2023年6月24日发(作者：)

名姓

号学 宁波大学 2011 / 2012 学年第 1 学期考试卷（A）

学号：______________姓名：______________

课号：_

101G09X0X_ 课名： 计算机网络__ (答题卡和每页试卷均请写上姓名学号，答案请填在答题卡上)

I. Choose the single correct answer from following choose. (1.5*20=30)

[Correct checked:1.5; Other wise:0]

physical media has high-speed operation and low error rate: client browses remote directory by sending commands over:

[] optic cable [] tion-less

[] l cable [] connection

[] d pair [] connection

[] [] l connection

no free buffers in router, the arriving packets will be: can satisfy client request without involving origin server:

[] d [] caches

[] [] caches

[] ed [] buffer

[] [] buffer

can provides delay measurement from source to router along end-end Internet path towards socket identified by:

destination：

[] -tuple (source IP address, source port number)

[] [] -tuple (dest IP address, dest port number)

[] oute [] -tuple (source IP address, dest port number)

[] ig [] -tuple (dest IP address, source port number)

[] up GBN,when receiver receive a out-of-order packet,then discard and re-ACK the packet with:

TCP/IP, which layer can make routing of datagrams from source to destination: [] A. highest in-order sequence #

[] aion [] B. lowest in-order sequence #

[] ort [] C. highest in-order port #

[] k [] D. lowest in-order port #

[] Link RDT Approachs, which is designed for performance:

page consists of ( ) which includes several referenced objects：

[] A. checksum

[] nced HTML-file [] B. pipeline

[] HTML-file [] C. sequence #

[] HTML-file [] D. ACK or NAK

[] HTML-file datagram at front of router’s queue prevents others in queue from moving forward is:

is the default persistent model in HTTP/1.1: [] -of-the-Line (HOL) blocking

[] sistent HTTP [] -of-the-Line (HOL) blocking

[] tent without pipelining [] -of-the-List (HOL) blocking

[] tent with pipelining [] -of-the-List (HOL) blocking

[] sistent with pipelining

’s a network ? From IP address perspective they can physically reach each other without

server maintains no information about past client requests, so HTTP is: intervening router and the device interfaces with:

[] ul [] A. same IP address

[] ess [] B. same TCP port #

[] ied [] C. same network part of IP address

[] sfied [] D. same host part of IP address

第 1 页 共 4 页 宁波大学 2011 / 2012 学年第 1 学期考试卷（A）

学号：______________姓名：______________

课号：_

101G09X0X_ 课名： 计算机网络__ (答题卡和每页试卷均请写上姓名学号，答案请填在答题卡上)

15. Large IP datagram divided (“fragmented”) within network,it will be reassembled:

[] A. only at last router

[] B. only at final destination

[] C. only at next router

[] D. maybe at next router

is not a common Intra-AS routing protocols:

[] : Routing Information Protocol

[] : Open Shortest Path First

[] : Interior Gateway Routing Protocol

[] : Interior Control Message Protocol

is not a MAC Random Access protocol in Ethernet:

[]

[] /CA

[] /CD

[] d SCMA

DHCP client-server scenario, which message has DHCP-options field:

[] A. host broadcasts “DHCP discover”

[] B. DHCP server responds with “DHCP offer”

[] C. host requests IP address: “DHCP request”

[] D. DHCP server sends address: “DHCP ack”

to determine MAC address of host B, If knowing host B’s IP address?

[]

[]

[]

[]

20. Which device can break subnet into LAN segments:

[] mask

[]

[]

[]

II. Choose the multiple correct answer from following choose. (2*10=20)

[All correct checked:2; Part correct checked:1; No checked:0; Full checked:0]

is the part of network structure:

[] k edge

[] k core

[] k user

[] networks

to connect end systems to edge router?

[] oft access networks

[] ntial access networks

[] utional access networks

[] access networks

kind of transport service does an application need?

[] loss

[]

[] dth

[] ty

onic Mail three phases of transfer is:

[] aking (greeting)

[] er of messages

[] the 2nd TCP connection

[]

TCP Connection Management, initialize TCP variables include：

[] ce #

[] s

[] MTU

[] dow

does sender perceive congestion?

[] t

[] B.3 duplicate ACKs

[] C.3 duplicate data

[] start

Congestion Control use three mechanisms:

[] ve increase and multiplicative decrease

[] start

[] vative after timeout events

[] ve decrease and multiplicative increase

are the Key Network-Layer Functions:

[] ding

[] g

[] tion setup

[] control

学号

姓名

第 2 页 共 4 页 宁波大学 2011 / 2012 学年第 1 学期考试卷（A）

学号：______________姓名：______________

课号：_

101G09X0X_ 课名： 计算机网络__ (答题卡和每页试卷均请写上姓名学号，答案请填在答题卡上)

Layer Services include:

[] le delivery between adjacent nodes

[] Control between adjacent nodes

[] tion Manage

[] Detection and Correction

Protocol’s taxonomy, three broad classes is:

[] l Partitioning

[] Access

[] turns

[] isement

III. Fill the blank from options. (1.5*16=24)

1).The network protocols define 1 , 2 of message sent and received among

network entities, and 3 on message transmission, receipt.

(options: delay / format / policy / order / request / replay / actions taken / price / interface )

2).InTCP Congestion Control, after 3 duplicate ACKs CongWin is cut in ___4___ and window then

grows____5____. But after timeout event, CongWin instead set to___6___, window then

grows____7____, when it up to a ___8_____ again, then grows linearly.

