Cross-layer Interaction in Multihop 802.11 Networks(TCP FeW and DSR++)Kitae Nahm  nahm@sipi.usc.eduAhmed Helmy helmy@ceng.usc.eduC.-C. Jay Kuo   cckuo@sipi.usc.eduDepartment of Electrical EngineeringViterbi School of EngineeringUniversity of Southern California1. IntroductionThis package includes two mobile ad hoc network (MANET) subpackages for NS-2.29. One is TCP FeW,and the other is DAMPEN policy for DSR protocol. These schemes are propose to suppress theinefficient cross-layer interaction among TCP, dynamic routing, and medium access control ofIEEE 802.11, which leads to improvement of TCP performance and routing stability. More informationabout these schemes can be found inhttp://biron.usc.edu/~nahm/research.htm2. DSR++ (DSR with DAMPEN policy) package- The maximum end-to-end hop distance supported by DSR agent is changed from 16 hops to 50 hops- A new command "add-route" that provides a manual configuration of source route is added- DAMPEN policy with beta-factor is implemented for DSR protocoltcl/lib/ns-default.tcl - Initiating beta factor and other monitoring variablestcl/mobility/dsr.tcl - Adding "add-route" command for manual path configuration in DSR protocolcommon/packet.h - Adding a new 802.11 MAC message "XMIT_REASON_CONFIRM" for a callback functionmac/802.11.cc   - Adding callback function to routing agent when Tx is succeededdsr/dsragent.h  - Adding beta factor to control DSR's sensitivity to link failuredsr/dsragent.cc - Adding beta factor to control DSR's sensitivity to link failuredsr/hdr_sr.h    - Changing the maximum end-to-end hop distance allowed by DSR agent3. TCP FeW (fraction window increment) package- The alpha-factor of FeW scheme can be controlled via variable "increase_num_".- FeW scheme is primarily for low bandwidth-delay product networking environment, so slow start is de-activated for alpha<1.- Monitoring functions are added: event tracing in "tcp.cc"; throughput tracing in "tcp-sink.cc" and "tcp-sink.h" which is included in the separate simulation package.tcp/tcp.cc - FeW support and event tracing4. Usage- Uncompress the package in the NS-2.27 directory and replace the source code. Then, 'make' in NS-2.27 directory.- Alpha factor (TCP FeW) can be controlled via TCP variable "increase_num_" (existing in NS-2.27)  1: TCP default    less than 1: TCP FeW- Beta factor (DSR) can be controlled via DSR variable "beta_" (new in this package)  0: Static routing 1: DSR original   2: default in this package   3 or greater: supported- Manual static routing can be tested using DSR++ and a new command "add-route"    1) Format: "$node_( [a node id] ) add-route [path: a list of node id's]"    2) Example: $node_(0) add-route 0 1 2 3 4 5   (DSR agent at node id 0 has a pre-configured path from node id 0 to node id 5 via node 1, 2, 3, 4)- For simple test, a simulation package is separately available at http://biron.usc.edu/~nahm/research.htm5. History- June 12, 2005: First uploaded for ns-2.27- October 2005: Upgraded for ns-2.29- July 4, 2006: 1) "Event UID not valid" bug fix based on Federico's report ( http://www.dei.unipd.it/wdyn/?IDsezione=2435 )                2) "add-route" command for manual path configuration