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Computer Networking (TCP/IP networking model) (IPv4 Addressing and Routing…

- - - - How to send?
        
        Enterprise LANs Full Duplex Half Duplex
        
        For example
        
        PC1
        
        Switch 1 Crossover cable
        
        Switch n
        
        2 more items...
        
        Printer or other device
        
        Device....
        
        Hub
        
        Destination
        
        SOHO LANs Full Duplex Half Duplex
        
        For example
        
        PC1
        
        Switch
        
        PC2
        
        Device
        
        Hub
        
        Device
      - How to transmit?
        
        Using Twisted paid: RJ45 connectors
        
        Types #
        
        Crossover cable:
        
        for device, which transmit on same Pin pair
        
        How does it work?
        
        Transmit on Pins 3,6 and receive on Pins 1,2 (Speed no more than 100Mbps)
        
        Transmit on Pins 3, 6, 4, 5 and receive on Pins 1, 2, 7, 8
        
        Straight-through cable:
        
        for device, which transmit on different Pin pair
        
        How does it work?
        
        Transmit on Pins 1, 2, 4, 5 and receive on Pins 3, 6, 7, 8
        
        Transmit on Pins 1,2 and receive on Pins 3,6 (Speed no more than 100Mbps)
        
        Choosing the Right Cable Pinouts # #
        
        Transmit on Pins 1,2
        
        PC NICs (Network Interface Controler)
        
        Routers
        
        Wireless access point (Ethernet interface)
        
        Transmit in Pins 3,6
        
        Hubs
        
        Switch
        
        Types
        
        Informal IEEE Standard name: 100BASE-T
        
        Formal IEEE Standard name: 802.3u
        
        1 more item...
        
        Informal IEEE Standard name: 1000BASE-LX
        
        Formal IEEE Standard name: 802.3z
        
        1 more item...
        
        Informal IEEE Standard name: 10BASE-T
        
        Formal IEEE Standard name: 802.3
        
        1 more item...
        
        Informal IEEE Standard name: 1000BASE-T
        
        Formal IEEE Standard name: 802.3ab
        
        1 more item...
        
        Informal IEEE Standard name: 10GBASE-T
        
        Formal IEEE Standard name: 802.3an
        
        1 more item...
    - - Size: 6 bytes long (48 bits long) #
        
        Structure of Unicast Ethernet Addresses
        
        Vendor Assigned (NIC Cards, Interface): 24 Bits = 6 Hex Digits
        
        Organizationally (OUI): 24 Bits = 6 Hex Digits
      - Types?
        
        Broadcast address
        
        Frame sent to this address should be delivered to all devices on the Ethernet LAN. It has a value of FFFF.FFFF.FFFF.
        
        Multicast address
        
        Frame sent to a multicast Ethernet address will be copied and forwarded to a subset of the devices on the LAN that volunteers to the revice frames sent to a specific multicast address
    - - Format
        
        Preamble
        
        Start Frame delimiter (SFD)
        
        Destination MAC address
        
        Source MAC Address
        
        Type
        
        1 more item...
        
        Header # # # # #
        
        Data and Pad #
        
        Trailer #
      - Bytes:
        
        7 #
        
        1 #
        
        6 #
        
        6 #
        
        2 #
        
        1 more item...
  - - - LAN Switching concepts
        
        Overview of Switching logic
        
        LAN switches receive Ethernet frames and then make a switching decision: either forward the frame out some other ports or ignore the frame
        
        To accomplish this primary mission, switches perform three actions
        
        Prepairing to forward frames by learning MAC addresses by examining the source MAC address of each received by the switch.
        
        Preparing to forward one copy of the frame to the destination by creating a (Layer 2) loop-free environment with other switches by using Spanning Tree Protocol (STP)
        
        Spanning Tree Protocol (STP) A protocol that uses the Spanning Tree algorithm, allowing a switch to dynamically work around loops in a network topology by creating a spanning tree. Switches exchange bridge protocol data unit (BPDU) messages with other switches to detect loops and then remove the loops by blocking selected switch interfaces.
        
        Deciding when to forward a frame or when to filter (not forward) a frame, based on the destination MAC address.
        
        The LAN switch has one primary job: to forward frames to the correct destination (MAC) address.
        
