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Chapter 15 - Networks I

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  • Discuss how packets get to a classful destination
  • Picture of SONET with ATM/ISDN/DSL/Voice
  • Fill those buckets

Transcript

  • 1. Networks I Chapter 15
  • 2. Chapter Objectives
    • Understand basic network terminology.
    • Understand the basics of the TCP/IP protocol suite.
    • Understand the basics of IP addresses.
    • Understand basic IP routing.
      • Understand the basics of ARP, and DNS.
      • Understand the basics of layer 2 and layer 3 “routing”.
    • Understand common network hardware.
  • 3. Network Protocols
    • Internetworking - the process of connecting two computer networks together.
      • The interconnected networks may or may not use the same network technology.
      • The interconnected networks may or may not be in the same location.
      • The interconnected networks may or may not encompass the same hardware.
      • The interconnected networks may or may not employ the same software.
      • The Internet is one example of internetworking.
  • 4. Network Protocols
    • WARNING :
      • Networking seems to encompass every two, three, four, five, and six character combination of letters into an acronym.
  • 5. Network Protocols (ISO)
      • The International Standards Organization adopted a networking model called the Open System Interconnect.
      • This network model breaks the task of networking down into seven layers (then arranged them like a top-ten list):
        • 7) Application layer - Provide end-user services
        • 6) Presentation Layer - Deal with problems & compression
        • 5) Session Layer - Authentication and Authorization
        • 4) Transport Layer - Guarantee end-to-end (correct) delivery
        • 3) Network Layer - Routing and Accounting
        • 2) Data Link Layer - Transmit/receive packets & addressing
        • 1) Physical Layer - The cable or media itself
  • 6. Network Protocols (ISO)
    • The ISO/OSI model was the result of design by committee.
    • The layers had little base in reality: They did not match real-world protocol stacks.
    • The ISO/OSI model suffered a horrible “death” (nobody could make it work).
    • Network theory courses still hold the ISO model up as the “right way to do things.”
  • 7. Network Protocols (TCP/IP)
    • Internet Protocol (TCP/IP model)
      • The TCP Protocol is designed around a simplified four layer approach:
        • Link Layer - Network hardware and device drivers
        • Network Layer - Basic Communications, addressing, routing
          • The network layer protocol is the Internet Protocol (IP).
        • Transport Layer - Communication among programs on a net.
          • There are two data Transport protocols In TCP/IP:
            • User Datagram Protocol (UDP)
            • Transmission Control Protocol (TCP)
        • Application Layer - End user application programs
          • Utilities like ftp, ssh, rlogin, rsh, DNS, NFS, CIFS, …
  • 8. Network Protocols (TCP/IP)
  • 9. Network Protocols (TCP/IP)
    • In order for all of the computers on the Internet to communicate, we have to:
      • Ensure that the computers speak the same language.
        • The language used on the Internet is TCP/IP .
          • IP is the Internet Protocol
            • IP provides a communication channel, including addressing, and routing.
          • TCP is the Transmission Control Protocol.
          • UDP is the User Datagram Protocol..
            • TCP and UDP provide data delivery over the IP channel.
      • Ensure that each network device has a unique address .
      • Ensure that the computers have access to some form of bridging hardware in order to connect dissimilar network technologies.
  • 10. Network Protocols (TCP/IP)
    • Internet Protocol (Packets)
      • As a packet travels through the levels of the TCP/IP protocol, each layer adds it’s own header information to the datagram.
        • This process of each layer encoding it’s own management information into the existing datagram is called nesting , or encapsulation .
      • Various headers contain the source and destination address, checksum, protocol specific information, and other handling instructions.
      • At the receiving end the headers are stripped off by the appropriate level, the header contents are examined for special handling information, and the datagram is delivered to the appropriate application.
  • 11.  
  • 12. Network Protocols (TCP/IP)
    • Internet Protocol Version 4 (IPv4)
      • An IP address consists of four byte values separated by periods. For Example: 123.45.67.89
      • This notation is also known as the dotted quad format.
