CCNA基础知识题(英文版）

来源：vlan9.com 作者：出处：巧巧读书 2007-12-12 进入讨论组

101 What IP command would you use to test the entire IP stack?

A.) Stack-test B.) Arp C.) Telnet D.) Ping E.) Trace

Ans C Because Telnet is an application and it resides at the top of the stack it traverses
down the stack and up the stack at the receiving end.

102 Identify the 2 hardware components used to manage and/or configure a
router?

A.) Auxiliary port B.) ROM port C.) Management port
D.) Console port

Ans A D
The 2 hardware ports used to configure the router are the console and auxiliary ports.

103 What is the default bandwidth of a serial connection?

A.) 1200 baud B.) 1.544 Mbps (T1) C.) 10 Mbps D.) 96Kpbs

Ans B

The default bandwidth is T1.

104 Identify 2 functions of IPX access-lists?

A.) Control SAP traffic B.) Limit number of Novell servers on a network C.) Limit number
of workstations on a network D.) Block IPX traffic

Ans A D
IPX access lists are used to restrict IPX traffic and SAP broadcasts.

105 Identify 2 HDLC characteristics?

A.) Default serial encapsulation B.) Open standard C.) Supports Stacker compression D.)
Supports point-to-point and multipoint

Ans A D HDLC is the default serial encapsulation and supports point-to-point and
multipoint. It is not an open standard and does not support compression.

106 Identify 3 IP applications?

A.) AURP B.)
ARP C.) Telnet
D.) SMTP E.)
DNS F.) RARP

Ans C D E ARP and AURP are not part the application layer of the TCP/IP stack. SMTP
-Simple Mail Transfer Protocol, Telnet, DNS - Domain Name Services (name to IP
resolution).

107 Identify 3 LAN technologies?

A.) FDDI B.)
HDLC C.) HSSI
D.) X.25 E.)

802.3 F.) 802.5
Ans A E F The question is asking for 3 LAN technologies, HDLC, HSSI and X.25 are all
WAN technologies.

108 Identify the 4 that are not LAN technologies?

A.) HDLC B.) FDDI C.) 802.5 D.) HSSI E.) SDLC F.) Frame Relay

Ans A D E F

802.5 and FDDI are LAN technologies
109 Which OSI layer supports the communication component of an application?

A.) Data-Link B.) Physical C.) Session D.) Presentation E.) Application F.) Transport

Ans E
Layer 7 the Application layer performs this function.

110 Identify the length of an IPX address and it's components?

A.) 80 bits, 48 bits network and 32 bits node B.) 32 bits, 16 bits network and 16 bits node
C.) None of the above D.) 80 bits, 32 bits network and 48 bits node Ans D IPX address has
2 components; network and node. The network address is 32 bits and the node is 48 bits,
total of 80 bits.

111 Identify the administrative distance and appropriate routing protocol?

A.) RIP = 255, IGRP = 100 B.) RIP = 100, IGRP = 120 C.) RIP = 1, IGRP = 0 D.) RIP =
120, IGRP = 100

Ans D The administrative distance for RIP is 120 and IGRP is 100. The lower the AD the
better the routing information.

112 Which OSI layer incorporates the MAC address and the LLC?

A.) Data link B.)
Network C.)
Physcial D.)
Transport

Ans): A Layer 2 the Data-Link layer incorporates the MAC and LLC sublayers

113 If configuring a Cisco router to connect to a non-Cisco router across a Frame
Relay network, which encapsulation type would you select?

A.) Q933a B.) ISDN C.)
IETF D.) CISCO E.)
ANSI

Ans C There are two types of Frame Relay encapsulations; Cisco and IETF. IETF is
required when connecting a Cisco to a non-Cisco router.

114 Identify the 2 items that TCP and UDP share in common?

A.) Both use port numbers to identify upper level applications B.) Operate at the Network
layer C.) Both are Transport protocols D.) Both are reliable communications

Ans A C TCP and UPD are both layer 4 Transport protocols and both use port number to
identify upper level applications.

115 Identify 3 characteristics of IP RIP?

A.) Distance vector B.) Administrative distance is 120 C.) Periodic updates every 60
seconds D.) Uses a composite metric E.) Can load balance

Ans A B E IP RIP is a distance vector protocol, it can load balance up to 4 equal cost paths
and it's rating of trustworthiness is 120.

