UNDERSTANDING THE NETWORK ARCHITECTURE

1. UNIT 4: UNDERSTANDING THE
NETWORK ARCHITECTURE

2. OUTLINE
• Ethernet
• Performance considerations
• Segmentation
• Network operating systems or Ethernets
• Token ring
• Apple talk and arcnet

3. Network Architecture - Protocols
• Physical: Actual signal transmission
• Data-Link: Framing / Error Detection
• Network: Routing / Addressing
• Transport: Congestion / Flow Control
• Application: Specific to user needs

4. Layered Protocols – (HTTP)

5. Data Link Layer - Ethernet
• Invented in 1973 @ Xerox. (IEEE 802.3)
• Originally a LAN technology – extended to MAN / WAN.
• Same frame format, different wiring schemes, data rates across generations.
• Most common version (10BaseT) – 1990.

6. Ethernet Generations
• Original Ethernet:
• Coaxial cable (10Base5)
• Thicknet.
• Next Generation:
• Thin coax cable (10Base2)
• Thinnet.
• Modern Ethernet:
• Twisted pair ethernet
(10BaseT)
• Uses hub: physical star but
logical bus.

7. Ethernet Components
• NIC – Network Interface Card
• Integrated Tx/Rx – direct interface to medium.
• MAU – Media Attachment Unit
• Attaches network interface to the medium (integrated into NIC).
• AUI – Attachment Unit Interface
• Decouple physical layer -reuse MAC design with different media.
• MII – Media Independent Interface
• Like AUI for gigabit / faster ethernets.

8. Ethernet Addressing
• 48-bit address
• Address assigned when NIC card is manufactured.
• Packets can be sent to
• Single address – Unicast
• All stations on network – Broadcast (address = all 1s.)
• Subset of stations – Multicast
• Broadcast (address = all 1s.)
• All receivers accepts unicast / broadcats.
• Half addresses reserved for multicast (247)
• NIC can accepts zero or more multicasts.

9. Ethernet Frame
Sender adds:
• Senders address is source
• Recipients address in destination
• Type of data in frame type
• Error check data (CRC)
Receiver NIC:
• Gets transmitted frame.
• Examines address and either accepts or rejects.
• Passes frame to system software.

10. Media Access Control - MAC
• Shared medium – stations take turns at sharing the medium.
• Media access control ensures fairness.
CSMA / CD
• Carrier Sense: wait till medium is idle before sending frame.
• Multiple Access: multiple computers use the same shared media.
Each uses same access algorithm.
• Collision Detection: Listen to medium – detect if another station’s
signal interferes – back off and try again later.

11. CSMA / CD
• If collision occurs: wait a random time t1 - 0< t1<d.
• D depends on transmission speed – time for frame width or 512 bits.
• If second collision occurs, wait a random time t2 - 0< t2<2d.
• Double range for each succesive collision.
• Exponential backoff
• No acknowledgement like TCP.
• CSMA/CA used in wireless networks where not all stations receive message.
• Both sides send small message followed by data:
• X is about to send to Y
• Y is about to receive from X
• Data frame sent from X to Y.

12. Recent Developments
• 100Base-FX
• LED light source / MMF / 2 km max distance.
• Modal dispersion – limited bandwidth
• 100Base-SX (IEEE 802.3z)
• Short wavelength laser (850 nm)
• Max distance = 5 km.
• 100Base-LX
• Long wavelength laser (1310 nm)
• Max distance = 5 km.

13. Beyond Gigabit Ethernet
• 10 Gb/s Ethernet
• No CSMS/CD, same frame format.
• Applications
• Upgrade LANs / Backbone.
• MAN applications.

14. Segmentation
• Segmentation divides a computer network into smaller parts. The
purpose is to improve network performance and security.
• Other terms that often mean the same thing are network
segregation, network partitioning, and network isolation.

15. How does segmentation work?
• Segmentation works by controlling how traffic flows among the parts.
• You could choose to stop all traffic in one part from reaching another,
or you can limit the flow by traffic type, source, destination, and
many other options.
• How you decide to segment your network is called a segmentation
policy.

