TCP/IP Protocols

Match the well known transmission control port (TCP) port numbers with the associated applications.

20 - FTP data 21 - FTP control 23 - Telnet 25 - SMTP Simple Mail Transfer Protocol 53 - DNS Domain Name System)

How many fragments will the transmitting device have to create to match the datagram to the segment's 512 maximum transfer unit (MTU) size, having a 1,500-byte datagram, and a 20-byte IP header?

4

Identifies the application, within a host, to which the transmission should be delivered.

Destination Port (16 bits)

Because IP is a best effort protocol, few implementations use the Type of Service (ToS) fields as Request for Comments (RFC) 791 defines them. QoS services used for such delay-sensitive, bandwidth-intensive services as video and Voice over Internet protocol (VoIP) modify these bits to classify packets based on the type of traffic they carry. Network devices all along the packet's route must recognize these bit settings and provide the appropriate network services.

Differentiated Services Code Point (DSCP)

Precendence, Delay, Throughput, Reliability, and cost bits

Differentiated Services Code Point (DSCP) Field

Explicit congestion notification-Echo If SYN is 1 the TCP peer is ECN capable If SYN is 0 there is network congestion impending or occurring

ECE

The 13-bit Fragment Offset field specifies the fragment's location in the original datagram. The first fragment has offset 0, and the remaining fragments are measured as eight 8-byte units, representing the fragment's beginning in relation to the start of the original payload.

Fragment Offset

This 16-bit field is used as an IP header checksum only. Because some Header fields change as the packet traverses the network (for example, the TTL or the DSCP fields), each hop where the header is processed recomputes the checksum.

Header Checksum

Specifies the hardware and protocol address lengths in bytes, respectively. MAC addresses are 6, and IP addresses are 4.

Header Length (HLEN) and Protocol Length (PLEN) (8 bits each)

How does the user datagram protocol (UDP) support multiple application destinations on the same host?

It carries port numbers in its header, used to logically address a destination application.

How does a transmission control protocol (TCP) process handle a failed connection?

It sends an RST segment when the maximum retry count is exceeded.

How does the transmission control protocol (TCP) receiver control the data flowing from the source?

It sets the receive window size with each ACK segment it returns.

Match the well known user datagram protocol (UDP) port numbers with their associated application.

Port 67 - BOOTP Server Port 68 - BOOTP Client Port 69 - TFTP Trivial File Transfer Protocol Port 161 - SNMP Simple Network Management Protocol

The 8-bit Protocol field specifies which high-level protocol was used to create the message carried in the Data area of a datagram. For example, TCP is assigned protocol number 6, and UDP is assigned protocol number 17.

Protocol

Specifies the Network Layer protocol the sender is mapping to the hardware address (for example, IP = 0 x 0800).

Protocol type (16 bits)

Which statement best describes proxy address resolution protocol (ARP)?

Proxy ARP allows a router to answer an ARP request on behalf of a remote host.

A host on the local IP network segment has data to send to another host, located on another IP network. The source host needs to resolve the destination host's IP address to a media access control (MAC) address. Which protocol might the gateway router run in order to answer the local host's address resolution protocol (ARP) request?

Proxy ARP.

The destination transmission control protocol (TCP) process has set a 1,000-byte receive buffer window. The source TCP sequence number starts at 23,100 and sends the following segments, in order: Segment 1-200 bytes; Segment 2-300 bytes; Segment 3-200 bytes; and Segment 4-300 bytes. The last acknowledgment the source received was sequence number 23,600 saying the receive buffer can now hold 800-300 byte streams. The retransmission timer for sequence number 23,600 has expired, so what will the source TCP do next?

Resend segments 3 and 4.

Consists of the 6 bits following the Data Offset field, which are reserved and always zero.

Reserved

Which IP protocol allows a diskless workstation to contact a server and obtain an IP address?

Reverse address resolution protocol (RARP).

Synchronize sequence numbers

SYN

Which type of packet does the receiving transmission control protocol (TCP) send to the source indicating its receipt of the source's SYN packet?

