TCP Chapter 3

Processes

Programs running on host machine - it is like a house

sockets

Processes communicate by sending messages into \___________ (they're like a door)

SSL

Brings security to TCP (which normally doesn't have encryption)

persistent

TCP uses \________ connection

TCP Socket

Souce - IP address

Source - Port # (Socket #)

Dest - IP address

Dest - Port Number

16

Port Numbers are \____ bits

UDP

Error detection is usually in the data link layer, but this isn;t a universal truth, so \________ has checksum error detection as a backup

rdt2.0

\________ deals with channels with errors

Network Layer

Logical communication between hosts

Transport Layer

Logical communication between processes

TCP

* reliable
* in-order delivery
* flow/congestion control

UDP

* unreliable
* best effort
* no in-order delivery

multiplexing

is a method by which multiple analog or digital signals are combined into one signal over a shared medium - Many to One - happens at source socket

demultiplexing

reconverts a signal containing multiple analog or digital signal streams back into the original separate and unrelated signals- One to Many - happens at destination socket

UDP

sends all data packets with the same port \# but different IP addresses will get sent to the same socket regardless with \_____

UDP Headers

Source Port #

Dest Port #

Length

Checksum

checksum

adding n bit strings and then adding the 1's compliment at the end to get a series of 1111111111's is the method for UDP ________ .

If anything is a 0, then there was an error

True

T/F UDP only has error detection, not error correction

1

rdt_.0 does not take errors or loss into account

only has

send(data)/make(data)+send(packet)

or

rcv(packet)/extract(packet, data)+deliver(data)

2

rdt_.0 used Ack/Nack to let sender know about erroneous packets

2.1

rdt_._ adds sequence numbers to Ack/Nack calls to help against duplicate packets

fast retransmit

TCP (two words) uses repeated Ack (triple ack) to know when there has been a packet loss

3

rdt_.0 deals with errors and loss

implements a countdown timer to resend packets if an Ack with the appropiate sequence number was not received within a certain timeframe

pipelining

sender allows multiple, "in-flight", yet-to-be-acknowledged pkts

can multiply the utilization rate of rdt

receiver window

the \______ \______ is 16 bits and used for flow control

UARPSF

these are single-bit flags in TCP

URG (not important)

Ack Valid # (0 or 1)

PSH (push data)

RST

SYN

FIN

32

both sequence number and acknowledgment number are \_________ bits in TCP

previously

Ack num

num is the __________ received number with no errors

current

Sequence num

num is the _________ message number of the connection

Estimated RTT

(1 - a ) * Estimated RTT + a * SampleRTT \=

DevRTT

(1 - B) * DevRTT + B * | SampleRTT - EstimatedRTT |

TimeOutInterval

TimeoutInterval \= EstimatedRTT + 4 • DevRTT

congestion

we experience packet loss / delay because of \________

skyrocket

queing delays \________ when packet arrival rate nears link capacity (La/R approaches 1)

goodput

the amount of usable data that crosses a given point in a network over a certain period of time (whats actually received)

R/4

retransmission causes throughput to go from R/2 to

T

T/F TCP adjusts send rate depending on congestion

Slow Start

the TCP protocol of starting to send data at 1 MSS ( maximum segment size )

double congestion window every RTT (exponential)

either restart this process or go down to congestion window/2 whenever a packet is lost

Reno

the TCP protocol of increasing linearly after a packet loss during a slow start

Tahoe

the TCP protocol of repeating the exponential growth of slow start, but starting at the cwnd/2 at the time of the packet loss

utilization

(L/R) / (RTT + L/R)

2(prop delay)

1 RTT \= \________ seconds