16. What is an example of segmentation?
• Imagine a large bank with several branch offices.
• The bank's security policy restricts branch employees from accessing
its financial reporting system.
• Network segmentation can enforce the security policy by preventing
all branch traffic from reaching the financial system.
• And by reducing overall network traffic, the financial system will work
better for the financial analysts who use it.

17. What enforces segmentation policy?
• Some traditional technologies for segmentation included:
• internal firewalls, and Access Control List (ACL) and Virtual Local Area
Network (VLAN) configurations on networking equipment. However, these
approaches are costly and difficult.
• Today, software-defined access technology simplifies segmentation by
grouping and tagging network traffic.
• It then uses traffic tags to enforce segmentation policy directly on the
network equipment, yet without the complexity of traditional approaches.

18. Firewall segmentation
• Firewalls are deployed inside a network or data center to create
internal zones to segment functional areas from each other in order
to limit attack surfaces, thereby preventing threats from spreading
beyond a zone.

19. Segmentation with SDN
• Software-defined networking (SDN) is relied on for greater network
automation and programmability through centralized controllers that
are abstracted from the physical hardware of the network.

20. Micro-segmentation

21. Micro-segmentation…
• Micro-segmentation creates secure zones across cloud and data
center environments to isolate application workloads from one
another and secure them individually.
• Micro-segmentation, firewall policies limit east-west traffic between
workloads based on a zero-trust security approach to reduce attack
surfaces, prevent the lateral movement of threats to contain
breaches, and strengthen regulatory compliance.
• Micro-segmentation is also referred to as application segmentation or
east-west segmentation in a multicloud data center.

22. Benefits of network segmentation
• Improve operational performance
• Segmentation reduces network congestion. For example, a hospital's medical devices can be
segmented from its visitor network so that medical devices are unaffected by web browsing.
• Limit cyberattack damage
• Segmentation improves cybersecurity by limiting how far an attack can spread. For example,
segmentation keeps a malware outbreak in one section from affecting systems in another.
• Protect vulnerable devices
• Segmentation can stop harmful traffic from reaching devices that are unable to protect
themselves from attack. For example, a hospital's connected infusion pumps may not be
designed with advanced security defences. Network segmentation can stop harmful Internet
traffic from ever reaching them.
• Reduce the scope of compliance
• Segmentation reduces the costs associated with regulatory compliance by limiting the
number of in-scope systems. For example, segmentation separates the systems that process
payments from those that don't. That way, the expensive compliance requirements and audit
processes apply only to the in-scope systems, not the entire network.