SYN-ACK

Sender hardware or IP address. The addresses are carried as follows: Packet bytes 8-13—The sender's hardware (MAC) address Packet bytes 14-17—The sender's logical (IP) address

Sender hardware/IP

Identifies the sequence number of the first data byte in the segment (except when the SYN bit is set). When SYN is set, the sequence number is the initial sequence number (ISN) and the first data byte is ISN+1. For example, if SYN is set, the ISN is 100, and the data starts at sequence number 101.

Sequence Number (32 bits)

The 16 bit sending host port number. This is optional, and if unused is set to 0.

Source Port

Identifies the application, within a host, that originated the transmission.

Source Port (16 bits)

These 32-bit fields specify the sender and expected recipient IP addresses. They do not change as the packets traverse the network, unless the datagram passed through a network address translation (NAT) device.

Source and Destination IP Addresses

is a reliable, byte-stream-oriented, virtual circuit protocol.

TCP

use several mechanisms to reliably carry data between host ports.

TCP segments

Which best describes IP's use of the time-to-live (TTL) field?

The TTL specifies the time a datagram is allowed to remain on the network.

What happens first when an IP host needs to resolve an IP address to a media access control (MAC) address?

The sending host looks in its address resolution protocol (ARP) cache for the necessary mapping.

What happens to a datagram marked as "do not fragment" if it must be transmitted across a network segment with a maximum transmission unit field (MTU) smaller than the datagram?

The transmitting network device will drop the datagram, and notify the source.

is a connectionless counterpart to TCP.

UDP

The 16-bit UDP datagram size indicator, expressed in bytes, represents the length of the header and the data combined. The minimum datagram size is 8 bytes (the header alone).

UDP Message Length

A variation of ARP, where an intermediate device, such as a router, sends an ARP response to the requesting host on behalf of the end node.

proxy address resolution protocol (ARP)

This 4-bit field contains the IP version used to create the datagram. This field ensures that the sender, receiver, and intervening gateways agreterm-6e on the correct datagram format. The most widely used IP version is Internet protocol version 4 (IPv4); Internet protocol version 6 (IPv6) is now being deployed. These bits will read 0100 for IPv4.

version

Which user datagram protocol (UDP) port address do simple network management protocol (SNMP) agents use to send and receive management requests?

161.

On an IP network, all hosts must be able to handle a packet size of at least how many bytes?

576

Which is the Internet protocol (IP) header protocol number used to specify that the packet's contents were created with transmission control protocol (TCP)?

6

The local transmission control protocol (TCP) process sends four segments, each 4 bytes long. The first sequence number is 7,806,002. Which is the acknowledgment number the receiving process returned to indicate it received segment one?

7,806,006

Main Menu5of12 What provides user datagram protocol (UDP) with the ability to demultiplex data for an application?

A UDP destination port number.

Indicates Acknowledgment Number field is significant

ACK

Which types of transmission control protocol (TCP) segments contain window size advertisements?

ACK

Which three parts of the transmission control protocol (TCP) header help the protocol ensure reliable communications between applications? (Choose three.)

ACK control bits Sequence numbers Checksum

resolves IP addresses to MAC addresses.

ARP

Which portion of the transmission control protocol (TCP) header specifies the next sequence number the receiver expects from the connection source?

Acknowledgment number.

In TCP/IP, what does a network host use to find a physical address, given a logical address?

Address resolution protocol (ARP).

You know the logical address of an associate's computer on the company's local network and you want to learn the media access control (MAC) address of your associate's computer. Which of the following tools would you use?

Address resolution protocol (ARP).

The 16-bit checksum generated from the UDP header, and the data. Since IP only calculates a header checksum, this is UDP's only mechanism for verifying data integrity.

Checksum

Verifies a segment was transmitted without errors. The devices calculate the checksum from the TCP header and the application data. If the checksum fails when the data is received, an error is detected, and the segment is discarded.

