Internetworking and Routing featuring Internet Technology

1
Internetworking and Routing(featuring Internet
Technology)

• MSIT 191 Computer-based Comm. Systems and
  Networks
• Topic 7

2
Inter-network Connections (same as 2nd section of
Handout 6)
3
Section Preview
In this section we will study

• LAN-to-LAN connections
• Repeaters, bridges, routers, and gateways
• Switches and virtual LANs
• Remote access
• Common carrier services

4
LAN-to-LAN Connections

• Companies that have LANs in separate geographical
  locations or LANs that cover distances greater
  than the maximum medium distance allowed, or
  companies with more nodes that can be
  accommodated by one LAN, must segment their
  network into two or more LANs.
• Having separate LANs allows a company to split
  functions and gives an additional level of
  security.
• LANs may also be connected in order to
  consolidate independent LANs that may have been
  formed in an ad-hoc manner.
• Responsiveness of the system can be maintained
  while the number of users increases by adding
  more resources to an existing LANmemory, disks,
  another server, etc. or by splitting the LAN
  into two or more smaller LANs.

5
Repeaters

• Every LAN has a distance restriction. IEEE
  standards specify a maximum segment length of 500
  meters. If you want to span longer distances, you
  can use a repeater to connect two segments.
• As signals travel along the medium, they lose
  strength through attenuation. Weak signals can
  cause transmission errors. A repeater accepts a
  signal, regenerates it, and passes it along at
  full strength.
• A repeater does not separate one segment of the
  network from another.

6
A Repeater, Bridge, and Router and the OSI
Reference Model
Processor 1
Processor 2
Application Layer
Application Layer
Presentation Layer
Presentation Layer
Session Layer
Session Layer
Transport Layer
Transport Layer
Router
Network Layer
Network Layer
Data Link Layer
Data Link Layer
Bridge
Repeater
Physical Layer
Physical Layer
7
Bridges

• Early bridges were used to connect two networks,
  each of which used the same MAC protocol. Today,
  bridges also connect LANs having different MAC
  protocols. This device may be called a brouter
  or multiprotocol bridge.
• Most bridges being sold today are called learning
  bridges, or transparent bridges. A learning
  bridge builds its routing table from messages it
  receives and does not need to be loaded with a
  predefined routing table.

8
Basic Bridge Functions
Packet Routing Function Additional
Functions
1. Accept packet from LAN A. 2. Examine address
of packet. 3. If packet address is a LAN A
address, allow the packet to continue on LAN
A. 4. If packet address is a LAN B address,
transmit the packet onto the LAN B medium. 5. Do
the equivalent for LAN B packets. Media
conversion Learning Remote connection Signal
conversion Speed conversion Packet
statistics Token ring to ethernet conversion
9
Token Rings Connected by a Bridge
LAN A Token-Ring Network
Bridge
LAN B Token-Ring Network
10
Spanning Tree Algorithms

• Spanning tree algorithms, in which bridges
  exchange routing information with each other, can
  be used on any type of LAN.
• The advantages of the spanning tree algorithm are
  that it is MAC-layer-independent, bridges can
  learn the topology of the network without manual
  intervention, and paths can change if an existing
  path becomes inoperable or if a better path is
  introduced. The algorithm overhead is the size of
  the routing table for networks with many
  communicating nodes, and the extra network
  traffic resulting from status messages and
  flooding.

11
Source Routing

• Source routing is an IEEE standard used as a
  routing algorithm for token-passing networks.
• The advantage of the source routing algorithm is
  that bridges are not responsible for maintaining
  large routing tables for extensive networks. Each
  node is responsible for maintaining routing
  information only for the nodes with which it
  communicates. The disadvantages are the overhead
  of sending numerous packets during discovery and
  the extra routing data that must be appended to
  each message.