      • Each of the values must be in the range of 0 - 255 (8 bits).
      • An IPv4 address is therefore 32 bits (4 bytes * 8 bits/byte).
    • There are five classes of IP Addresses in IPv4:
      • Class A, B, and C addresses are used for single host addressing.
      • Class D addresses are used for multicast connections.
      • Class E addresses are experimental .
  • 13. Network Protocols (TCP/IP)
    • Internet Protocol (IPv4)
        • Class A Networks - The first byte is in the range of 1 - 127.
          • The first four bits of the address are Binary 0 X X X
          • There are 127 Class A networks.
          • The first byte of a class A address is the network number.
          • The remaining three bytes are the host address on that network.
          • 110 .32.4.18
          • network host address
          • Each Class A network can address up to 16 million hosts.
          • All Class A networks are currently assigned and in use . (lie)!
  • 14. Network Protocols (TCP/IP)
    • Internet Protocol (IPv4)
        • Class B Networks - The first byte in the range of 128 - 191.
          • The first four bits of the address are BINARY 1 0 X X
          • There are 16,384 Class B networks.
          • The first two bytes of a class B address are the network number.
          • The remaining two bytes are the host address on that network.
          • 129.74. 25.98
          • network host address
          • Each Class B network can address up to 65,000 hosts.
          • Notre Dame holds a Class B license (129.74.X.Y)
          • All Class B networks are currently assigned and in use. (lie)!
  • 15. Network Protocols (TCP/IP)
    • Internet Protocol (IPv4)
        • Class C Networks - The first byte in the range of 192 - 223.
          • The first four bits of the address are 1 1 0 X
          • There are 2,097,152 Class C networks.
          • The first three bytes of a class C address is the network number.
          • The remaining byte is the host address on that network.
          • 210.43.2 .8
          • network host address
          • Each Class C network can address up to 254 hosts.
          • Most of the Class C networks are assigned and in use.
  • 16. Network Protocols (TCP/IP)
    • Internet Protocol (IPv4)
        • Class D Networks - The first byte in the range of 224 - 239.
          • The first four bits of the address are 1 1 1 0
          • These addresses are used for “one to many” communications (multicasting).
        • Class E Networks - The first byte in the range of 240 - 254.
          • The first four bits of the address are 1 1 1 1
          • These addresses are reserved for experimental use by the IANA/IETF.
  • 17. Network Protocols (TCP/IP)
    • The numbers 0, and 255 have special meaning in some fields of IP addresses.
      • A Zero host address refers to “this network”
        • For example 129.74.0.0 refers to the Class B network 129.74.
      • A host address of all ones is called the broadcast address.
        • For example 129.74.255.255 refers to all hosts on the 129.74 Class B network.
    • The address 127.0.0.1 is the loopback address.
      • This address is used for inter-process communications, and for network testing.
      • All of the 127 network is reserved (127.0.0.0 - 127.255.255.255).
  • 18. Network Protocols (TCP/IP)
    • Subnets and Supernets
      • Subnets provide a way of chopping up large networks into smaller entities:
      • Networks might be split up to segment traffic.
      • Networks might be split up to facilitate better use of an assigned IP address space.
        • A class A could be made to look like several class B/C networks.
        • A class B could be made to look like several Class C networks.
        • Even a Class C network can be sub-networked.
      • To subnet a network, we apply a netmask.
        • Standard netmask for Class A is 255.0.0.0
        • Standard netmask for Class B is 255.255.0.0
        • Standard netmask for Class C is 255.255.255.0
      • By logically ANDING the address and the netmask, we can determine the NETWORK portion of the address.
  • 19. Network Protocols (TCP/IP)
    • Subnets
    • Network routers look at the destination IP address, and the netmask for the address to make delivery (routing) decisions.
      • Once the router determines the class of the destination address, it consults a table to find the appropriate netmask.