Checksum (16 bits)

sets the first three bits of the DSCP field to match the IP packet header ToS bits. This assures backward compatibility in networks where ToS bits are used to represent service classes. DiffServ nodes must support these PHBs where IP precedence bits are used.

Class-Selector PHB

Main Menu139of143 At which Open Systems Interconnection reference model (OSI/RM) layer does the physical address reside?

Data Link

Which of the following two ports are contained in the transmission control protocol (TCP) header?

Destination and source.

the EF PHB sets a specific PHB for assignment to a single preferred traffic flow within the DiffServ domain. This preferred flow would be one that absolutely must receive low jitter, low delay, and low loss treatment across the network. By setting the DSCP to '101110', we guarantee that this one flow receives at least the EF PHB-defined bandwidth at each departure point. The EF PHB is frequently used in DiffServ domains with two traffic flow classes, such as realtime voice traffic carried over the same network as non-realtime data

Expedited Forwarding (EF) PHB

This two-bit field tracks end-to-end network congestion between network devices.

Explicit Congestion Notification (ECN)

Finished, no more data from sender

FIN

The 3-bit Flags field controls fragmentation. Bit 0-Reserved Bit 1—Don't fragment (DF) bit: - 0—May fragment - 1—Don't fragment Bit 2—More fragments (MF) bit: - 0—Last fragment - 1—More fragments If a network device is preparing to send a datagram longer than the network MTU and sees the DF bit set, it returns an ICMP error message to the sender and discards the packet. With the exception of the last fragment, all fragments have the MF bit set to 1.

Flags

Which three choices are transmission control protocol (TCP) features? (Choose three.)

Flow control. Packet error recovery. Demultiplexing multiple applications.

Which Internet protocol (IP) packet fragmentation header field specifies where the fragment belongs in the original datagram?

Fragment Offset.

Specifies the hardware interface for which the requester requires a response (for example, l for Ethernet).

Hardware type (16 bits)

provides connectionless delivery of datagrams across a TCP/IP network.

IP

Which addresses combine to create a transmission control protocol (TCP) socket?

IP and port.

Each datagram must have a unique identification number so receiving hosts can reassemble the fragmented datagram. The Identification field is 16 bits long.

Identification

these fields control a datagram's fragmentation and reassembly. Most datagrams are fragmented and encapsulated into multiple smaller frames. For example, a 2,500-byte-long packet, carried over an Ethernet network, is fragmented by the transmitting host into two pieces to fit the Ethernet MTU of 1,500 bytes.

Identification, Flags, and Fragment Offset

This 4-bit field provides the number of 32-bit words in the header. IP headers must be a minimum of 20 bytes long. IP options can extend the header length by 4 bytes (32 bits) at a time. The most common header, which contains no padding or IP options, measures 20 bytes long and has an IHL field of 5 (0101).

Internet Header Length (IHL)

Also known as IP next generation, is an IP standard designed to add undecillions of host IP addresses to the nearly exhausted IPv4 address space. provides additional features compared to the current IPv4, including longer addresses (128 bits) and integrated security and Quality of Service (QoS) support.

Internet Protocol version 6 (IPv6)

Which best describes transmission control protocol's (TCP) use of the Window header field?

It is bidirectional, so both ends can control data flow.

What happens if the retransmission timer set by the sending transmission control protocol (TCP) times out before it receives an acknowledgment.

It retransmits the outstanding segments.

How does a sending transmission control protocol (TCP) process handle a zero receive window size?

It sends periodic probe segments and waits for an ACK with a nonzero window size.

The maximum amount of information that can be carried by a datagram or frame. For example, the ___ of Ethernet is 1,500 bytes of information.

MTU

the maximum frame or packet size a network topology is designed to transport

Maximum Transmission Unit (MTU)

Which three of the following terms refer to a physical address? (Choose three.)

Media access control (MAC) address. Adapter address. Hardware address.