23. NOS Architectures
• Peer-to-peer
• Client/server

24. Peer to Peer and Client- Server NOS

25. Overview
• A network operating system (NOS) provides services to
clients over a network.
• Both the client/server and peer-to-peer networking
models use network operating systems
• NOSs must be able to handle typical network duties.
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26. Major Tools of NOS
1. Providing access to remote printers, managing which
users are using which printers when, managing how
print jobs are queued, and recognizing when devices
aren't available to the network
2. Enabling and managing access to files on remote
systems, and determining who can access what—and
who can't
3. Granting access to remote applications and resources,
such as the Internet, and making those resources seem
like local resources to the user (the network is ideally
transparent to the user)
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27. Major Tools of NOS
3. Providing routing services, including support for major
networking protocols, so that the operating system
knows what data to send where
4. Monitoring the system and security, so as to provide
proper security against viruses, hackers, and data
corruption.
5. Providing basic network administration utilities (such as
SNMP, or Simple Network Management Protocol),
enabling an administrator to perform tasks involving
managing network resources and users.
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28. UNIX / Linux
• UNIX, created originally by Bell Labs (under AT and T), is a
powerful server operating system that can be used in
peer-to-peer or client/server networks.
• UNIX was the first operating system written in the C
programming language.
• Linux was first developed in the late 1980s by a young
student at the University of Helsinki in Finland
named Linus Torvalds.
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29. UNIX / Linux Features
• UNIX (and Linux by extension) systems offer the
following features:
• Fully protected multitasking: This means that UNIX can
easily switch between tasks without the operating system
crashing, because all UNIX processes are separate from
those of the operating system. Even if an application
crashes, unless it somehow manages to take down the X
Windows system with it (which does happen), the
operating system just keeps right on humming.
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30. UNIX / Linux Features
• High performance and stability : Many servers running UNIX or
Linux have run for years without crashing once. The multitasking
capabilities of UNIX, along with the rapid rate at which the operating
system matures (especially with Linux, which is free and can be
changed by anyone), make UNIX or Linux a powerful solution,
especially for server systems.
• Multiuser capabilities : True multiuser systems enable different
users to be logged in to the same system simultaneously. In UNIX
and Linux, not only can a user log in to the same system at the same
time as other users, that user can log in multiple times on the same
system as the same user without the operating system batting an
eyelash (such things are often necessary when administrating a
network, particularly when managing users).
•
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31. UNIX / Linux Features
• Tons of high-quality software : From Apache Server (a Web server that’s
used on a whopping 6 in 10 major Web servers on the Internet) to the long-
awaited Mozilla.org Mozilla 1.0 open source Web browser/e-mail software
(Mozilla is an open source version of the venerated Netscape Communicator)
to the powerful free Gimp graphics manipulation software, Linux is packed
with tons of free, high-quality software. The trick is that, with UNIX/Linux,
you give up compatibility with commercial software that’s available only for
Windows and/or Macintosh, currently.
• Easy customization : While other operating systems seem to offer less and
less choice to the user about which applications to install with the operating
system (Windows XP is this way), UNIX and especially Linux are the exact
counterpoint to that model. With UNIX or Linux, you can actually customize
your operating system kernel, stripping it down to just drivers and
networking or installing everything possible.
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32. UNIX / Linux Features
• Modular architecture : The modular architecture of UNIX (and especially Linux) is
directly responsible for how customizable UNIX is. Modular really means just what
it sounds like: The operating system is built with a kernel that attaches modules to
itself based on what the user needs.
• POSIX compliance: With a free operating system like UNIX, the different
distributions (or flavors) of UNIX quickly became difficult to manage. Currently,
hundreds of different implementations of UNIX are available. To enable
programmers to have some idea of how to code their software such that it would
run on any version of UNIX, the Institute of Electrical and Electronics Engineers,
Inc. (IEEE) defined the Portable Operating System Interface (POSIX).
• Use of TCP/IP as the standard protocol stack: UNIX overwhelmingly uses TCP/IP as
the protocol stack of choice. If you consider that the vast majority of the servers
that help make up the Internet are UNIX computers of one form or another, you
start to get the idea why TCP/IP is so popular.
•
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33. UNIX / Linux Features
• A shell interface: All versions of UNIX include a shell interface of some sort. If you
have ever seen your computer use a completely black screen with white words
written on it, that’s a shell interface. You simply type in commands at the prompt
and hit Enter to execute those commands. The hard part in using these interfaces
is simply the effort it takes to learn all of those rather cryptic commands. Making
life even more difficult, UNIX is ultimately customizable and can use different
shells. The bash shell (likely the most popular shell in use today) and the tcsh
shell, for example, have different commands for the same action.
