计算机网络网络层,计 算 机 网 络 原 理 网 络 层

()

Internet

x.25ATMARPANETINTERNET

(virtual circuit)(datagram)()

(circuit switching)(message switching)()

(Store and Forward)

MMMMM

(packet switching)(packet)(datagram)(virtual circuit)

/QoS(Quality of Service)

MM1M2M3M1M2M3

()

()()()()

(datagram)(virtual circuit)

(correctness)(simplicity)(robustness)(stability)(fairness)(optimality)

()(off-line)()

(optimality principle) J I K J K (sink tree)

(Shortest Path Routing) (Flooding Routing) (Flow-Based Routing)

(Distance Vector Routing) (Link State Routing) (Hierarchical Routing)

Dijkstra

Dijkstra0

DijkstraDijkstra

Dijkstra

Dijkstra

10(selective flooding)

FijijCijij

T=1/(C-) 1/=800 bit

ARPANET,DECnet()1ECHO2XXiXiXmXiXi + mXi + m

JCJAC=8+25=33msJIC=10+18=28msJHC=12+19=31msJKC=6+36=42ms

JICJC28msI

NN

XXBACBC1CBDCA2BCADCEDA3CDAABACBABACBBADCDACAEA

ABD2CD1CDABCDCDCDABD2B3DBD1

1979ARPANET

1HELLOLAN

2/3ECHO2

41()

0

432(age)1()

5Dijkstra

Open Shortest Path First (OSPF)Intermediate System-Intermediate System (IS-IS)

CPU

(regions)(clusters)(zones)(groups)

Dijkstra

(congestion)(congestion control)(flow control)

()()

(Jitter) (probe)

(Traffic Shaping)ATM(The Leaky Bucket Algorithm) ATMIP

(The Token Bucket Algorithm) T

25MB/s2MB/s1M

CSp/M/C+pS=MS > S=C/(M-p) cdeM=25MB/s, p=2MB/s, C=250/500/750KBfM=10MB/s, p=2MB/s, C=500KB

(Flow Specification)

(admission control)

(Choke Packets)()

(fair queueing)

Hop-by-HopHop-by-Hop

Hop-by-Hop Choke Packets

(Load Shedding)

winemilk

()()Hop-by-Hop

(internet)()

(NIC Card) (Modem)(Repeater) (Hub)

(Bridge)

(Multiprotocol Router) (Switch)ATM()

(Ttransport Gateway)

(Application Gateway)

(Concatenated Virtual Circuits)

(Connectionless Internetworking)

1IP(PPP)IP = 2-2IPIP = 2-MAC2

(Tunneling)1IP = 2-IP = 1-MAC

(Internetwork Routing)(interior gateway protocol)RIPOSPF(exterior gateway protocol)BGPAS(Autonomous System)

512

(fragment)(/)

00.0, 0.1, 0.20.00.0.0, 0.0.1, 0.0.2

ATM

(firewall)