Explicit congestion notification (ECN)-nonce concealment (experimental Request for Comments [RFC] 3540)

NS

Which network segment hosts respond to an address resolution protocol (ARP) request?

Only the target host responds

Specifies whether this is an ARP or reverse address resolution protocol (RARP) request or response. Possible values, as defined in Request for Comments (RFC) 826 and 903, include: 1—ARP Request 2—ARP Reply 3—Request reverse (RARP request) 4—Reply reverse (RARP reply)

Operation (16 bits)

This variable-length field is used for various options, such as recording the route taken, specifying the route to be taken, and time stamping. The option field can be zero or more bits in length. Padding is used to ensure that the option field fills at least 32 bits.

Options

Variable-length field available to indicate TCP options. For example, this field might be used to indicate the maximum segment size the sender is willing to accept.

Options (multiple of 8 bits)

Push function; no more data is being generated, send current data

PSH

Indicates specific number of 0 bits added to ensure that the header ends on a 32-bit boundary.

Padding

This field consists of a specific number of 0 bits added to guarantee the IP header ends on a 32-bit boundary.

Padding

Which two of the following are examples of local area network (LAN) logical addresses? (Choose two.)

Port 23 201.90.35.78

Which transmission control protocol (TCP) function forces data delivery before filling the transmit buffer?

Push

Which two flags can a sending application set to force the transmission control protocol (TCP) process to send data before filling the transmit buffer? (Choose two.)

Push (PSH). Urgent (URG).

Reset connection

RST

Which protocol allows a diskless workstation to contact a server and obtain an Internet protocol (IP) address?

Reverse address resolution protocol (RARP).

Which transmission control protocol (TCP) header control bit represents that the message is initiating a connection?

SYN.

Main Menu10of12 What is the primary difference between transmission control protocol (TCP) and user datagram protocol (UDP)?

TCP messages are tracked to ensure they are received; UDP messages are sent without tracking.

Target hardware address (RARP) or IP address (ARP). The addresses are carried as follows: Packet bytes 18-23—The destination hardware (MAC) address. Set to the target MAC address (RARP), or all 0s (ARP). Packet bytes 24-27—The destination logical (IP) address. Set to the target IP address (ARP), or all 0s (RARP).

Target hardware/IP

Which address resolution protocol (ARP) feature allows the local host to maintain a mapping of recently discovered IP-to-media access control (MAC) addresses?

The ARP cache

Which statement best describes Handshake #1?

The initiator sends a SYN segment to the target host's transmission control process (TCP) process.

The five steps of (1) obtaining logical addresses, (2) obtaining physical addresses, (3) establishing a connection between applications, (4) the transfer of information, and (5) the termination of the connection are necessary to accomplish what?

The transfer of information across a transmission control protocol/Internet protocol (TCP/IP) network.

Which statement best describes transmission control protocol's (TCP) use of sequence numbers?

They identify the sequence number of the first data byte in the segment.

This 8-bit field specifies the time (in seconds) the datagram can remain on the internetwork. Each gateway and host the packet traverses decrements this field by one; after the packet's TTL expires, network devices remove it from the network. Because network devices almost always forward a packet in less than one second, the TTL is used as the packet's hop count.

Time-to-Live (TTL)

This 16-bit field provides an IP datagram's length in bytes, including the header and data (Data Length = Total Length - IHL). The maximum size is 65,535 bytes, and all hosts must be able to handle a packet of at least 576 bytes. Modern network devices handle larger datagrams.

Total Length

Which three of the following applications utilize user datagram protocol (UDP)? (Choose three.)

Trivial file transfer protocol (TFTP). Simple network management protocol (SNMP). Domain Name System (DNS).

Main Menu140of143 Transmission control protocol (TCP) establishes which type of circuit between applications?

