The Transport Layer of the Hybrid TCP OSI Model - Essay Example

Message Ordering and Reliability The Transport Layer of the Hybrid TCP/IP OSI Model. The of the College This paper is prepared as a fulfillment to the requirements for …........ Abstract The research paper, presents the Design and Implementation of the Hybrid TCP/IP OSI Model. The TCP/IP OSI protocol is a hybrid model under OSI which is a 4-layer transport protocol (Kozierok, 2005). It has two facet approach. First, it acts as the improved end-to-end transport protocol which integrates and implements TCP protocol improvements (Kozierok, 2005). Second, in the shared IP-layer network connections, it provides quality of service. Compared to other transport layers TCP/IP OSI is easily deployed. The unique features of the TCP/IP OSI model are its adaptive nature and its automatic gateway discovery. The Transport Layer of the Hybrid TCP/IP OSI Model. Transport Functions: Application Support and Network Control Transport layers main function is to establish a logical end-to-end communication path between the sender and the receiver application (Fall & Stevens, 2011). It shields the applications from the “actual network that may consist of heterogeneous pieces with different technologies, topology, bandwidth, routing behaviors and reliability levels” (Kozierok, 2005). Each transport packet consists of identifiers used for sending and receiving data packets. The identifiers include the port numbers. Sometimes the network corrupt data packets through delays, packets drop, or routing packets in different network paths, which causes packets to arrive out-of-order at the receiver (Fall & Stevens, 2011). For reliability in communication, transport protocol such as TCP corrects these packet errors when used. Transport layer helps in recovering packet losses “through retransmission of the lost packets, re-sequence packets that are misordered, and detect duplicated or erroneous packets”(Meinel & Sack, 2013, p.50). This is accomplished through a reverse communication channel. Differences of Hybrid TCP/IP OSI Model with Other Layer-4 Approaches Hybrid TCP/IP OSI Models feedback control loop runs between two gateways and does not go through the normal sequence of runnning end-to-end. This helps break down an end-to-end network control loop into smaller numerous control loops (Kozierok, 2005). Hybrid TCP/IP OSI Model feedback control loop uses segment-by-segment network control. It also uses integrated congestion control where it implements bandwidth allocation through “schedule packet transmissions” (Meinel & Sack, 2013, p.36). There are many advantages of the Hybrid TCP/IP OSI Model compared to the other layer-4 protocol like TCP. Protocol and Architecture Encapsulation of TCP Hybrid TCP/IP OSI Model has bimodal operation. This includes the native and the non-native. In native mode, Hybrid TCP/IP OSI Model usually replaces TCP on the host ends with a complete set of end-to-end transport protocol. Whereas in non-native mode, applications on the host ends do not recognize the Hybrid TCP/IP OSI Model but use TCP as their transport (Kozierok, 2005). The Hybrid TCP/IP OSI gateways capture and encapsulate TCP packets into Hybrid TCP/IP OSI packets. Discovery of Hybrid TCP/IP OSI Gateways Adjacent Hybrid TCP/IP OSI gateways easily detect each other and initiates the closing of the control loop of a pipe between them (Fall & Stevens, 2011). The main considerations when designing the Hybrid TCP/IP OSImodel is to enable incremental deployment of Hybrid TCP/IP OSI gateways (Kozierok, 2005). The gateway discovers its peer on its IP route automatically. Hybrid TCP/IP OSI’s Feedback Scheme In the native mode, Hybrid TCP/IP OSI does not require the correct receipt of all packets (Kozierok, 2005). Hybrid TCP/IP OSI is mainly used in congestion control only. The bi-directional nature of the pipe allows the Hybrid TCP/IP OSI data packets to be transmitted in both directions (Fall & Stevens, 2011). Each Hybrid TCP/IP OSI data packet has a pipe-level sequence number, found in the Packet Number field. After arriving at the receiving Hybrid TCP/IP OSI gateway, Hybrid TCP/IP OSI returns an acknowledgment packet as purely as ACK packet, or a data packet travelling in the reverse direction of the pipe, the piggybacked ACK (Kozierok, 2005). Hybrid TCP/IP OSI Transmission Scheduling The available bandwidth of the pipe is distributed so as to achieve achieve some quality of service differentiation (Fall & Stevens, 2011). For a large number of connections passing through high-bandwidth networks, it is easy to predict the bandwidth hence guaranteeing the quality of service. Implementation of Hybrid TCP/IP OSI Model Hybrid TCP/IP OSI model process has three threads, alarm module, queueing module, and Network input and output module (Kozierok, 2005). The alarm module generates timeout events, the event queue module services the event linning while the Network input and output module is for waiting for any incoming packets (Fall & Stevens, 2011). The network input and output does two main functions; (i) it extracts network packets and calls for initiates processing (ii) It feeds packets back into the network whenever a request is made. The implementation of the protocol is done in Linux. Capturing Packets into the User-Space The model uses the user-space tool and Iptables to establish filtering rules that enable the kernel to capture and queue packets. There are two cases in use; (i) transit TCP, or Hybrid TCP/IP OSI packets using current machine as a gateway (ii) capture Hybrid TCP/IP OSI packets that are directed to this machine. The filtering rules are usually set on “the FORWARD chain in the case (i) above and are set on the INPUT chain for case (ii)” above (Meinel & Sack, 2013, p.29). Raw IP Hybrid TCP/IP OSI uses the RAW IP facility to transmit a packet into a network. The packets are accessible by opening “a socket of the SOCK RAW type” (Meinel & Sack, 2013, p.30). Packet comes with its own IP header. Mapping Tables and Algorithms A map comes in the form of a hash table using the host IP address as its search key. There are three unique fields on each entry of the mapping table. These include; (i) a state denoting the availability of the next-hop gateway, (ii) the next-hop gateway’s IP address, and (iii) a timeout counter. “Possible states are AVAILABLE, UNAVAILABLE or UNKNOWN” (Meinel & Sack, 2013, p.35). Scheduler In the implementation of Hybrid TCP/IP OSI model, the scheduler consists of its own flow and pipe control blocks. It contain scheduling data linked to the control blocks in the control blocks module (Fall & Stevens, 2011). Congestion Control Hybrid TCP/IP OSI emulates the TCPs window control algorithm in bid to carry out the congestion control (Meinel & Sack, 2013). A phase of congestion avoidance the pipe’s congestion window size is increased by a unit when on positive acknowledgment. When congestion is detected, the pipe is decreased by half. Conclusion In conclusion there is need to emphasize that the Hybrid TCP/IP OSI model protocol is a unique platform for providing differentiated quality of service easily incorporated in todays network topologies. For example, a start point can be the two Hybrid TCP/IP OSI model gateways placed at the entry points of two network sites of the intranet. Such a connection can control bandwidth allocations to different points. Hybrid TCP/IP OSI model is ease to deploy due to its capability to automatically discover Hybrid TCP/IP OSI gateways. References Fall, K. R., & Stevens, W. R. (2011). TCP/IP illustrated, volume 1: The protocols. Addison-Wesley. Kozierok, C. M. (2005). The TCP/IP guide: a comprehensive, illustrated Internet protocols reference. No Starch Press. Meinel, C., & Sack, H. (2013, January). The Foundation of the Internet: TCP/IP Reference Model. In Internetworking (pp. 29-61). Springer Berlin Heidelberg. Read More