606 – TCP/IP for Networking Professionals

Author: Maureen Fitzgerald Maureen.Fitzgerald@us.origin-it.com

Obj #		Objective Text
1	Identify the layers of the DoD model and how they relate to the TCP/IP stack. Process Application = Acts as the interface for the user. Provides applications that transfer data between hosts. OSI Model - Application/Presentation/Session TCP/IP Suite – -Telnet = terminal emulation -FTP (File Transfer Protocol) and TFTP (Trivial File Transfer Protocol = file transfer -NFS (Network File System) = file sharing -Xwindows = application sharing -SMTP (Simple mail Transfer Protocol) = electronic mail -LPD (Local Print Daemon) and RPR (Remote Printing)=printing -SNMP (Simple Network Management Protocol=network mgmt Host-To-Host = TCP only: Maintains data integrity and sets up reliable, end-to-end communication between hosts. Ensures error-free delivery of data units in proper sequence and with no loss or duplication. OSI Model – Transport Layer TCP/IP Suite – -TCP (Transmission Control Protocol)= establishes a virtual circuit, provides a reliable connection, and sends packets that are sequenced and acknowledged. (like a telephone conversation) -UDP (User Datagram Protocol)= connectionless/unreliable, but less overhead Is used by any protocol that uses broadcasts. (like sending a letter) Internet = Routes data packets between difference hosts or networks. The Internet Layer is the foundation of the TCP/IP protocol suite. OSI Model - Network Layer TCP/IP Suite – IP = (Internet Protocol) handles packet routing, fragmentation, and reassembly between hosts. ICMP = (Internet Control Message Protocol) used to send error and control messages to hosts and routers. BOOTP = (used by workstations to discover 3 items: 1. their IP address 2. the IP address of the server 3. the name of a file loaded into memory that is executed at ARP = (Address Resolution Protocol) = translates a software address to a hardware (MAC) address RARP = (Remote Adddress Protocol) = used by diskless Workstations to translate their hardware (MAC) address to A software address. Network Access = defines physical interconnection between hosts. OSI Model - DataLink/Physical Layers TCP/IP Suite – Ethernet, Token Ring, FDDI, and Others
1 (cont) 2	The TCP/IP Protocol Suite specifies functions above the Network Access Layer of the DOD Model and above the DataLink Layer of the OSI Model. TCP (Transmission Control Protocol) = responsible for establishing communication between 2 hosts. IP (Internet Protocol) = responsible for the transfer of data. ------------------------------------------------------------------------------------------------------------------------ Describe TCP/IP addressing concepts. 32-bit Internet address value 4-bytes long identifies IP network and node 1^st byte determines class each host must have a unique host number each byte of a node address falls in the range of 0 to 255 0 and 255 are usually not used in addressing (reserved for broadcasting packets) 8-bits in an octet use Windows calculator on desktop to convert binary number to decimal
3	List TCP/IP addressing classes and characteristics. Class A = 0 – 127 first byte Network last 3 bytes Host first bit must be zero up to 12 classes created each having 16+Million hosts. Class B = 128 – 191 first 2 bytes Network last 2 bytes Host first 2 bits of first byte are 1 and 0. Possible 16,384 class B networks each having up to 65,584 hosts. Class C = 192 – 223 first three bytes Network last byte Host First 3 bits of first byte are 1, 1, and 0. Possible 2+Million class C networks each having up to 255 hosts. Class D = 224 – 239 (MultiCast) First 4 bits of first byte are 1, 1, 1, and 0. Use for multicast packets Multicast packets are used by a host to transmit messages to a specific group of hosts on network Packets exchanged between routers only Class E = 240 – 255 (Reserved for Experimental or Broadcast First 5 bits of byte are 1, 1, 1, 1, and 0. Reserved for experimental use and potential future addressing modem Class E addresses typically used for broadcasts.
4	Define TCP/IP addressing types. Unicast Includes addresses that allow for communication between one source sending data and one source receiving it. The single interface, is specified by the destination address. Communication between any 2 hosts in the shared network doesn’t affect any of the other hosts. Multicast Includes addresses that refer to a group of hosts by using a single IP address; identified by Ipv4 class D addresses. Simply, a subnet of the PCs on a network agree to listen to a given multicast address. Every PC in this multicast group can be reached with a single packet transmission. Broadcast Includes messages that are transmitted to every host on the network. 255.255.255.255 used to identify a broadcast message. the message is directed to all hosts on the network from which it originated. routers do not typically forward broadcast messages to other networks. Anycast similar to multicast; references a group of systems. Transmits data by finding the closest member of a group and sends messages only to that member. Only available with Ipv6.
