GossipSub shadow simulation scripts

README.md

@@ -2,21 +2,20 @@
 
 * DST gossipsub test node
 * incl shadow simulation setup
-* incl awk scripts for detailed analysis
 
-Three simulation cases are supportes
-
-## Scenario1 - Basic Simulation Scenario 
-### Shadow example
+## Shadow example
 
 ```sh
 nimble install -dy
 cd shadow
 # the default shadow.yml will start 5k nodes, you might want to change that by removing
 # lines and setting PEERS to the number of instances
-./run.sh
-# the output is a "latencies" file, or you can find each host output in the
-# data.shadow folder
+./run.sh <runs> <nodes>
+# the first parameter <runs> tells the number of simulation runs, and second parameter <nodes> tells the 
+# number of nodes in simulation, for example ./run.sh 2 3000
+# the output for each run creates latencies(X) and shadowlogX files. where X is the simulation number.
+
+# the run script (run.sh) uses awk to summarize latencies(X) and shadowlogX files
 
 # you can use the plotter tool to extract useful metrics & generate a graph
 cd ../tools
@@ -26,44 +25,3 @@ nim -d:release c plotter
 ```
 
 The dependencies will be installed in the `nimbledeps` folder, which enables easy tweaking
-
-
-## Scenario2 - (P2P-Research Branch) - 
-Homogeneous nodes/links (100 Mbps bandwidth and 100ms latency)
-supports variable network/message size, variable number of publishers and message fragments
-automatically updates shadow.yaml file to accomodate different network sizes 
-awk scripts for detailed analysis
-
-```sh
-cd shadow
-#the run.sh script is automated to meet different experiment needs, use ./run.sh <num_runs num_peers msg_size num_fragments>
-#The below example runs the simulation twice for a 1000 node network. each publisher publishes a 15000 bytes messages, and every message is partitioned into 4 fragments. Total 10 publishers use  
-
-./run.sh 2 1000 15000 4 10
-# The number of nodes is maintained in the shadow.yaml file, and automatically updated by run.sh.
-# The output files latencies(x), stats(x) and shadowlog(x) carries the outputs for each simulation run.
-# The summary_dontwant.awk, summary_latency.awk, summary_latency_large.awk, and summary_shadowlog.awk parse the output files.
-# The run.sh script automatically calls these files to display the output
-# a temperary data.shadow folder is created for each simulation and removed by the run.sh after the simulation is over
-```
-
-## Scenario3 - (Realistic-Scenarios Branch) - 
-Heterogeneous nodes/links (bandwidth/latency/packet_loss_ratio controllable through run.sh)
-run.sh uses topogen.py to create a realistic gml file to emulate a real-world network scenario
-supports variable network/message size, variable number of publishers and message fragments
-automatically generates network_topology.gml and shadow.yaml files to accomodate different network sizes 
-awk scripts called from run.sh for detailed analysis
-
-```sh
-cd shadow
-#The following sample command runs simulation 1 time, for a 1000 node network. Each published message size
-#is 15KB (no-fragmentation), peer bandwidth varies between 50-130 Mbps, Latency between 60-160ms, and
-#bandwidth,latency is roughly distributed in five different groups. 
-
-./run.sh 1 1000 15000 1 10 50 130 60 160 5 0.0
-# The number of nodes is maintained in the shadow.yaml file, and automatically generated by run.sh.
-# The output files latencies(x), stats(x) and shadowlog(x) carries the outputs for each simulation run.
-# The summary_dontwant.awk, summary_latency.awk, summary_latency_large.awk, and summary_shadowlog.awk parse the output files.
-# The run.sh script automatically calls these files to display the output
-# a temperary data.shadow folder is created for each simulation and removed by the run.sh after the simulation is over
-```

shadow/main.nim

@@ -1,22 +1,12 @@
 import stew/endians2, stew/byteutils, tables, strutils, os
 import libp2p, libp2p/protocols/pubsub/rpc/messages
 import libp2p/muxers/mplex/lpchannel, libp2p/protocols/ping
-#import libp2p/protocols/pubsub/pubsubpeer
-
 import chronos
 import sequtils, hashes, math, metrics
 from times import getTime, toUnix, fromUnix, `-`, initTime, `$`, inMilliseconds
 from nativesockets import getHostname
 