• A graphical user interface: Although most versions of UNIX (such as Red Hat
Linux) include a graphical user interface (GUI) these days, this has not always been
the case. Historically, UNIX has been derided for its cryptic interface, and the
advent of the GUI into popular UNIX systems was a direct result of this. Popular
UNIX GUIs include KDE and GNOME. KDE is mostly used with Linux, but GNOME
has versions for the Sun Solaris operating system, and therefore crosses the
border from Linux into UNIX proper.
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34. UNIX / Linux Features
• Support for dumb terminals:
• Traditionally, UNIX was used for dumb terminals, and just about all versions of
UNIX still include this capability. The traditional dumb terminal model involves one
central UNIX server that is used by remote terminals to execute applications.
Basically, a user logs in to a UNIX system via Telnet or some other remote
connectivity application and uses UNIX commands to tell the remote system what
functions to perform. In this way, users can download and check e-mail via a text-
based e-mail client such as Pine. The dumb terminal in this form isn’t used much
anymore; Web browsers are definitely more than just dumb terminals— and Web
browsers are now the clients most often seen by UNIX servers (at least those that
make up the Internet). However, wireless devices such as cell phones and mobile
Internet e-mail clients such as AOL’s Mobile Communicator device are good
examples of modern dumb terminals. The devices have nearly no storage at all,
and don’t carry large e-mail clients on the device; the message is simply
transferred as text from one end to the other.
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35. UNIX / Linux Features
• Interoperability
Open source software such as SAMBA is used to provide Windows users with
Server Message Block (SMB) file sharing.
• Authentication:-Centralized login authentication
• File and Print Services
Network File System (NFS) is a distributed file system that allows users to access
files and directories located on remote computers and treat those files and
directories as if they were local.
LPR/LPD is the primary UNIX printing protocol used to submit jobs to the printer.
The LPR component initiates commands such as "print waiting jobs," "receive
job," and "send queue state," and the LPD component in the print server responds
to them.
• Security
With most Unix operating systems, the network services can be individually
controlled to increase security.
•
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36. MAC OS X Server
• OS X Server, formerly Mac OS X Server, was a
separately sold Unix server operating
system from Apple Inc.
• It is architecturally identical to its desktop
counterpart OS X—with additional server programs
and management and administration tools.
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37. MAC OS X Server
• Client Support
TCP/IP file sharing with Macintosh clients using
Network File System (NFS), and File Transfer Apple
File Protocol 3.0
• Interoperability
Mac OS X Server uses the Open Source SAMBA to
provide Windows users with Server Message Block
(SMB) file sharing. Network File System (NFS) lets you
make folders available to UNIX and Linux users.
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38. MAC OS X Server
• File and Print Services
Mac OS X Server provides support for native Macintosh, Windows, UNIX, and Linux
file sharing. Protocols supported include:
• Apple file services (AFP 3.0) from any AppleShare client over TCP/IP
• Windows (SMB/CIFS) file sharing using Samba
• Network File System (NFS) for UNIX and Linux file access
• Internet (FTP)
• Built-in print services can spool files to any PostScript-capable printer over TCP/IP,
AppleTalk, or USB. Macintosh customers can use the LPR support in Print Center or
the Desktop Printer utility to connect to a shared printer. Windows users can use
their native SMB/CIFS protocol to connect to a shared printer.
• Print services for OS X Server
• Macintosh and UNIX (LPR/LPD)
• Windows (SMB/CIFS)
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39. MAC OS X Server
• Security
• Multiple-user architecture and user-level access
privileges.
• Secure Sockets Layer (SSL) support provides
encrypted and authenticated client/server
communications.
• Secure Shell (SSH) provides encryption and
authentication for secure remote administration.
• Kerberos support for centralized login authentication.
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40. NetWare
• NetWare is a computer network operating
system developed by Novell, Inc. It initially
used cooperative multitasking to run various services
on a personal computer, using the IPX network
protocol.
• NetWare has been a great LAN operating system for
years, but only recently (with NetWare 5.x has
NetWare moved beyond the LAN to where it can
easily be a part of larger networks. Until quite
recently, Novell NetWare used to be the single most-
used network operating system (NOS).
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41. NetWare
• However, first Windows NT, and Windows 2000 and
Linux, have steadily eaten into the NetWare market
share for network operating systems.
• Currently, all three operating systems have a roughly
equal share of the network operating system market,
which means that NetWare is still used in at least one-
third of all server systems.
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42. Netware Feature
• NetWare offers the following features :
• Multiprocessor kernel: This feature enables one NetWare
operating system to utilize multiple processors. This
process is called symmetric multiprocessing (SMP).
• SMP enables processors to share memory and bus paths,
even coordinating the processing of a single application in
parallel.
• NLMs: Where UNIX uses daemons and Windows uses
services, NetWare uses NetWare Loadable Modules (or
NLMs) to provide services from the server. NLMs are
programs that run in the background on the server to
provide consistent services to the network.