        • Class A netmask is 255.0.0.0
        • Class B netmask is 255.255.0.0
        • Class C netmask is 255.255.255.0
    • For example, a packet bound from a random host on the Internet, to my office host would generate the following operation:
      • 129.74.25.98 = 10000001 . 01001010 . 00011001 . 01100010
      • 255.255.0.0 = 11111111 . 11111111 . 00000000 . 00000000
    10000001 . 01001010 . 00000000 . 00000000 == 129.74.0.0 or 129.74/16
  • 20. Network Protocols (TCP/IP)
    • The lab 129.74.46 network is subnetted into several smaller networks.
      • By “stealing” bits from the host number, we can make the network number larger. This allows us to make a class B or C network look like many smaller (classless) networks.
        • These networks are denoted by the formula N.S.H (network.subnet.host)
      • By using a 27 bit netmask we can divide a network up into several “32” host networks. 11111111 . 11111111 . 11111111 . 11100000
        • 27 bits of network address, 5 bits of host address.
          • 129.74.46.0 through 129.74.46.31 is one such network.
          • 129.74.46.32 through 129.74.46.63 is one such network.
          • 129.74.46.64 through 129.74.46.95 is one such network.
        • 129.74.46.32/27 denotes a host on a classless network which employs a 27 bit netmask.
        • This is referred to as Classless InterDomain Routing (CIDR)
  • 21. Network Protocols (TCP/IP)
    • Subnets and Supernets
      • Supernets allow us to aggregate several smaller networks into one larger routing entity:
        • This is the opposite of subnetting.
          • Supernetting is employed to minimize routing table entries.
            • If an ISP has a customer who needs addresses for 400 hosts, a single class C address will not suffice.
            • By combining two class C networks, the ISP can make a single routing entity:
            • 203.14.7.0 = 11001011 00001110 00000111 00000000
            • 203.14.6.0 = 11001011 00001110 00000110 00000000
            • The first 23 bits are the same for both addresses so the ISP can advertise a single external route:
            • 203.14.6/23
            • This only works if the ISP also owns 203.14.4.0 and 203.14.5.0.
  • 22. Network Protocols (TCP/IP)
    • Classless Inter Domain Routing (CIDR)
      • CIDR is the result of incorporating subnetting and supernetting into the classful IP address structure.
        • We are no longer limited to class A, B, and C addresses.
        • By passing the netmask along with the address we can make arbitrarily large/small networks, as we see fit, to simplify routing and network design.
      • CIDR allows simplified routing tables.
      • CIDR is the basis of IPv6.
      • You may also hear the term Variable Length Subnet Mask (VLSM).
        • This is the practice of using various length subnet masks within a single network domain.
  • 23. Network Protocols (TCP/IP)
    • Internet Protocol (IPv4 trivia)
      • We are running out of addresses under the current (IPv4) addressing scheme.
      • If every class A, Class B, and Class C network address was in use using classful addresses, there would be ((127 * 16,000,000) + (16384 * 65,000) + (2,097,152 * 254)) (or 3,629,636,608) hosts on the Internet. (3.6 gigahosts)
        • The remainder of the addresses are the “zero”, and “broadcast hosts (overhead).
        • If subnetworking is in use, even more of the address space is lost to “overhead”.
      • Real Soon Now a new version of IP will be released. This version is known as IPV6 (Internet Protocol version 6).
  • 24. Network Protocols (TCP/IP)
    • IPv6
      • Addresses go from 32 bit to 128 bit.
      • Addresses will be colon separated hexadecimal quads:
        • 0xFEDC:BA98:7654:3210:0123:4567:89AB:CDEF
        • 0x0000:0000:0000:0000:0000:FFFF:222.33.44.55
          • Shorthand ::FFFF:222.33.44.55
      • IPv6 will not contain address classes – but prefix ranges will have meaning (geographic regions).
      • IPv6 will use multicasts instead of broadcasting.
      • IPv6 will use CIDR routing
      • IPv6 will facilitate data encryption
      • IPv6 contains provisions for new services (bandwidth reservation, guaranteed signal quality, more multicasting)
      • IPv6 will provide 340 undecillion addresses
        • 340 with 24 zero’s after it
  • 25. Network Protocols (TCP/IP)
    • Internet Protocol (packet delivery)
      • The Internet protocol actually uses multiple layers of addressing to deliver packets.