-#These parameters are passed from yaml file, and each defined peer may receive different parameters (e.g. message size)
-var
-  publisherCount = parseInt(getEnv("PUBLISHERS"))
-  msg_size = parseInt(getEnv("MSG_SIZE")) 
-  chunks = parseInt(getEnv("FRAGMENTS"))
-
-#we experiment with upto 10 fragments. 1 means, the messages are not fragmented
-if chunks < 1 or chunks > 10:     
-  chunks = 1
+const chunks = 1
 
 proc msgIdProvider(m: Message): Result[MessageId, ValidationResult] =
   return ok(($m.data.hash).toBytes())
@@ -25,7 +15,9 @@ proc main {.async.} =
   let
     hostname = getHostname()
     myId = parseInt(hostname[4..^1])
-    isPublisher = myId <= publisherCount      #need to adjust is publishers ldont start from peer1
+    #publisherCount = client.param(int, "publisher_count")
+    publisherCount = 10
+    isPublisher = myId <= publisherCount
     #isAttacker = (not isPublisher) and myId - publisherCount <= client.param(int, "attacker_count")
     isAttacker = false
     rng = libp2p.newRng()
@@ -53,7 +45,7 @@ proc main {.async.} =
       anonymize = true,
       )
     pingProtocol = Ping.new(rng=rng)
-  gossipSub.parameters.floodPublish = false 
+  gossipSub.parameters.floodPublish = false
   #gossipSub.parameters.lazyPushThreshold = 1_000_000_000
   #gossipSub.parameters.lazyPushThreshold = 0
   gossipSub.parameters.opportunisticGraftThreshold = -10000
@@ -87,9 +79,6 @@ proc main {.async.} =
       sentNanosecs = nanoseconds(sentMoment - seconds(sentMoment.seconds))
       sentDate = initTime(sentMoment.seconds, sentNanosecs)
       diff = getTime() - sentDate
-
-    #  pubId = byte(data[11])
-    
     echo sentUint, " milliseconds: ", diff.inMilliseconds()
 
 
@@ -132,7 +121,7 @@ proc main {.async.} =
   let connectTo = parseInt(getEnv("CONNECTTO"))
   var connected = 0
   for peerInfo in peersInfo:
-    if connected >= connectTo+2: break
+    if connected >= connectTo: break
     let tAddress = "peer" & $peerInfo & ":5000"
     echo tAddress
     let addrs = resolveTAddress(tAddress).mapIt(MultiAddress.init(it).tryGet())
@@ -148,64 +137,24 @@ proc main {.async.} =
   #  warmupMessages = client.param(int, "warmup_messages")
   #startOfTest = Moment.now() + milliseconds(warmupMessages * maxMessageDelay div 2)
 
-  await sleepAsync(12.seconds)
-  echo "Mesh size: ", gossipSub.mesh.getOrDefault("test").len, 
-      ", Total Peers Known : ", gossipSub.gossipsub.getOrDefault("test").len,
-      ", Direct Peers : ", gossipSub.subscribedDirectPeers.getOrDefault("test").len,
-      ", Fanout", gossipSub.fanout.getOrDefault("test").len, 
-      ", Heartbeat : ", gossipSub.parameters.heartbeatInterval.milliseconds
+  await sleepAsync(10.seconds)
+  echo "Mesh size: ", gossipSub.mesh.getOrDefault("test").len
 
