Clyde Notes Flashcards
How many messages does it take to translate server name into IP
6
How many messages setup TCPIP connection
3
How many messages to send HTTP Get request
4
How many messages to tear down connection
4
What is a network at the lowest level
2+ Computers connected by a link
TCP/IP
Transport Control Protocol/Internet Protocol. Defines how information is transmitted over the internet
IP Address
4 numbers separated by a . that uniquely identify each host on the internet. Used to route information, no two hosts can have the same IP.
SMTP
Simple Mail Transfer Protocol. Defines how email is sent online
How did packet switching come about
Military swapped to packet switching because circuit switching was too fragile
First packet switched network
ARPANET in 1969
Internetting Project
When packet switched networks were connected together
WAN Transmission Lines
There are many transmission lines that connect routers in a WAN
Network Layer in terms of transmission
Lowest Layer that deals with end to end transmission. Wants to get packets to destination.
Routing algorithms
Determine how network chooses path to take, decides which output line an incoming packet should be transmitted on.
Store and Forward (Packet Switching)
Host sends a packet to nearest router, packet stored there until it has arrived and verified checksum.
Forwarded to next router until destination is reached.
Issues with Store and Forward for Transport Layer
Services are to be independent from router technology.
Transport layer should be shielded from info of router.
Network Address shared with Transport layer should use uniform numbering plan.
Issues with Store and Forward in general
No error control.
Not reliable connection oriented service.
QoS
Flow control done by
Hosts
What technology failed to take over IP
ATM technology
Each packet in a network should
carry full destination address as each packet is sent independently
Unicast
Sent to a single destination
Multicast
Sent to multiple destinations
Classes of Failure
Bit Error, 2nd Class, Semantic Gap
Packet Switched networks
Split messages into small packets, store and forward to next node, every node has an address, efficient.
Bit Error
Rare but may call for retransmission
2nd Class
Packet loss by network
Semantic Gap
Difference between what app expects and what network provides
Layering
Manage abstraction which leads to layers in network system. Modular
Objects making up layers
protocols
Protocols in layers
Define operations performed by local objects
Service interface
defined to objects that want to use communication service
Request/Reply protocol
supports operations by which app can receive and send messages
Peer interface
defined by protocol to its counterpart on remote machine. Implements exchange of messages, defining form and meaning
