IP: Internet Protocol Flashcards
What path are two consecutive IP datagrams guaranteed to take?
None, IP is a connectionless protocol.
What happens when something goes wrong delivering a Datagram? (Such as a router with a full buffer)
The Datagram is dropped and a ICMP message is send to the source address.
What byte ordering is required of all data in an IP header?
Big-Endian.
What is in the header length field of a 20 byte IP header?
- Header length is the number of 32-bit words in a header.
How large is the header length field in an IP header and what limitations does that put on the size of the header?
4 bits. Which limits the header size to 60 bytes.
What does TOS stand for in an IP header?
Type of service.
How large is the TOS field in an IP header and how is it laid out at the bit level?
8 bits. 3-bit precedence field (now ignored), 4-bit TOS, 1-bit trailer that must be set to zero.
What types of service can be specified in the TOS field in the IP header?
Minimize delay, maximize throughput, maximize reliability, minimize monetary cost.
How many of the TOS bits in the IP header can be set at one time?
1
If none of the bits in the TOS field of the IP header are set, what type of service does that signify?
Normal service.
What does the total length field in an IP header represent?
The total size of the datagram in bytes.
How large is the total length field in an IP header and what is the size limitation that imposes?
Total length field is 16-bits which limits the total datagram size to 65535 bytes (64k).
What does Ethernet do to an IP datagram that is less than 46 bytes in length?
Adds padding of zeroes until the minimum length (46 bytes) is reached.
What does the identification field in an IP header do?
Uniquely identifies each datagram sent by a host.
What is the maximum size of an IP datagram that a host is required to receive?
576 bytes
What layer of the OSI model populates the identification field in an IP header and what are the implications of that?
The transport layer, meaning it’s possible to receive a TCP and UDP datagram with the same identifier.
What does the time-to-live (TTL) field in an IP header represent?
The maximum number of routers the datagram can pass through.
What happens to the TTL field every time it passes through a router?
It is decremented by one.
What happens when the TTL field reaches zero?
The datagram is dropped and an ICMP message is sent back to the source.
How large is the protocol field in an IP header and what does it represent?
8-bits. It represents the protocol that is asking IP to send the datagram.
What protocol value in an IP header signifies TCP?
6
What protocol value in an IP header signifies UDP?
17
What is the range for class A IP addresses?
0.0.0.0 - 127.255.255.255
What is the range for class B IP addresses?
128.0.0.0 - 191.255.255.255