Virtual

A technique used in best-effort delivery systems to avoid packet loops. Each Internet protocol (IP) packet is assigned an integer TTL within the IP header field when it is created. IP gateways/routers decrement the TTL field when they process a packet and discard that packet when the TTL value reaches zero.

time-to-live (TTL)

Applies only if the acknowledgement (ACK) control bit is set. The ACK number is the next sequence number the sender of the segment is expecting to receive. For example, if a host receives sequence number 101, it sends a segment back with the ACK number set to 102. It expects to receive sequence number 102 next. If a connection is established, this value is always sent.

Acknowledgment Number (32 bits)

four classes of forwarding to guarantee a certain amount of bandwidth to an AF based on required throughput, delay, jitter, loss or according to priority of access to network services. When using the AF PHBs, packets within each class are marked to one of three drop precedence levels. AF assigns resources to each class and allocates those resources according to a packet's drop precedence. AF provides for a total of 12 class-to-precedence pairings.

Assured Forwarding (AF) PHB

Address resolution protocol (ARP) requests are sent as which type of Ethernet frame?

Broadcast

How does a diskless workstation identify itself when requesting an IP address using reverse address resolution protocol (RARP)?

By its media access control (MAC) address.

Congestion window reduced flag is set by the sending host to indicate ECE flag was set for congestion

CWR

Accomplishes handshaking and other specific functions. They are from left to right:

Control Bits (9 bits)

The Application Layer data to which the header is appended. This field may be padded with 0s as necessary to fill the field.

Data

Specifies the number of 32-bit words in the TCP header. The Data Offset indicates where the TCP header ends, and where the upper-layer protocol data begins. Because the TCP header can vary in size, the Data Offset field ensures that the receiver knows where the data begins. Even with options, the offset is always a multiple of 32 bits.

Data Offset (4 bits)

Internet protocol (IP) provides which three of the following services to transmission control protocol (TCP)? (Choose three.)

Datagram routing. Time-to-live (TTL). Differentiated Services Code Point (DSCP)

represents no special handling, which is the network's default best-effort service. All DiffServ nodes support the default PHB, which sets all six bits to zero: 000000.

Default PHB (Per Hop Behavior)

Which IP packet bits does open shortest path first (OSPF) use to provide Type of Service (ToS) routing?

Delay, throughput, reliability, and cost (D-T-R-C) bits.

The 16-bit destination host port number. This is the communication's endpoint and is demultiplexed by the destination computer's processes.

Destination Port

A client Domain Name System (DNS) resolver wishes to resolve a Web server fully qualified domain name (FQDN) to an IP address. It sends its first message to its designated DNS server, requesting name to IP address resolution. This message contains: 1) The LAN protocol Data Link Layer header and trailer. 2) The IP header. 3) The user datagram (UDP) header. 4) The DNS resolver request. Why did the resolver send the DNS request in the first packet, rather than send an initial empty SYN packet?

UDP does not use SYN and ACK packets.

Which is a true statement concerning user datagram protocol (UDP)?

UDP servers must listen for service requests on well known ports, or else the transactions may fail.

Which best describes the user datagram protocol (UDP) demultiplexing process?

UDP uses port numbers to allow multiple applications to communicate simultaneously on the same host.

Indicates Urgent Pointer field is significant

URG

Only significant if the URG control bit is set. This value is a positive offset from the urgent data sequence number, and indicates the beginning of the nonurgent data.

Urgent Pointer (16 bits)

Which IP packet frame field ensures that the gateways handling a datagram agree on the datagram's format?

Version.

Used for end-to-end flow control. Indicates the number of bytes, beginning with the one in the Acknowledgment Number field, that the receiver is willing to accept. The Window field is bidirectional; that is, either the sender or receiver can set this value. Thus, both ends of a connection can control data flowing from the other.

Window (16 bits)

The Internet protocol (IP) process of dividing a datagram into smaller pieces that will better suit the transporting network's maximum transmission unit (MTU).

fragmentation

The primary purpose of TCP

is to provide a reliable, connection-oriented delivery service between processes residing on different hosts If it is to provide reliable communications over a best-effort network (the Internet, for example), TCP must provide the following services: Name service File transfer services Virtual terminal Web servers