System Administration Guide: IP Services

TCP/IP Protocol Architecture Model

The OSI model describes idealized network communications with a family of protocols. TCP/IP does not directly correspond to this model. 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 Oracle Solaris implementation of TCP/IP. The table lists the layers from the topmost layer (application) to the bottommost layer (physical network).

Table 1–2 TCP/IP Protocol Stack

OSI Ref. Layer No. 

OSI Layer Equivalent 

TCP/IP Layer 

TCP/IP Protocol Examples 


Application, session, presentation 


NFS, NIS, DNS, LDAP, telnet, ftp, rlogin, rsh, rcp, RIP, RDISC, SNMP, and others






IPv4, IPv6, ARP, ICMP 

Data link 

Data link

PPP, IEEE 802.2 


Physical network

Ethernet (IEEE 802.3), Token Ring, RS-232, FDDI, and others  

The table shows the TCP/IP protocol layers and the OSI model equivalents. Also shown are examples of the protocols that are available at each level of the TCP/IP protocol stack. Each system that is involved in a communication transaction runs a unique implementation of the protocol stack.

Physical Network Layer

The 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 Layer

The 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 Layer

The Internet layer, also known as the network layer or IP 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).

IP Protocol

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:

Oracle Solaris supports both IPv4 and IPv6 addressing formats, which are described in this book. To avoid confusion when addressing the Internet Protocol, one of the following conventions is used:

ARP Protocol

The Address Resolution Protocol (ARP) conceptually exists between the data-link and Internet layers. ARP assists IP in directing datagrams to the appropriate receiving system by mapping Ethernet addresses (48 bits long) to known IP addresses (32 bits long).

ICMP Protocol

The Internet Control Message Protocol (ICMP) detects and reports network error conditions. ICMP reports on the following:

Chapter 8, Administering a TCP/IP Network (Tasks) contains more information on Oracle Solaris commands that use ICMP for error detection.

Transport Layer

The TCP/IP transport layer ensures 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), User Datagram Protocol (UDP), and Stream Control Transmission Protocol (SCTP). TCP and SCTP provide reliable, end-to-end service. UDP provides unreliable datagram service.

TCP Protocol

TCP enables applications to communicate with each other as though they were 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 the following:

TCP attaches a header onto the transmitted data. This header contains many parameters that help processes on the sending system connect to peer processes on the receiving system.

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.

SCTP Protocol

SCTP is a reliable, connection-oriented transport layer protocol that provides the same services to applications that are available from TCP. Moreover, SCTP can support connections between systems that have more than one address, or multihomed. The SCTP connection between sending and receiving system is called an association. Data in the association is organized in chunks. Because SCTP supports multihoming, certain applications, particularly applications used by the telecommunications industry, need to run over SCTP, rather than TCP.

UDP Protocol

UDP 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.

Application Layer

The 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” Commands

The 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 the rcp(1), rlogin(1), and rsh(1) man pages.

Name Services

Oracle Solaris provides the following name services:

Directory Service

Oracle Solaris supports LDAP (Lightweight Directory Access Protocol) in conjunction with the Sun Open Net Environment (Sun ONE) Directory Server, as well as other LDAP directory servers. The distinction between a name 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 Services

The NFS application layer protocol provides file services for Oracle Solaris. You can find complete information about the NFS service in System Administration Guide: Network Services.

Network Administration

The Simple Network Management Protocol (SNMP) enables you to view the layout of your network and the status of key machines. SNMP also enables you to obtain complex network statistics from software that is based on a graphical user interface (GUI). Many companies offer network management packages that implement SNMP.

Routing Protocols

The Routing Information Protocol (RIP) and the Router Discovery Server Protocol (RDISC) are two available routing protocols for TCP/IP networks. For complete lists of available routing protocols for Oracle Solaris 10, refer to Table 5–1 and Table 5–2.