        • Protocol addressed packet delivery is referred to as ISO Layer 3 (Network layer) routing.
        • In addition to the IP address, each network adapter card is assigned a unique hardware address (Media Access Controller or MAC address).
        • Ethernet MAC addresses are 6 bytes long.
        • MAC addresses of other network technologies vary from 2 bytes to 20 bytes in length.
      • The mapping between the MAC address and the IP address is handled at the Link Layer of the TCP/IP stack by the Address Resolution Protocol ( ARP ).
  • 26. Network Protocols (TCP/IP)
    • Address Resolution Protocol
      • By design, the network interface (the board in the host) wants to communicate with another network interface board.
        • Network interface boards work with multiple protocols.
        • This means that they must have a way of addressing other NICs that is independent of the software protocol address.
        • All packets on the media are addressed to another MAC address.
      • If the packet is bound for a host not known to the local host what happens?
        • One way to resolve such a MAC address is for the host to send out a broadcast packet saying “Hi, I’m at MAC address x:y:z:a:b:c, how do I get to MAC address f:g:h:i:j:k?”.
          • If the host with address f:g:h:i:j:k is on the same network, it will reply and the address is resolved.
  • 27. Network Protocols (TCP/IP)
    • Otherwise an intermediate can be programmed to reply “send the packet to me, and I will forward it for you.”
      • In this case the packet is sent from the host’s MAC address to the MAC address of the intermediate!
        • source addr = host MAC,
        • destination addr = intermediate MAC
      • The intermediate then forwards the packet on the way to the final destination.
        • source addr = intermediate MAC,
        • destination addr = next hop MAC
      • The host software maintains a table (the ARP cache) of these MAC addresses.
    • This is ISO layer 2 (Data Link Layer) routing (switching)
  • 28. Network Protocols (TCP/IP)
  • 29. Network Protocols (TCP/IP)
    • Internet Protocol (packet addressing)
      • IP addresses identify machines.
        • This allows us to get a datagram from one host to another.
          • How do we deliver data to programs and services on these hosts?
        • The TCP and UDP protocols extend the IP addressing concept through the use of “ ports ”.
          • A port is a two byte number that identifies a particular service.
          • These port numbers are mapped to services through the /etc/services file.
          • Ports with numbers less than 1024 are called privileged ports.
            • These ports are (supposed to be) only accessible by root, in an attempt to prevent impostors.
  • 30.  
  • 31. Network Protocols (TCP/IP)
    • Internet Protocol (packet addressing)
      • Because humans have a difficult time dealing with all of these numbers (MAC address / IP address / Port number), the computers/services are also allowed symbolic names.
      • Computers do not understand these names…the computer wants to work with numbers.
        • The names are mapped to numbers by a variety of means.
          • The most commons means of mapping system names to IP addresses are the /etc/hosts file, Network Information Services (NIS), and the Domain Name Service (DNS).
          • I will talk more about how these name services work in a few days.
  • 32. Other Protocols
    • NetBEUI
      • Net Bios Extended User Interface
        • An extension of NetBIOS.
        • Not a routable protocol, as it has no network layer.
        • Can have bridged networks, but not routers.
        • Relies on broadcasts for many functions.
        • Connection Oriented - Connectionless communications
        • Self configuration - self tuning
        • Error protection
        • Small memory overhead
        • Active Directory cannot use NetBEUI.
  • 33. Other Protocols
    • NetBIOS over TCP/IP (NBT)
      • Replaces NetBEUI, allows applications to use TCP/IP
    • Winsock
      • Interface between socket based applications and TCP/IP.
    • Server Message Block (SMB) networking.
      • Used in previous versions of Windows.
      • Basis for Windows file and print sharing.
      • Uses NetBEUI - not routable.
      • Relies on Windows Internet Naming Services (WINS).
      • Being replaced by Common Internet File Service (CIFS).
        • TCP/IP based networking for Windows!
        • Both SMB and WINS are unpublished protocols.
          • Can change on a whim!