-  await sleepAsync(5.seconds)  
-
-  # Actual message publishing, one message published every 3 seconds
-  # First 1-2 messages take longer than expected time due to low cwnd. 
-  # warmup_messages can set cwnd to a desired level. or alternatively, warmup messages can be set to 0
-  let
-    warmup_messages = 2 
-    #shadow.yaml defines peers with changing latency/bandwith. In the current arrangement all the publishers 
-    #will get different latency/bandwidth
-    pubStart = 4                                                       
-    pubEnd = pubStart + publisherCount + warmup_messages
-
-
-  #we send warmup_messages for adjusting TCP cwnd  
-  for i in pubStart..<(pubStart + warmup_messages):
-    await sleepAsync(2.seconds)
-    if i == myId:
-      #two warmup messages for cwnd raising
-      let
-          now = getTime()
-          nowInt = seconds(now.toUnix()) + nanoseconds(times.nanosecond(now))
-      var nowBytes = @(toBytesLE(uint64(nowInt.nanoseconds))) & newSeq[byte](msg_size)
-      doAssert((await gossipSub.publish("test", nowBytes)) > 0)
-  #done sending warmup_messages , wait for short time
-  await sleepAsync(5.seconds)
-
-
-  #We now send publisher_count messages
-  for msg in (pubStart + warmup_messages) .. pubEnd:#client.param(int, "message_count"):
-    await sleepAsync(3.seconds)
-    if msg mod (pubEnd+1) == myId:
+  for msg in 0 ..< 10:#client.param(int, "message_count"):
+    await sleepAsync(12.seconds)
+    if msg mod publisherCount == myId - 1:
+    #if myId == 1:
       let
         now = getTime()
         nowInt = seconds(now.toUnix()) + nanoseconds(times.nanosecond(now))
-    #[    
-      if chunks == 1:
-        var nowBytes = @(toBytesLE(uint64(nowInt.nanoseconds))) & newSeq[byte](50000)
-      else:
-        var nowBytes = @(toBytesLE(uint64(nowInt.nanoseconds))) & newSeq[byte](500_000 div chunks)
-    ]#
-      var nowBytes = @(toBytesLE(uint64(nowInt.nanoseconds))) & newSeq[byte](msg_size div chunks)
+      #var nowBytes = @(toBytesLE(uint64(nowInt.nanoseconds))) & newSeq[byte](500_000 div chunks)
+      var nowBytes = @(toBytesLE(uint64(nowInt.nanoseconds))) & newSeq[byte](50)
+      #echo "sending ", uint64(nowInt.nanoseconds)
       for chunk in 0..<chunks:
         nowBytes[10] = byte(chunk)
         doAssert((await gossipSub.publish("test", nowBytes)) > 0)
-      echo "Done Publishing ", nowInt.nanoseconds
 
-  #we need to export these counters from gossipsub.nim
-  echo "statcounters: dup_during_validation ", libp2p_gossipsub_duplicate_during_validation.value(),
-       "\tidontwant_saves ", libp2p_gossipsub_idontwant_saved_messages.value(),
-       "\tdup_received ", libp2p_gossipsub_duplicate.value(),
-       "\tUnique_msg_received ", libp2p_gossipsub_received.value(),
-       "\tStaggered_Saves ", libp2p_gossipsub_staggerDontWantSave.value(),
-       "\tDontWant_IN_Stagger ", libp2p_gossipsub_staggerDontWantSave2.value()
+  #echo "BW: ", libp2p_protocols_bytes.value(labelValues=["/meshsub/1.1.0", "in"]) + libp2p_protocols_bytes.value(labelValues=["/meshsub/1.1.0", "out"])
+  #echo "DUPS: ", libp2p_gossipsub_duplicate.value(), " / ", libp2p_gossipsub_received.value()
+
 waitFor(main())

shadow/run.sh

@@ -1,65 +1,33 @@
 #!/bin/sh
-set -e
 
-if [ $# -ne 11 ]; then
-    echo "Usage: $0 <runs> <nodes> <Message_size> <num_fragment> <num_publishers>
-            <min_bandwidth> <max_bandwidth> <min_latency> <max_latency> <anchor_stages <packet_loss>>"
-    
-    echo "The following sample command runs simulation 1 time, for a 1000 node network. Each published message size \
-            is 15KB (no-fragmentation), peer bandwidth varies between 50-130 Mbps, Latency between 60-160ms, and \
-            bandwidth,latency is roughly distributed in five different groups. \
-            see the generated network_topology.gml and shadow.yaml for peers/edges details"   
-    
-    echo "$0 1 1000 15000 1 10 50 130 60 160 5 0.0" 
+if [ $# -ne 2 ]; then
+    echo "Usage: $0 <runs> <nodes>"
     exit 1
 fi
 
-runs="$1"			        #number of simulation runs
-nodes="$2"			        #number of nodes to simulate
-msg_size="$3"			    #message size to use (in bytes)
-num_frag="$4"			    #number of fragments per message (1 for no fragmentation)
-num_publishers="$5"         #number of publishers 
-min_bandwidth="$6"
-max_bandwidth="$7"
-min_latency="$8"
-max_latency="$9"
-steps="${10}"
-pkt_loss="${11}"
+runs="$1"			#number of simulation runs
+nodes="$2"			#number of nodes to simulate
+shadow_file="shadow.yaml"	
+sed -i '/environment:/q' "$shadow_file"
+sed -E -i "s/\"PEERS\": \"[0-9]+\"/\"PEERS\": \"$nodes\"/" "$shadow_file"
 