12
Remote Bridge Connection Alternatives
RS-232 serial lines Synchronous transmission at
56 Kbps or 64 Kbps Fractional T-1 at multiples of
64 Kbps Integrated services digital network
(ISDN) Digital subscriber lines (DSL) RS-422
serial lines at 19.2 Kbps to 2 Mbps T-1 Line at
1.5 Mbps X.25 packet-switching network Frame
relay Asynchronous Transfer Mode (ATM)
13
Routers

• Routers operate at the network layer of the OSI
  Reference Model. The network layer is responsible
  for packet routing and for collecting accounting
  information.
• Some networks use a static routing algorithm,
  meaning that packet routing between two nodes
  never changes. In a CSMA/CD bus LAN, a packet is
  broadcast to every node in a token ring, a
  packet is transmitted from one node to the next
  node in the ring.
• A Novell network uses a protocol called sequenced
  packet exchange/internetwork packet exchange
  (SPX/IPX) to transfer packets between nodes. SPX
  operates at the transport layer and IPX at the
  network layer.
• Another protocol used by many networks is the
  transmission control protocol/internet protocol
  (TCP/IP). TCP/IP is the protocol used on the
  Internet.

14
Gateways

• The interface between two dissimilar networks is
  called a gateway. A gateway is basically a
  protocol converter. It reconciles the differences
  between the networks it connects.
• The components of a gateway are the network
  interfaces and the logic that carries out the
  conversion necessary when moving messages between
  networks. The conversion must change the header
  and trailer of the packet to make it consistent
  with the protocol of the network or data link to
  which the message is being transferred. (In some
  cases considered as a device for connecting two
  networks with different application layer
  protocols.)

15
Ways to Increase LAN Media Throughput

• Faster hardware
• Higher network speeds
• Lower bandwidth demands
• LAN segmentation
• Full duplex
• Switching hubs

16
LAN Switches

• LAN switches work similarly to the way in which a
  telephone switch works. In the idle state, you
  are not connected to anything except the
  telephone switch and cannot communicate with
  anyone until a circuit is set up. When you dial
  someones number, the complete transmission
  capacity of the telephone network is not
  dedicated to your call instead, a connection is
  made between your telephone and the telephone of
  the person you are calling and a single circuit
  is used, leaving other circuits available to
  other subscribers.
• LAN switches, also called switching hubs, look
  much like standard wiring hubs. The switching hub
  examines the data link header of the packet and
  obtains the destination address. The switch then
  establishes a dedicated connection between the
  senders port and the recipients port, and the
  two communicate.

17
A LAN Switch
Common Server
Common Server
Switching Hub 10/100 Mbps
To/From Other Hubs
Conventional Hub-10/100 Mbps
Conventional Hub-10/100 Mbps
To Workstations or Segment Servers
To Workstations or Segment Servers
18
Some Benefits of Switching Hubs
Efficient network segmentation to balance
traffic. Good price/performance. Availability of
shared and dedicated bandwidth. Support of new
technologies such as asynchronous transfer mode
and other network protocols. Preservation of
investment in cabling and LAN adapters. Devices
can communicate at NIC speeds as long as
necessary. Provide bridging and routing as well
as integration with faster technologies, such as
FDDI, 100 Mbps ethernet. Multiple connections can
be established concurrently. Ability to define
virtual LANs (VLANs)
19
Virtual LANs

• The benefit of VLANs is the ability to collect
  existing computers into a VLAN and to move
  workstations while maintaining their VLAN
  connection. Because VLANs are identified by
  addresses or switch ports and not by physical
  connections, LAN nodes can be moved from one
  location to another and remain on the same VLAN
  without having to change connections at the
  wiring hubs.
• A variety of methods are used to determine how
  users are grouped into a VLAN
• Port
• MAC Address
• Packet Tagging
• Network layer addresses

20
LAN-to-Host Connections

• The Host as a LAN Node
• Some hosts have the ability to connect to the LAN
  as a node. This is the most effective way to
  establish the connection.
• Asynchronous Connections
• Virtually every computer has the ability to send
  and receive by using an asynchronous data link
  protocol. Because most computers support the
  asynchronous data link protocol, it is sometimes
  used to link a microcomputer to a host. Usually,
  a microcomputer attached to a host asynchronously
  operates in one of two modes file transfer or
  terminal emulation.
• Dedicated Connection Per Microcomputer
• One way to connect a LAN node to a host is to
  provide a dedicated connection between a port on
  the host and each microcomputer needing a host
  connection. A dedicated connection provides
  direct host access, and the microcomputer does
  not use LAN resources for communicating with the
  host.

