Hands-on Networking Fundamentals
Chapter 3 Using Network Communication Protocols
Objectives
• Explain network protocols, including IPX/SPX, NetBEUI, AppleTalk, and TCP/IP • Discuss how IP addressing works • Understand the promise of IPv6 • Explain and use application protocols in the TCP/IP suite • Compare TCP/IP to the OSI model • Discuss WAN protocols used for remote communications • Understand how to design a network to use TCP/IP and application protocols
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– Protocols enable effortless interchange – Nodes must use the same protocol to communicate – Protocols provide basic services, for TCP/IP to work (i.e. DNS, DHCP) – LAN can have more than 1 protocols • Routers translate from protocol to another protocol • Example: Linux/Windows TCP/IP. AppleTalk for Macintosh computer • Pro: Communication between separate systems • Con: volume of network traffic increases; additional maintenance
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Properties of a LAN Protocol
• Enable reliable network links • Communicate at relatively high speeds • Handle source and destination node addressing (MAC, IP, Port) • Follow standards IEEE 802 standards • Protocols have different strengths and drawbacks
– Example 1: some (not all) protocols are routable – Example 2: some protocols have poor error checking
• Protocols typically used on LANs
– IPX/SPX, NetBEUI, AppleTalk, and TCP/IP – TCP/IP is the protocol of choice for computes today
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Legacy Protocols
• IPX/SPX
– Developed by Novell for NetWare operating system – Modeled after Xerox Network System (XNS) protocol – Considered a Chatty protocol
• • • • •
IPX is equivalent to the IP protocol in functionality SPX is equivalent to the TCP protocol in functionality IPX/SPX used on NetWare servers through version 4 TCP/IP used for NetWare 5.x above New NetWare versions can still implement IPX/SPX
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Legacy Protocols NetBEUI
• NetBEUI (NetBIOS Extended User Interface)
– Developed for LAN Manager and LAN Server – Predates Windows NT
• NetBEUI used in early versions of Windows NT • NetBEUI not supported in Windows XP or Windows Server 2003 (or higher) • Disadvantages of NetBEUI
– Cannot be routed – Causes unnecessary traffic
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AppleTalk • peer-to-peer network protocol for Macintosh – Windows Server 2003 and Novell use AppleTalk • Enables communication with Mac computers – AppleTalk Phase II • Handles more networked computers than Phase I • Interoperable with heterogeneous networks hosting multiple protocols
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– Modern network devices use the OSI model to implement a “network stack” •Each Layer provides a “piece” that is needed so a node can communicate on the network •Application Layer – client / redirector provided by operating system, IP Address of DNS Server (can be provided via DHCP Protocol) • Network layer protocol – IP Address, Subnet Mask, Default Router or Gateway (In most cases provided via DHCP Protocol) • Data Link – NIC Card Wired or Wireless Driver •Physical Layer – Patch Chords Access Point
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Basic IP Addressing
• • • • • • • Four fields or Octets– 10.1.2.3 Octet is 8 bits 8*4 = 32 bits for addressing Part of address is network ID, part is host ID Five IP address classes A,B,C,D,E Each node must have a unique IP address Router is requited to communicate to different subnet Three types of transmission
– Unicast: packet sent to each requesting client – Multicast: packet sent to group of requesting clients – Broadcast: communication sent to all network nodes
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Ip address: 10.1.1.1 (dotted decimal notation) Binary: 00001010.00000001.00000001.00000001 Subnet Mask: 255.0.0.0 Binary: 11111111.00000000.00000000.00000000 Binary total of 32 bits, 8 bits per octect
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Subnet Mask / Default Router
• Default Router who to send the packet to if the node does not know a path / route to the destination • Default Router not required, if not specified: no routing • Subnet mask – Divide networks into sub networks or logical networks – Identify Network / Host portion of IP address
• Example of a subnet mask:
– 11111111.00000000.00000000.00000000 (255.0.0.0) – Ones represent network/subnet identification bits – Zeroes represent host identification bits
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Creating Subnetworks
• Default mask(s) for Class based IP Addressing: – Class A 255.0.0.0, Class B 255.255.0.0, Class C 255.255.255.0 • Subnet Identified by 1's, Host identified by 0's • Ex: 11111111.11111111.11111111.00000000 255 . 255 . 255 .0 |---------------- Subnet--------------|.|---Host--| • Classless Interdomain Routing (CIDR) addressing (A,B,C ignored) – Puts a slash ( / ) after the dotted decimal notation • Number after slash represents “1” bits in network ID – Example (decimal): 165.100.18.44/18 • 18 bits needed for network ID, 14 for host ID (32 -18)
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IP Address Rules
• Loopback 127.0.0.0 cannot be assigned • Certain IP network numbers reserved as private (10.0.0.0/8, 192.168.0.0/16, 172.16.0.0/12) RFC 1918 • Private addresses used on internal net usually with NAT • Network number cannot be assigned (i.e. 206.10.1.0 / 255.255.255.0) • Highest number on a network cannot be assigned
– Example: cannot assign 198.92.4.255 Broadcast
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The Promise of IPv6