  • 34. Other Protocols
    • AppleTalk
      • Originally developed by Apple as a printer sharing protocol.
      • Later expanded to allow more complete network services.
      • Very little administration required.
        • Hardware address is used, no IP address required.
        • Plug in a new machine, and it works!
          • The new node sends a broadcast packet that says “Hi!, I’m Joe. I want to use address X. Does anyone object?”
          • If there is no objection, Joe is now at address X.
          • If there is an objection, the node with the lowest address sends back a message stating “Hello Joe. I’m sorry, but you will have to use Y as your address, as X is already in use.”
      • Routers are very complex.
      • Works with a variety of hardware and media.
        • Twisted pair, coaxial cable, Ethernet, PC’s UNIX hosts.
  • 35. Other Protocols
    • EtherTalk
      • Actually AppleTalk over Ethernet.
      • Two flavors are available:
        • Phase 1 was Apple’s first Ethernet network. It was very buggy, and tended to flood the network with broadcast packets. Phase 1 also had it’s own packet types which were not known by TCP/IP.
        • Phase 2 changed the broadcast packets to Multicast packets, and encapsulated their odd packets as acceptable packets.
  • 36. Other Protocols
    • LocalTalk
      • Is actually Apple’s AppleTalk protocol implemented on twisted pair cabling.
        • AppleTalk was originally implemented with an odd coaxial cable.
      • Network speed reaches a blazing 230 Kilobits/second!
      • LocalTalk allows star topology with active or passive hubs and multiple hosts on a leg.
      • Ethernet to LocalTalk bridges are very common.
      • MacIP is used to encapsulate Ethernet packets in LocalTalk packets.
  • 37. Other Protocols
    • AppleTalk
      • AppleTalk addressing uses a multi-layer address system like IP.
      • The MAC address is hardware based.
      • The Node number is dynamically assigned by AppleTalk Address Resolution Protocol (AARP).
      • AppleTalk networks are grouped into zones.
      • Each AppleTalk entity has an object name (Billy Bob’s Office Printer), an object type (LaserWriter) as well as the zone name.
      • The zone entities are bound to network and node numbers by the AppleTalk Name Binding Protocol (ANBP).
  • 38. Other Protocols
    • IPX
      • IPX is the Internet Packet Exchange Protocol.
      • IPX was developed by Novell for the NetWare product. Novell is the most common network protocol in use for PC’s.
      • Novell is in the process of converting the Novell Network to use TCP/IP protocol.
      • Current IPX implementations use standard Ethernet packet headers.
      • Older versions of IPX used non-standard Ethernet packet headers, and would not co-exist on a network with non-IPX Ethernet packets.
  • 39. Other Protocols
    • IPX
      • IPX was derived from The Xerox Network System Internet Datagram Protocol (XNS IDP).
      • IPX uses a UDP like packet type. Headers have an unused checksum field, a packet length, packet type, a hop count, and the network, node, and socket numbers of the source and destination machines.
      • IPX packets are thrown away after 15 hops!
      • IPX is not a standardized protocol! It is a proprietary protocol and is subject to frequent unannounced changes.
      • Novell Loadable Modules (NLM’s) are available to add functionality to Novell IPX based networks.
  • 40. Other Protocols
    • IPX
        • The IPX protocol has many “helper” protocols:
          • Routing Information Protocol (RIP)
          • Sequenced Packet Exchanger : reliable delivery (SPX)
          • ECHO (a packet echo facility)
          • ERRORS (an error reporting facility)
          • Packet Exchange Protocol (PEP)
            • VERY inefficient, as it requires an ACK for each packet before the next packet is sent!
            • On top of PEP are the Network Core Products which provide authentication, file service, RPC, print spooling, accounting).
          • Service Advertisement Protocol (SAP) (address broker)
  • 41. Other Protocols
    • DECnet
      • DECnet is an implementation of the Digital Network Architecture (DNA)
      • DECnet first appeared in 1974. The first version to support Ethernet was DECnet phase IV released in 1984.