116 Which of the following is a layer 2 device?

A.) Switch B.)
Router C.) Repeater
D.) Hub

Ans A
A Hub and Repeater are layer 1 devices. A Router is a layer 3 device.

117 Identify the definition of demarcation?

A.) Date in which the WAN service contract expires B.) Cabling which extends from the
WAN service provider to the customerC.) Division of responsibility, where the CPE ends
and the local loop begins D.) Equipment which is located at the customer premises

Ans C
Demarcation is the point in which responsibility changes hands.

118 Identify the 3 key features of the Cisco Discovery Protocol?

A.) Off by default B.) Will allow for the discovery of layer 3 addresses on neighbor routers
C.) Verify connectivity D.) Open standard E.) Does not require any layer 3 protocols to be
configured Ans B C E CDP is used for 2 basic reasons; neighbor connectivity and layer 3
discovery if configured. It is proprietary and is on by default.

119 Identify the 3 characteristics of IPX RIP?

A.) Distance vector B.) Does not support multiple paths C.) 60 second updates D.) Default
encapsulation is SAP E.) Uses ticks and hop count as a metric

Ans A C E IPX RIP is a distance vector routing protocol, it does support multiple paths, the
default encapsulation is 'novell-ether', it uses tick count as a primary metric and hop count
as a tie breaker and it sends it’s updates every 60 seconds.

120 Identify the access-list range for an extended IP access-list?

A.) 800 - 899 B.) 1 - 99 C.) 1000 - 1099 D.) 100 - 199

Ans D
IP extended access-lists use the number range of 100-199.

121 Identify the X.25 addressing standard?

A.) X.121 B.)
X.25a C.) ITU-1
D.) Q933a

Ans A
The X.25 layer 3 addressing standards is X.121.

122 Identify 3 features of IGRP?

A.) Composite metric B.) New horizon C.) Flash updates D.) 60 periodic updates E.) Poison
reverse

Ans A C E IGRP uses a composite metric made up of bandwidth and delay by default, it
updates every 60 seconds and will trigger an update if the topology changes.

123 Where is the backup configuration file stored?

A.) RAM B.) ROM
C.) Console D.)
NVRAM

Ans D
One location to store the backup configuration is NVRAM.

124 Identify the correct pair of Novell Ethernet encapsulation and Cisco
terminology?

A.) Ethernet II, Snap B.) Ethernet 802.3, Novell-Ether C.) Ethernet SNAP, Arpa D.)
Ethernet 802.2, Snap

Ans B The default IPX LAN encapsulation is Novell-Ether which is 802.3

125 Identify 3 characteristics regarding IP access-lists?

A.) Can be configured as a standard access-list B.) Can be run from another router running
IP C.) Can be configured as a named access-list D.) Are the same as IPX access-lists E.)
Can be configured as an extended access-list

Ans A C E There are 3 types of IP access-lists; standard, extended and named. Named
access-lists can be either standard or extended depending on how they are configured.

126 Identify 3 ways in which a router can be configured?

A.) TFTP B.) Nvram C.)
Ping D.) Console E.)
Trace

Ans A B D Changes to the configuration can be entered via the console, a config stored in
NVRAM or on a TFTP server. Trace and ping are tools to verify connectivity.

127 A traffic light is an example of what type of mechanism?

A.) Collision detectionB.) Flow control C.) Sequence numbering D.) Network management

Ans B
A Traffic light is an example of flow control.

128 Windowing is a type of?

A.) Negative acknowledgement B.) Address resolution C.) Layer transition mechanism D.)
Flow control

Ans D Windowing allow the sender and receiver to dictate how much information that can
be received prior to an acknowledgement. It is a form of flow control.

129 Identify the 2 types of access-list filters that control SAP traffic?

A.) Novell-ether B.) Arpa C.) Input-sap-filter D.) Round-robin E.) Output-sap-filter

Ans C E
SAP's can be blocked by 2 methods; inbound and outbound.

130 Identify the 3 guidelines for routers in the same autonomous system?

A.) Must be configured for IGRP or RIP B.) Interconnected C.) Assigned the same
autonomous system number D.) Configured for the same routing protocol E.) Must be same
model of router

Ans B C D Autonomous system must be interconnected, assigned the same AS # and
configured with the same routing protocol.