        Forwarding Known Unicast Frames
  - - - Analyzing Collision Domains and Broadcast Domain
        
        Ethernet Collision Domain: A set of network interfaces cards (NIC) for which a frame sent by one NIC could result in a collision with a frame sent by any other NIC in the same collision domain
        
        Router, Switch and Bridge create Collision Domain
        
        Bridges sat between hubs and divided the network in to multiple collision domains.
        
        Bridges increase the capacity os the entire Ethernet, because each collision domain is basically a separate instance of CSMA/CD, so each collision domain can have one sender at a time.
        
        Hub operation causing a collision. Hubs do not place each interface in to separate collision domain.
        
        The term collision domain does not apply to WAN interfaces
        
        A modern LAN, with all LAN switches and routers, with full duplex on each link, would not have collisions at all.
        
        Broadcast Domain: A set of all devices thet receive broadcast frames originating from any device within the set. Devices in the same VLAN are in the same broadcast domain.
        
        Routers separate a network in to separate broadcast domain
        
        Vitual LANs (VLANs) by definition are broadcast domains created though configuration
        #
      - Analyzing LAN physical Standar Choices
        
        Choosing the right Ethernet standar for each link
        
        The maximum distance allowed between devices when using that standard/cabling
        
        The cost of the cabling and switch hardware
        
        The speed
        
        The availability of that type of cabling already installed at your facilities.
        
        Wireless LANs combined with wired ethernet
        
        Home Office Wireless LANs
        
        Enterprise Wireless LANs and Wireless LAN controllers
        
        Wireless LAN controller: Controls and manages all AP functions
        
        Light weight AP (LWAP): Forwards data between the wired and wireless LAN, and specifically forwarding data through the WLC using a protocol like Control And Provisioning of Wireless Access Point (CAPWAP)
      - Analyzing Campus LAN Topology
        
        The Term Campus LAN refer to the LAN created to support the devices in a buiding or in multiple buildings in somewhat close proximity to one another.
        
        Two-Tier Campus Design (Collapsed Core)
        
        2 Layer
        
        Distribution Layer
        
        Distribution switches provide a path through which the access switches can forward traffic to each other. Note that most designs use at least two uplinks to two different distribution switches for redundancy.
        
        Access Layer
        
        Access switches connect directly to end users, providing user device access to the LAN
        
        Topology Terminology Seen Within a Two-Tier Design
        
        Full mesh
        
        Partial mesh
        
        Star
        
        Hybrid
        
        Three-Tier Campus Design (Core)
        
        3 Layer
        
        Core
        
        Distribution
        
        Access
        
        Topology Design Terminology
        
        Star
        
        Uplinks: Partial mesh
    - - Vitual LAN Concept
        
        Creating multiswitch VLANs Using Trunking
        
        VLAN trunking causes the switches to a process called VLAN tagging, by which the sending switch adds another header to the frame before sending it over the trunk
        
        VLAN tagging concepts
        
        The 802.1Q and ISL VLAN trunking protocol
        
        Inter-Switch Link (ISL)
        
        IEEE 802.1Q
        
        802.1Q Trunking
        
        format
        
        2 more items...
        
        12 bit VLAN ID
        
        range of VLAN ID: 1-4094
        
        2 more items...
        
        Forwarding Data Between VLANs
        
        Routing packets between VLANs with a router
        
        Router and switch in difference device
        
        Routing packets between VLANs with layer 3 switch
        
        Layer 2 switching with layer 3 routing in one device
        
        Device called Multilayer Switch
      - VLAN and VLAN trunking configuration and verification
        
        do not use VLAN trunking
        
        Creating VLANs and Assigning Access VLANs to an Interface
        
        2 step
        
        Use VLAN trunking
    - - Perspective on applying troublleshooting methodologies
        
        3 Step
        
        Step 2: Resolve or escalate
        
        Step 3: Verify or monitor
        
        Step1: Problem isolation and documentation
      - Analyzing Switch Interface status and statics
        
        Interface Status Codes and Reasons for Nonworking States
        
        having bad cable is just one of many reasons for the down/down state
        
        The cable could be damaged
        
        Although optical cables do not suffer from electromagetic interference (EMI), someone can try to be helpful and move a fiber-optic cable out of the way - bending it too much
        
        The installation of any equipment that uses electricity, ever non-IT equipment, can interfere with the reansmission on the cabling, and make the link fail.
        
        interface speed and duplex issues
        
        Common Layer 1 problems on working interfaces
        
        Input errors: A total of many counters, including runts, giants, no buffer, CRC, frame, overrun, and ignored counts.
        