      • DECnet Phase V was released in 1991 and is referred to as DECnet/OSI. It supports TCP/IP, OSI, and Digital’s Network Services Protocol (NSP).
  • 42. Other Protocols
    • DECnet
      • DECnet Addressing is somewhat different from the other protocols:
      • DECnet addresses are independent of the transport media.
      • A DECnet address is a one byte “area” and a two-byte node number.
        • An area is a logical grouping.
          • One area may equate to one or more networks.
          • One network may contain one or more areas.
        • The machine’s address is derived from the area and node number, not the hardware MAC address.
        • All interfaces on the system use the same address!
  • 43. Other Protocols
      • DECnet
        • Until DECnet Phase V all routing tables were static.
        • Static routing limited DECnet to small network configurations.
      • DECnet Phase V implemented dynamic routing via DECdns which is actually a distributed routing protocol.
        • The routing is performed by DECnet routers.
        • A level one router routes information within one area.
        • A level two router routes information between two areas.
  • 44. Protocol Translators
    • As you may have guessed by now, there are ways to make systems running these “other” protocols talk to a TCP/IP network.
      • Some of these protocols include TCP/IP modules.
      • Other protocols use a trick called “tunneling” to allow them to “talk on” TCP/IP networks. Tunneling is a form of packet encapsulation.
        • In order for tunneling to work, the source and destination machines have to be on the same type of network.
          • There may be one (or many) other types of networks between these two hosts and their networks.
      • Another method of interconnecting dissimilar networks requires special hardware/software which acts as a translator (bridges).
  • 45.  
  • 46. Network Hardware
    • Working With Current Network Hardware
      • So far all we’ve talked about is the software side of networking.
        • We saw that there are many different protocols in use on current communications networks.
      • There is also a hardware component to networking.
        • Unfortunately, there are almost as many hardware standards as there are protocols.
        • We will talk about four types of network hardware:
          • Ethernet
          • Token Ring
          • FDDI (token ring in disguise)
          • ATM
  • 47. Network Hardware
    • Working With Current Network Hardware
        • Network hardware has to take proximity into account.
          • Local Area Networks (LANs) consist of machines in close proximity to each other. Example: Notre Dame campus, or networking within a small company building.
            • LANs typically employ high speed technologies ( 1Mb - 10 Gb / second throughput).
          • Metropolitan Area Networks (MANs) - consist of machines within a metropolitan area. Notre Dame could also be considered a Metropolitan Area Network.
            • MANs typically operate at lower speeds (56 Kb - 622 Mb / second throughput).
  • 48. Network Hardware
    • Working With Current Network Hardware
          • Wide Area Networks (WANs) consist of machines separated by large distances. Example the Internet.
            • WANs typically operate at rates of 56 Kb to 622 Mb / second throughput.
        • The type of hardware selected for a network must be capable of working within the boundaries of the particular network.
  • 49. Network Hardware
    • Working With Current Network Hardware
      • Ethernet - developed by Xerox in the 1970’s.
        • Still has bugs !
        • Ethernet is the most common network technology.
        • Ethernet employs Carrier Sense Multiple Access with Collision Detect to determine who gets to talk at any given time.
        • Ethernet does not include built-in error detection/correction. That is left to the software!
        • Most of the protocols we discussed run on Ethernet hardware.
        • Ethernet is a LAN technology that the users wanted (desperately) to become a WAN technology.
  • 50. Network Hardware
    • Working With Current Network Hardware
        • There are many flavors of Ethernet available:
          • 802.5 - Thicknet - 10Base-5 - Screaming Yellow 50 Ohm Coaxial cable.
            • Attachment Unit Interface (AUI) connectors (DB15).
            • This is the oldest form of Ethernet.
            • Length Limit 500 Meters / segment.
            • Up to three segments connected via repeaters.
            • 10 Mb/s shared bandwidth
  • 51.  
  • 52. Network Hardware
    • Working With Current Network Hardware
          • 802.2 - Thinnet - 10Base-2 - cheapernet,
            • Cheap coaxial cable
            • cheap BNC style connectors.
            • length limit: 200 Meters/segment.
