5. (10pts) An IPv6 datagram consists of the following (in the stated order): Bas

Question

5. (10pts) An IPv6 datagram consists of the following (in the stated order): Base Header Encapsulating security Payload Header Hop-by-Hop Header Routing Header and TCP Segment. a) Draw the datagram and show what the contents of each of the Next Header fields would contain. You don't have to look up the actual numeric value, just explain what it would be referencing next. b) If each extension header is 42bytes long and the value of the payload length field in the Base Header is 204bytes, what is the size of the IPv6 datagram? What percentage of the datagram size is overhead?

Explanation / Answer

Answer for Question A:
This below is the Ipv6 Datagram header and associated fields definitions.

Version (4-bits): It represents the version of Internet Protocol, i.e. 0110.  
Traffic Class (8-bits): These 8 bits are divided into two parts. The most significant 6 bits are used for Type of Service to let the Router Known what services should be provided to this packet. The least significant 2 bits are used for Explicit Congestion Notification (ECN).
Flow Label (20-bits): This label is used to maintain the sequential flow of the packets belonging to a communication. The source labels the sequence to help the router identify that a particular packet belongs to a specific flow of information. This field helps avoid re-ordering of data packets. It is designed for streaming/real-time media.
Payload Length (16-bits): This field is used to tell the routers how much information a particular packet contains in its payload. Payload is composed of Extension Headers and Upper Layer data. With 16 bits, up to 65535 bytes can be indicated; but if the Extension Headers contain Hop-by-Hop Extension Header, then the payload may exceed 65535 bytes and this field is set to 0.
Next Header (8-bits): This field is used to indicate either the type of Extension Header, or if the Extension Header is not present then it indicates the Upper Layer PDU. The values for the type of Upper Layer PDU are same as IPv4’s.
Hop Limit (8-bits): This field is used to stop packet to loop in the network infinitely. This is same as TTL in IPv4. The value of Hop Limit field is decremented by 1 as it passes a link (router/hop). When the field reaches 0 the packet is discarded.
Source Address (128-bits): This field indicates the address of originator of the packet.
Destination Address (128-bits): This field provides the address of intended recipient of the packet.

Answer for Question B:

There are 2 extension headers at 20 = 40 + 40 for the
base header = 5080 bytes is size of datagram.
The overhead amount is 40 + 40 /5080 *100 = 1.574803149606299%

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