The Big Picture

Although the protocol suite is called "TCP/IP," there are more members of this family than just TCP and IP. Figure 2.1 shows an overview of these protocols.

Figure 2.1. Overview of TCP/IP protocols.

We show both IPv4 and IPv6 in this figure. Moving from right to left, the rightmost five

applications are using IPv6; we will talk about the AF_INET6 constant in Chapter 3, along with the sockaddr_in6 structure. The next six applications use IPv4.

The leftmost application, tcpdump, communicates directly with the datalink using either the BSD packet filter (BPF) or the datalink provider interface (DLPI). We mark the dashed line beneath the nine applications on the right as the API, which is normally sockets or XTI. The interface to either BPF or DLPI does not use sockets or XTI.

There is an exception to this, which we will describe in more detail in Chapter 28: Linux provides access to the datalink using a special type of socket called SOCK_PACKET.

We also note in Figure 2.1 that the traceroute program uses two sockets: one for IP and another for ICMP. In Chapter 28, we will develop IPv4 and IPv6 versions of both ping and traceroute.

We now describe each of the protocol boxes in this figure.

[ Team LiB ]

• Table of Contents

UNIX® Network Programming Volume 1, Third Edition: The Sockets Networking API

By W. Richard Stevens, Bill Fenner, Andrew M. Rudoff

Publisher: Addison Wesley Pub Date: November 21, 2003

ISBN: 0-13-141155-1 Pages: 1024

"Everyone will want this book because it provides a great mix of practical experience, historical perspective, and a depth of understanding that only comes from being intimately involved in the field. I've already enjoyed and learned from reading this book, and surely you will too."

-Sam Leffler

The classic guide to UNIX networking APIs... now completely updated!

To build today's highly distributed, networked applications and services, you need deep

mastery of sockets and other key networking APIs. One book delivers comprehensive, start-to-finish guidance for building robust, high-performance networked systems in any environment:

UNIX Network Programming, Volume 1, Third Edition.

Building on the legendary work of W. Richard Stevens, this edition has been fully updated by two leading network programming experts to address today's most crucial standards, implementations, and techniques. New topics include:

POSIX Single UNIX Specification Version 3

IPv6 APIs (including updated guidance on IPv6/IPv4 interoperability) The new SCTP transport protocol

IPsec-based Key Management Sockets

FreeBSD 4.8/5.1, Red Hat Linux 9.x, Solaris 9, AIX 5.x, HP-UX, and Mac OS X implementations

New network program debugging techniques

Source Specific Multicast API, the key enabler for widespread IP multicast deployment IPv4 Internet Protocol version 4. IPv4, which we often denote as just IP, has been the

workhorse protocol of the IP suite since the early 1980s. It uses 32-bit addresses (Section A.4). IPv4 provides packet delivery service for TCP, UDP, SCTP, ICMP, and IGMP.

IPv6 Internet Protocol version 6. IPv6 was designed in the mid-1990s as a replacement for IPv4. The major change is a larger address comprising 128 bits (Section A.5), to deal with the explosive growth of the Internet in the 1990s. IPv6 provides packet delivery service for TCP, UDP, SCTP, and ICMPv6.

We often use the word "IP" as an adjective, as in IP layer and IP address, when the distinction between IPv4 and IPv6 is not needed.

TCP Transmission Control Protocol. TCP is a connection-oriented protocol that provides a reliable, full-duplex byte stream to its users. TCP sockets are an example of stream sockets. TCP takes care of details such as acknowledgments, timeouts,

retransmissions, and the like. Most Internet application programs use TCP. Notice that TCP can use either IPv4 or IPv6.

UDP User Datagram Protocol. UDP is a connectionless protocol, and UDP sockets are an example of datagram sockets. There is no guarantee that UDP datagrams ever reach their intended destination. As with TCP, UDP can use either IPv4 or IPv6.

SCTP Stream Control Transmission Protocol. SCTP is a connection-oriented protocol that provides a reliable full-duplex association. The word "association" is used when referring to a connection in SCTP because SCTP is multihomed, involving a set of IP addresses and a single port for each side of an association. SCTP provides a

message service, which maintains record boundaries. As with TCP and UDP, SCTP can use either IPv4 or IPv6, but it can also use both IPv4 and IPv6 simultaneously on the same association.

