Total length 16-bit field Total length- header length length of data Limited to 65, 535 bytes Some physical networks are not able to encapsulate a datagram of 65535 bytes CSIE NTUT TANAN
CSIE, NTUT, TAIWAN 16 Total Length • 16-bit field • Total length = header length + length of data • Limited to 65,535 bytes • Some physical networks are not able to encapsulate a datagram of 65,535 bytes
Note The total length field defines the total length of the daiaopo including the header CSIE NTUT TANAN
CSIE, NTUT, TAIWAN 17 The total length field defines the total length of the datagram including the header
Time to Live(Ttl) Specifies how long, originally in seconds, the datagram is allowed to remain in the internet Routers and hosts that process datagrams must decrement this field as time passes The datagram was discarded when the value b ecame zero Today, this field is mostly used to control the maximum number of hops visited by the datagram CSIE NTUT TANAN
CSIE, NTUT, TAIWAN 18 Time to Live (TTL) • Specifies how long, originally in seconds, the datagram is allowed to remain in the internet • Routers and hosts that process datagrams must decrement this field as time passes • The datagram was discarded when the value became zero • Today, this field is mostly used to control the maximum number of hops visited by the datagram
Protocol Higher-level protocol that uses the services of the ip layer Several higher-level protocols such as TCP UDP ICMP and Igmp CSIE NTUT TANAN
CSIE, NTUT, TAIWAN 19 Protocol • Higher-level protocol that uses the services of the IP layer • Several higher-level protocols such as TCP, UDP, ICMP, and IGMP
Multiplexing TCP UDP Transport lay ICMP IGMP [ EGP [OSPF Network layer Header CSIE NTUT TANAN Figure 8-5
CSIE, NTUT, TAIWAN 20 Figure 8-5 Multiplexing