• IPv6 developed through IETF initiative • IPv6 overcomes limitations of IPv4 • Five prominent features of IPv6
– – – – – 128-bit address capability Single address associated with multiple interfaces Address autoconfiguration and CIDR addressing 40-byte header instead of IPv4’s 20-byte header New IP extension headers for special needs
• Includes more routing and security options
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The Promise of IPv6 (continued)
• Three IPv6 packet types: unicast, anycast, multicast • DES (Data Encryption Standard)
– Network symmetric-key encryption standard
• IPv6 supports DES compatible encryption techniques • Benefits of IPv6 encryption capability
– Security over Internet – Security over other types of LANs and WANs
• Disadvantage of IPv6 encryption capability
– Increases latency of network communications
• Latency: travel time from sending node to receiving node
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The History and Role of TCP/IP
• Advanced Research Projects Agency (ARPA)
– Networking goal: enable university, research, and Defense Department to communicate
• ARPANET WAN: prototype for modern networks • An early protocol: Network Control Protocol (NCP)
– Enabled DEC, IBM, and other hosts to communicate – Did not provide wholly reliable communication
• TCP/IP combination: an improvement over NCP
– TCP (Transmission Control Protocol) – IP (Internet Protocol)
• TCP/IP has become the main protocol suite
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The History and Role of TCP/IP (continued)
• Five advantages of TCP/IP
– – – – Used worldwide on most networks and the Internet Influences design of wide range of network devices Main protocol of most computer operating systems Subject to many troubleshooting and network analysis tools – Understood by large body of network professionals
• TCP/IP associated with a suite of protocols and applications • Associations enable TCP/IP to underlie vast range of communications capabilities
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TCP/IP and the OSI reference model
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Basic IP Functions • packet addressing • packet routing • Path discovery • Fragmentation • detection of errors • Change packet size, type (i.e. Ethernet, DSL, Wireless) – Datagram: TCP segment formatted with IP header – IP packet header consists of thirteen fields
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How TCP Works
• • • • • TCP is a transport protocol (Layer 4 in OSI model) Establishes / tear down sessions connection oriented, guaranteed delivery Sequences and acknowledges frames Sequence number placed in TCP frame header
– Shows frame sequence in stream of frames – Indicates amount of data in frames
• TCP Ports: Virtual Circuit, Enable Multiple process • Sliding window: number of bytes before acknowledge
– May be dynamically adjusted if two nodes agree
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User Datagram Protocol (UDP)
• Connectionless protocol • Operates at OSI Layer 4 (like TCP) • Alternative to TCP when high reliability not required Frame has four-field header and data Relies only checksum to ensure reliability Connectionless protocol • No flow control, sequencing, or acknowledgement Advantages: adds little overhead onto IP • Used with transaction processing applications • Carries important network status messages
– – – –
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TCP/IP Application Protocols
• Useful protocols and applications in TCP/IP suite
– Telnet – Secure Shell (SSH) – FileTransfer Protocol (FTP), Trivial FileTransfer Protocol (TFTP), and Network File System (NFS) – Simple Mail Transfer Protocol (SMTP) – Domain Name System (DNS) – Dynamic Host Configuration Protocol (DHCP) – Address Resolution Protocol (ARP) – Simple Network Management Protocol (SNMP) – Hypertext Transfer Protocol (HTTP), Secure Hypertext Transfer Protocol (S-HTTP), HTTP Secure (HTTPS)
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Telnet / SSH
• • • • • Application protocol for terminal emulation Allow access to resources at a remote host Used for remote access (i.e. Router, switch config) Connect to older mainframe / mini that use terminals Hyperterminal Windows Telnet application
• SSH – Authentication security for TCP/IP on Unix/Linux and MAC OS X • Used for remote access, upload/download of files • Under linux man ssh for more information
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File Transfer Protocol (FTP), Trivial File Transfer Protocol (TFTP), and Network File System (NFS)
• FTP: allows transfer of data between remote devices
– Transmissions may be binary or ASCII formatted files – Transmissions ensured by connection-oriented service
• Designed to transfer “the whole enchilada” only • TFTP: intended for transfer of small files
– Use for non-critical and non-secure transmissions – Connectionless protocol running UDP instead of TCP
• NFS: Sun Microsystem's alternative to FTP
– Uses connection-oriented protocol running in TCP
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Simple Mail Transfer Protocol (SMTP)
• Designed for exchange of electronic mail • Two implementations
– For e-mail exchange between networked systems – In local e-mail systems for Internet transport
• Provides alternative to FTP for file transfer
– Limited to sending text files; Binaries via encoding to text – Requires e-mail address on receiving end – Does not require logon ID and password
• Two part message: address header and message text • Supported in TCP by connection-oriented service
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Domain Name System (DNS)
• Domain: logical grouping of network resources • Domains given unique names; e.g., Microsoft.com • DNS resolves domain names
