Re: [ns] TCP over 802.11b dropping ACKs
FTP is modeled as bulk data transfer, so in your case the source data rate is larger than available 11b bandwidth. ACKs at node 1 are dropped since IFQ becomes full after some point in time (dropped from tail). If you may increase the IFQ length or use another type agent, you may decrease the probability of such drops. Cheers, Inanc -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Lars Lars Sent: Tuesday, December 19, 2006 3:43 PM To: [EMAIL PROTECTED] Cc: ns-users@ISI.EDU Subject: Re: [ns] TCP over 802.11b dropping ACKs Hi Dan, still getting dropped ACKS from node1 with column4=IFQ, indicating dropped because of queue??? Is tis some sort of NS error? Am I correct in thinking that this isn't a feature of the network/protocol and it should be ignored in my analysis? L From: Dan Dechene [EMAIL PROTECTED] To: 'Lars Lars' [EMAIL PROTECTED] Subject: RE: [ns] TCP over 802.11b dropping ACKs Date: Tue, 19 Dec 2006 18:06:43 -0500 This shouldn't happen. However try: Queue/DropTail/PriQueue as interface queue type instead of Queue/DropTail Dan Dechene, B.Eng. -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Lars Lars Sent: Tuesday, December 19, 2006 5:29 PM To: ns-users@ISI.EDU Subject: [ns] TCP over 802.11b dropping ACKs Hi, I've a 2-node(static) wireless link(802.11b). The tracefile is showing me that ACK packets being sent from node1 to node0 are being dropped(which is OK), however, the fourth column in the tracefile is IFQ which implies that these packets are being dropped due to the ifq. How can this be? PAckets on the return path don't enter a queue at any point surely??? My simulation is transferring FTP data from node0 to node1. The TCP agent is on node0 and the sink is on node1. below is a section from my trace file. What does IFQ mean in column 4. If (as I understand it) this means that these packets are being dropped by the ifq, then why is there an IFQ on the return path as all the traffic is going from node0 to node1? (My simulation script is below also). Thanks L D 30.32288741 _0_ IFQ --- 15598 tcp 1084 [0 D 30.34824777 _0_ IFQ --- 15611 tcp 1084 [0 D 30.62936723 _1_ IFQ --- 15759 ack 60 [0 D 30.6869282 _1_ IFQ --- 15792 ack 60 [0 D 30.70534317 _1_ IFQ --- 15801 ack 60 [0 D 30.72629153 _1_ IFQ --- 15813 ack 60 [0 set val(chan) Channel/WirelessChannel;# channel type set val(prop) Propagation/TwoRayGround ;# radio-propagation model set val(netif) Phy/WirelessPhy;# network interface type set val(mac) Mac/802_11 ;# MAC type Mac/802_11 set dataRate_ 11Mb ;# Data Rate 11 Mbps Mac/802_11 set basicRate_ 1Mb ;# Basic Rate 1 Mbps # Mac/802_11 set RTSThreshold_ 3000 ;# Turn off RTS / CTS Mac/802_11 set SlotTime_ 0.20 ;# 20us Mac/802_11 set sifs_ 0.10 ;# 10us Mac/802_11 set PreambleLenght_ 144 ;# 144 bits Mac/802_11 set PLCPHeaderLength_ 48 ;# 48 bits Mac/802_11 set PLCPDataRate_ 1Mb;# 1Mbps set val(ifq)Queue/DropTail;# interface queue type/PriQueue set val(ll) LL ;# link layer type set val(ant)Antenna/OmniAntenna;# antenna model set val(ifqlen) 10 ;# max packet in ifq set val(nn) 2 ;# number of mobilenodes set val(rp) DSDV ;# routing protocol DSDV set ns [new Simulator] $ns color 0 blue $ns color 1 red # set up topography object set topo [new Topography] $topo load_flatgrid 400 200 #Open the trace file set tf [open out.tr w] $ns trace-all $tf #Open the nam trace file set nf [open out.nam w] $ns namtrace-all-wireless $nf 400 200 # Create God create-god $val(nn) Agent/DSDV set perup_ 1500 ;# ~ infinite periodic update $ns node-config -adhocRouting $val(rp) \ -llType $val(ll) \ -macType $val(mac) \ -ifqType $val(ifq) \ -ifqLen $val(ifqlen) \ -antType $val(ant) \ -propType $val(prop) \ -phyType $val(netif) \ -channelType $val(chan) \ -topoInstance $topo \ -agentTrace OFF \ -routerTrace OFF \ -macTrace ON \ -movementTrace OFF # Create and configure nodes set nodeA [$ns node] $nodeA random-motion 0 $nodeA set
Re: [ns] Help required for ns2HCCA patch - setting TXOP value
Up to my knowledge, the 802.11e standard specifies it to be Min_PHY_rate for the example scheduler provided within. But it surely depends on the scheduling algorithm that you are using. Inanc -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Ritwik Mitra Sent: Saturday, May 06, 2006 7:07 AM To: ns-users@ISI.EDU Subject: [ns] Help required for ns2HCCA patch - setting TXOP value Hi! I am using the ns2HCCA patch to simulate ARROW scheduler using NS-2.27. One thing is not clear to me, when calculating the txop of a stream, should i use the minimum PHY rate specified in the TSPEC or should i call the mac getDataRate() function which returns the data rate of the physical layer. Suppose i want to set my TXOP according to the Queue Size of the stations and den want to poll each station for that much time. What should my txop be: 1. Poll_overhead+SIFS+ACK+SIFS+(Queue_Size/Min_PHY_rate) 2. Poll_overhead+SIFS+ACK+SIFS+(Queue_Size/mac_-getDataRate()) Also, does anyone know the difference between backlog_ and queue_size_ define in the oneflow.cc file. Both correspond to the queue_size but what exactly is the difference between the two? Eagerly waiting for a response. Thanks in advance Ritwik Mitra M.Sc. Computer Science Department of Computer Science, Delhi University - How low will we go? Check out Yahoo! Messenger's low PC-to-Phone call rates.
