3/19

*퀴즈

1. BE Best Effort

BE delivery

BE service model

최선을 다하지만 guarantee를 하지 못한다.

BE means a network service that does not guarantee its delivery satisfies any quality of service or even the data is properly delivered or not ex) IP, UDP

TCP는 재전송의 기능은 있지만...위아래에서 해주지는 못한다.

QoS:  Internet, IEEE 802.11 

2. topology

*bus topology 

the well known feature adopted in the early Ethernet is the Carrier Sense Multiple Access with Collision Detection (CSMA/CD) scheme

-which is designed to be used over a shared link

*star topology

3. IHL

IP Header Length 4bit->32비트 단위로!

4. State 

TCP: stateful

state는 history정보가 있어야 한다!

5. Layer

-Layer (or layering) in computer networks denotes a separation of concerns for functions of the computer networking as a hierarchy

-It encapsulates the details of the other functions the designer not interested in- so as to provide the easiness of design and implementation of a targeted networking function

6. ALOHA

The Pure ALOHA protocol implemented in ALOHAnet works as follows:

-Users transmit data when they have data to be sent 무조건 보낸다!

-If there is a collision, the sender waits a random amount of time and sends it again

collision: 충돌! congestion: 많은 사용자가 접속해서 상황이 열악해지는것

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edge

core

현재는 edge가 더 strong한 것들이 일반적

끝단은 smart

atm같은 경우는 가운데가 중요 (core)

bandwidth(bits per second) of access network?

4G->5G