Understanding TCP/IP Model Internals and Interfaces

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1508 Understanding TCP/IP Model Internals and Interfaces Sending a Packet to IP The MAC process receives a packet from the network, it decapsulates the IP packet from the MAC packet and sends it to the ARP module. No ICIs are involved here. In the simple_mac process model this is performed in the function simple_mac_packet_from_ntwk_handle (no need to make any coding changes): FIN (simple_mac_packet_from_ntwk_handle (mac_pkptr)); /* Decapsulate the IP datagram from the packet. */ op_pk_nfd_get (mac_pkptr, "data", &ip_pkptr); /* Print a trace Message */ if (SMC_LTRACE_ACTIVE) { /* Get the source address from the packet */ op_pk_nfd_get (mac_pkptr, "source address", &source_address); sprintf (msg, "Source Address: %d", source_address); op_prg_odb_print_major ("Received a Packet from the” “Network", msg, OPC_NIL); } /* Send the packet to the higher layer. */ op_pk_send (ip_pkptr, SMC_OUT_STRM_INDEX_TO_ARP); /* Destroy the MAC packet. */ op_pk_destroy (mac_pkptr); FOUT; Save and Compile the Process Model 1. Save and compile the process model. 2. If you are having problems in compilation, you may a. Close the simple_mac process model. b. Open the simple_mac_ref process model. c. Save it as simple_mac. d. Recompile. CONFIDENTIAL – RESTRICTED ACCESS: This information may not be disclosed, copied, or transmitted in any format without the prior written consent of OPNET Technologies, Inc. © 2010 OPNET Technologies, Inc. 36
1508 Understanding TCP/IP Model Internals and Interfaces Test the Network Open the Test Project We will now use a simple network to verify that the MAC layer is working correctly. 1. Open the project 1508_lab_3. If you did not make the coding changes to the simple_mac process model, you may use the 1508_lab_3_Ref project. The project should open up in the scenario named simple_ping_network. Network Description The network consists of two nodes of type simple_mac_wkstn connected to each other. A ping demand has also been configured from wkstn_1 to wkstn_2. The MAC and the IP addresses on both the nodes are set to Auto Assigned. The simulation IP auto-addressing package works with custom wireline MAC layers also. Shown below are the attributes for the wkstn_1 and wkstn_2 nodes which effect IP addressing. These attributes can be accessed by right-clicking on the node and selecting Edit Attributes. CONFIDENTIAL – RESTRICTED ACCESS: This information may not be disclosed, copied, or transmitted in any format without the prior written consent of OPNET Technologies, Inc. © 2010 OPNET Technologies, Inc. 37
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Understanding TCP/IP Model Internals and Interfaces

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