        CRC: Received frames that did not pass the FCS math; can be caused by collisions.
        
        Late Collisions: The subnet of all collisions that happen after the 64th byte of the frame has been transmitted.
        
        Frame: Received frames that have an illtegal format.
        
        Giants: Frames that exceed the maximum frame size requirement (1518 bytes, includeing the 18-byte dextination MAC, source MAC, and FCS).
        
        Output Errors: Total number of packets (frames) that the switch port tried to transmit, but for which some problem occurred.
        
        Runts: frames that did not meet the minimum frame size requirement (64 bytes, including the 18-byte destination MAC, source MAC, type and FCS). Can be caused by by collisions.
        
        Packets Output: Total number of packets (frames) forwarded out the interface.
        
        Collisions: Counter of all collisions that occur when the interfaces is transmitting a frame.
      - Predicting where switch will forward frames
        
        Predicting the contents of thw MAC address table
        
        Analyzing the forwarding path
        
        2 Steps
        
        Step 2. Make a forwarding decision. Look for the frame's destination MAC address in the MAC address table, but only for entries in the VLAN identified in Step 1. If the destination MAC is.....
        
        Found (unicast), forward the frame out the only interface listed in the matched address table entry
        
        Not Found (unicast), flood the frame out all other access ports (except the incoming port) in that same VLAN, plus out trunks that have not restricted the VLAN from that trunk .
        
        Broadcast, flood the frame, with the same rules as the previous step
        
        Step 1: Process functions on the incoming interface, if the interface is currently in an up/up (connected) state, as follows
        
        A. If configured, apply port security logic to filter that frame as approprivate
        
        B. If the port is an access port, determine the interface's access VLAN
        
        C. If the port is a trunk, determine the frame's tagged VLAN
    - - 3 basic features
        
        Limit with specific MAC addresses cen send and receive frames on a switch interface, discarding frame to/from other MAC addresses
        
        Limit the number of MAC addresses using the interface, discarding frame to/from MAC addresses learned after the maximum limit is reached
        
        A combination of the previous two points
- - - - When the device has an IP address and the appropriate software and hard ware, it can send and receive IP packets. Any device that has ai least one interface with an IP address can send and receive IP packets and is called an IP host
      - a 32-bit number
        
        Each byte (8 bits) of the 32-bit IP address is shown as its decimal equivelent. # #
        
        For example
        
        168.1.1.1 #
        
        10101000 00000001 00000001 00000001
      - written in dotted-decimal natation (DDN)
        
        dotted-decimal notation (DDN): The format used for IPv4 addresses, in which four decimal values are used, separated by periods (dots).
        
        Each DDN has for decimal octets
    - - Rules
        
        IP addresses separate from each other by a router must be in different groups
        
        All IP address in the same group must not be separated from each other by a router
      - each LAN and WAN link will use either an IP network or IP subnet
        
        IP subnet: Subdivisions of a Class A, B, or C network, as configured by a network administrator. Subnets allow a single Class A, B, or C network to be used instead of multiple networks, and still allow for a large number of group of IP addresses, as is required for efficient IP routing.
        
        classful IP network: An IPv4 Class A, B, or C network; called a classful network because these networks are defined by the class rules for IPv4 addressing.
    - - IP defines network layer addresses that identify any host os router interface that connect to a TCP/IP network. The idea basically works like a postal address
      - TCP/IP group IP addresses together so that IP addresses used on the same physical network are part of the same group. IP calls these address groups an IP network or an IP subnet # #
      - IP defines specific rules about which IP address should be in the same IP network or IP subnet. Numerically, the address in the same group have the same value in the first part of the addressing
    - - Class A, B, and C define unicast IP addresses
        
        unicast IP address: An IP address that represents a single interface. In IPv4, these addresses come from the Class A, B, and C ranges.
      - Division of the Entire IPv4 Address Space by Class (Figure 4-6)
        
        Class B #
        
        128-191
        
        Unicast #
        
        Number of Networks: 16 384
        
        Hosts per Network: 65 534
        
        Class C #
        
        192-223
        
        Unicast #
        
        Number of Network: 2 097 152
        
        Host per Network: 254
        
        Reserverd
        
        127
        
        Class D
        
        224-239
        
        Multicast
        
        Class A #
        
        1-126
        
        Unicast #
        
        Number of Networks: 126
        
        Hosts per Network: 16 777 214
        
        Class E
        
        240-255
        
        Reverved (For eexperimental)
        