– Resolution: converts host / domain name to IP address
• Internet host domain names have two to three parts
– – – – Top-level domain name (TLD): organization or country Optional subdomain name: university/business name Host name: name of computer Example: myname@myorganization.com
• ICANN coordinates and registers root domain names
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Domain Name System (DNS) (continued)
• Namespace: logical area with list of named objects • Zones: partitions in DNS server with resource records
– Forward lookup zone links computer name to IP address – Reverse lookup zone links IP address to computer name
• Three servers related to DNS
– Primary DNS server: authoritative server for zone – Secondary DNS server: backup servers – Root servers: find TLDs on the Internet
• Two DNS standards
– Service resource record (SRV RR) – DNS dynamic update protocol
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Dynamic Host Configuration Protocol (DHCP)
• Enables automatic assignment of IP address • Process of assigning address by DHCP server
– – – – Newly configured computer contacts DHCP server DHCP server leases an IP address to new computer Lease length set on DHCP server by network admin Server or host may be given lease that does not expire
• IP address will never change with permanent lease
• OSI – Application Layer
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Address Resolution Protocol (ARP)
• Enables sender to retrieve MAC address • Process of obtaining MAC address
– Sending node sends ARP broadcast frame
• Frame has MAC address, IP address of recipient
– Receiving node sends back its MAC address
• Reverse Address Resolution Protocol (RARP)
– Used by network node to determine its IP address – Used by applications to determine IP address of workstation or server
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Simple Network Management Protocol (SNMP)
• Enables steady monitoring of network activity • Advantages
– Operates independently on the network – Management functions carried out on special node – Has low memory overhead
• Node types: network management station (NMS) and network agents • SNMPv2 offers better security, error handling, multiprotocol support, transmissions • SNMP and SNMPv2 monitor LANs and WANS
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HTTP, S-HTTP, and HTTPS
• Hypertext Transfer Protocol (HTTP)
– Enables establishment of a Web connection – Provides for exchange of resources
• Example: displaying Web page in browser
• Secure Hypertext Transfer Protocol (S-HTTP)
– Used primarily in native HTTP communications – Does not encrypt data in IP-level communications
• Hypertext Transfer Protocol Secure (HTTPS)
– Uses Secure Sockets Layer to implement security – More common than S-HTTP
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LAN Protocols Over WANs
• WAN protocols enable transport from LANs to WANs • Accomplished via encapsulation or changing framing • Encapsulate TCP/IP packet place an envelope transmitted removed from envelope at destination • Serial Line Internet Protocol (SLIP),Compress Line Internet Protocol (CSLIP) – Dial up protocols, no authentication • PPP – Point-to-Point PPTP – more protocols, Authentication (PAP) and encryption (CHAP) • PPTP – Point to point tunnelling protocol i.e. Vpn • L2TP – Layer Two Tunneling Protocol – used vpns, forward based on mac address • Hands-on Networking for cellular, lata and ixc communication SS7 – Telco Fundamentals 35
Designing A Network To Use TCP/IP And Application Protocols
• Scenario: network personnel in medical office on DSL
– Workstations and servers configured for TCP/IP
• Automatic (DHCP-based) IP addressing used
– DHCP used to lease IP addresses to workstations
• All servers given permanent IP addresses
– SNMP used in certain nodes for network monitoring – WAN comunication set up to use PPPoe for Internet over DSL – Workstations set up to use FTP/HTTP through router / firewalls – E-mail system configured to employ SMTP – Primary DNS server and secondary DNS server set up
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Putting it all together
• PC is turned
– Using IP DHCP request sent out – DHCP uses ARP to ensure IP address is free
• PC receives an IP address • User wants to surf to www.yahoo.com - IP / HTTP
– IP / DNS obtain IP address for www.yahoo.com – IP / ARP mac address of next hop / nic card
• Request sent to yahoo via routers ... IP, ICMP • Web Page data is sent to PC from yahoo (IP, TCP,HTTP)
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Summary
• • • • • • • • • • Protocols are the language of networks IPX/SPX and NetBEUI used on older networks AppleTalk used by Macintosh systems ARPANET WAN was a network prototype TCP establishes links and ensures reliability IP enables data transfer, routing and packet addressing TCP/IP suite universal used on networks and Internet UDP used with IP in certain non-critical situations Dotted decimal notation address: IP address format Five IP address classes (A through E)
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Summary (continued)
• IP enables data transfer and routing with packet addressing • TCP/IP combination universal used on networks and Internet • UDP used with IP in certain non-critical situations • Dotted decimal notation address: IP address format • Five IP address classes (A through E) • Networks subdivided using subnet mask or CIDR • IPv6 is newest version of IP • TCP/IP maps with layers of OSI model • Supported by TCP/IP : Telnet, SSH, FTP, SMTP, DNS, DHCP, ARP, SNMP, and HTTP • Basic WAN protocols: SLIP, PPP, PPTP, L2TP
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