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43. Netware Feature
• PCI Hot Plug: This feature enables administrators to
dynamically configure PCI network components while the
system is running. You can replace, upgrade, or add new
cards with the Hot replace, Hot upgrade, and Hot
expansion features, respectively.
• Client Support
NetWare 5 comes with Novell Client software for three client
platforms: DOS and Windows 3.1x, Windows 95/98, and
Windows NT.
• Interoperability
You can set the Novell Clients for Windows 95/98 and
Windows NT to work with one of three network protocol
options: IP only, IP and IPX, or IPX only.
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44. Netware Feature
• Authentication
Centralized login authentication
• File and Print Services
File Services NetWare offers two choices of mutually compatible file
services: Novell Storage Services (NSS) and the traditional NetWare File
System. Both kinds of file services let you store, organize, manage, access,
and retrieve data on the network. NSS gathers all unpartitioned free space
that exists on all the hard drives connected to your server, together with
any unused space in NetWare volumes, and places it into a storage pool.
You create NSS volumes from this storage pool during server installation or
later through NWCONFIG. Novell Distributed Print Services (NDPS) is the
default and preferred print system in NetWare. NDPS supports IP-based as
well as IPX-based printing.
• Security
Novell has support for a public key infrastructure built into NetWare 5 using
a public certificate, developed by RSA Security.
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45. Windows
• Directory Services
A directory service is a database of user accounts and
other information that network administrators use to
control access to shared network resources. When users
connect to a network, they have to be authenticated
before they can access network resources. Authentication
is the process of checking the user's credentials (usually a
user name and a password) against the directory. Users
that supply the proper credentials are permitted access
according to the permissions specified by the network
administrator.
•
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46. Windows
• Client Support
Windows 3.x, Windows 95, Windows 98, and
Windows NT Workstation 4.0 Windows 2000
Professional, Xp Pro. Vista Ultimate, Vista Business.
• Interoperability
Windows 2000,2003,2008 Server supports UNIX,
Novell NetWare, Windows NT Server 4.0, and
Macintosh.
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47. Windows
• Authentication
Successful user authentication in a Windows 2000,2003,2008
computing environment consists of separate processes:
interactive logon, which confirms the user's identification to
either a domain account or a local computer, and network
authentication, which confirms the user's identification to any
network service that the user attempts to access.
• Types of authentication
Kerberos V5 is used with either a password or a smart card for
interactive logon. It is also the default method of network
authentication for services.The Kerberos V5 protocol verifies
both the identity of the user and network services Secure
Socket Layer/Transport Layer Security (SSL/TLS) authentication,
is used when a user attempts to access a secure Web server.
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48. Windows
• File and Print Services
You can add and maintain printers in Windows server using the
print administration wizard, and you can add file shares using
Active Directory management tools. Windows server also
offers Distributed File Services, which let you combine files on
more than one server into a single share.
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49. Windows
• Active Directory
After many years of anticipation, Microsoft introduced an
enterprise directory service in the Windows 2000 Server
product line, called Active Directory. It uses a hierarchical tree
design comprised of container and leaf objects. The
fundamental unit of organization in Active Directory directory
service is the domain, but; you can group domains together
into a tree, and even group multiple trees together into
a forest. Domains that are in the same tree automatically have
bidirectional trust relationships established between them,
which eliminates the need for administrators to create them
manually. The trust relationships are also transitive , meaning
that if Domain A trusts Domain B and Domain B trusts Domain
C, then Domain A trusts Domain C.
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50. Windows
• Security
User-level security protects shared network resources by requiring that a
security provider authenticate a user’s request to access resources. The
domain controller , grants access to the shared resource by verifying that
the user name and password are the same as those on the user account list
stored on the network security provider. Because the security provider
maintains a network-wide list of user accounts and passwords, each client
computer does not have to store a list of accounts. Share-level security
protects shared network resources on the computer with individually
assigned passwords. For example, you can assign a password to a folder or
a locally attached printer. If other users want to access it, they need to type
in the appropriate password. If you do not assign a password to a shared
resource, every user with access to the network can access that resource.
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51. Token Ring
• Token Ring protocol is a communication protocol used in Local Area
Network (LAN).
• In a token ring protocol, the topology of the network is used to define
the order in which stations send.
• The stations are connected to one another in a single ring. It uses a
special three-byte frame called a “token” that travels around a ring.
• It makes use of Token Passing controlled access mechanism.
• Frames are also transmitted in the direction of the token.
• This way they will circulate around the ring and reach the station
which is the destination.