        Reserved
        
        0
      - The Actual Class A, B, and C IP Networks
        
        Class B
        
        First Octet Range
        
        128 to 191
        
        Valid Network Numbers
        
        128.0.0.0 to 191.255.0.0
        
        Class C
        
        Valid Network Numbers
        
        192.0.0.0 to 223.255.255.0.0
        
        First Octet Range
        
        192 to 223
        
        Class A
        
        First Octet Range
        
        1 to 126
        
        Valid Network Numbers
        
        1.0.0.0 to 126.0.0.0
  - - - Host Forwarding Logic: Send the Packet to the Default Router
        
        (Router) R1 and R2's Logic: Routing Data Across the Network
        
        R3's Logic: Delivering Data to the End Destination
      - PC1: Destination is in Another Group; Send to Nearby Router #
        
        My router says: Send to R2 #
        
        My router says: Send to R3 #
        
        My router says: Send directly to PC2 #
      - PC1 #
        #
        
        Router R1 # #
        
        Router R2 # # #
        
        Router R3 # #
        
        PC2
        
        R3 uses almost the same logic as R1 and R2. But R3 needs to forward the packet directly to PC2, not to some other router.
        
        All router use the same general process to route the packet. Each router keep an IP routing table. This table list IP address groupings, called IP networks and IP subnet. When a router receives a packet, it compares the packet's destination IP address to the entries in the routing table and makes a match. This matching entry also lists directions that tell the router where to forward the packet next.
        The routing concept works a little like driving down the free way approaching a big interchange. The Router look at the IP routing table and direct each packet over the correct next LAN or WAN link.
        
        To send the IP packet to the default Router, the sender sends a data-link frame across the medium to the nearby Router; this frame include the packet in the data portion of the frame. That frame uses data link layer (Layer 2) addressing in the data-link header to ensure that the nearby router receivers the frame
    - - PC1: Encapsulate IP Packet in Ethernet #
        
        Extract IP Packet and Encapsulate in HDLC #
        
        Extract IP Packet and Encapsulate in Ethernet #
        
        Extract IP Packet and Encapsulate in New Ethernet #
      - Format
        
        | Eth | IP Packet | Eth |
        
        | HDLC| IP Packet | HDLC |
        
        | Eth | IP Packet | Eth |
        
        | Eth | IP Packet | Eth |
      - Routing as covered so far has two main concepts:
        
        The process of routing forward Layer 3 packets, also call Layer 3 protocol data units (L3 PDU), based on the destination Layer 3 address in the packet.
        
        The routing process uses the data link layer to encapsulate the Layer 3 packets in to Layer 2 frames for transmission across each successive data link.
      - Because the routers build the new data-link headers and trailer, and because the new header contain data-link address, the PCs and routers must have some way to decide that what data-link address to use
  - - - 2 Step:
        
        Step 1: If the destination IP address is in the same IP subnet as I am, send the packet directly to that destination host.
        
        Step 2: Otherwise, send to the packet to my default gateway, also known as a default router. (This router ha an interface on the same subnet as the host.
      - For example
        
        PC1: 150.9.1.10 2 1
        
        Switch
        
        Default router: 150.9.1.1 2
        
        Router B1 2
        
        Switch
        
        1 more item...
        
        PC11: 150.9.1.11
    - - When such a frame arrives, the router uses the following logic on the data-link frame:...
        
        Step 1: Use the data-link Frame Check Sequence (FCS) Field to ensure that the frame had no errors; If errors occurred, discard the frame.
        
        Step 2: Assuming that the frame was not discarded at step 1, discard the old data-link header and trailer, leaving thr IP packet.
        
        Step 3: Compare the IP packet's destination IP address to the routing table, and find the route that best matches the destination address. This route identifies the outgoing interface of the router, and possibly the next-hop router IP address
        
        Step 4: Encapsulate the IP packet inside a new data-link header and trailer, appropriate for the outgoing interface, and forward the frame.
  - - - To dynamically learn and fill the routing table with a route to
        each subnet in the internetwork
      - If more than one route to a subnet is avaiable, to place the best route in the routing table
      - To notice when routers in the table are no longer valid, and to remove them from the routing table
      - If a route is removed from the routing table and another route through another neighboring router is avaiable, to add the route to the routing table. (Many people view this goal and the preceding one as a single goal.)
      - To work quickly when adding new routes or replacing lost routes. (The time between losing the route and finding a working replacement route is called convergence time,)
      - To prevent routing loops
    - - Step 1: Each router, independent of the routing protocol, adds a route to its routing table for each subnet directly connected to the router.
        
