Hi 
I am running a simple ns script with 128 nodes sending traffic(TCP)
when it reaches 128 nodes it gives me following error.
can somebody help me with possible solutions

C:\tcl>ns 128node2v0d.tcl
Number of nodes exceeds node-field-size of 7 bits
    while executing
"error "Number of nodes exceeds node-field-size of $nodebits_ bits"
    (procedure "_o3" line 4)
    (Simulator check-node-num line 4)
    invoked from within
"$self check-node-num"
    (procedure "_o3" line 18)
    (Simulator node line 18)
    invoked from within
"$ns node"
    (file "128node2v0d.tcl" line 42)

--- sanjeev barala <s_barala@yahoo.com> wrote:

> HI All 
> Can anybody help me in this
> 
> 
> Basic Project Specification
> You are the Senior Engineer for a telecommunications equipment manufacturer in
> charge of the design of a new Voice over IP (VoIP) capable router. The router is
> intended for use by small ISPs with customers on multiple ADSL links or cable
> modems. It will be capable of giving priority to voice traffic over data traffic.
> Small ISPs typically have access to a limited range of uplink speeds. This router is to
> have options for 2.048 Mbps and 34 Mbps.
> The main design issues you need to resolve are buffer sizing and buffer management.
> Because large buffers add to the cost and delay through the router, the buffer needs to
> be as small as possible while still providing adequate service.
> Your initial investigations into Voice over IP show the following:
> &#8226;&#61472;Voice traffic is transmitted using the UDP protocol while data traffic is
> transmitted using the TCP protocol.
> &#8226;&#61472;Each voice stream generates a constant bit rate stream of packets with a fixed
> packet size of 40 bytes (including UDP and IP headers and trailers) arriving at the
> input buffer every 2.5 milliseconds.
> &#8226;&#61472;The maximum tolerable delay for voice traffic end to end is 500 milliseconds. For
> your router, the maximum delay is 100 milliseconds.
> &#8226;&#61472;Data traffic is mostly made up of web page requests and emails. An average user
> generates messages according to an exponential distribution with an average
> interarrival time of 10 seconds with an exponentially distributed size of 40 kbytes.
> &#8226;&#61472;Most households comprise one or two data users and one or two VoIP users who
> are active at any one time.
> &#8226;&#61472;Data traffic is fragmented into 8 kbyte packets.
> &#8226;&#61472;Most subscribers have a duplex link speed of 256 kbps.
> &#8226;&#61472;The Internet &#8216;diffserv&#8217; architecture allows for a choice of
scheduling &#8211; either FIFO
> server schedule or a schedule giving priority to constant bit rate packets. The
> priority scheme is to service the oldest voice packet, or service the oldest data
> packet only if there are no voice packets in the queue.
> You decide to develop a simulation program to help with the router design. The
> typical scenario you wish to understand is where there are one or two concurrent VoIP
> users and one or two data traffic users on each line.
> Your router is to support as many lines as possible, subject to 99.9% of voice packets
> being delayed less than 100 milliseconds.
> You report on the following:
> &#8226;&#61472;Comparison of delay for different number of users user type (VoIP, data)
> &#8226;&#61472;Buffer size necessary to provide a loss probability for data traffic of 10-6
> &#8226;&#61472;Comparison of delay for voice traffic with FIFO queueing and with priority
> queueing.
> 
> Extension 1
> You decide that it is important for the board to have confidence in your
> simulation. You choose a number of techniques to verify it and include the results
> of them in your report.
> Extension 2
> You decide to experiment with different levels of packet fragmentation to see
> what effect it has on voice delay. The IP standard specifies a maximum packet
> size of 64 kilobytes per packet. You are using 8 kbyte packets. You report on the
> effect on voice traffic delay of fragmenting the data traffic into packet sizes
> ranging from 512 bytes up to the maximum of 64 kbytes. You are to report on the
> effect of fragmentation with both FIFO and priority queueing.
> Extension 3
> There is the possibility that link speeds will dramatically improve over the next
> few years. Consequently, the board is undecided as to whether they should
> produce a number of products with different buffer sizes and different uplink data
> rates or whether a single buffer size with different interfaces will be satisfactory.
> To help them make this decision, you decide to produce an extensive set of
> simulation results for different household uplink speeds (256 bps, 512 bps and
> 1024 bps), number of users and buffer sizes. You use the results to make a
> recommendation as to which option should be chosen.
> Extension 4
> Voice over IP across WLAN interface is becoming more popular. However, the
> Board is concerned that the additional delay of the WLAN interface may have an
> impact on the router design. You decide to investigate the effect of using VoIP
> across an 802.11b wireless interface and how it affects delay from the user to the
> ISP through the new router.
> Households
> Router
> Internet
> 
> Sanjeev
> 
> 
> 		
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