Protocols
define format, order of messages sent and received among network entities, and actions taken on message transmission, receipt |
network structure
access networks, physical media:wired, wireless communication links |
TDM = time division multiplexing time divided into frames fixed duration fixed number time slots |
network core: •interconnected routers•network of networks |
FDM = frequency division multiplexing: diff CHs transmitted in diff frequency bands |
|
|
Equations
4 Sources of packet delays |
dnodal = dproc + dqueue + dtrans +dprop |
dproc : nodal processing, check bit errors, determine output link |
dqueue: queueing delay, time waiting at output link for transmission, depends on congestion of router |
dtrans: how long it takes to get on link |
L (bits)/R(bps) |
dprop: propagation delay |
d (m)/s |
|
|
Stacks
IP |
application(http), transport(TCP), network(IP), link(WiFi), physical(bits) |
ISO/OSI |
app, session(checkpointing), transport, network, link, physical |
|
|
TCP / UDP
transmission control protocol |
user datagram protocol |
reliable transport, flow control, congestion control, DNP( timing, minimum throughput guarantee, security), connection-oriented |
unreliable data transfer, DNP |
|
1 IP & 1 port |
|
streaming, DNS (domain name system) |
|