            • Up to two segments connected via repeater.
            • Multiport repeaters allowed.
            • 10 Mb/s shared bandwidth
  • 53.  
  • 54. Network Hardware
    • Working With Current Network Hardware
        • 10Broad36 - Broadband Ethernet.
          • Not used very often
          • EXPENSIVE
          • Multiplex Ethernet packets onto a broadband carrier system.
          • 36 Kilometer length limit
          • Cable modems use similar technology.
  • 55.  
  • 56. Network Hardware
    • Working With Current Network Hardware
        • 10BaseF - Fiber based Ethernet .
          • Two fibers required (one for transmit, one for receive)
          • Optical to copper repeaters handle the collision detection.
          • Typical segments 2.2 Km maximum.
          • Multiple segments may be connected via repeaters
          • Two repeaters/route maximum
          • 10 Mb/s shared bandwidth
  • 57.  
  • 58. Network Hardware
    • Working With Current Network Hardware
        • 10 BaseT - Twisted pair Ethernet
          • Category 4 or Category 5 twisted pair wiring, or fiber.
          • Star topology - all hosts connect to hubs/routers/switches.
          • Length limit: 100 meters per connection, 500 meters between the two most distant hosts (if shared bandwidth).
          • Cheap RJ45 connectors (telco style)
          • 10 Mb/s shared or switched bandwidth
            • Switched connections allow full 10Mb/s to the host instead of shared bandwidth.
            • Connections can be “full duplex”
  • 59. Network Hardware
    • Working With Current Network Hardware
        • 100BaseT - Twisted pair Ethernet
          • Category 4 or category 5 twisted pair wiring, or fiber.
          • Star topology - all hosts connect to hubs/routers/switches.
          • Length limit: 100 meters per connection
          • Cheap RJ45 connectors (telco style)
          • 100 Mb/s switched bandwidth
            • Switched connections allow full 100Mb/s to the host instead of shared bandwidth. Half, or Full Duplex connections.
  • 60.  
  • 61. Network Hardware
    • Working With Current Network Hardware
      • Token Ring Networks
        • Token Rings utilize a special data structure called a token to determine who gets to talk.
        • Token Rings are typically built on a copper based media.
        • Token Rings are very common on PC systems, but not found very often on UNIX systems (with the exception of FDDI/CDDI).
        • Token Ring systems have two modes of operation: receive and transmit.
        • Typical Token Rings run at 1, 4, 10, or 16 Mbit/second.
  • 62.  
  • 63. Network Hardware
    • Working With Current Network Hardware
      • Fiber Distributed Data Interconnect (FDDI)
        • FDDI is a token ring in disguise.
        • FDDI uses fiber optical cabling instead of copper. Copper Distributed Data Interconnect (CDDI) is FDDI over copper.
        • FDDI is capable of 100 Mbit/second data rates.
        • Single Attachment Stations (SAS) require a pair of fibers and have little fault tolerance.
          • SAS FDDI networks are star-topology networks.
        • Dual Attachment Stations (DAS) provide for fault tolerance and require two pairs of fibers.
          • DAS FDDI networks are ring topology networks.
  • 64.  
  • 65.  
  • 66. Network Hardware
    • Working With Current Network Hardware
      • Automatic Teller Machines (ATM)
        • ATM networks have been in use for many years by the banking industry.
        • Users put a card in a slot and can magically get money out of the ATM machine.
      • OOPS. Sorry. Wrong ATM!
  • 67. Network Hardware
    • ATM is part of a larger network:
      • SONET (Synchronous Optical Network) is used for (extremely) high speed connections between telephone switches.
        • Current Telco operations can handle 100 Gigabit/second over SONET.
        • Test frames currently running at 350+ Gb/second!
      • Computer network hardware is available which allows you to use SONET connections between systems.
      • SONET is VERY expensive!
  • 68. Network Hardware
    • Working With Current Network Hardware
      • Asynchronous Transfer Mode (ATM)
        • The basic foundations for ATM were developed by people who know about wide area networks and packet switching: Long Distance Telephone carriers.