131 Identify the hardware component used to store buffers, tables,
running-configuration etc?

A.) NVRAM B.)
ROM C.) RAM D.)
Flash

Ans C RAM is the dynamic memory area. ROM contains the boot strap code, NVRAM
contains the startup-config and Flash contains the IOS.

132 Identify 3 UDP characteristics?

A.) Reliable communication protocol B.) Applications that use UDP must incorporate
reliability C.) Connection-less oriented D.) Incorporates no handshaking

Ans B C D UPD is a layer 4 Transport protocol. It is connection-less because it does
establish a connection therefore the 3 step handshake is not needed, it does NOT implement
any flow control or acknowledgments. Any application that uses UDP must incorporate

any needed reliability.

133 Identify the IPX standard access-list number range?

A.) 600 - 699 B.) 1000 - 1099 C.) 1 - 99 D.) 100 - 199 E.) 800 - 899

Ans E
IPX standard access-list range is 800-899.

134 Which OSI layer provides best effort end to end packet delivery?

A.) Data-Link B.) Presentation C.) Network D.) Transport E.) Physical F.) Application

Ans C
Layer 3 the Network layer performs this function.

135 Identify the 2 methods to modify the routers boot sequence?

A.) Setup programB.) Boot system commands C.) RXBootD.) Config-register

Ans B D
'Boot system' command the 'config-register' are used to manipulate the boot sequence.

136 Identify the 3 pieces of hardware you would not install to prevent broadcasts?

A.) Switch B.)
Repeater C.)
Bridge D.)
Router

Ans A B C Router are implemented not only to break up networks into smaller segments
but they are used to block broadcasts.

137 Identify 2 features of PPP PAP authentication?

A.) Username and password is sent in clear text B.) Authentication messages are sent
periodically during the connection C.) More secure than CHAP D.) Remote node is control
of authentication process

Ans A D PPP PAP authentication sends the username and passwords in clear text and the
remote node initiates the authentication process.

138 Identify the switching method that examines the destination MAC address as the

frame is being received then begins forwarding the frame prior to receiving the entire
frame?

A.) Fragment-free B.) Store and Forward C.) Cut-through D.) Fast forward

Ans C Cut through examines the destination MAC address and begins forwarding the frame
prior to receiving the entire frame.

139 Identify 1 characteristic of RARP?

A.) IP to MAC address translation B.) Connectionless delivery of packets C.) Can be used
to initiate remote O/S load sequence D.) Generates error and control messages

Ans C Reverse Address Resolution Protocol is used to obtain a layer 3 address if the MAC
address is known which then facilitates the loading of the O/S.

140 Identify the protocol to test connectivity without configuring any layer 3
protocols?

A.) TCP B.) Ping C.)
IP D.) CDP E.)
Telnet

Ans D CDP can be used to verify connectivity prior to any layer 3 protocols being
configured.

141 LMI operates between the Frame Switch and what other device?

A.) CPE device B.) Another Frame Switch C.) X.25 switch D.) Novell File Server

Ans A LMI stands for local management interface. It operates between the Frame Relay
switch and the customer equipment.

142 Identify IPX SAP and it's purpose?

A.) Sonet Access Pipe - interface to Sonet ring B.) Service Advertising Protocol - advertise
services C.) Server Appletalk Protocol - appletalk directory services D.) Service Access
Point - identify upper layer protocols

Ans B
SAP is an Novell protocol to advertise services.

143 Identify the default values that make up IGRP's composite metric?

A.) Bandwidth B.) Load C.) Reliability D.) MTU E.) Delay

Ans A E IGRP can be configured to use all 5 within it's metric. By default it uses
bandwidth and delay.

144 Identify the default serial encapsulation?

A.) ISDN B.) HDLCC.) SDLC D.) Frame Relay E.) PPP

Ans B
The default serial encapsulation is HDLC.

145 Identify the purpose of ARP?

A.) Avoiding routing loops B.) Determining a workstation's IP address C.) Sending a
directed broadcast D.) Determining a workstation's MAC address

Ans D
ARP is used to find a devices MAC address given an IP address.

146 What is the purpose of the DLCI?

A.) Identifies the remote routers B.) Contained with a 802.2 frame for routing purposes C.)
Used with PPP during authentication D.) Identifies the PVC in a Frame Relay network

Ans D
DLCI stands for Data Link Connection Identifier. It identifies the local PVC.