        Step 2: Each router's routing protocol tells its neighbors about the routes in its routing table, include the directly connected router and routes learned from other routers.
        
        Step 3: After learning a new route from a neighbor, the router's routing protocol adds a route to its IP routing table, with the next-hop router of that route typically being the neighbor from which the route was learned.
  - - - An application layer protocol used throughout the Internet for translating host names into their associated IP addresses
      - Using Names and the Domain Name System
        
        Basic DNS Name Resolution Request
        
        PC11 IP address of sever 1?
        
        DNS Sever Sever 1 = 10.1.2.6
        
        PC11 IP
        
        Server 1: 10.1.2.6
    - - An Internet protocol used to map an IP address to a MAC address. Defined in RFC 826
      - The Address Resolution Protocol
        
        TCP/IP defines the ARP as the method by which ant host or router on a LAN can dynamically learn the MAC address of another IP host or router on the same LAN.
        
        ARP defines a protocol that includes the ARP Request, which is a message that asks tho simple request "If this is your address, please reply your MAC address".
        
        ARP also defines the ARP Reply message, which indeed lists both the original IP address and the matching MAC address
        
        Note that host remember the ARP results, keeping the information in their ARP cache or ARP table. A host or router only needs to use ARP occasionally, to build the ARP cache the first time. Each time a host or router needs to send a packet encapsulated in a Ethernet frame, it first checks its ARP cache for the correct IP address and matching MAC address. Hosts and routers will let ARP cache entries time out to clesn up the table, so occasional ARP Request can be seen.
    - - An Internet Control Message Protocol (ICMP) echo message and its reply; ping often is used in IP networks to test the reachability of a network device
      - ICMP Echo and the ping Command
- - - - TCP and UDP
        Some feature
        
        What different? #
        
        TCP provicdes a wide variety of service too applications, whereas UDP doesn't
        
        TCP provides retransmission (error recovery) and helps to avoid congrestion (flow control), whereas UDP doesn't
        
        By providing fewer services, UDP needs fewer bytes in its header compared to TCP, resulting in fewer bytes of overhead in the network
        
        UDP software doesn't slowdown data transfer in cases where TCP can purposefully slow down
        
        Also, some application, notably to day Voice over IP (VoIP) and video over IP, don't need error recovery, so they use UDP, So, UDP also has an importanr place in TCP/IP network today.
        
        Transmission Control Protocol mechanisms at the endpoint computers
        
        Each TCP/IP application typically chooses to use either TCP or UDP based on the application's requirements.
        
        TCP Header Fields (figure 5-1)
        
        .
        
        Sequence Number
        
        .
        
        .
        
        .
        
        Acknowledgement Number
        
        2 more items...
        
        .
        
        2 more items...
        
        .
        
        Window
        
        Flag Bits
        
        1 more item...
        
        .
        
        Urgent
        
        Checksum
        
        1 more item...
        
        .
        
        4 Bytes
        
        .
        
        1 more item...
        
        The message create by TCP that begins with the TCP header, followed by any application data. is called a TCP segment. Alternatively, the more generic term Layer 4 PDU, or L4PDU, can also be used
        
        User Datagram Protocol (UDP)
        
        UDP header (figure 5-10)
        
        .
        
        4 Bytes
        
        .
        
        .
        
        1 more item...
        
        Destination Port
        
        Source Port
        
        .
        
        .
        
        .
        
        Checksum
        
        Lenght
        
        1 more item...
        
        UDP does so with fewer bytes of overhead and less processing required than TCP.
      - TCP/IP transport Layer Features
        (Only Multiplexing using port is supported by UDP, whereas all are supported by TCP)
        
        3.
        
        Flow control using windowing:
        
        Description: Process that uses window sizes to protect buffer space and routing devices from being overloaded with traffic.
        
        The window concept lets the receiving host tell the sender how much data it can receive right now, giving the receiving host a way to make the sending host slow down or speed up.
        