52. Token Ring

53. How Does A Token Ring Work?
• The frame or packet reaches the next station according to the
sequence of the ring.
• Whether the frame contains a message addressed to them is
determined by the current node. If yes, then the message is removed
by the node from the frame. If not, then there is an empty frame(an
empty frame is called the token frame).
• A Station that has the token frame, only has the access to transfer the
data. If it has data then insert that data into the token frame
otherwise release that token for the next station.
• The next station picks up that token frame for further transmission.

54. Networks: Token Ring and FDDI
54
IEEE 802.5 and Token Ring
• Proposed in 1969 and initially referred to as a
Newhall ring.
Token ring :: a number of stations connected by
transmission links in a ring topology. Information
flows in one direction along the ring from source
to destination and back to source.
Medium access control is provided by a small frame,
the token, that circulates around the ring when all
stations are idle. Only the station possessing the
token is allowed to transmit at any given time.

55. Advantages of token rings
• Token rings reduce the chances of data collision.
• Token passing performs better than bus topology under heavy traffic.
• A server is not needed to control connectivity among the nodes.

56. Disadvantages of token rings
• Data packets must pass through all the nodes, slowing routing.
• It is susceptible to failures that may occur in the network.
• Due to a fault in the ring, all network operation ceases.

57. AppleTalk
• AppleTalk is a network operating system designed to connect Apple
computers. Its components are built on Macintosh operating systems.
• The network topology is a bus or tree.

58. AppleTalk…
• AppleTalk is a network operating system designed to
connect Apple computers. Its components are built on
Macintosh operating systems. There are two main
versions of AppleTalk depending on how many years in
the past the network was implemented, Phase 1 and
Phase 2.

59. History
• Just prior to its release in early 1985,AppleBus
was renamed AppleTalk.
• The system had a number of limitations, including
a speed of only 230.4 Kbit/s ,a maximum distance
of 1000 feet from end to end , and only 32 nodes
per LAN.

60. Design
AppleTalk was designed with a transparent network interface
-that is, the interaction between Client computers and
network servers requires little interaction from the user.
Two versions of AppleTalk exist :
AppleTalk Phase 1 and AppleTalk Phase 2.

61. Network Components
AppleTalk Internetwork consists of a Hierarchy of Components

62. Sockets
• An AppleTalk socket is a unique, addressable location in
an AppleTalk node. It is the logical point at which
upper-layer AppleTalk software processes and the
network layer Datagram Delivery Protocol (DDP)
interact.
Socket Clients Use Socket to Send and Receive Datagrams

63. Nodes
• An AppleTalk node is a device that is
connected to an AppleTalk network.
• This device might be a Macintosh computer,
a printer, an IBM PC, a router, or some other
similar device.

64. Networks
• It consists of a single logical cable and multiple
attached nodes.
• A single physical cable or multiple physical
cables interconnected by using bridges or
routers may be found.

65. Networks…
• Non extended Networks
It is a physical network segment that is assigned
only a single network number, which can range
between 1 and 1024.
• Extended Networks
Also known as a cable range. It is a physical network
segment that can be assigned multiple network
numbers.

66. Zones
• An AppleTalk zone is a logical group of nodes or
networks that is defined when the network
administrator configures the network.
• The nodes or networks need not be physically
contiguous to belong to the same AppleTalk
zone.

67. Addressing in AppleTalk
• Network Number :- 16 bit number.
• Node Id :- 8 bit number identifies node on an AppleTalk network.
• Socket Number :- unique 8 bit number that identifies a socket. A
maximum of 254 different socket number can be assigned in a
node.
• Zone Name :- A name assigned to an arbitrary subset of node
within an AppleTalk Internet.

68. AppleTalk Manager
 Our Application accesses the Services of the AppleTalk
protocol through the AppleTalk manager.
 It is a collection of Application Programming Interface
to AppleTalk protocol.