147 Identify 3 characteristics of the Network layer (OSI layer 3)?

A.) Connection oriented B.) Path determination
C.) Supports multiplexing D.) Manages
sessions E.) Packet forwarding

Ans B C E The network layer is responsible for routing which entails learning the paths,
selecting the best path and forwarding the packet. Because it services multiple layer 4
protocols it multiplexes.

148 Identify 3 characteristics of switches?

A.) Increase available bandwidth B.) Decrease broadcast traffic C.) Support full duplex in a
multipoint topology D.) Make forwarding decision using MAC address E.) Create collision
domains

Ans A D E Switches operate at layer 2. They increase bandwidth by reducing the number
of devices sharing the media. They isolate collisions. Like a bridge they forward traffic
based upon layer 2 address/ MAC address.

149 Which OSI layer handles physical address, network topology?

A.) Presentation B.)
Physical C.) Transport D.)
Application E.) Data-Link
F.) Network

Ans E
Layer 2 the Data-Link layer performs this function.

150 Identify 2 reasons for disabling CDP?

A.) If the router is not configured for RIP B.) Save
bandwidth by eliminating overhead C.) If the router is
configured for Appletalk D.) When connected to a
non-Cisco router

Ans B D CDP can be disabled here are a couple of reasons. Connecting a Cisco router to
a non-Cisco router. Don't want to exchange CDP information to save bandwidth.

151 Identify 3 characteristics of ISDN?

A.) Transports voice and data B.) Transports voice only C.) Support both BRI and PRI D.)
Runs over existing phone lines E.) Same as X.25

Ans A C D ISDN supports voice, data, and video. It runs over existing phone lines and
supports 128K (BRI) and T1 (PRI).

152 Identify the 3 characteristics of IGRP?

A.) Uses hop count as a metric B.) Supports multiple unequal paths C.) Administrative
distance is 100 D.) Configured with an Autonomous system number E.) Link state

Ans B C D IGRP is a distance vector routing protocol, it's degree of trustworthiness is 100,
it can support up to 6 un-equal paths and must be configured with an autonomous system
number.

153 Identify 2 features of PPP CHAP authentication?

A.) Username and password is sent in clear text B.) Authentication messages are sent
periodically during the connection C.) Less secure then PAP D.) Local router 'challenges'
the remote router

Ans B D PPP CHAP authentication message are sent periodically during the connection by
challenging the other end of the connection. It is more secure than PAP and passwords and
username are encrypted.

154 Identify the default IPX serial encapsulation?

A.) Novell-Ether B.) SDLC C.) SNAP D.) HDLC

Ans D
The default IPX serial encapsulation is HDLC.

155 Identify the hardware component that stores the backup configuration?

A.) RAM B.) NVRAM
C.) Flash D.) ROM

Ans B NVRAM contains the backup config. RAM is the dynamic memory area, ROM
contains the boot strap code and Flash contains the IOS.

156 Identify the extended IP access-list number range?

A.) 600 - 699 B.) 1 - 99 C.) 900 - 999 D.) 100 -
199

Ans D
The extended IP access-list range is 100-199.

157 Identify 3 Fast Ethernet technologies?

A.) 100 Base FastEther B.) 100 Base FX C.) 100 Base T4 D.) 100 Base TX

Ans B C D
100 BaseFastEther is false. 100 Base FX, TX and T4 are all valid.

158 Identify the OSI layer which is responsible for end-to-end connections?

A.) Network B.)
Transport C.) Session D.)
Data link E.) TCP

Ans B
Layer 4 is the Transport layer and is responsible for end-to-end connections.

159 Identify the 2 characteristics regarding MAC addresses?

A.) Contains a network portion and host portion B.) Always assigned by System
Administrator C.) 48 bits long D.) Contains a vendor code and serial number

Ans C D MAC addresses are assigned by the vendor. Each MAC address is 48 bits long and
made up of 24 bits vendor code and 24 bits serial number.

160 Identify the number range for IPX SAP filters?

A.) 900 - 999 B.) 1000 -
1099 C.) 800 -899 D.)

100 - 199

Ans B
The IPX SAP filtering range is 1000-1099.

