AppleTalk Filing Protocol (AFP)

AppleTalk Filing Protocol (AFP)

Before there was ever a Windows file sharing system in place, Apple had the AppleTalk Filing Protocol (AFP) for its AppleShare servers. AFP is the Presentation layer protocol that is used to
access AppleShare and Mac OS File Sharing files. It is the only protocol that accesses Apple- Share servers natively. Any system wanting to access an AppleShare server must be running
some version of AFP (or at least AFP over another transport protocol, like TCP/IP).

Note: 
See Chapter 2 for more on AFP.

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Real World scenario  

A Better Windows Server?

I was working at a local networking service establishment when I was presented with a problem.
A customer wanted a server capable of doing some file sharing. The server had to be
robust and capable of interacting with all of the company’s Windows clients. But they were at
the end of a budget cycle and the new budget wouldn’t be approved for at least a month and
they needed the server for one of their workgroups immediately. They had the hardware but
couldn’t afford the Windows 2000 Server licenses they needed and Windows 98 just wasn’t up
to par. The solution we came up with was to install Red Hat Linux on one of their machines and
then install Samba. It allowed them to have SMB-compatible file sharing and use their existing
Windows clients while not having to purchase a Windows server. To my knowledge, that server
is still running today.

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Server Message Block (SMB) + Samba

Server Message Block (SMB)

Server Message Block (SMB) is a Presentation layer protocol developed through the efforts of corporations the likes of Xerox, 3Com, and IBM and further developed by (and currently attributed
to) Microsoft, providing a networking command message format used when sending networking commands to servers. These commands allow a client to do things like browse for resources; open connections, access files, printers, and communications ports; and list directories. SMB can be run over any number of lower-layer protocols, such as NetBEUI, NetBIOS over TCP/IP, NetBIOS over IPX/SPX, and others.

Samba
SMB is not limited to Windows machines (although they are where SMB commands are usually found). SMB is being developed for the world community as the Common Internet File System
(CIFS), a term now synonymous with SMB. Through Samba, one popular application of SMB/CIFS for the non-Microsoft market (visit samba.org), UNIX and Linux servers can use SMB commands
to communicate with Windows clients. Samba is a free open-source protocol suite that provides file and print services to SMB/CIFS clients. Samba allows for interoperability between Linux/UNIX servers and Windows-based clients by running on a platform other than Microsoft Windows, such as UNIXLinux, IBM OpenVMS, and so on. Samba uses TCP/IP installed on the host server, allowing that host to interact with a Microsoft Windows client or server as if it were a Windows file and print server.
The two primary programs, or daemons, of Samba, called smbd and nmbd, are responsible for two each of the four common CIFS services:

• File and print services
• Authentication and authorization
• Name resolution
• Service announcement (browsing)

Arguably the foundation of CIFS, file and print services are performed by smbd, as are authentication and authorization. The nmbd daemon provides NetBIOS name services to clients,

including name resolution and service announcement, often referred to as browsing services.

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User Datagram Protocol (UDP)

User Datagram Protocol (UDP)

User Datagram Protocol (UDP) is a Transport layer connectionless protocol that does not provide the reliability services available with TCP but instead provides best effort transmission services to
application protocols. UDP gives applications a direct interface with IP and the ability to address a specific application protocol running on a host via a port number without setting up an end-toend
virtual circuit or connection. UDP, like TCP, uses IP to deliver its packets.
Figure 3.4 shows how some of these components fit together.

FIGURE 3 . 4 The components in a TCP/IP block diagram

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Other Upper-Layer Protocols

Other Upper-Layer Protocols

Various other upper-layer protocols play an important role in the success of the TCP/IP protocol suite as a flexible, well-rounded, self-contained group of protocols:

• UDP
• SMB
• AFP
• ICS

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Line Printer Remote (LPR)

Line Printer Remote (LPR)

When using pure TCP/IP printing (as with UNIX workstations or when used for cross-platform printing), the LPD/LPR pairing is used most often. The Line Printer Daemon (LPD) is installed
on the print device and manages the printer as well as the print jobs. The Line Printer Remote (LPR) software is the printing client that sends the print jobs to the LPD via TCP/IP.

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Internet Group Management Protocol (IGMP)

Internet Group Management Protocol (IGMP)

The Internet Group Management Protocol (IGMP) is a TCP/IP protocol that is used to manage IP multicast sessions. It uses special IGMP messages to learn the layout of the multicast groups
and which hosts belong to which groups. Additionally, the individual hosts in an IP network use IGMP messages to join and leave a multicast group. IGMP messages help keep track of group
membership and active multicast streams. IGMP is in its second version, as specified in RFC 2236, with a third version (RFC 3376), currently proposed.

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Network Time Protocol (NTP)

Network Time Protocol (NTP)

Network Time Protocol (NTP), originally developed by Professor David Mills at the University of Delaware, is used to synchronize (or set) computer clocks to some standard time source, which is
usually a nuclear clock. This protocol (along with synchronization utilities) keeps all computers on a network set to the same time. Time synchronization is important because many transactions
are time and date stamped (in a database, for example). If the time on a server is out of synchronization with the time on two different computers, even by just a few seconds, the server will get confused. For example, one computer can seemingly enter a transaction, but the server will indicate that it occurred before it actually did. Because this time problem will crash the database server, it is important that these servers (and workstations) use NTP.

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Hypertext Transfer Protocol Secure (HTTPS)

Hypertext Transfer Protocol Secure (HTTPS)

Hypertext Transfer Protocol Secure (HTTPS), also referred to as Secure Hypertext Transfer Protocol (which you will see abbreviated as SHTTP or S-HTTP), is a secure version of HTTP that provides a variety of security mechanisms to the transactions between a web browser and the server. HTTPS allows browsers and servers to sign, authenticate, and encrypt an HTTP message.

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Hypertext Transfer Protocol (HTTP)

Hypertext Transfer Protocol (HTTP)

Hypertext Transfer Protocol (HTTP) is the command and control protocol used to manage communications between a web browser and a web server. When you access a web page on the
Internet or on a corporate intranet, you see a mixture of text, graphics, and links to other documents or other Internet resources. HTTP is the mechanism that opens the related document
when you select a link, no matter where that document is actually located.

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Secure Shell (SSH)

Secure Shell (SSH)

The Secure Shell (SSH) protocol is used to establish a secure Telnet session over a standard TCP/IP connection. It is used to run programs on remote systems, log in to other systems, and move
files from one system to another, all while maintaining a strong, encrypted connection. It replaces such utilities as rsh and rlogin as well as Telnet.

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Telnet

Telnet

Telnet is a terminal emulation protocol that provides a remote logon to another host over the network. It allows a user to connect to a remote host over a TCP/IP connection as if they were sitting
right at that host. Keystrokes typed into a Telnet program will be transmitted over a TCP/IP network to the host. The visual responses are sent back by the host to the Telnet client to be displayed.

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Network File System (NFS)

Network File System (NFS)

UNIX systems are unique in the way they access files and are actually fairly elegant. The Network File System (NFS) Application layer protocol was originally designed to allow shared file
systems on UNIX servers to appear as local file systems on UNIX clients.

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