ch4 14~32

• Why each port has a FIB? -- In order to implement line speed forwarding
• Decentralized switching means FIB lookup is done using FIB stored in input port memory.

 

• Router architecture includes 

1. control plane (routing protocol and middleboxes) <-- Software-oriented
2. switching fabric : its performance is measured as multiples of N x R where N=number of ports, R=line rate (line speed) <-- Hardward-oriented
3. Ports in line cards : link bandwidth may vary  <-- Hardward-oriented
4. Control plane은 라우팅 software가 동작하는 모듈로 라우터들끼리 주고 받는 메세지(IP payload)를 처리하나,Data plane은 IP payload에 host들 사이에 주고 받는 layer 5 application message를 포함한 패킷을 포워딩하는 기능이다. 그러나 라우터들 끼리 주고 받는 라우팅 메시지도 Data plane을 통해서 포워딩된다.

 

• Head-of-line (HoL) blocking

1.  can occur at an input(ingress) buffer(queue) 
2. due to a drawback of crossbar switching (Two pkts destined to the same output port cannot be switched at the same time)

• The output buffer size at routers is proportional to (link bandwidth and average RTT), but inversely proportional to the number of TCP sessions.  Why?
  • 더 높은 대역폭은 대용량 데이터 처리 위해 큰 버퍼필요, longer RTT는 큐잉 지연을 증가.
  • TCP 세션 증가 - 버퍼 공간 경쟁하는 세션들 증가 - 세션 당 할당되는 버퍼 크기 감소 따라서 라우터의 버퍼 확장해야함

• Queue scheduling algorithms 

1.  FIFO (First In First Out)
2.  Priority 
3.  Round robin (RR)
4.  Weighted Fair Queueing (WFQ)

• What is Network Neutrality? Net neutrality is the principle that Internet service providers and governments regulating most of the Internet must treat all data on the Internet the same, and not discriminate or charge differentially by user, content, website, platform, application, type of attached equipment, or method of communication. For instance, under these principles, internet service providers are unable to intentionally block, slow down or charge money for specific websites and online content.