(options: half / double / 1 MSS / 0 MSS / linearly / exponentially / threshold / top / bottom )

3).Please fill the general format of Http request message:

HTTP request message general format

9.[ ]

sp

10.[ ]

sp

11.[ ]

12.[ ]

Host A ：1025

–> Host D：80

IV. Question (26)

follow, LAN1 connect to LAN2 via a router:

In session 1, Host A send a HTTP connection to WEB server D，if Host A initial TCP port 1025，Host D use TCP port 80；

In session 2, Host A send a HTTP connection to WEB server B，if Host A initial TCP port 1026，Host B use TCP port 80；

学号

姓名

Fill it: (9)

Session Step

Host A –>

ROUTER

ROUTER

–> Host D

Host A ：1026 Host A –>

Host B

–> Host B：80

Source

MAC

Destination

MAC

Source

IP

Destination

IP

Source

Port#

Destination

Port#

…

…

13.[ ]

16. [ ]

:

14.[ ]

15. [ ]

and answer：(17)

Two of the most important fields in the TCP segment header are the sequence

number field and the acknowledgment number field. These fields are a critical part of

TCP's reliable data transfer service. But before discussing how these fields are used to

provide reliable data transfer, let us first explain what exactly TCP puts in these fields.

TCP views data as an unstructured, but ordered, stream of bytes. TCP's use of

sequence numbers reflects this view in that sequence numbers are over the stream of

transmitted bytes and not over the series of transmitted segments. The sequence

Entity Body

(options: header field name / URL / field value / version / method / Cr Lf/ 200 OK )

第 3 页 共 4 页

名姓

号学 宁波大学 2011 / 2012 学年第 1 学期考试卷（A）

学号：______________姓名：______________

课号：_

101G09X0X_ 课名： 计算机网络__ (答题卡和每页试卷均请写上姓名学号，答案请填在答题卡上)

number for a segment is the byte-stream number of the first byte in the segment. to the people programming a TCP implementation. There are basically two choices:

Let's look at an example. Suppose that a process in host A wants to send a stream of either (i) the receiver immediately discards out-of-order bytes; or (ii) the receiver

data to a process in host B over a TCP connection. The TCP in host A will implicitly keeps the out-of-order bytes and waits for the missing bytes to fill in the gaps. Clearly,

number each byte in the data stream. Suppose that the data stream consists of a file the latter choice is more efficient in terms of network bandwidth, whereas the former

consisting of 500,000 bytes, that the MSS is 1,000 bytes, and that the first byte of choice significantly simplifies the TCP code. Throughout the remainder of this

the data stream is numbered zero. As shown in Figure 3.5-3, TCP constructs 500 introductory discussion of TCP, we focus on the former implementation, that is, we

segments out of the data stream. The first segment gets assigned sequence number assume that the TCP receiver discards out-of-order segments.

0, the second segment gets assigned sequence number 1000, the third segment gets In Figure 3.5.3 we assumed that the initial sequence number was zero. In truth,

assigned sequence number 2000, and so on.. Each sequence number is inserted in both sides of a TCP connection randomly choose an initial sequence number. This is

the sequence number field in the header of the appropriate TCP segment. done to minimize the possibility a segment that is still present in the network from an

earlier, already-terminated connection between two hosts is mistaken for a valid

segment in a later connection between these same two hosts (who also happen to be

using the same port numbers as the old connection) .

Question 1: Does TCP's use of sequence numbers over the series of transmitted segments? (3)

Figure 3.5-3: Dividing file data into TCP segments.

Question 2: What does the sequence number for a segment means? For example. (4)

Now let us consider acknowledgment numbers. These are a little trickier than

Question 3: What does the acknowledgment number means, that host A puts in its segment to host B?(3)

sequence numbers. Recall that TCP is full duplex, so that host A may be receiving data

Question 4: How does TCPs to choose an initial sequence number? (3)

from host B while it sends data to host B (as part of the same TCP connection). Each

Question 5: What does a host do when it receives out of order segments in a TCP connection? (4)

of the segments that arrive from host B have a sequence number for the data flowing

from B to A. The acknowledgment number that host A puts in its segment is sequence

number of the next byte host A is expecting from host B. It is good to look at a few

(所有答案请填在答题卡上，答在试卷上的答案一律无效)

examples to understand what is going on here. Suppose that host A has received all

bytes numbered 0 through 535 from B and suppose that it is about to send a segment

to host B. In other words, host A is waiting for byte 536 and all the subsequent bytes

in host B's data stream. So host A puts 536 in the acknowledgment number field of

the segment it sends to B.

As another example, suppose that host A has received one segment from host B

containing bytes 0 through 535 and another segment containing bytes 900 through

1,000. For some reason host A has not yet received bytes 536 through 899. In this

example, host A is still waiting for byte 536 (and beyond) in order to recreate B's data

stream. Thus, A's next segment to B will contain 536 in the acknowledgment number

field. Because TCP only acknowledges bytes up to the first missing byte in the stream,

TCP is said to provide cumulative acknowledgements.

This last example also brings up an important but subtle issue. Host A received the

third segment (bytes 900 through 1,000) before receiving the second segment (bytes

536 through 899). Thus, the third segment arrived out of order. The subtle issue is:

What does a host do when it receives out of order segments in a TCP connection?

Interestingly, the TCP RFCs do not impose any rules here, and leave the decision up

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