5	Identify the purpose of subnets. Subnet Masking – process of creating subnets on the network. All hosts and networks must have a unique address. Subnet Mask – is an extension of the IP addressing scheme that allows a site to use a single network address for multiple physical networks. Purpose of subnets: To expand the network – by adding routers and creating subnets To reduce congestion – by splitting single network into smaller, separate subnets reducing bandwidth problems and number of hosts. To reduce CPU use – more hosts on network causes more broadcasts on network. Each host must listen to every broadcast before accepting or discarding it. Uses CPU capabilities. To isolate network problems – by splitting larger networks into smaller networks, limit the impact of one subnet’s problems on another. To improve security – by restricting sensitive network traffic to only one network, other users on other subnets can be prevented from accessing secure data. Subnets also ensure that network structure is never visible outside organization’s private network. To use multiple media – allows you to combine different media by putting each type of media on a different subnet.
6	Determine an appropriate subnet mask. A subnet mask is a 4-byte number that is logically “ANDed” with an IP address to identify the network and host address of a host. TCP/IP requires that all IP addresses be assigned a subnet mask even if the network is not segmented into subnets. Any bit that is part of the network address is assigned a value of “1” in the mask. Any bit that is part of the host address is assigned a value of “0” in the mask. Subnet mask is defined using part of the host portion of the IP address. The host portion used depends on the class of the network address you were assigned.
7	Choose a subnet address given a subnet mask. The subnet mask depends on how many bits you choose to use for subnet addressing
8	Demonstrate the ability to use subnet masks to divide a network. Classful Hierarchy – the standard IP address conforms to a standard number of bits for the network address and host address for each type of class. Classless Hierarchy – when you add a subnet address to the IP address, the host address is divided into a subnet address and a host address. The number of bits used by the subnet address and the host address can vary. Assigning Subnet Addresses After the subnet value has been assigned to a network, you must assign IP addresses to each device using the following rules: Each address must be unique The network and subnet numbers must be the same for all devices on the same network The host (physical) portion of the address must not be set to all 1’s or all 0’s/ When you create subnet addresses, you need to Plan for growth Avoid using IP addresses reserved for special use To prepare for possible changes in the number of subnets required, RFC 1219 suggests that you assign subnet addresses from the left-most bit of the subnet address field, and that you assign hosts in numeric order from the right-most bit of the host address field. To create a subnet, you must Determine the number of subnets you need When you are deciding how many subnets your network needs, you must take into account future network growth. Determine your subnet mask and subnet addresses To assign subnet mask and address values, complete the following: 1) determine the number of available subnet address values and the number of available host address values per subnet. 2) calculate the subnet address values: identify the rightmost [1] bit in the subnet mask and convert its binary value to decimal. The number you obtain is referred to as ‘delta’. Assign IP addresses to each host on the subnet
9	Define supernetting and identify the number of hosts available on a network that uses supernetting. Developed in 1993 to extend the lifetime of a 32-bit IP address Working with Ipv6, a new version of IP with larger addresses. To accommodate growth until Ipv6 is standardized and adopted, supernetting used as a temporary solution. Opposite of subnet addressing; (instead of using a single IP network address for multiple physical networks in an organization, it uses many IP network address for a single organization). Number of bits used for the subnet mask is “reduced” to increase the number of available hosts. Number of hosts available on a Class C Network – 510
10	Describe the TCP/IP communication process. Connection-oriented Reliable communications 2 hosts using TCP must establish a TCP connection with each other before they can exchange data 1) server’s OS delivers the raw data to TCP in a byte stream. 2) If data stream too large for lower-layer protocols, TCP divided the stream into segments, adds sequence numbers, and passes each segment to IP. 3) IF forms IP datagrams by adding source and destination logical addresses to each segment. 4) Through ARP, the physical address of the destination or next immediate device is determined and passed, with the IP datagrams, to the DataLink Layer. 5) Based upon the DataLink Layer chosen, several other steps are performed until the DataLink frames reach the client device. When an internetwork is involved, several additional IP encodings and decodings occur with each hop to determine the next IP address in the route. 6) The client DataLink Layer receives the frames and passes its data to the client IP. 7) The client IP discards the IP header and passes the IP datagrams to the client TCP. 8) TCP acknowledges receipt if each datagram. 9) TCP combines the datagrams into one continuous byte stream by examining the sequence numbers and reordering the segments. 10) The service requester’s application receives the same byte stream that was submitted by the server’s OS, as if it were directly connected.