        Sliding window: For protocols such as TCP that allow the receiving device to dictate the amount of data the sender can send before receiving an acknowledgment—a concept called a window—a reference to the fact that the mechanism to grant future windows is typically just a number that grows upward slowly after each acknowledgment, sliding upward.
        
        dynamic window
        
        Connection establishment and termination: Process used to initialize port numbers and Sequence and Acknowledgment fields.
        
        2.
        
        Error recovery (reliability):
        
        Description: Process of numbering and acknowledging data with Sequence and Acknowledgment header fields
        
        To acomplish reliability, TCP numbers data bytes using the Sequence and Acknowledgment fields in the TCP header. TCP achieves raliability in both directons, using the Sequence Number field of one direction combined with the Acknowledgment field in the opposite direction.
        
        For examble:....
        
        Ordered data transfer and data segmentation: Continuous stream of bytes from an upper-layer process that is "segmented" for transmission and delivered to uppper-layer processes at the receiving device, with the bytes in the same oder.
        
        1.
        
        Multiplexing using ports:
        
        TCP and UDP both use a concept called multiplexing
        
        TCP and UDP solve this problem by using a port number field in the TCP or UDP header, respectively. Each of TCP and UDP segment ues a different destination port number so that user knows which application to give the data. #
        
        For examble
        
        PC1
        
        1 more item...
        
        Description: Funtion that allows receiving hosts to choose the correct appliication for which data is destined, based on the port number
        
        Multiplexing by TCP and UDP involves the process of how computer thinks when receiving data. TCP and UDP multiplexing tells the receiving computer to which application to gi the received data
        
        Multiplexing relies on a concept called a socket. A socket sonsits of 3 things:
        
        A transport protocol
        
        A port number
        
        An IP address
        
        .
        
        Port Numbers? # # #
      - The TCP/IP transport layer includes a smaller of protocol than TCp/IP application layer protocols. THe two most commonly used transport layer protocol are the Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP) #
      - = Layer 4 of OSI networking model
      - Connection Establishment and Termination
        
        TCP establishes and terminates connections between the endpoints, whereas UDP does not.
        
        Establishment
        
        TCP connection establishment occurs before any of the other TCP feature can begin their work. Connection establishment refers to the process of initializing Sequence and Acknowledgment fields and agreeing on the port numbers used
        
        TCP signals connection establishment using 2 bits inside tha flag fields of the TCP header. Called the SYN and ACK flags, these bits have a particularly interesting meaning. SYN means "synchronize the sequence number", which is one necessary component in initialization for TCP.
        
        Many protocols operate under these same concepts, so the terms connection-oriented and connectionless are used to refer to the general idea of each.
        
        Connection-oriented protocol: A protocol that requires an exchange of messages before data transfer begins, or that has a required pre-established correlation between two indpoints.
        
        Connectionless protocol: A protocol that does not require an exchange of messages and that does not required a pre-established correlation between two end points.
      - Popular TCP/IP Applications
        
        The World Wide Web (www) application
        
        Although it is often thought of as an end-user application, you can actually use WWW to manage a router or switch. You enable a web server function in the router or switch and use a browser to access the router or switch.
        
        The Domain System (DNS) #
        
        DNS allows to use names to refer to computers, with DNS being used to find the corresponding IP addresses.
        
        Simple Network Management Protocol (SNMP)
        
        SNMP is an application layer protocol used specifically for network device management.
        
        Traditionally, to move files to and from a router or switch, Cisco used Trivial File Transfer Protocol (TFTP). TFTP defines a protocol for basic file transferhence the word trivial. Alternatively, routers and switches can use File Transfer Protocol (FTP), which is a much more functional protocol, to transfer files.
    - - Uniform Resource Identifiers
        
        Formal: URI
        
        Scheme #
        
        Authority #
        
        Path #
        
        For example
        
        Web:
        
        Protocol #
        
        Server's Name #
        
        Web Page #
        
        http:
        
        //
        
        www.certskills.com
        
        /
        
        1 more item...
      - Finding the Web Server Using DNS #
        
        a host can use DNS to discover the IP address that corresponds to a particular host name. URIs typically list the name of the server - a name that can be used to dynamically learn the IP address.
        URI
      - Transfer Files with HTTP
      - How the Receiving Host Identifies the Correct Receiving Application