NS2 Classifiers

Classifiers: Multi-Target Packet Forwarder by Teerawat Issariyakul http://www.ns2ultimate.com April 2010 http://www.ns2ultimate.com 1

Outline  Introduction  Packet classification and forwarding mechanism  Classifier configuration  Summary http://www.ns2ultimate.com 2

Introduction http://www.ns2ultimate.com 3

Introduction  Multi-target packet forwarder  When you need to forward packet to various places.  Two main functionalities 1. Routers 2. Transport layer bridges FTP 2 targets 2 targets HTTP http://www.ns2ultimate.com 4

Classifiers: Overview  Main idea: target1 classifier target2 target3  Responsibility ◦ Receive and classify packets (e.g., based on color) ◦ Send packets of each classification to related targets  Example Green  target1 Pink  target2 Blue  target3 http://www.ns2ultimate.com 5

Classifiers: Target attachment  A variable slot_ ◦ A variable of class Classifier target1 slot_ ◦ An array of pointers ◦ Each pointer points to target2 a certain target …  You job? target3 classifier ◦ Tell the classifier that Green packets must be forwarded to NsObject in slot_[0] Pink packets must be forwarded to NsObject in slot_[1] Blue packets must be forwarded to NsObject in slot_[2] http://www.ns2ultimate.com 6

Meaning of the colors  An Example: classifier FTP slot_ Green packets must be forwarded to slot_[21] 21 Pink packets must be forwarded to slot_[25] 25 SMTP Blue packets must be forwarded to slot_[80] 80 … HTTP ◦ Green: FTP packets  FTP Server in slot_[21] ◦ Pink: Mail packets  SMTP Server in slot_[25] ◦ Blue: Web packets  HTTP server in slot_[80] Note: It’s ok to leave slot_[0], slot_[1],…, slot_[20] empty. http://www.ns2ultimate.com 7

Packet classification and forwarding mechanism http://www.ns2ultimate.com 8

Two key questions?  Conceptually, classifiers work as in this picture classifier FTP slot_ 21 25 SMTP 80 … HTTP  The key questions are 1. How does a classifier know the color? 2. What does it do when receiving a packets? http://www.ns2ultimate.com 9

Port Classifier  We shall proceed with an example: PortClassifier ◦ C++ class PortClassifier classifier  Base class = Classifier FTP ◦ OTcl class Classifier/Port slot_ 21 25 SMTP 80 ◦ File location: … HTTP ns-2.35/classifier/classifier-port.cc,h http://www.ns2ultimate.com 10

C++ Declaration class Classifier : public NsObject { public: virtual void recv(Packet* p, Handler* h); virtual NsObject* find(Packet*); virtual int classify(Packet *); virtual void clear(int slot); virtual void do_install(char* dst, NsObject *target); virtual void install(int slot, NsObject*); protected: NsObject** slot_; }; Derive class PortClassifier : public Classifier { protected: int classify(Packet *p); }; http://www.ns2ultimate.com 11

Q1: Color?  Function classify(p)  What it does? ◦ Input = A pointer to an input packet p ◦ Return the slot number to forward the packet  Example: FTP Input classify(p) slot_ will return 21 A FTP packet (green) 21 25 SMTP A SMTP packet (pink) 25 80 … A HTTP packet (blue) 80 HTTP  After getting the slot number, we know where to send the packet. http://www.ns2ultimate.com 12

Function Classify: Internal Mechanism FTP int PortClassifier::classify(Packet *p) slot_ { 21 hdr_ip* iph = hdr_ip::access(p); return iph->dport(); 25 SMTP } 80 … HTTP  Look at IP packet header (*iph)  Return the destination port stored in the IP packet header (iph->dport();) Port Classifier: Slot Number = Attached TCP/UDP port - Given: An application is attached to TCP/UDP port XXX - What you have do: Associate the application to slot XXX of the port classifier http://www.ns2ultimate.com 13

Q2: When Receiving a packet  Review: NS2 packet forwarding mechanism  Suppose UOBJ wants to send a packet *p to Dobj *p UOBJ DOBJ  UOBJ will execute Dobj.recv(p,h) where h is a handler.  For simplicity, let ignore h for the moment. http://www.ns2ultimate.com 14

Q2: When Receiving a packet  To send a packet *p to a classifier, we have to call the function Classifier::recv(p,h) void Classifier::recv(Packet* p, Handler *h) { (1) NsObject* node = find(p); node->recv(p,h); } NsObject* Classifier::find(Packet* p) { (2) NsObject* node = NULL; int cl = classify(p); node = slot_[cl]; return (node); } int PortClassifier::classify(Packet *p) { (3) hdr_ip* iph = hdr_ip::access(p); return iph->dport(); } http://www.ns2ultimate.com 15

Q2: When Receiving a packet  Summary: ◦ Here are the key steps Step Function Class 1 recv(p,h) Classifier 2 find(p) Classifier 3 classify(p) PortClassifier ◦ Port Classifiers: Port Number= Slot Number http://www.ns2ultimate.com 16

Classifier configuration http://www.ns2ultimate.com 17

What’s Else?  Recap classifier FTP slot_ 21 25 SMTP 80 … HTTP  If we have a classifier like in the above figure, we know how the classifier classifies and forwards the packet  But how do we set up (i.e., configure) a classifier like in the above figure? http://www.ns2ultimate.com 18

Objective  Let’s keep it simple.  Our job is to put a pointer to an NSObject ftp in the slot number 21 slot_ p 21 ftp … clsfr  In NS2 terminology, this can be done by “Install the pointer p in slot_[21]” http://www.ns2ultimate.com 19

C++ Function install(slot,p)  Put (i.e., install) the pointer p in slot_[slot] void Classifier::install(int slot, NsObject* p) { slot_[slot] = p; }  So to set up the classifier clsfr as in our example, invoke clsfr.install(21,pt); slot_ pt 21 ftp … clsfr http://www.ns2ultimate.com 20

OTcl Instproc install(slot,p)  Similarly, in OTcl, we can execute $clsfr install 21 $ftp int Classifier::command(int argc, const char*const* argv) { if (strcmp(argv[1], "install") == 0) { int slot = atoi(argv[2]); NsObject* node = (NsObject*)TclObject::lookup(argv[3]); install(slot, node); return (TCL_OK); which invokes C++ function } install(slot,node); } http://www.ns2ultimate.com 21

Summary http://www.ns2ultimate.com 22

Summary  Classifier is a multi-target packet forwarder target1 classifier target2 target3  Example Green  target1 Pink  target2 Blue  target3  Usage 1. Routers 2. Transport layer agent bridges http://www.ns2ultimate.com 23

Summary  Internal Mechanism ◦ Here are the key steps Step Function Class 1 recv(p,h) Classifier 2 find(p) Classifier 3 classify(p) PortClassifier ◦ Port Classifiers: Port Number= Slot Number http://www.ns2ultimate.com 24

Summary  To setup a classifier as follows, slot_ 21 ftp … clsfr ◦ C++ statement: clsfr.install(21,&ftp); ◦ OTcl statement: $clsfr install 21 $ftp http://www.ns2ultimate.com 25

For more information about NS 2 Please see chapter 6 in this book from Springer T. Issaraiyakul and E. Hossain, “Introduction to Network Simulator NS2”, Springer 2009 http://www.ns2ultimate.com 26

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NS2 Classifiers

by Teerawat Issariyakul on Apr 11, 2010

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