1、BGP is an application layer protocol because it uses TCP to transport its messages, and RIP because it uses UDP for the same purposes. Other routing protocols such as OSPF are said to operate at the internet layer because they encapsulate their messages directly into IP packets.
2、The minimum length of the IP header is 20 octets, and the options might increase this size up to a maximum of 60 octetsthe maximum length in 32-bit words that can be described by this field.
3、The IOS Extended Ping utility allows the setting of the DF bit to test MTUs across a network.
4、。。。continue
