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icnd1 ch2

Terms

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def: adjacent-layer interaction?
the general topic of how on one computer, 2 adjacent layers in a networking arch model work together, with the lower layer providing services to the higher layer.
tcp/ip architecture layer: application example protocols?
HTTP, pop3, smtp
tcp/ip arch layer: transport example protocols?
tcp, udp
tcp/ip arch layer: internet example protocols?
IP
tcp/ip arch layer: network access example protocols?
ethernet, frame relay
Same-layer interaction on different computers. Description?
2 computers use a protocol to comm with the same layer on another comp. the protocol defined by each layer uses a header that is transmitted between the comps to comm what each comp wants to do.
Adjacent-layer interaction on the same computer. description?
On a single comp, on layer provides a svc to a higher layer. The sw or hw that implements the higher layer requests that the next lower layer perform the needed function.
5 steps of data encapsulation in tcp/ip?
1. application = data 2. transport = tcp header added 3. Internet = IP header added 4. Network access = link header/trailer added 5. Transmit bits
tcp/ip: encapsulation term for each level's headers?
segment: transport (tcp) packet: internet (IP) frame: network access (LH, LT)
What is OSI?
Open Systems Interconnection. Alternative set of protocols to tcp/ip. Many terms are used in tcp/ip.
Layers of OSI:
7. Application - provides interface btwn the comm's fw and any apps that need to comm outside the comp on which the app resides. It also defines processes for user authentication. 6. Presentation - define and negotiate data formats (ascii text, binary, jpeg). Encryption also is defined by OSI as a presentation layer svc. 5. Session - defines how to start, control, and end conversations/sessions. This includes the control and mgmnt of mult. bidirectional msgs so that the app can be notified if only some of a series of msgs are completed. This allows the presentation layer to have a seamless view of an incoming stream of data. 4. Transport - focuses on issues related to data delivery to another computer - for instance error recovery and flow control. 3. Network - defines 3 main features: logical addressing, routing (fwd'ing), and path determination. The routing concepts define how devices/routers fwd packets to their final dest. Logical addressing defines how each device can have an address that can be used by the routing process. Path determination refers to the work done by routing protocols by which all possible routes are learned, but the best route is chosen for use. 2. Data link - defines the rules/protocols that determine when a device can send data over a particular medium. Data link protocols also fefine the format of a header and trailer that allows devices attached to the medium to send and receive dtat successfully. The dta link trailer, which follows the encapsulated data, typically fefines a Frame Check Sequence (FCS) field, which allows the receiving device to detect transmission errors. 1. Physical - refers to standards from other org's. These standards deal with the physical char's of the trans medium (connectors, pins, use of pins, electrical currents, encoding, light modulation, and the rules for how to activate and deactivate the use of the physical medium).
OSI: example devices and protocols. Application, presentation, session (L5-7). Protocols/specs?
Telnet, http, ftp, smtp, pop3, voip, snmp. Firewall, intrusion detection system.
OSI: example devices and protocols. Transport (L4). Protocols/specs?
tcp, udp.
OSI: example devices and protocols. Network (L3) Protocols/specs?
IP. router.
OSI: example devices and protocols. Data Link (L2). Protocols/specs?
ethernet (IEEE 802.3), hdlc, frame relay, PPP. LAN switch, wireless access point, cable modem, DSL modem.
OSI: example devices and protocols. Physical (L1) Protocols/specs?
rj45, ethernet. LAN hub, repeater.
def: decapsulation?
on a computer that receives data over a network, the process in which the device interprets teh lower-layer headers and, when finished with each header, removes the header, revealing the next-higher-layer PDU.
def: encapsulation?
the placement of data from a higher-layer protocol behind the header (or header and trailer) of the next-lower-layer protocol. For example, an IP packet could be encapsulated in an ethernet header and trailer before being sent over an ethernet.
def: frame?
in tcp/ip, a PDU of the network access layer (uses LH and LT, layer header and trailer.) a term referring to a data-link heder and trailer, plus the data encapsulated between the header and trailer.
def: networking model?
a generic term referring to any set of protocols and standards collected into a comprehensive grouping that, when followed by the devices in a network, allows all the devices to communicate. Examples include tcp/ip and OSI.
def: packet?
in tcp/ip, a PDU of the internet layer (IP header with data from application layer). logical grouping of information that includes the network layer header and encapsulated data, but specifically does not include any headers and trailers below the network layer.
def: (PDU)?
Protocol Data Unit. term referring to the header defined by some layer of a networking model, and the data encapsulated by the header (and possibly trailer) of that layer, but specifically not including any lower-layer headers and trailers.
def: same-layer interaction?
comm' between 2 networking devices for the purposes of the functions defined at a particualr layer of a networking model, with that comm' happening by using a header defined by that layer of the model. The 2 devices set values in the header, send the header and encapsulated data, with the receiving device(s) interpreting the header to decide what action to take.
def: segment?
in tcp/ip, a PDU of the transport layer (uses a TCP header with data from the application layer encapsulated). in TCP, term used to describe a tcp header and its encapsulated data (aka: L4PDU). Also, the process of accepting a large chunk of data from the app layer and breaking it into smaller pieces that fit into tcp segments. In Ethernet, a segment is either a single ethernet cable or a single collision domain (no matter how many cables are used).

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