s1...r1,s2...,r2), does it matter? Could total latency be shorten in the case of asynchronous send.

Upvotes: 0

Views: 149

Answers (2)

Jerry Coffin
Jerry Coffin

Reputation: 490178

You basically have three choices:

  1. Point to point
  2. Multicast
  3. Broadcast

A point to point message goes from one source to one destination.

A multicast message goes from the source, to the router, and from there gets distributed to the multiple recipients. There are some relatively intelligent switches (usually called "layer 2+" or something on that order) that can handle multicasting as well, but your average "garden variety" switch usually can't/won't handle it.

A broadcast goes from the source to everything else on the local subnet. There are a cople of ways this can be done. Probably the most common is to send to the address 255.255.255.255. Broadcasting is supported directly by Ethernet, which has a "broadcast" MAC address of FF:FF:FF:FF:FF:FF.

Note that IPv6 no longer supports broadcasting, but does have an "all hosts" multicast group that's vaguely similar.

Upvotes: 1

ninjalj
ninjalj

Reputation: 43698

Yes, they can. A NIC just transmits the frames the driver tells it to, and does it as soon as it can. NICs don't care about destinations.

Higher layers (e.g: TCP) are responsible for retransmissions, and have their own buffering. NICs usually can have several frames ready to be sent, but they stay little time in the NIC, as soon as the medium is free, and the NIC has transmitted a frame without collisions, it can take another frame ready for transmission.

Upvotes: 1

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