CSE 4/589 Midterm Review. Hengtong Zhang SUNY Buffalo 10/30/2018

Transcription

1 CSE 4/589 Midterm Review Hengtong Zhang SUNY Buffalo 10/30/2018

2 Chapter 1 overview: what s the Internet? what s a protocol? network edge; hosts, access net, physical media network core: packet/circuit switching, Internet structure performance: loss, delay, throughput security protocol layers, service models history Remember Calculation Remember

3 Chapter 2 principles of network applications transport-layer service models client-server paradigm peer-to-peer paradigm content distribution networks 2.2 Web and HTTP FTP electronic mail SMTP, POP3, IMAP DNS socket programming with UDP and TCP

4 Chapter 3 transport layer services (logical communications): transportation layer vs network layer Remember multiplexing, demultiplexing reliable data transfer flow control Understand in depth congestion control connection management transport layer protocols: UDP: connectionless transport TCP: connection-oriented reliable transport TCP congestion control

5 Chapter 3 Reliable data transfer protocols: How do we polish the protocols step-by-step (rdt )? What s the problem of each protocol? Pipelined protocols (GBN, SR) and analysis. What do you learn from PA2?

6 Chapter 3 Connection management: TCP connections, start and close. Start Close client state server state client state server state LISTEN SYNSENT ESTAB choose init seq num, x send TCP SYN msg received SYNACK(x) indicates server is live; send ACK for SYNACK; this segment may contain client-to-server data SYNbit=1, Seq=x SYNbit=1, Seq=y ACKbit=1; ACKnum=x+1 ACKbit=1, ACKnum=y+1 choose init seq num, y send TCP SYNACK msg, acking SYN received ACK(y) indicates client is live LISTEN SYN RCVD ESTAB ESTAB FIN_WAIT_1 FIN_WAIT_2 TIMED_WAIT clientsocket.close() can no longer send but can receive data wait for server close timed wait for 2*max segment lifetime FINbit=1, seq=x ACKbit=1; ACKnum=x+1 FINbit=1, seq=y ACKbit=1; ACKnum=y+1 can still send data can no longer send data ESTAB CLOSE_WAIT LAST_ACK CLOSED CLOSED

7 Chapter 3 Congestions and congestion control Why do congestions happen? What s the intuitions behind congestion control methods? How does TCP handle congestions? TCP Tahoe TCP Reno TCP throughput Is TCP fair?

8 Chapter 4 Overview of Network layer data plane control plane What s inside a router IP: Internet Protocol datagram format fragmentation IPv4 addressing network address translation IPv6 Understand Remember Understand Remember

9 Chapter 4 network-layer functions: forwarding: move packets from router s input to appropriate router output routing: determine route taken by packets from source to destination routing algorithms analogy: taking a trip forwarding: process of getting through single interchange routing: process of planning trip from source to destination

10 Chapter 4 Data plane local, per-router function determines how datagram arriving on router input port is forwarded to router output port forwarding function values in arriving packet header Control plane network-wide logic determines how datagram is routed among routers along end-end path from source host to destination host two control-plane approaches: traditional routing algorithms: implemented in routers software-defined networking (SDN): implemented in (remote) servers

11 Chapter 4 Calculation questions: Forwarding table related calculation questions. Please refer to homework 3.

12 Destination-based forwarding forwarding table Destination Address Range through through through otherwise Link Interface Q: but what happens if ranges don t divide up so nicely? Network Layer: Data Plane 4-12

13 Chapter 5 Routing protocols link state (Dijkstra's Algorithm) distance vector (Distance vector Algorithm) limitations and problems Routing in action intra-as routing in the Internet: OSPF routing among the ISPs: BGP The SDN control plane ICMP: The Internet Control Message Protocol Network management and SNMP Understand Remember Remember