Which layer of the TCP or IP model determines the best path through the network?
The OSI model describes an idealized network communications with a family of protocols. TCP/IP does not correspond to this model directly. TCP/IP either combines several OSI layers into a single layer, or does not use certain layers at all. The following table shows the layers of the Solaris implementation of TCP/IP. The table lists the layers from the topmost layer (application) to the lowest (physical network). Show
OSI Ref. Layer No. OSI Layer Equivalent TCP/IP Layer TCP/IP Protocol Examples 5,6,7 Application, session, presentation Application NFS, NIS+, DNS, telnet, ftp, rlogin, rsh, rcp, RIP, RDISC, SNMP, and others 4 Transport Transport TCP, UDP 3 Network Internet IP, ARP, ICMP 2 Data link Data link PPP, IEEE 802.2 1 Physical Physical network Ethernet (IEEE 802.3) Token Ring, RS-232, others The table shows the TCP/IP protocol layers. Also shown are the OSI Model equivalents with examples of the protocols that are available at each level of the TCP/IP protocol stack. Each host that is involved in a communication transaction runs a unique implementation of the protocol stack. Physical Network LayerThe physical network layer specifies the characteristics of the hardware to be used for the network. For example, physical network layer specifies the physical characteristics of the communications media. The physical layer of TCP/IP describes hardware standards such as IEEE 802.3, the specification for Ethernet network media, and RS-232, the specification for standard pin connectors. Data-Link LayerThe data-link layer identifies the network protocol type of the packet, in this instance TCP/IP. The data-link layer also provides error control and “framing.” Examples of data-link layer protocols are Ethernet IEEE 802.2 framing and Point-to-Point Protocol (PPP) framing. Internet LayerThis layer, also known as the network layer, accepts and delivers packets for the network. This layer includes the powerful Internet Protocol (IP), the Address Resolution Protocol (ARP), and the Internet Control Message Protocol (ICMP). The IP protocol and its associated routing protocols are possibly the most significant of the entire TCP/IP suite. IP is responsible for the following:
Previous releases of the Solaris operating environment implement version 4 of the Internet Protocol, which is abbreviated as IPv4. However, because of the rapid growth of the Internet, a new Internet Protocol was created. The new protocol increases address space. This new version, known as version 6, is abbreviated as IPv6. The Solaris operating environment supports both versions, which are described in this book. To avoid confusion when addressing the Internet Protocol, one of the following conventions is used:
ARP ProtocolThe Address Resolution Protocol (ARP) conceptually exists between the data-link and Internet layers. ARP assists IP in directing datagrams to the appropriate receiving host by mapping Ethernet addresses (48 bits long) to known IP addresses (32 bits long). ICMP ProtocolInternet Control Message Protocol (ICMP) detects and reports network error conditions. ICMP reports on the following:
The ping Command contains more information on the operating system commands that use ICMP for error detection. Transport LayerThe TCP/IP transport layer protocols ensure that packets arrive in sequence and without error, by swapping acknowledgments of data reception, and retransmitting lost packets. This type of communication is known as “end-to-end.” Transport layer protocols at this level are Transmission Control Protocol (TCP) and User Datagram Protocol (UDP). TCP ProtocolTCP enables applications to communicate with each other as though connected by a physical circuit. TCP sends data in a form that appears to be transmitted in a character-by-character fashion, rather than as discrete packets. This transmission consists of a starting point, which opens the connection, the entire transmission in byte order, and an ending point, which closes the connection. TCP attaches a header onto the transmitted data. This header contains a large number of parameters that help processes on the sending machine connect to peer processes on the receiving machine. TCP confirms that a packet has reached its destination by establishing an end-to-end connection between sending and receiving hosts. TCP is therefore considered a “reliable, connection-oriented” protocol. UDP ProtocolUDP, the other transport layer protocol, provides datagram delivery service. UDP does not verify connections between receiving and sending hosts. Because UDP eliminates the processes of establishing and verifying connections, applications that send small amounts of data use UDP rather than TCP. Application LayerThe application layer defines standard Internet services and network applications that anyone can use. These services work with the transport layer to send and receive data. Many application layer protocols exist. The following list shows examples of application layer protocols:
Standard TCP/IP Services
UNIX “r” CommandsThe UNIX “r” commands enable users to issue commands on their local machines that run on the remote host. These commands include the following: Instructions for using these commands are in rcp(1), rlogin(1), and rsh(1) man pages. Name ServicesThe Solaris operating environment provides the following naming services:
Directory ServiceThe Solaris operating environment supports LDAP (Lightweight Directory Access Protocol) in conjunction with the iPlanet Directory Server 5.x, as well as other LDAP Directory Servers. The distinction between a Naming Service and a Directory Service is in the differing extent of functionality. A directory service provides the same functionality of a naming service, but provides additional functionalities as well. See System Administration Guide: Naming and Directory Services (DNS, NIS, and LDAP). File ServicesThe NFS application layer protocol provides file services for the Solaris operating environment. You can find complete information about the NFS service in System Administration Guide: Resource Management and Network Services. Network AdministrationThe Simple Network Management Protocol (SNMP) enables you to view the layout of your network and view the status of key machines. SNMP also enables you to obtain complex network statistics from software that is based on a graphical user interface. Many companies offer network management packages that implement SNMP. SunNet ManagerTM software is an example. Routing ProtocolsThe Routing Information Protocol (RIP) and the Router Discovery Protocol (RDISC) are two routing protocols for TCP/IP networks. They are described in Routing Protocols. What layer determines the best path through the network?The Layer 3, or Network Layer, is responsible for finding the right path for the data packet to reach its destination based on Logical Addresses (means addresses not really present on the network node).
What layer of the TCP IP reference model is responsible for selecting the best path through the network from source to destination?The network layer is responsible for routing the data via the best physical path based on a range of factors including network characteristics, best available path, traffic controls, congestion of data packets, and priority of service, among others.
Which is the most important layer of the TCP IP and why?At the top of the TCP/IP protocol architecture is the Application Layer. This layer includes all processes that use the Transport Layer protocols to deliver data. There are many applications protocols.
Which layer of the TCP IP model provides a route to?c. In TCP/IP model, there are mainly four layers: application, network access, internet, and transport. Out of these four layers, the Internet layers route the message between the sender and receiver in an internetwork, that is, the internet layer performs the routing of the messages and it is the correct answer.
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