11	Compare and contrast the IPv4 and IPv6 protocols. IPv4= established late 1960’s Defines a 32-bit address Decreasing ability to route traffic between an increasing number of networks and the Internet Is a 20-byte header and has 12 required fields and 1 optional field IPv6= being developed and implemented to resolve the short comings of IPv4 Designed to address the current growth trends affecting TCP/IP-based networks. Is one solution that will be deployed to deal with issues of addressing and routing. Benefits: Expanded routing and addressing capabilities Header format simplification Improve support for options Quality-of-service capabilities Authentication and privacy capabilities Is a 40-byte (fixed) header and has 8 fields of information Interoperate Similar language Embedded address communication Allow checksum Migration Strategies from IPv4 to IPv6: Dual Stack – have both loaded/bound to NIC boards. Communicates regardless of which stack being used. Tunneling – Encapsulate IPv6 datagram inside IPv4 datagrams. Allows IPv6 to cross over IPv4 network segments. Header Translation – Software on routers connecting both network segments, strips headers, replace with one appropriate for network segment entering. 2 Types of IPv6 addresses can be embedded: IPv4-compatible = understand IPv6 IPv4-mapped = do not understand IPv6
12	Describe utilizing private network addresses to overcome the IPv4 address shortage. 10-Netting = using private network address to overcome shortages Approach Addresses reserved for private networks are filtered out by Internet routers and do not conflict with registered addresses. Private Address Blocks Class A = 10.0.0.0 ßà 10.255.255.255 Class B = 172.16.0.0 ßà 172.31.255.255 Class C = 192.168.0.0 ßà 192.168.255.255 Implement 10-netting by assigning hosts on the private, internal part of network IP address and placing a router between the private internal network and the public network (Internet). Private interface on router assigned address from private network Public interface on router assigned registered IP address. Router runs network address translation (NAT) software, which translates addresses when packets pass through from private to public network. Advantages If the 10.0.0.0 range selected, private network can have entire Class A network address. Only 1 registered IP address is required for entire private network Security is increased because entire private network appears to have only 1 IP address on the public network.
13	Identify the role of TCP/IP ports. IP Port number assigned to a service running on an IP host number used to link incoming data to correct service Divided into 3 Ranges: Well-Known Ports = 0 - 1023 Registered Ports = 1024 – 49151 Dynamic or Private Ports = 49152 – 65535 Well-Known Ports are standard port numbers used by everyone. Assigned by the IANA (internet Assigned Numbers Authority) and on most systems can only be used by system processes or by programs executed by privileged users. See chart, page 1-40 for Well-Known Port number assignments.
14	List sources of TCP/IP information. RFCs Request for Comments Series of technical reports about the Internet Discuss different aspects of computing, including new and revised protocols, standards, procedures and programs. Defined documents of the Internet protocol suite (standards) by the IETF. ARIN American Registry for Internet Numbers Non-profit organization created to manage IP address space for assigned territories Similar to RIPE and APNIC, pleased management of IP space under user control (ISPs, corporate entities, colleges, and individuals) APNIC Asia-Pacific Network Information Center 1 of 3 regional Internet Registries (IRs) of the IANA Serves the Asia-Pacific area Allocates Internet resources, including IP addresses, autonomous systems (AS) numbers, and domain delegations ICANN Internet Corporation for Assigned Names and Numbers Supercedes the IANA Has authority over all number spaces used in Internet Allocates parts of the Internet address space to 3 regional IRs. Responsible for managing Internet address, domain names, and protocol parameters IETF Internet Engineering Task Force Group dedicated to identifying problems on and proposing technical solutions for the Internet InterNIC Internet Network Information Center 1 of 3 regional IRs of the IANA serves North America and handles Internet domain name registration managed by Network Solutions, Inc. (NSI) RIPE NCC Reseaux IP Europeans Network Coordination Center Is 1 of 3 regional IRs of IANA Handles internet domain name registration for Europe.