-connect_to=5                #number of peers we connect with to form full message mesh
+counter=2
+while [ $counter -le $nodes ]; do
+  echo "  peer$counter: *client_host" >> "$shadow_file"
+  counter=$((counter + 1))
+done
 
-
-#topogen.py uses networkx module from python to generate gml and yaml files
-PYTHON=$(which python3 || which python)
-
-if [ -z "$PYTHON" ]; then
-    echo "Error: Python, Networkx is required for topology files generation."
-    exit 1
-fi
-
-"$PYTHON" topogen.py $nodes $min_bandwidth $max_bandwidth $min_latency $max_latency $steps $pkt_loss $msg_size $num_frag $num_publishers
-
-
-
-rm -f shadowlog* latencies* stats* main && rm -rf shadow.data/
+rm -f shadowlog* latencies* main && rm -rf shadow.data/
 nim c -d:chronicles_colors=None --threads:on -d:metrics -d:libp2p_network_protocols_metrics -d:release main 
 
 for i in $(seq $runs); do
     echo "Running for turn "$i
-    shadow shadow.yaml > shadowlog$i && 
-        grep -rne 'milliseconds\|BW' shadow.data/ > latencies$i && 
-        grep -rne 'statcounters:' shadow.data/ > stats$i
-    #uncomment to to receive every nodes log in shadow data (only if runs == 1, or change data directory in yaml file)
-    #rm -rf shadow.data/
+    shadow shadow.yaml > shadowlog$i && grep -rne 'milliseconds\|BW' shadow.data/ > latencies$i
+    rm -rf shadow.data/
 done
 
 for i in $(seq $runs); do
     echo "Summary for turn "$i
-    if [ "$msg_size" -lt 1000 ]; then
-    	awk -f summary_latency.awk latencies$i		#precise per hop coverage for short messages only
-    else
-	awk -f summary_latency_large.awk latencies$i	#estimated coverage for large messages (TxTime adds to latency)
-    fi
+    awk -f summary_latency.awk latencies$i
     awk -f summary_shadowlog.awk shadowlog$i
-    awk -f summary_dontwant.awk stats$i    
-done
+done

shadow/summary_dontwant.awk

@@ -1,30 +0,0 @@
-BEGIN {
-	FS = " ";		#default column separator
-	idontwant_saves = min_idontwant = max_idontwant = 0;
-    dup_received = min_dup = max_dup = 0;
-    unique_msg_received        = 0;
-    stagger_saves           = 0;
-    stagger_DontWantSaves   = 0;
-}
-
-{
-	#print $5, $7, $9
-    idontwant_saves += $5
-    if ($5 < min_idontwant || min_idontwant == 0)  min_idontwant  = $5
-    if ($5 > max_idontwant) max_idontwant = $5
-
-    dup_received += $7
-    if ($7 < min_dup || min_dup == 0)  min_dup  = $7
-    if ($7 > max_dup) max_dup = $7
-
-    unique_msg_received     += $9
-    stagger_saves           += $11
-    stagger_DontWantSaves   += $13
-
-}
-
-END {
-    print "idontwant_saves min, max, avg, total : ", min_idontwant, "\t", max_idontwant, "\t", idontwant_saves/NR, "\t", idontwant_saves 
-    print "dup_received    min, max, avg, total : ", min_dup, "\t", max_dup, "\t", dup_received/NR, "\t", dup_received
-    print "Unique_msg_received: ", unique_msg_received, "\tStagger Saves : ", stagger_saves, "\tStaggerDontWantSaves", stagger_DontWantSaves
-}