Re: [ns] simulate an access point
As far as I understood, you are trying to generate a simulation setup for a wired-wireless scenario where the AP is a gateway to the wired domain. Please take a look at Marc Greis' tutorial, chapter 10. Base station (described in detail in that chapter) provides the connection of the wireless domain to the wired domain (that may be what you have meant by 'connection to exterior'). You may define a mobile node as an AP as stated in the thread you mentioned. But this won't enable the node to be a gateway to the wired domain. When the AP is defined, all WLAN traffic, whether it is destined to another wireless node or not, will traverse the AP as the first hop. Hope this helps. Regards, Inanc -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Hai Nam Sent: Thursday, April 20, 2006 11:22 AM To: ns-users@ISI.EDU Subject: [ns] simulate an access point Hello, I've installed and used NS-2 to test a protocol in ad hoc network. However, there're also AP (Access Points) in this network to provide connection to exterior. The problem is that I don't know how to simulate an AP. I tried to search on the web and the only example is at http://mailman.isi.edu/pipermail/ns-users/2005-June/050548.html but I don't understand the reply in that thread. Taking a look at ~ns/tcl/lib/ns-mobilenode.tcl I found nothing to make a MN become an AP (from line 55: Node/MobileNode instproc init args). Might anyone tell me, or give me a link, how to make a MN become an AP ? Thanks in advance. -- Hai-Nam http://www.jcisio.com
Re: [ns] Fw: Reset CW
Please check mac-802_11.h. Regards, Inanc -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Sebastián Guazzini Sent: Friday, April 14, 2006 8:00 AM To: usuarios_ns Cc: meschoyez3 Subject: [ns] Fw: Reset CW I have found a call to function rst_cw in mac-802_11.cc but the function is not there. Do you know where it is? Thak you - Original Message - From: Sebastián Guazzini To: usuarios_ns Cc: meschoyez3 ; meschoyez2 ; meschoyez Sent: Friday, April 14, 2006 10:43 AM Subject: [ns] Reset CW Hi, people. I try to do some modifications in the manner that 802.11 decrement the Contention Window (CW) but I can't find the function in mac-802_11.cc that return this variable to CWmin when the tx is successful. Anybody can help me? Thank you a lot
[ns] 802.11 Timeouts
Hello all, Although I searched the ns-users list on this subject, I could not find a satisfactory answer. I am wondering why ns 802.11 MAC code guesses RTS/CTS and Data retransmission timeouts as are? For example retransmission timeout for RTS packets is calculated as: timeout = txtime(phymib_.getRTSlen(), basicRate_) + DSSS_MaxPropagationDelay + sifs_ + txtime(phymib_.getCTSlen(), basicRate_) + DSSS_MaxPropagationDelay; If we assume RTS packets have been in collision, the transmitter may figure out a collision has occurred if no other transmission starts at the slot after SIFS (CTS transmission should have been started). So timeout can be (this approach can save considerable bandwidth in some scenarios): timeout = txtime(phymib_.getRTSlen(), basicRate_) + DSSS_MaxPropagationDelay + sifs_ + 1 slot. A similar discussion holds for data timeout. So, I wonder about the reasoning behind the guess of the 802.11 ns MAC code. I'll appreciate any help/answer. I'm including a paragraph from 802.11 document if it may help. But Ack-timeout value is not specified anywhere in the document. Best regards, Inanc Inan After transmitting an MPDU that requires an ACK frame as a response (see 9.7), the STA shall wait for an ACKTimeout interval, starting at the PHY- TXEND.confirm. If a PHY-RXSTART.indication does not occur during the ACKTimeout interval, the STA concludes that the transmission of the MPDU has failed, and this STA shall invoke its backoff procedure upon expiration of the ACKTimeout interval. If a PHY-RXSTART.indication does occur during the ACKTimeout interval, the STA shall wait for the corresponding PHY-RXEND.indication to determine whether the MPDU transmission was successful. The recognition of a valid ACK frame sent by the recipient of the MPDU requiring acknowledgment, corresponding to this PHY-RXEND.indication, shall be interpreted as successful acknowledgment, permitting the frame sequence to continue, or to end without retries, as appropriate for the particular frame sequence in progress. The recognition of anything else, including any other valid frame, shall be interpreted as failure of the MPDU transmission. In this instance, the STA shall invoke its backoff procedure at the PHY-RXEND.indication and may process the received frame. The sole exception is that recognition of a valid data frame sent by the recipient of a PS-Poll frame shall also be accepted as successful acknowledgment of the PS-Poll frame.
