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Multiplexing
segments from 2/+ msgs shuffling 2 share media
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Service
provide response 2 request
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Process
provide direction & movement of msgs, each occurrence in RAM <-- instance of running program, server SW
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Hubs/Switches/WAPs
examples of Network Access Devices
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Encoding
way data converted 2 energy patterns
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Interface
allows Networks 2 communicate
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IEEE & IETF
standardize protocols
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Transceivers
on NICs 2 implement standards
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APSTNDP
reference model acro
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HW->best path->comm&ec->reps data
NITA path
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Frame->Packet->Segment
PDU path
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Port
4 specific process/service
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Physical Layer responsibilities
coding, compression, & encryption
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Session Layer responsibilities
initiate, maintain, & restart
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Protocol
rules a service uses
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daemon
service that listens
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P2P
no server/centralized resources
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Index Server
P2P centralized directory
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DNS
domain name 2 IP addy
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nslookup
DNS cmd 2 list default server(s)
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DNS Record Types
A,NS,CNAME, & MX
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ipconfig/displaydns
DNS cmd 2 list cached DNS entries
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DNS Hierarchy
root->top level->secondary level
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HTTP Message Types
GET,POST, & PUT
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SMTP
from client 2 MDA & from MTA 2 MTA
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SMTP Commands
HELO,EHLO,MAIL FROM, RCPT TO, & DATA
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SMB
sharing resources as if local
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Gnutella Packet Types
ping, pong, query, query hit, & push
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VTY Session
Telnet connection
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Telnet Commands
AYT, EL, & IP
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end-to-end transfer
Transport Layer responsibility
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Transport Layer
flow control, segmentation/desegmentation, & error checking
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connection-oriented
keeps track of segments & resends failures
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UDP
connectionless, RF768, 8 bytes overhead
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TCP
connection-oriented, RFC793, 20 bytes overhead, performs sequencing
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socket
port # + IP addy - xx.xx.xx.xx:#
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well-known ports
ports 4 services & apps (0-1023)
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registered ports
ports 4 programs (1024-49151)
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dynamic/private ports
ports 4 dynamic connection initiation, aka ephemeral (49,152-65,535)
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netstat
command 2 list active TCP connections on host
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3-way handshake
SYN(100)-ACK(101)SYN(300)-ACK(301)
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TCP segment header fields
URG, ACK, PSH, RST, SYN, FIN
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windowing
acknowledgment indicating next expected (expectational) byte #
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window size
amount of data which can be sent b4 ACK required
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selective acknowledgments
acknowledges non-contiguous segment bytes
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Network Layer
addresses w/IP addy, encapsulation/decapsulation, routing
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Network Layer protocols
IP, IPX, AppleTalk, CLNS (telecomm.)
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IPv4 characteristics
connectionless, best-effort, & media-independent
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stack
protocols working together, TCP/IP
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MTU
Maximum Transmission Unit, max. size of a PDU on some networks
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fragmentation
when smaller packet needed (is done by router)
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TTL
max. hops packet travels b4 considered "lost"
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packet lengths
min.=20 bytes, max=65,535 bytes, includes header
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3 reasons 2 subnet
geography, specific purpose, & ownership
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common network issues
performance, security, & address management
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ipconfig
cmd 2 check host IP addy, SM, & default gateway
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3 features of routing tables
destination network, next-hop, & metric
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metric
2 decide between 2/> possible routes
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show ip route
router cmd 2 show routing table
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netstat - r OR route print
cmds 2 display host routing table
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0.0.0.0
default route, aka gateway of last resort
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routing protocols
RIP, EIGRP, & OSPF ... have algorithms used by routers
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high-order bits
network portion of IP addy
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directed broadcast
2 all hosts on specific remote network
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limited broadcast
regular, all 1s & all Fs
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multicast
regular & 4 routers 2 xchange routing info.... 224.0.0.0 - 239.255.255.255
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reserved link local
multicast groups on local network
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globally scoped
multicast groups across Internet
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NTP
2 synch network device clocks, 224.0.1.1
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prefix length
# of network bits represented by slash 4mat
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private addresses
10.0.0.0 - 10.255.255.255 , 172.16.0.0 - 172.31.255.255 , & 192.168.0.0 - 192.168.255.255
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NAT
change private addresses 2 public 1s
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link local
APIPA, 169.254.0.0 - 169.254.255.255
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IP class order
A, B, C, D (MC), & E
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Class A
0.0.0.0 - 127.0.0.0
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Class B
128.0.0.0 - 191.255.0.0
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Class C
192.0.0.0 - 223.255.255.0
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ARIN
division of RIR, has IP addys
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3 ISP tiers
1 (connected 2 Internet backbone), 2 (business customers - servers), 3 (local/retail - small/med. businesses)
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3 reasons network is subnetted
2 overcome issues with: location, size, & control
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ping
uses ICMP, reply = echo
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traceroute
uses TTL & TE 2 limit hops incrementally
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ICMP
used 4 messaging also, unreachable (H) / time xceeded (R) / redirection(R) / quench (source)
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