shadow/summary_latency_large.awk

@@ -1,73 +0,0 @@
-# we parse the latencies(x) file produced by run.sh to receive results summary (Max/Avg Latency --> per packet, overall)
-# runs $awk -f result_summary.awk latencies(x)
-
-BEGIN {
-	FS = " ";		#default column separator
-	network_size = 0
-	max_nw_lat = sum_nw_lat = sum_max_delays = 0
-	hop_lat = 100	#should be consistent with shadow.yaml
-}
-
-{
-	clean_int = $3
-	gsub(/[^0-9]/, "", clean_int); 
-	if ($3 == clean_int){	#get rid of unwanted rows
-		sum_nw_lat += $NF 
-		if (max_nw_lat < $NF) {max_nw_lat = $NF} 
-		if (split($1, arr, "peer|/main|:.*:")) {
-				#$3 = rx_latency,	arr[4] = publish_time,	arr[2] = peerID
-				
-				#We compute network-wide dissemination latency for each message
-				if (max_msg_latency[arr[4]] < $NF) {max_msg_latency[arr[4]] = $NF}
-				
-				#we round to values to nearest hop_lat to estimate hop coverage
-				rounded_RxTime = (int($3/hop_lat + 0.5)) * hop_lat
-				lat_arr[arr[4], rounded_RxTime]++;	
-				msg_arr[arr[4]] = 1;	#we maintain set of messages identified by their publish time
-				if (network_size < arr[2]) {network_size = arr[2]}
-		}
-	}
-}
-
-END {
-
-	print "Total Nodes : ", network_size, "Total Messages Published : ", length(msg_arr), 
-            "Network Latency\t MAX : ", max_nw_lat, "\tAverage : ", sum_nw_lat/NR
-	print "   Message ID \t       Avg Latency \t Messages Received"
-	for (value in msg_arr) {
-		sum_rx_msgs = 0;
-        latency = 0;
-		spread[1] = spread[2] = spread[3] = spread[4] = spread[5] = spread[6] = spread[7] = spread[8] = spread[9] = 0 
-		spread[10] = spread[11] = spread[12] = spread[13] = spread[14] = spread[15] = spread[16] = spread[17] = spread[18] = 0
-		for (key in lat_arr) {
-			split(key, parts, SUBSEP);
-			if (parts[1] == value) {
-				#parts[2] recv time
-				#10% 20% 30%....90% under parts[2]
-				sum_rx_msgs = sum_rx_msgs + lat_arr[key]; 					#total receives / message
-				latency = latency + (lat_arr[key] * parts[2]) 
-				spread[ int((parts[2]) / hop_lat) ] = lat_arr[key]           #hop-by-hop spread count of messages
-	    	}
-	    }
-
-		print value, "\t", latency/sum_rx_msgs, "\t  ", sum_rx_msgs, "spread is", 
-                spread[1], spread[2], spread[3], spread[4], spread[5], spread[6], spread[7], spread[8], spread[9], 
-		spread[10], spread[11], spread[12], spread[13], spread[14], spread[15], spread[16], spread[17], spread[18],
-		spread[19], spread[20], spread[21], spread[22], spread[23], spread[24], spread[25], spread[26], spread[27],
-		spread[28], spread[29], spread[30], spread[31], spread[32], spread[33], spread[34], spread[35], spread[36],
-		spread[37], spread[38], spread[39], spread[40], spread[41], spread[42], spread[43], spread[44], spread[45],
-		spread[46], spread[47], spread[48], spread[49], spread[50], spread[51], spread[52], spread[53], spread[54]		   
-        	delete spread
-    	}
-    	
-    	for (delay_val in max_msg_latency) {
-    		print "MAX delay for ", delay_val, "is \t", max_msg_latency[delay_val]
-    		sum_max_delays = sum_max_delays + max_msg_latency[delay_val]
-    	}
-    	
-    	print "Total Messages Published : ", length(max_msg_latency), "Average Max Message Dissemination Latency : ", sum_max_delays/length(max_msg_latency) 
-    
-    
-}
-
-