69. Security
• AppleTalk, like many network protocols, makes no
provisions for network security. The design of the
AppleTalk protocol architecture requires that security
measures be implemented at higher application levels.
Cisco supports AppleTalk distribution lists, allowing
control of routing updates on a per-interface basis.
This security feature is similar to those that Cisco
provides for other protocols.

70. Advantages
• Apple automatically includes AppleTalk in the
Macintosh operating system.
• Easy to implement and configure.
• Setting up a small workgroup is simple and
inexpensive.

71. Disadvantages
• It is not suitable for very large networks.
• It is very slow compared to other LAN links at 230.4
Kbps.
• It is unsuitable for bandwidth intensive
applications.

72. ⦁ Attached Resource Computer NETwork
⦁ Token-Passing Local Area Network (LAN)
⦁ Originally 2.5 Mbps data rate
⦁ 255 Nodes or Stations
⦁ Variable Packet Length
⦁ Bus or Distributed Star Wiring
⦁ Unicast or Broadcast Messages
⦁ One to one or one to all
What is ARCNET?

73. ⦁ Coaxial, Fiber Optic, Twisted-pair Cabling
⦁ Over 11 Million Installed Nodes
⦁ Originally developed by Datapoint Corporation as an
office network
⦁ Chip sets available from SMSC
⦁ ANSI/ATA 878.1-1999 Standard
⦁ Ideally suited for an industrial network
What is ARCNET?

74. ⦁ Broad Acceptance
⦁ Large Installed Base
⦁ Deterministic Performance
⦁ Simple to Install
⦁ Low Cost per Node
⦁ Robust Design
⦁ Multiple Cable Media Support
⦁ Multi-master Communication
What are ARCNET’s Benefits?

75. ⦁ HVAC
⦁ Motor Drives
⦁ Power Generation
⦁ Data Acquisition and Control
⦁ Manufacturing Information Systems
⦁ OfficeAutomation
⦁ Shipboard Automation
Where is ARCNET Used?

76. ⦁ Printing Press Controls
⦁ Telecommunications
⦁ Gaming Machines
⦁ Vehicular Navigation
⦁ Security Systems
Where is ARCNET Used?
Any application where real-time performance, high
security and robust design is important.

77. ⦁ Distributed Star topology requires the use of hubs
How Does ARCNET Work?
NODE
NODE
NODE
NODE
NODE
NODE
NODE
NODE
NODE
HUB
HUB
HUB

78. Application
Presentation
Session
Transport
Network
Data Link
Physical
⦁ OSI Reference Model
How Does ARCNET Work?
ARCNET defines the bottom two layers of the OSI
model

79. ⦁ Only Five Simple Commands
⦁ ITT - Invitation to transmit
⦁ FBE - Free buffer enquiry
⦁ PAC - Packet
⦁ ACK - Acknowledgement
⦁ NAK - Negative acknowledgement
ARCNET Protocol

80. ⦁ Deterministic Token Passing
⦁ Packet Flow Control
⦁ Error Detection
⦁ Auto Reconfiguration
⦁ Variable Packet Size
⦁ Supports Various Transceivers & Media
⦁ Supports Various Software Drivers
⦁ Up to 255 Nodes Per Network
ARCNET Protocol Features

81. ⦁ Token Passing - Transmitting on the network is only
permitted when a node has the token
⦁ Every node can transmit once during each token rotation
✯Benefits:
⦁ Every node has a guaranteed response time to transmit
⦁ Deterministic behavior
ARCNET Protocol Features

82. ⦁ Auto-Reconfiguration - Network is automatically
reconfigured when a node joins or leaves the network
⦁ Token pass is automatically reconfigured
⦁ Typical time 20 - 30 ms
⦁ Supports live node insertion and deletion
⦁ Variable Packet Size
⦁ From 1 to 507 bytes per packet
ARCNET Protocol Features

83. ⦁ Packet Flow Control - Transmitter checks receiver to
make sure it is ready to receive a packet
⦁ Reduced software overhead
⦁ Increased bandwidth
⦁ No lost packets due to input buffer overruns
ARCNET Protocol Features

