How can I force "no splines" in GraphViz html-like labels?

Question

I am interested in making all of the edges in this graph straight.

From what I understand, setting splines to false should do this.

In one case, an edge has no splines, and goes right over the top of another node.

In the case of the html-like label, splines appear, causing the edge to look like a large loop.

Is there a way to force "no splines"?

[View output image here.]

Thanks in advance for any help or suggestions!

strict graph G {
    splines=false;
    "html" [
            shape = none
            margin = 0
            label = <<TABLE>
                       <TR>
                          <TD PORT="d">Isend(0)</TD>
                       </TR>
                       <TR>
                          <TD PORT="e">Irecv(1)</TD>
                       </TR>
                    </TABLE>>
            ];

    html -- a;
    html -- b;
    html -- c;
    a -- c;
    html:d -- html:e;
}

Answer 1

I found that "no splines" is only enforced at the global level. To resolve this problem, I ended up making separate graphs for each cluster, exporting them to .png files, and then using the png files as nodes in my higher-order graph.