Networking answers
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The document discusses network protocols and packet analysis using Wireshark. It provides answers to questions about the TCP/IP protocol stack and concepts like encapsulation, service access points, and unicast, multicast, and broadcast packets. Regarding question 1, the document states that the data link layer attaches a trailer to messages to detect bit errors. It then discusses that the trailer's main function is to detect bit errors using techniques like CRC.
![4. Capture packets using Wireshark and describe the concept of “Service Access
Points (SAP)” between layers. Show the necessary portions between each layer
pair, e.g. Application layer and TCP, between TCP and IP, …
Answer:
The Captured Packet using Wireshark is;
No. Time Source Destination Protocol Info
1 0.000000 192.168.2.3 mail.packet0.com TCP 1061 > http
[SYN] Seq=0 Ack=0 Win=16384 Len=0 MSS=1460
2 0.063590 mail.packet0.com 192.168.2.3 TCP http > 1061
[SYN, ACK] Seq=0 Ack=1 Win=5840 Len=0 MSS=1380
3 0.063665 192.168.2.3 mail.packet0.com TCP 1061 > http
[ACK] Seq=1 Ack=1 Win=16560 Len=0
4 0.064056 192.168.2.3 mail.packet0.com HTTP GET / HTTP/1.1
5 0.163470 mail.packet0.com 192.168.2.3 TCP http > 1061
[ACK] Seq=1 Ack=399 Win=6432 Len=0
6 0.193849 mail.packet0.com 192.168.2.3 HTTP HTTP/1.1 200 OK
(text/html)
7 0.201317 mail.packet0.com 192.168.2.3 HTTP Continuation
8 0.201408 192.168.2.3 mail.packet0.com TCP 1061 > http
[ACK] Seq=399 Ack=2761 Win=16560 Len=0
9 0.208895 192.168.2.3 mail.packet0.com TCP 1062 > http
[SYN] Seq=0 Ack=0 Win=16384 Len=0 MSS=1460
10 0.280617 mail.packet0.com 192.168.2.3 HTTP Continuation
11 0.287876 mail.packet0.com 192.168.2.3 HTTP Continuation
The captured packets and the service access point shortly SAP is the label for the two
end-point of the network according to OSI system.
The service access point is virtually the point where one layer makes a request to
another layer for providing its service. The requests are made by the protocol like TCP
or IP in the respective layers. Another example is in IEEE 802.15.4, there are two SAP
requesting service to the physical layer and from MAC of the OSI. SAP can also be
used in Ethernet of Logical Link Control of IEEE format protocol.
In OSI model, the Network Layer is divided into two parts namely CONS and CLNS
used for construction an address.](https://image.slidesharecdn.com/networking-answers-151020184909-lva1-app6892/85/Networking-answers-3-320.jpg)
Networking answers
- 1. Solutions 1. On TCP/IP protocol suite, which layer has a “Trailer” that is the control bits attached at the end of a message? Answer: The data link layer has a “Trailer” attached at the end of a message to detect bit error. The data link layer adds the Trailer like the diagram below. 2. What is the function of the Trailer? Answer: The “Trailer” is a binary message bit on TCP/IP protocol suite; the trailer is attached at the end of the message. The header and trailer are encapsulated at data link layer. The system allocates memory for the trailer bits and the allocated memory is very special. The sequence of the bit transferred throughout the network The main function of the “Trailer” is the attached message detects the bit error like CRC (cyclic redundancy check). The trailer also corrects the bit error; detection and correction both are done by the trailer.
- 2. 3. Capture packets using Wireshark and show the concept of “Encapsulation” on the captured packets. Answer: The screen-shot of Captured packets using Wire shark is below. The concept of Encapsulation is Ethernet and it is as below; $capinfos _tmp_v6-http.cap File name: _tmp_v6-http.cap File type: Wireshark/tcpdump/... - libpcap File encapsulation: Ethernet Packet size limit: file hdr: 65535 bytes Number of packets: 55 File size: 9159 bytes Data size: 8255 bytes Capture duration: 325 seconds Start time: Sun Aug 05 15:11:19 2007 End time: Sun Aug 05 15:16:44 2007 Data byte rate: 25.40 bytes/sec Data bit rate: 203.16 bits/sec Average packet size: 150.09 bytes Average packet rate: 0.17 packets/sec SHA1: 7fd9486dea4cd77ae58cefab62fe3adf28f50cad RIPEMD160: decfdd7e46f540674bb1c3c796fd97af8c639e1a MD5: 803acd7573a6bd87baa777fedb432364 Strict time order: True
- 3. 4. Capture packets using Wireshark and describe the concept of “Service Access Points (SAP)” between layers. Show the necessary portions between each layer pair, e.g. Application layer and TCP, between TCP and IP, … Answer: The Captured Packet using Wireshark is; No. Time Source Destination Protocol Info 1 0.000000 192.168.2.3 mail.packet0.com TCP 1061 > http [SYN] Seq=0 Ack=0 Win=16384 Len=0 MSS=1460 2 0.063590 mail.packet0.com 192.168.2.3 TCP http > 1061 [SYN, ACK] Seq=0 Ack=1 Win=5840 Len=0 MSS=1380 3 0.063665 192.168.2.3 mail.packet0.com TCP 1061 > http [ACK] Seq=1 Ack=1 Win=16560 Len=0 4 0.064056 192.168.2.3 mail.packet0.com HTTP GET / HTTP/1.1 5 0.163470 mail.packet0.com 192.168.2.3 TCP http > 1061 [ACK] Seq=1 Ack=399 Win=6432 Len=0 6 0.193849 mail.packet0.com 192.168.2.3 HTTP HTTP/1.1 200 OK (text/html) 7 0.201317 mail.packet0.com 192.168.2.3 HTTP Continuation 8 0.201408 192.168.2.3 mail.packet0.com TCP 1061 > http [ACK] Seq=399 Ack=2761 Win=16560 Len=0 9 0.208895 192.168.2.3 mail.packet0.com TCP 1062 > http [SYN] Seq=0 Ack=0 Win=16384 Len=0 MSS=1460 10 0.280617 mail.packet0.com 192.168.2.3 HTTP Continuation 11 0.287876 mail.packet0.com 192.168.2.3 HTTP Continuation The captured packets and the service access point shortly SAP is the label for the two end-point of the network according to OSI system. The service access point is virtually the point where one layer makes a request to another layer for providing its service. The requests are made by the protocol like TCP or IP in the respective layers. Another example is in IEEE 802.15.4, there are two SAP requesting service to the physical layer and from MAC of the OSI. SAP can also be used in Ethernet of Logical Link Control of IEEE format protocol. In OSI model, the Network Layer is divided into two parts namely CONS and CLNS used for construction an address.
- 4. 8. Among the packet you capture, can you identify “Unicast”, “Multicast”, and “Broadcast” packets? Answer: The answer is “Yes” “When capturing the Ethernet traffic other than Unicast traffic to and from the host on which you're running Wireshark, Multicast traffic, and Broadcast traffic, the adapter will have to be put into promiscuous mode, so that the filter is switched off and all packets received are delivered to the host”. (http://wiki.wireshark.org/CaptureSetup/Ethernet) Yes, we can identify the three packets. The “Unicast” is that, which is sent address or to the host. The “Multicast” are sent address of multicast, for which they are being sent for filtration of the host. All the sent packets are “Broadcast” packets in the captured packets *******************************END*******************************