Author: mrogers
Date: 2006-07-27 08:59:44 +0000 (Thu, 27 Jul 2006)
New Revision: 9790
Modified:
trunk/apps/load-balancing-sims/phase5/Packet.java
trunk/apps/load-balancing-sims/phase5/Peer.java
Log:
Don't send empty packets if txHeadSize > cwind - inflight - Packet.HEADER_SIZE
Modified: trunk/apps/load-balancing-sims/phase5/Packet.java
===================================================================
--- trunk/apps/load-balancing-sims/phase5/Packet.java 2006-07-26 23:14:46 UTC
(rev 9789)
+++ trunk/apps/load-balancing-sims/phase5/Packet.java 2006-07-27 08:59:44 UTC
(rev 9790)
@@ -4,17 +4,18 @@
abstract class Packet
{
- public final static int HEADER_SIZE = 50;
+ public final static int HEADER_SIZE = 80; // Including IP & UDP headers
public final static int MAX_PAYLOAD = 1400;
+ public final static int SENSIBLE_PAYLOAD = 1000; // Nagle's algorithm
public int src, dest; // Network addresses
public int size; // Packet size in bytes, including headers
- public int seq; // Sequence number or explicit ack
public double latency; // Link latency (stored here for convenience)
}
class DataPacket extends Packet
{
+ public int seq; // Sequence number
public ArrayList<Message> messages = null; // Payload
public double sent; // Time at which the packet was (re)transmitted
@@ -23,14 +24,7 @@
size = dataSize + HEADER_SIZE;
}
- /*
- In real life the payload would be an array of bytes, but here the
- payload is represented by an ArrayList of Messages. A large message can
- be split across more than one packet, in which case the message only
- appears in the payload of the *last* packet. This means it's possible
- for a full packet to have an apparently empty payload.
- */
-
+ // In real life the payload would be an array of bytes
public void addMessage (Message m)
{
if (messages == null) messages = new ArrayList<Message>();
@@ -40,9 +34,11 @@
class Ack extends Packet
{
- public Ack (int seq)
+ public int ack; // Explicit ack of a DataPacket's sequence number
+
+ public Ack (int ack)
{
size = HEADER_SIZE;
- this.seq = seq;
+ this.ack = ack;
}
}
Modified: trunk/apps/load-balancing-sims/phase5/Peer.java
===================================================================
--- trunk/apps/load-balancing-sims/phase5/Peer.java 2006-07-26 23:14:46 UTC
(rev 9789)
+++ trunk/apps/load-balancing-sims/phase5/Peer.java 2006-07-27 08:59:44 UTC
(rev 9790)
@@ -9,9 +9,6 @@
public double location; // The remote node's routing location
private double latency; // The latency of the connection in seconds
- // Nagle's algorithm
- public final static int SENSIBLE_PAYLOAD = 1000; // Minimum packet size
-
// Retransmission parameters
public final static double TIMER = 0.5; // Coarse-grained timer, seconds
public final static double RTO = 4.0; // Retransmission timeout in RTTs
@@ -78,11 +75,23 @@
return false;
}
- if (cwind - inflight <= Packet.HEADER_SIZE) {
+ // Work out how large a packet we can send
+ int payload = Packet.MAX_PAYLOAD;
+ if (payload > txQueueSize) payload = txQueueSize;
+ if (payload > cwind - inflight - Packet.HEADER_SIZE)
+ payload = (int) cwind - inflight - Packet.HEADER_SIZE;
+
+ if (payload < txHeadSize) {
log ("no room in congestion window");
return false;
}
+ // Nagle's algorithm - try to coalesce small packets
+ if (payload < Packet.SENSIBLE_PAYLOAD && inflight > 0) {
+ log ("delaying transmission of " + payload + " bytes");
+ return false;
+ }
+
// Return to slow start when the link is idle
double now = Event.time();
if (now - lastTransmission > RTO * rtt) {
@@ -92,18 +101,6 @@
}
lastTransmission = now;
- // Work out how large a packet we can send
- int payload = Packet.MAX_PAYLOAD;
- if (payload > txQueueSize) payload = txQueueSize;
- if (payload > cwind - inflight - Packet.HEADER_SIZE)
- payload = (int) cwind - inflight - Packet.HEADER_SIZE;
-
- // Nagle's algorithm - try to coalesce small packets
- if (payload < SENSIBLE_PAYLOAD && inflight > 0) {
- log ("delaying transmission of " + payload + " bytes");
- return false;
- }
-
// Put as many messages as possible in the packet
DataPacket p = new DataPacket (payload);
while (payload >= txHeadSize) {
@@ -208,14 +205,14 @@
private void handleAck (Ack a)
{
- log ("received ack " + a.seq);
+ log ("received ack " + a.ack);
double now = Event.time();
Iterator<DataPacket> i = txBuffer.iterator();
while (i.hasNext()) {
DataPacket p = i.next();
double age = now - p.sent;
// Explicit ack
- if (p.seq == a.seq) {
+ if (p.seq == a.ack) {
log ("packet " + p.seq + " acknowledged");
i.remove();
inflight -= p.size;
@@ -232,7 +229,7 @@
break;
}
// Fast retransmission
- if (p.seq < a.seq && age > FRTO * rtt) {
+ if (p.seq < a.ack && age > FRTO * rtt) {
p.sent = now;
log ("fast retransmitting packet " + p.seq);
log (inflight + " bytes in flight");
@@ -265,7 +262,7 @@
private void log (String message)
{
- // Event.log (node.net.address + ":" + address + " " + message);
+ Event.log (node.net.address + ":" + address + " " + message);
}
// Event callback