84. ⦁ Error Detection - 16 bit CRC checks each packet
⦁ Corrupted packets automatically rejected
⦁ Transmitter is aware of the error
⦁ Reduced software overhead
⦁ Better CPU utilization
ARCNET Protocol Features

85. ⦁ Token passes from low to high address
ARCNET Logical Ring
109
122
255
6

86. PAC = ALERT SOH SID DID DID CP DATA ... DATA CRC CRC
ARCNET Frames
Only PAC has a variable length frame
ITT =
FBE =
ALERT EOT DID DID
ALERT ENQ DID DID
ACK= ALERT ACK
NAK= ALERT NAK

87. Token Pass
Destination
Node
Source
Node
ITT

88. Packet Transmission
Destination
Node
Source
Node
FBE
PAC
ACK
ACK

89. Receiver Unavailable
Destination
Node
Source
Node
FBE
NAK

90. Failed Packet Transmission
Destination
Node
Source
Node
FBE
PAC
ACK

91. ⦁ ITT 15.6 (invitation to transmit)
⦁ Tta 12.6 (turnaround time)
⦁ FBE 15.6 (free buffer enquiry)
⦁ Tta 12.6 (turnaround time)
⦁ ACK 6.8 (acknowledge)
⦁ Tta 12.6 (turnaround time)
⦁ PAC 33.2 +4.4 sec/byte
⦁ Tta 12.6 (turnaround time)
⦁ ACK 6.8 (acknowledge)
⦁ Tta 12.6 (turnaround time)
ARCNET Message Timing in Microseconds (2.5 Mbps)
141 sec + 4.4 sec/byte
Minimum Message: 141 Microseconds

92. If You Cut ARCNET...
...You Just Get Two ARCNETS Within Milliseconds

93. ⦁ Flexibility
⦁ Distributed Star Topology Requiring Hubs
⦁ Hub-less Bus Topology
⦁ Coaxial Cable
⦁ Twisted Pair
⦁ Fiber Optics
ARCNET Cabling

94. ⦁ Coaxial Cable In a Star Topology
⦁ Either a star or distributed star topology
⦁ Utilize active or passive hubs
Traditional ARCNET
NODE NODE
NODE
NODE
NODE
NODE
NODE
NODE
NODE
HUB
HUB
HUB

95. ⦁ Coaxial Star
⦁ Original method of communication
⦁ RG-62/u coaxial cable
⦁ BNC connectors
⦁ Only two transceivers per segment
⦁ Segment length up to 2,000 feet
⦁ Requires the use of a hub to go beyond two stations
Traditional ARCNET
We call this –CXS.

96. ⦁ Coaxial Bus
⦁ Lower cost hub-less network
⦁ RG-62/u coaxial cable
⦁ Up to eight NIMs per bus segment
⦁ Segment length limited to 1,000 feet
⦁ BNC connectors and Tees
⦁ Requires end of line terminators
Traditional ARCNET
We call this –CXB.

97. ⦁ Twisted-Pair Star
⦁ Requires active hubs for network expansion
⦁ Only 328 foot segment length
⦁ RJ-11 connectors
⦁ Utilizes BALUN’s to convert from coaxial cable to twisted-pair
Traditional ARCNET
We call this –TPS.

98. ⦁ Twisted-Pair Bus
⦁ Modified circuitry of coaxial bus implementation
⦁ Supports eight nodes
⦁ Reduction in segment length to 400 feet
⦁ RJ-11 or RJ-45 connectors
⦁ Requires end of line terminators
Traditional ARCNET
We call this –TPB when using RJ-11 connectors
and –TB5 when using RJ-45 connectors.

99. ⦁ Fiber Optics
⦁ 850 nm wavelength with ST connectors
⦁ 62.5/125 duplex multimode fiber cable
⦁ 6000 foot segment length
⦁ Large networks can be achieved by cascading hubs
⦁ ARCNET controller chips may need to be set to extended timeouts
Traditional ARCNET
We call this –FOG.

100. ⦁ Fiber Optics
⦁ 1300 nm wavelength with ST connectors
⦁ 62.5/125 duplex multimode or duplex single-mode fiber cable
⦁ 10,000 m multimode and 14,000 m single-mode
Traditional ARCNET
We call this –FG3.