21
LAN-to-Host Connections (cont.)

• A dedicated connection has several disadvantages.
  First, as with all asynchronous connections, the
  sped of the link is slow. These connection speeds
  can be over 100,000 bps, but typically for
  microcomputer connections they are 33.6 Kbps or
  less. If many LAN nodes must communicate with the
  host, many host ports are required.
• Multiplexing
• A multiplexer is a hardware device that allows
  several devices to share one communication
  channel. Multiplexing is typically used to
  consolidate the message traffic between a
  computer and several remotely located terminals.
  This technique can also be used to allow several
  microcomputers to share a communication link to a
  host processor.
• Shared Asynchronous Connections
• In some applications, each LAN node needs
  occasional access to the host, but the number of
  concurrent connections is far fewer than the
  number of LAN nodes. In such situations, a
  dedicated line per node is excessive. A better
  solution is to share asynchronous connections.

22
Common Features of Asynchronous Communications
Software
Scripts Mouse support File transfers (CompuServe,
Xmodem, Ymodem, Kermit) Terminal emulation (ANSI,
DEC VT220, IBM 3101, TTY) Electronic mail Phone
directory Capture of data to a disk Text
editor Password security
23
Interconnection Utilities

• File Transfer Utilities
• File transfer utilities allow you to move files
  between network nodes. File transfer capabilities
  are an intrinsic part of many routers part of
  the TCP/IP protocol suite is a file transfer
  capability.
• Remote Logon
• A remote logon essentially establishes a remote
  user as a local user on the remote node. Once a
  user has successfully logged onto the remote
  node, commands issued by that user are processed
  and acted on by the remote node rather than by
  the local node.
• Remote Access
• Through remote connections, LAN administrators
  can resolve problems from home or other work
  locations users can perform some of their work
  at home and telecommute and travelers can
  conduct work while away form the office.

24
Interconnection Utilities (cont.)

• Integrated Services Digital Networks (ISDNs)
• One objective of ISDNs is to allow international
  data exchange. This requires interfaces between a
  number of national and regional providers of such
  services. The first mission of the ISDN program
  has been to define the functions and
  characteristics of the network and to establish
  implementation standards.
• ISDN was the first high-speed alternative to
  switched, analog connections for Internet access.
  ISDN when used for Internet access usually
  provides speeds of 128 Kbps.
• Digital Subscriber Lines (DSL)
• Digital subscriber lines are an emerging service
  that provides much faster transmission rates than
  analog modems and ISDN.

25
Internet Technology
26
Section Preview
In this section we will study

• Describe the TCP/IP protocol
• Discuss Internet addressing
• Describe several protocols used on the Internet
• Define a subnet and describe how they are used
• List several components of the TCP/IP protocol
  suite

27
Internet Addresses

• Internet addresses are represented in a variety
  of formats however, all the formats are
  ultimately resolved to a 32-bit number known as
  an IP address.
• A 128-bit address is part of a new version of the
  IP protocol.
• On the Internet, all network addresses must be
  unique. Within a network, all subnet addresses
  must be unique, and within a subnet all node
  addresses must be unique.
• Currently there are four address classes, A
  through D Class E is defined but reserved for
  future use.

28
Internet Address Class Summary
Class
Subnets
Nodes
Comments
A B C D
27 128 214 16,000 221 2 million
224 16 million 216 64,000 28 256
Address begins with a 0 bit Address begins with
bits 10 Address begins with bits 110 Address
begins with bits 1110
29
Subnet Addresses

• An Internet address is composed of three basic
  parts the class type identifier, the network
  address, and the node addresses. An installation
  that was fortunate to have a Class A address
  space has the potential for approximately 16
  million node addresses. It is unlikely that the
  company would want all these nodes associated
  with a single network address. Consequently, it
  is possible for a company to divide the node
  address range into two parts, a subnet address
  and a node address within the subnet.
• This is accomplished by placing a subnet mask
  over the local or node address part of the IP
  address.