161 What is the purpose of ARP?

A.) IP to host name resolution B.) Host name to IP address resolution C.) Mac to IP address
resolution D.) IP to Mac address resolution

Ans D Address Resolution Protocol resolves the MAC address if the IP address is known.
It is a layer 3 protocol.

162 Which OSI layer establishes, maintains and terminates sessions between hosts?

A.) Application B.) Physical C.) Data-Link D.) Presentation E.) Network F.) Session

Ans F
Layer 5 the Session layer performs this function.

163 Which statement is true regarding Administrative distance?

A.) It is a metric B.) Number of hops between two routers C.) Trustworthiness of the
routing information D.) RIP Administrative distance is 100

Ans C Administrative distance is rating of trustworthiness of the routing information. The
lower the AD the better the information.

164 Identify the purpose of the Ping command?

A.) Share routing information with a neighbor router B.) Transmit user data when buffers
are full C.) Test connectivity at layer 3 D.) Test entire protocol stack

Ans C
The ping command tests layer 3 connectivity.

165 Identify the order of the 5 step encapsulation?

1 1. Create the segment
2 2. Convert the frame to bits
3 3. Create the packet
4 4. Create the frame
5 5. User creates the data A.) 1,2,4,2,5 B.) 2,1,3,4,5 C.) 5,1,3,4,2 D.) 5,3,4,1,2
Ans C Cisco 5 step encapsulation. 1) User creates Data 2) Data is converted into a segment
at layer 4 3) The segment is converted to packet at layer 3 4) The packet it converted into a

frame at layer 2 5) The frame is converted into bits at layer 1

166 The Cisco IOS is stored where?

A.) ROM B.) CD C.) Flash D.) NVRAM

Ans C
By default the Cisco IOS is stored in flash.

167 Sequence and acknowledgement numbers are used for?

A.) Layer transitioning B.) Flow control C.) Port number addressing D.) Reliability

Ans D
TCP uses sequence numbers and acknowledgements to implement reliability.

168 Identify IPX GNS and it's purpose?

A.) Go Network Server - sends a print job to a network server B.) Get Nearest Server -
locate the nearest server C.) Guaranteed Network Services - allocates resources to users D.)
Get Notes Server - locates Domino Server

Ans B
GNS stands for Get Nearest Server, initiated by a workstation.

169 Identify the true statement regarding subnetting?

A.) Allows for more host address B.) Borrow bits from the network portion of the address
C.) Allows for unlimited number of networks D.) Borrow bits from the host portion of the
address

Ans D Subnetting involves borrowing bits for the host portion of the address to be used to
subnet addressing.

170 Inverse ARP serves what purpose?

A.) Method for a local router to introduce itself to the remote end of the connection B.)
Broadcast a routing table update C.) Identify MAC addresses if the IP address is known D.)
Sent every 10 seconds used to verify the Frame Switch is still active

Ans A Inverse ARP operates in a Frame Relay network so the two end points can identify
themselves to each other.

171 Identify 3 characteristics of a MAC address?

A.) Burned into the NIC B.) 48 bits long C.) Length is 32 bits D.) Used to deliver the frame
to the end device E.) Contains a network portion and a host portion

Ans A B D The MAC address is 48 bits long not 32. It does NOT contain a network and
host portion with the address. It is used to deliver the frame to the destination device.

172 Identify 3 IP routing protocols?

A.) RIP B.)
AURPC.) OSPF D.)
IGRP E.) ARP F.)
ICMP

Ans A C D
AURP and ICMP are not routing protocols.

173 Identify the type of routing protocol that exchanges entire routing tables at
regular intervals?

A.) Link state B.) Interior gateway protocols C.) Appletalk routing D.) Distance vector

Ans D Distance Vector routing protocols exchange entire routing tables with it's neighbors.
Link State routing protocols exchange LSP's to share information regarding the networks
they know.

174 Identify the type of hardware required to connect a Token ring network to an
Ethernet network?

A.) Repeater B.) TR-Enet C.) Router D.) Token Ring to Ethernet translation hub

Ans C Routers are used to connect dissimilar networks with different access-methods, like
connecting Token Ring to Ethernet.

175 Identify 3 characteristics regarding CDP?

A.) On by default B.) Shows only directly connected neighbors C.) Requires IP or IPX D.)
60 second update interval by default E.) 30 second updates interval by default

Ans A B D CDP stands for Cisco Discovery Protocol. It is used to discover directly
connected neighbors, it is on by default and has a 60 second update interval by default.