15	Identify the purpose of the Internet Protocol (IP). Used in packet-switched networks (CATENET) Transmits blocks of data, called datagrams, from sources to destinations. Sources and destinations are hosts identified by fixed-length addresses. Can also fragment and reassemble long datagrams, if necessary, for transmission through small-packet networks Does not provide end-to-end data reliability, flow control, sequencing, or other services commonly found in host-to-host protocols. Relies on the services of its supporting networks to provide various types and qualities of services.
16	Identify the fields that compose the IP header and the function of each. Version – indicates the format of the IP header IHL – (Internet Header Length) indicates the length of the IP in 32-bit words, and thus points to the beginning of data. The minimum value for a correct header is 5. Type of Service – specifies the treatment of the datagram during its transmission through the Internet system. Total Length – length of datagram measured in octets, including Internet Header and data. This field allows the length of a datagram to be up to 65,535 octets (whether they arrive whole or in fragments.) Identification –an identifying value assigned by the sender to aid in assembling the fragments of a datagram. Flags –identifies the amount a packet is fragmented. Fragments Offset – indicates where in the datagram this fragment belongs. Time To Live (TTL) – indicates the maximum time the datagram can remain in the Internet system. Protocol – indicates the next-level protocol used in the data portion of the IP datagram. Header Checksum –displays a checksum of the header only. Source Address –displays the source address of the datagram. Destination Address –displays the destination address of the datagram. Options –displays options that might appear in datagrams. Padding –used to ensure that the Internet header ends on a 32-bit boundary. the padding is zero. IP provides 2 basic functions: Addressing Fragmentation IP sees the addresses carried in the header to transmit datagrams to their destination. IP uses fields in the header to fragment and reassemble Internet datagrams for transmission through small-packet networks. 4 Key features in providing its services: Type of Service Indicates the quality of the service wanted. Type of service provides a generalized set of parameters that characterize the service choices provided in the network that make up the Internet Time To Live Indicates an upper boundary on the lifetime of an Internet datagram It is set by the sender of the datagram and reduced at the points along the route where it is processed Can be thought of as a self-destruct time limit. Options Provides control functions that might be useful in some situations but that are unnecessary for the most common communication Options include functions for time stamps security, and special routing. Header Checksum Verifies that the information used in processing the Internet datagram has been transmitted correctly.
17	Identify the purpose of Transmission Control Protocol (TCP). Highly reliable Host-to-Host protocol in packet-switched networks and internetworks Provides process-to-process communications in multi-network environments Interacts between user or application processes and a lower-level protocol such as IP. Provides a set of calls for manipulating data. Can also communicate with application programs asynchronously. Designed to work in a very general environment of interconnected networks
18	Identify the purpose of User Datagram Protocol (UDP). Provides a datagram mode of packet-switching in an internetwork Assumes that IP is used as the underlying protocol Allows application programs to send messages to other programs with a minimum of protocol mechanism. Is transaction oriented; duplicate and delivery protection are not guaranteed. Offers a minimal transport service-non-guaranteed datagram delivery—and gives applications direct access to the datagram service of the IP layer. The only services UDP provides over IP are check summing of data and multiplexing by port number. Does not maintain end-t-end connection with the remove UDP module; it only pushes the datagram out on the network and accepts incoming datagrams off the network. Used by application that do not require level of service provided by TCP or applications that want to use communications services (such as multicast or broadcast delivery) not available from TCP. NFS (Network File System) and SNMP (Simple Network Management Protocol) use UDP. The service is little more than an interface to IP. Cannot provide: Retransmission for reliably delivery Packetization and reassembly Flow control Congestion avoidance 1 of 2 main protocols that resides on top of IP
19	Identify the purpose of Internet Control Message Protocol (ICMP) and the types of ICMP messages. Although layered on IP, ICMP is a control protocol that is an integral part of IP. Provides error reporting, congestion reporting, and first-hop gateway redirection ICMP messages are grouped into 2 classes: Error messages Destination unreachable Redirect Source quench Time exceeded Parameter problem Query messages Echo Information Time stamp Address mask If an ICMP message of unknown type is received, it is silently discarded.
20