EECS 340 Study
Terms in this set (39)
Broadcast communication networks
Information transmitted by any node is received by every other node in the network
Examples: usually in LANs (Ethernet)
Problem: coordinate the access of all nodes to the shared communication medium (Multiple Access Problem)
Switched communication networks
Information is transmitted to a sub-set of designated nodes
Examples: WANs (Telephony Network, Internet)
Problem: how to forward information to intended node(s)
This is done by special nodes (e.g., routers, switches) running routing protocols
What does TCP stand for?
Transmission Control Protocol
What does UDP stand for?
User Datagram Protocol
What is the Network Edge and Network Core?
Network Edge: Applications and hosts...the end systems
Differences between TCP and UDP
TCP is reliable, in-order
TCP provides congestion control and flow control
Layers of the Internet Protocol Stack
Packet-switched network vs. Circuit-switched network
Circuit-switched reserves resources, does not share.
Great for bursty data
simpler, no call setup
Excessive congestion: packet delay and loss
protocols needed for reliable data transfer, congestion control
Q: How to provide circuit-like behavior?
bandwidth guarantees needed for audio/video apps
still an unsolved problem
Types of delay in packet-switched networks
Structure of Packet
Header, Data, Trailer
Header and trailer carry destination address and checksum
Types of multiplexing in circuit-switched networks
Frequency-division multiplexing (FDM)
Time-division multiplexing (TDM)
What are examples of guided media and unguided media?
Guided media: copper, fiber, coaxial cable
Unguided media: radio
What are the two types of packet-switched networks?
Datagram packet-switched networks
Virtual circuit packet-switched networks
What does store-and-forward transmission mean?
The switch must receive the entire packet before it can begin to transmit the first bit of the packet onto the outbound link
Why does packet loss occur?
The packet switch's output buffer is full when a new packet arrives
What does statistical multiplexing mean?
Link transmission capacity is shared on a packet-by-packet basis only among those users who have packets that need to be transmitted over the link.
It is on-demand rather than pre-allocated
What sort of networks use statistical multiplexing?
Packet-switched networks (both datagram and virtual circuit)
Datagram Packet Switching (Connectionless)
Each packet has destination in the header but may not take the same route
No destinations are pre-allocated(reserved)
Example: IP networks
Similar to a post office
Virtual-Circuit Packet Switching (Connection-Oriented)
Hybrid of circuit switching and packet switching
All packets are sent along pre established path (virtual circuit) and carry a tag (Virtual Circuit ID) to determine next hop
Guarantees in-Sequence delivery of packets <+>
Packets from different virtual circuit may be interleaved
Requires per-flow state in network, understanding the sequence of flows <->
How does Virtual Circuit Packet Switching work?
Note: Headers don't need to contain full destination of the packet
Ratio for traffic intensity
- L = # bits per packet
- a = average rate at which packets arrive at queue (packets/sec)
- R = transmission rate (bits/sec)
What type of delay is traffic intensity relevant to?
If traffic intensity ~ 0, queuing delay is small.
If traffic intensity > 1, queuing delay is infinite because bits arrive at the queue faster than they leave.
Does TCP provide any encryption?
Does UDP provide any encryption?
What is SSL?
Secure Sockets Layer
An enhancement to TCP that provides critical process-to-process security services, including encryption, data integrity, and end-point authentication.
What is the difference between persistent and non-persistent connections?
With persistent connections, all request/response pairs can be sent over the same TCP connection (until timeout).
With non-persistent connections, all request/response pairs are sent over separate TCP connectons.
How do cookies work?
The first time you make a request to a server (on a certain browser on your device), the server creates a unique ID number and creates an entry in a database that is indexed by this ID number. Then in the response, the server includes a set-cookie header.
Now, when you make a request, a cookie header with your ID number is included in the header of the request.
True or False: A user requests a Web page that consists of some text and three images. For this page, the client will send one request message and receive four response messages.
True or False: Two distinct Web pages (for example, www.mit.edu/research.html and www.mit.edu/students.html) can be sent over the same persistent connection.
True or False: With nonpersistent connections between browser and origin server, it is possible for a single TCP segment to carry two distinct HTTP request messages.
True or False: The Date: header in the HTTP response message indicates when the object in the response was last modified
True or False: HTTP response messages never have an empty message body.
True or False: Host A is sending Host B a large file over a TCP connection. Assume Host B has no data to send Host A. Host B will not send acknowledgments to Host A because Host B cannot piggyback the acknowledgments on data.
True or False: The size of the TCP rwnd never changes throughout the duration of the connection.
True or False: Suppose Host A is sending Host B a large file over a TCP connection. The number of unacknowledged bytes that A sends cannot exceed the size of the receive buffer.
True or False: Suppose Host A is sending a large file to Host B over a TCP connection. If the sequence number for a segment of this connection is m, then the sequence number for the subsequent segment will necessarily be m + 1.
True or False: The TCP segment has a field in its header for rwnd.
True or False: Suppose that the last SampleRTT in a TCP connection is equal to 1 sec. The current value of TimeoutInterval for the connection will necessarily be >= 1 sec.
True or False: Suppose Host A sends one segment with sequence number 38 and 4 bytes of data over a TCP connection to Host B. In this same segment the acknowledgment number is necessarily 42.