ICMP Internet C ontrol Message Protocol. ICMP handles error and control information between routers and hosts. These messages are normally generated by and

processed by the TCP/IP networking software itself, not user processes, although we show the ping and traceroute programs, which use ICMP. We sometimes refer to this protocol as ICMPv4 to distinguish it from ICMPv6.

IGMP Internet G roup Management Protocol. IGMP is used with multicasting (Chapter 21), which is optional with IPv4.

ARP Address Resolution Protocol. ARP maps an IPv4 address into a hardware address (such as an Ethernet address). ARP is normally used on broadcast networks such as Ethernet, token ring, and FDDI, and is not needed on point-to-point networks.

RARP Reverse Address Resolution Protocol. RARP maps a hardware address into an IPv4 address. It is sometimes used when a diskless node is booting.

ICMPv6 Internet Control Message Protocol version 6. ICMPv6 combines the functionality of ICMPv4, IGMP, and ARP.

BPF BSD packet filter. This interface provides access to the datalink layer. It is normally found on Berkeley-derived kernels.

DLPI Datalink provider interface. This interface also provides access to the datalink layer.

It is normally provided with SVR4.

Each Internet protocol is defined by one or more documents called a Request for Comments (RFC ), which are their formal specifications. The solution to Exercise 2.1 shows how to obtain RFCs.

We use the terms "IPv4/IPv6 host" and "dual-stack host" to denote hosts that support both IPv4 and IPv6.

[ Team LiB ]

• Table of Contents

UNIX® Network Programming Volume 1, Third Edition: The Sockets Networking API

By W. Richard Stevens, Bill Fenner, Andrew M. Rudoff

Publisher: Addison Wesley Pub Date: November 21, 2003

ISBN: 0-13-141155-1 Pages: 1024

"Everyone will want this book because it provides a great mix of practical experience, historical perspective, and a depth of understanding that only comes from being intimately involved in the field. I've already enjoyed and learned from reading this book, and surely you will too."

-Sam Leffler

The classic guide to UNIX networking APIs... now completely updated!

To build today's highly distributed, networked applications and services, you need deep

mastery of sockets and other key networking APIs. One book delivers comprehensive, start-to-finish guidance for building robust, high-performance networked systems in any environment:

UNIX Network Programming, Volume 1, Third Edition.

Building on the legendary work of W. Richard Stevens, this edition has been fully updated by two leading network programming experts to address today's most crucial standards, implementations, and techniques. New topics include:

POSIX Single UNIX Specification Version 3

IPv6 APIs (including updated guidance on IPv6/IPv4 interoperability) The new SCTP transport protocol

IPsec-based Key Management Sockets

FreeBSD 4.8/5.1, Red Hat Linux 9.x, Solaris 9, AIX 5.x, HP-UX, and Mac OS X implementations

New network program debugging techniques

Source Specific Multicast API, the key enabler for widespread IP multicast deployment Additional details on the TCP/IP protocols themselves are in TCPv1. The 4.4BSD

implementation of TCP/IP is described in TCPv2.

[ Team LiB ]

[ Team LiB ]

• Table of Contents

UNIX® Network Programming Volume 1, Third Edition: The Sockets Networking API

By W. Richard Stevens, Bill Fenner, Andrew M. Rudoff

Publisher: Addison Wesley Pub Date: November 21, 2003

ISBN: 0-13-141155-1 Pages: 1024

"Everyone will want this book because it provides a great mix of practical experience, historical perspective, and a depth of understanding that only comes from being intimately involved in the field. I've already enjoyed and learned from reading this book, and surely you will too."

-Sam Leffler

The classic guide to UNIX networking APIs... now completely updated!

To build today's highly distributed, networked applications and services, you need deep

mastery of sockets and other key networking APIs. One book delivers comprehensive, start-to-finish guidance for building robust, high-performance networked systems in any environment:

UNIX Network Programming, Volume 1, Third Edition.

Building on the legendary work of W. Richard Stevens, this edition has been fully updated by two leading network programming experts to address today's most crucial standards, implementations, and techniques. New topics include:

POSIX Single UNIX Specification Version 3

IPv6 APIs (including updated guidance on IPv6/IPv4 interoperability) The new SCTP transport protocol

IPsec-based Key Management Sockets

FreeBSD 4.8/5.1, Red Hat Linux 9.x, Solaris 9, AIX 5.x, HP-UX, and Mac OS X implementations

New network program debugging techniques

Source Specific Multicast API, the key enabler for widespread IP multicast deployment [ Team LiB ]