From f12a8a9432dda3ce3ba7ffef4276f2ea9c4437f8 Mon Sep 17 00:00:00 2001
From: scipio <scipio>
Date: Tue, 1 Apr 2008 17:01:30 +0000
Subject: [PATCH] David Gay's edits.

---
 doc/html/tep113.html | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/doc/html/tep113.html b/doc/html/tep113.html
index 7f502393..0e8b6d36 100644
--- a/doc/html/tep113.html
+++ b/doc/html/tep113.html
@@ -298,9 +298,9 @@ ul.auto-toc {
 <td>Ben Greenstein and Philip Levis</td></tr>
 <tr class="field"><th class="docinfo-name">Draft-Created:</th><td class="field-body">11-Jul-2005</td>
 </tr>
-<tr class="field"><th class="docinfo-name">Draft-Version:</th><td class="field-body">1.9</td>
+<tr class="field"><th class="docinfo-name">Draft-Version:</th><td class="field-body">1.11</td>
 </tr>
-<tr class="field"><th class="docinfo-name">Draft-Modified:</th><td class="field-body">2007-02-06</td>
+<tr class="field"><th class="docinfo-name">Draft-Modified:</th><td class="field-body">2008-04-01</td>
 </tr>
 <tr class="field"><th class="docinfo-name">Draft-Discuss:</th><td class="field-body">TinyOS Developer List &lt;tinyos-devel at mail.millennium.berkeley.edu&gt;</td>
 </tr>
@@ -529,6 +529,23 @@ may be slightly delayed. However, acknowledgement information is
 stored in a queue separate from the data buffer, so a data packet to
 be transmitted may begin spooling into SerialP while SerialP is
 actively sending an acknowledgement.</p>
+<p>Only the PC-to-mote communication path supports acknowledgements.
+SerialP does not request acknowledgements from the PC for two reasons.
+First, acks are not perfect reliable: they are used on the
+PC-to-mote path to raise reliability to a usable level. In the case of
+the PC-to-mote path, the UART receive buffer is typically a single
+byte, so a high interrupt load can easily lose (and sometimes does) a
+byte. This is in contrast to the PC receive buffer, which is much
+larger and does not have to deal with overflow. Second, adding support
+for acks would increase the code size and complexity of the serial
+stack. As code space is often at a premium, this would add little
+needed functionality at significant cost. Of course, any application
+that requires perfect reliability may layer its own scheme on top of
+the serial protocol.</p>
+<p>The acknowledgement protocol is stop-and-wait to minimize buffering on
+the mote side. This is considered more important on memory constrained
+devices than increased throughput in the PC-to-mote direction, which
+most applications only use for occasional control transmissions.</p>
 </div>
 <div class="section">
 <h2><a id="dispatcher-serialdispatcherc" name="dispatcher-serialdispatcherc">3.4 Dispatcher: SerialDispatcherC</a></h2>
-- 
2.39.2