shadow/topogen.py

@@ -1,106 +0,0 @@
-import sys, math, networkx as nx
-
-args = sys.argv
-if len(args) != 11:
-    print("Usage: python topogen.py <network_size> <min_bandwidth> <max_bandwidth> <min_latency> <max_latency> <anchor_stages> \
-          <packet_loss> <message_size> <num_frags> <num_publishers>")
-    print("Please note that bandwith and latency are integer values in Mbps and ms respectively")
-    print("Anchor stages represent the number of bandwidth and latency variations")
-    print("packet_loss [0-1], Message size [KB], num_frags [number of fragments/message 1-10], num_publishers [number of publishers]")
-    exit(-1)
-
-print (args[1:])
-try:
-    networkSize     = int(args[1])
-    minBandwidth    = int(args[2])
-    maxBandwidth    = int(args[3])
-    minLatency      = int(args[4])
-    maxLatency      = int(args[5])
-    steps           = int(args[6])
-    packetLoss      = float(args[7])
-    messageSize     = int(args[8])
-    numFrags        = int(args[9])
-    numPublishers   = int(args[10])
-
-except ValueError:
-    print("Usage: python topogen.py <network_size> <min_bandwidth> <max_bandwidth> <min_latency> <max_latency> <anchor_stages> \
-          <packet_loss> <message_size> <num_frags> <num_publishers>")
-    print("Please note that bandwith and latency are integer values in Mbps and ms respectively")
-    print("Anchor stages represent the number of bandwidth and latency variations")
-    print("packet_loss [0-1], Message size [KB], num_frags [number of fragments/message 1-10], num_publishers [number of publishers]")
-    exit(-1)
-
-gml_file  = "network_topology.gml"      #network topology layout in gml format, to be used by the yaml file
-yaml_file = "shadow.yaml"               #shadow simulator settings
-connections = 5                         #Initial connections to form full-message mesh
-bandwidthJump = (maxBandwidth-minBandwidth)/(steps-1)
-latencyJump = int((maxLatency-minLatency)/steps)
-
-"""
-We create network work graph, with 'steps' number of independent nodes. And all the nodes must be connected. 
-Shadow uses accumulative edge latencies to route traffic through the shortest paths (accumulative link latencies)
-
-Multiple hosts can connect with a single node. The node must define 'host_bandwidth_up' and 'host_bandwidth_down' 
-bandwidths, and each connected host gets this bandwidth allocated (bandwidth is not shared between hosts)
-
-We MUST have an edge connecting a node to itself. All the Intra-node communications (among the hosts connected to 
-the same node) happen by using that edge. 
-
-latency and packet loss are edge characteristics
-"""
-
-G=nx.complete_graph(steps)
-
-for i in range(0, steps):
-    nodeBw = str(math.ceil(i * bandwidthJump + minBandwidth)) + " Mbit"
-    G.nodes[i]["hostbandwidthup"] = nodeBw
-    G.nodes[i]["hostbandwidthdown"] = nodeBw
-    G.add_edge(i,i)
-    G.edges[i,i]["latency"] = str( max((steps-i)*latencyJump, minLatency) ) + " ms"
-    G.edges[i,i]["packetloss"] = packetLoss
-
-    for j in range(i+1, steps):
-        edgeLatency = min(math.ceil((steps-j)*latencyJump + minLatency), maxLatency)
-        G.edges[i,j]["latency"] = str(edgeLatency) + " ms"
-        G.edges[i,j]["packetloss"] = packetLoss
-
-nx.write_gml(G, gml_file)
-
-
-#networkx package can not write underscores. so we created gml without underscores. Now we embed them underscores 
-with open(gml_file, 'r') as file:
-    gml_content = file.read()
-
-modified_content = gml_content.replace("hostbandwidth", "host_bandwidth_")
-modified_content = modified_content.replace("packetloss", "packet_loss")
-
-with open(gml_file, "w") as file:
-    file.write(modified_content)
-    
-
-#we created the gml. now we create the yaml file required by shadow
-m1 = "\n    network_node_id: "
-m2 = "\n    processes:"
-m3 = "\n    - path: ./main"
-m4 = "\n      start_time: 5s"
-
-with open(yaml_file, "w") as file:
-    file.write("general:\n  bootstrap_end_time: 10s\n  heartbeat_interval: 12s\n  stop_time: 15m\n")
-    file.write("  progress: true\n\nexperimental:\n  use_memory_manager: false\n\n")
-    file.write("network:\n  graph:\n    type: gml\n    file:\n      path: " + gml_file)
-    file.write("\n\nhosts:\n")
-    
-    #we create 'steps' number of template peers, to be used by the remaining peers
-    for i in range(0,steps):
-        file.write("  peer" + str(i+1) + ": &client_host" + str(i))
-        file.write(m1 + str(i) + m2 + m3 + m4)
-        file.write("\n      environment: {\"PEERS\": \"" + str(networkSize) + 
-                   "\", \"CONNECTTO\": \"" + str(connections) + 
-                   "\", \"MSG_SIZE\": \"" + str(messageSize) + 
-                   "\", \"FRAGMENTS\": \"" + str(numFrags) +
-                   "\", \"PUBLISHERS\": \"" + str(numPublishers) + "\"}\n")
-        
-    #we populate remaining peers on populated samples    
-    for i in range(steps, networkSize):
-        file.write("  peer" + str(i+1) + ": *client_host" + str(i%steps) + "\n")
-