176 Identify 2 transport layer protocols?

A.) IP B.) TCP
C.) CDP D.)
ARP E.) UDP

Ans B E
TPC and UDP are 2 layer4 Transport protocols.

177 Identify 2 features of X.25?

A.) Supports only IP B.) Utilizes switched and permanent virtual circuits C.) Contains
minimal flow control and error recovery D.) Utilizes LAPB as it's data-link protocol

Ans B D

X.25 utilizes LAPB and uses switched and permanent VC's. It supports multiple layer
protocols and is heavy laden with error detection and correction mechanisms.
180 Identify the purpose of the Trace command?

A.) Explorer packet transmitting routing information B.) Test connectivity C.) Determine
the path a packet is taking through the network D.) Transmits user data when buffers are
full

Ans C The trace command is used to determine the path a packet has taken through the
network.

190 Identify the purpose of the TCP 3 step handshake?

A.) Setup a un-reliable connection B.) Initialize routing tables C.) Synchronize sequence
numbers between hosts D.) Connection tear down process

Ans C The 3 step handshake establishes the parameters required for a TCP connection.
During the handshake process sequence numbers are synchronized allowing for the end
points to properly acknowledge and re-assemble the segments.

191 Identify 2 PPP characteristics?

A.) Is proprietary to Cisco B.) Supports authentication C.) Support compression D.) Run on
a multi-access network

Ans B C PPP supports authentication; PAP and CHAP. It also supports compression;
Stacker and Predictor.

192 Which statement is true regarding half duplex?

A.) Only works in a point-to-point configuration B.) Allows for transmitting and receiving
but not a the same time C.) Allow for transmitting and receiving of data simultaneously
D.) Doubles the bandwidth

Ans B Half duplex is analogous to a single a lane bridge, it can handle traffic in both
directions but no at the same time.

193 Identify the purpose of the wildcard mask?

A.) Match a certain portion of the IP address while ignoring the rest of the address B.)

Determine the class of the IP address C.) Determine the network portion of an IP address D.)
Hide the host portion of an IP address

Ans A The purpose of the wildcard mask to match a certain portion of the IP address while
ignoring the rest.

194 Identify the OSI layer associated with bits?

A.) Physical B.) Network C.) Binary D.) Data link

Ans A
The Physical layer converts the frames to bits.

195 Identify the type of routing protocol that maintains a topological database of the
network?

A.) Topological state B.) Shortest Path First C.) Link state D.) Distance vector

Ans C Link State routing protocols maintain a database that lists all the networks in the
internetwork.

196 Identify the 3 major functions at layer 3 of the OSI model?

A.) Forwarding process B.) Logical addressing C.) End-to-end connections D.) Path
selection E.) MAC address examination F.) Network monitoring

Ans A B D Layer 3 determines the path, forwards the packet and implements software or
logical addressing.

197 Identify the 2 rules used when configuring a Distance Vector routing protocol?

A.) Physically connected network(s) B.) Configure the classful address, no subnets C.)
Enable CDP so neighbors can be detected D.) Configure all networks in Area0

Ans A B When configuring a Distance Vector routing protocol only assign the physically
connected networks with the classful address only.

198 Identify 3 characteristics of an IP address?

A.) Contains a network portion and a host portion B.) 32 bits long C.) Unique to each
network D.) Part of the default Cisco configuration E.) Referred to as the hardware address

Ans A B C An IP address is 32 bits long, it is referred as the logical or software address.
It contains a network and host portion. Each IP address is unique.

199 Identify 3 feature of access-lists?

A.) Implicit deny will deny any packets not matched B.) Processed sequentially from
bottom to top C.) Processed sequentially from top to bottom D.) If a packet is denied it
would be tested against the remaining statements in the access-list E.) Once a match is
made the packet is either denied or permitted F.) Enabled on all interfaces by default

Ans A C E Access-list are processed from top to bottom, once a match occurs the packet is
either denied or permitted and is no longer tested and if no match occurs the packet is
denied via the implicit deny.

200 Which OSI layer performs code conversion, code formatting and encryption?

A.) Physical B.)
Data-Link C.)
Application D.)
Transport E.)
Presentation F.)
Network

Ans E
Layer 6 the Presentation layers performs this function.