        • ATM is the underlying technology behind the Broadband Integrated Services Digital Network (B-ISDN).
          • B-ISDN is part of the “send a fax from the beach, tuck your kids into bed from around the world” technology.
        • ATM is currently running with 622Mbit/second links.
          • High-end Internet links are running at 155 Mbit/second.
          • NOTE: Most hosts cannot drive such links at speeds over 350 Mbit/second.
  • 69. Network Hardware
    • Working With Current Network Hardware
        • ATM comes in a variety of speeds. For example:
          • 25 Mbit/second IBM standard
          • 45 Mbit/second Digital Service-3 (DS3) (T-3)
          • 51 Mbit/second SONET(OC-1)
          • 100 Mbit/second Taxi interface
          • 155 Mbit/second Optical Carrier-3 (OC-3)
          • 622 Mbit/second Optical Carrier-12 (OC-12)
          • 1.2 Gbit/second Optical Carrier-24 (OC-24)
          • 2.4 Gbit/second Optical Carrier-48 (OC-48)
        • Speeds are based on Telco transmission rates.
  • 70. Network Hardware
    • Working With Current Network Hardware
      • ATM encompasses the Integrated Services Digital Network (ISDN),
        • ISDN is used for (relatively) high speed connections to homes and businesses. A typical ISDN connection is actually a multiple-channel connection over telephone wire.
          • ISDN uses two B channels, and a D channel.
          • The B channels are 64 Kb/second data channels.
          • The D channel is a 9.6 Kb/second signaling channel.
          • Current technology allows you to “bond” the two B channels together and use 4x data compression to get throughput up to 512 Kb/second.
  • 71. Network Hardware
    • Working With Current Network Hardware
      • xDSL technology (new) is similar to ISDN.
        • ADSL (Asymmetric Digital Subscriber Loop) has one channel running at high speed, and one running at low speed (for example 512Kb/sec one direction, and 128 Kb/sec the other direction).
        • ADSL has been tested at rates up to 1.544 Mbit/second (same speed as a T1 link).
        • ADSL runs over standard telco wiring (ISDN and DSL require some tweaks to run over telco infrastructure).
  • 72. Network Hardware
    • Working With Current Network Hardware
      • Because ATM is a telephone protocol, it has some odd “features” when used for data networking.
        • ATM is a connection oriented service. No packets can be sent until a channel is opened.
          • Ethernet/FDDI/Token Rings are all “ connectionless ”.
          • IP is also connectionless.
        • ATM sends/receives fixed length data cells, as opposed to the other technologies we discussed which send/receive variable length packets.
          • Ethernet exchanges 64 - 1500 byte packets
          • FDDI exchanges 64 - 4500 byte packets
          • ATM exchanges 53 byte “cells”
            • Each cell has a 5 byte header and 48 data bytes.
  • 73. Network Hardware
    • Working With Current Network Hardware
      • ATM
        • Fun with International Standards:
          • The European telephone industry wanted ATM to use 16 byte cells for voice traffic, but would compromise up to 32 bytes.
          • The United States telephone industry wanted 128 byte cells for data, but would compromise down to 64 bytes.
          • The CCITT split the difference, and ATM cells were defined to be 48 bytes.
            • Because headers were already defined as no more that 10% of the cell, headers became 5 bytes.
  • 74. Network Hardware
      • ATM
        • Result :
          • The ATM cell size is a poor choice for voice (packets are too big; bandwidth is wasted)
          • The ATM cell size is a poor choice for data (packets are too small; bandwidth is wasted with excessive overhead).
          • Welcome to the fascinating world of International Standards!
  • 75. Summary
    • Configuration, management, and troubleshooting network connections is a major portion of any system administrator’s job. The system administrator needs to:
    • Understand basic network terminology.
    • Understand the basics of the TCP/IP protocol suite.
    • Understand the basics of IP addresses.
    • Understand basic IP routing.
      • Understand the basics of ARP, and DNS.
      • Understand the basics of layer 2 and layer 3 “routing”.
    • Understand common network hardware.