30
Internet Node Addresses

• Static Addressing
• Static addressing means that a node is assigned a
  permanent IP address. This is common for nodes
  that are continuously operating on the Internet
  or network using TCP/IP.
• Dynamic Addressing
• In dynamic addressing, a node is assigned an
  Internet address when one is needed. With dynamic
  addressing, a node will be given any address that
  is not currently in use. The most common
  mechanism for dynamically assigning Internet
  addresses is the dynamic host configuration
  protocol (DHCP).
• Internet Addressing on LANs
• If a LAN node also has an IP address, an IP
  message can be delivered only if the IP address
  is first translated into MAC address. The
  protocol that performs this function is called
  the address resolution protocol (ARP).

31
IP Routing

• Devices called routers are responsible for
  internetwork message forwarding. Each router is
  connected to two (or more) networks (some routers
  have more than two ports), and each router port
  has an address on the attached subnet.
• Each router maintains a router table.
• Internet Naming Conventions
• For most Internet users, the four-octet address
  representation, called a dotted decimal, is too
  cumbersome. Therefore, most users substitute a
  naming convention called a uniform resource
  locator (URL). A URL uses names and abbreviations
  that are easier to use and remember than the
  dotted decimal representation.
• Domain names are a hierarchical word-oriented
  representation of an Internet address.

32
Root Level Domain Names
Commercial enterprise education, for example, a
university U.S. government U.S. military network
service nonprofit organization Austria Australia B
elgium Canada Denmark Spain Finland France Italy
Japan United States
Com edu gov mil net org at au be ca de es fi fr it
jp us
33
Domain Name Hierarchy
Countries Most General
AF AU CA CN DE FR JP...US...ZW
COM EDU GOV MIL NET ORG
Organizational
ABC Acme BGH.XYZ
Companies
grumpy doc sneezy bashful
Hosts
34
Some URL Protocols
hypertext transfer protocol file transfer
protocol file access Send mail to a
recipient. Access a newsgroup or new article. Use
the Gopher text-oriented access. Use utility to
access information about a user.
http ftp file mailto news Gopher finger
35
IP Routing Algorithm

• Source node obtains the destination nodes IP
  address.
• IP protocol builds the IP header and affixes it
  to the packet
• Send packet to router.
• Determine the network address of the destination
  node.
• If the network address is this network, use local
  delivery method and skip remaining steps.
• Router consults routing table for network
  address.
• Router sends message out on port addressed to
  next router
• Receiving router decrements time-to-live field.
• If time-to-live field is 0, packet is discarded.
• Return to step 3.

36
Internet Tools

• Finger
• Finger is a utility that allows a user to gather
  information about other network users. For
  security reasons, some systems do not allow the
  use of this utility.
• Tracert
• Tracert allows a user to trace the round trip
  between the users node and another node on the
  network.
• Ping
• Ping allows a user to determine if a given system
  is active on the network. Some versions of Ping
  also give performance information like number of
  hops to the system and speed of the links if the
  system is available.
• Talk and Internet Relay Chat (IRC)
• Talk is a UNIX utility that allows on user to
  communicate interactively with another user.
  Through the talk utility, characters typed at one
  station are immediately displayed on the other
  participants monitor.

37
Key Upgrades in IPv6

• Expanded Address Space
• Currently, the length of Internet addresses is 32
  bits. This gives an address space of
  approximately 4 billion however, the actual
  number of addresses available is less than that
  because some addresses are reserved and because
  some address in a class may not be used. IPv6
  increases the size of the address field to 128
  bits this will allow an address space from 0 to
  3x1038.
• Quality of Service
• To accommodate time-sensitive transmissions like
  audio and video, IPv6 will institute service
  categories to prioritize the flow of data.
  Transmissions declared as real-time will be
  provided with improved performance.
• IP Header Changes
• Changes will be necessary to provide for the
  larger address space and quality of service.
• Security and Privacy
• IPv6 will allow extensions to the header to
  provide security capabilities. The extensions
  will allow a variety of authentication algorithms
  and allow detection or elimination of known
  techniques for one node to impersonate another
  node for sending or receiving packets.

