Re: RING vs. ETHER - Theory and practice.

Lixia Zhang (Lixia@XX.LCS.MIT.EDU)
Sun 20 Jul 86 16:19:03-EDT

I wrote the original paragraph of

      Dave Clark once again observes that a token ringnet outperforms an
      Ethernet in handling back-to-back packets. The ringnet has an
      automatic retransmission function built into the network
      interface, and will retransmit rejected packets until they get
      accepted, while an Ethernet interface loses subsequent packets if
      they follow the first one too closely.

So I'd better clean up my own mistake. As Noel has pointed out, the
ringnet interface returns an acknowledgment; therefore when the receiving
interface cannot catch up with incoming packets, the source host network
driver quickly retransmits any negatively acknowledged packet till the
interface returns an positive-ACK (or till hits some max retrans number).
For Ethernet, if the receiving interface doesn't get a packet right, the
packet is lost.

Having buffers at the interface is helpful, for both ethernet and ring.
Ethernet is a loser in that, using Noel's word, it lacks a low-level ACK.


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