38
Ipv6 Header Format
Field
Size in Bits
Comments
Contains protocol version 6 for Ipv6 Message
priority Quality-of-service identifier Size in
octets of packet following the header Type of
header extension, if any Number of hops allowed
before datagram is discarded Senders IP
address Recipients IP address
Version Priority Flow control Payload length Next
header Hop limit Source address Destination
address
4 4 24 16 8 8 128 128
39
A Generic Firewall
LAN
The Internet
Protected Systems
Generic Firewall
40
A Gateway Firewall
The Internet
Private Network
Gateway Firewall
41
A Screened Subnet Firewall
Traffic Not Allowed
The Internet
Private Network
Traffic Allowed
Traffic Allowed
Screened Subnet (Private)
42
Information Superhighway Uses

• A business might use the information superhighway
  to conduct a conference among employees in
  different locations.
• A software company might use the information
  superhighway to distribute software directly to
  customers.
• A publishing company might distribute books or
  magazines directly to readers or perhaps to a
  local outlet for on-demand printing.
• Movies and games may be available on demand.
• Education classes at all levels may be available
  and allow people to learn new skills at their
  home or office.
• Electronic mail and video images may be
  exchanged. Interactive use of such technologies
  may give rise to online discussion groups and
  conferencing.

43
Potential Information Superhighway Implementation
Backbone Network
Large Business
Fiber Optic Cable
Fiber Optic Cable
Local Distribution Point
Coaxial Cable or Twisted-Pair Wires
Homes or Small Businesses
44
Assignment/Exercise 5/6/7 Local/Wide Area
Networks/Internetworking Routing

• Who is Robert M. Metcalfe? What is/are his
  contribution/s to the field of local area
  networks (LANs)?
• Read Metcalfe and Boggs paper entitled Ethernet
  Distributed Packet Switching for Local Computer
  Networks, Communications of the ACM, Vol. 19,
  pp. 395-404, July 1976 and comment on its
  relevance or irrelevance as far as local area
  networking is concerned in the 2000s. (Note
  Metcalfe and Boggs original Ethernet paper is
  available for free in some Internet sites use a
  search engine and search for the the article
  title - in quotation marks.)
• Note Underlined text signifies addition/changes
  to original Assignment/Exercise 5/6
  specifications.

45
Assignment/Exercise 5/6/7 Local/Wide Area
Networks/Internetworking Routing

• What is the Institute for Electrical and
  Electronic Engineers (IEEE) Committee 802? What
  are its functions and sub-committees?
• Describe the following (potential) wide area
  network physical/data link layer connection
  technologies
• plain old telephone system
• Leased line (64kbps, T1/E1, fractional T1/E1,
  etc.)
• Integrated Services Digital Network (ISDN)
• Digital Subscriber Lines (DSL)
• Frame Relay
• Asynchronous Transfer Mode (ATM)
• What is a repeater, a bridge, a switch, a router
  and a gateway? In what OSI layer does each of
  these devices functions?
• What are the different types of routing
  protocols? What is RIP, OSPF, BGP, IBGP, EBGP?
• Submit a 2-4 page write-up of your findings (be
  brief but concise!)
• Due 19/26 Jan. 2002/9 Feb. 2002

46
Assignment/Exercise 5/6/7 Local/Wide Area
Networks/Internetworking Routing

• Familiarize with USENET Newsgroups related to
  local area networks, that is
• comp.dcom.lans.ethernet
• comp.dcom.lans.fddi
• comp.dcom.lans.novell
• comp.dcom.lans.token-ring
• comp.dcom.lans.misc
• comp.dcom. (for data communication in general)
• Tip For starters, read the Frequently Asked
  Questions (FAQ) for each area.
• Where can you access USENET News? A lot of sites
  in the Internet
• Example http//www.google.com (then click on
  Groups)
• Submit (none)
• Due (N.A.)