Protocol numbers are used to configure firewalls, routers, and proxy servers. In Internet Protocol version 4 (IPv4, Request for Comments [RFC] 791I), the protocol number can be found in the Protocol field of an IP header.ICMP Echos are used mostly for troubleshooting. When there are 2 hosts which have communication problems, a few simple ICMP Echo requests will show if the 2 hosts have their TCP/IP stacks configured correctly and if there are any problems with the routes packets are taking in order to get to the other side ICMP Echo Information
Type Name Reference
Echo Reply [RFC792]
Codes
No Code
1 Unassigned [JBP]
2 Unassigned [JBP]
3 Destination Unreachable [RFC792]
Codes
0 Net Unreachable
1 Host Unreachable
2 Protocol Unreachable
3 Port Unreachable
4 Fragmentation Needed and Don’t Fragment was Set
5 Source Route Failed
6 Destination Network Unknown
7 Destination Host Unknown
8 Source Host Isolated
9 Communication with Destination Network is Administratively Prohibited
10 Communication with Destination Host is Administratively Prohibited
11 Destination Network Unreachable for Type of Service
12 Destination Host Unreachable for Type of Service
13 Communication Administratively Prohibited [RFC1812]
14 Host Precedence Violation [RFC1812]
15 Precedence cutoff in effect [RFC1812]
4 Source Quench [RFC792]
The Essay on Communications Controller
A communications controller running (normally) the LAP-B protocol. Rather than use an external device, such as a PAD, most computers use an internal interface to directly connect to the packet-switching network. These interfaces and their corresponding software drivers provide much of the same function provided by a PAD. The advantage to putting these interfaces into a computer is that computer ...
Codes
No Code
5 Redirect [RFC792]
Codes
Redirect Datagram for the Network (or subnet)
1 Redirect Datagram for the Host
2 Redirect Datagram for the Type of Service and Network
3 Redirect Datagram for the Type of Service and Host
6 Alternate Host Address [JBP]
Codes
Alternate Address for Host
7 Unassigned [JBP]
8 Echo [RFC792]
Codes
No Code
9 Router Advertisement [RFC1256]
Codes
0 No Code
10 Router Selection [RFC1256]
Codes
0 No Code
11 Time Exceeded [RFC792]
Codes
0 Time to Live exceeded in Transit
1 Fragment Reassembly Time Exceeded
12 Parameter Problem [RFC792]
Codes
0 Pointer indicates the error
1 Missing a Required Option [RFC1108]
2 Bad Length
13 Timestamp [RFC792]
Codes
0 No Code
14 Timestamp Reply [RFC792]
Codes
0 No Code
15 Information Request [RFC792]
Codes
0 No Code
16 Information Reply [RFC792]
Codes
0 No Code
17 Address Mask Request [RFC950]
Codes
0 No Code
18 Address Mask Reply [RFC950]
Codes
1 No Code
PORT NUMBERS
Service names are assigned on a first-come, first-served process, as documented in [RFC6335].
Port numbers are assigned in various ways, based on three ranges: System Ports (0-1023), User Ports (1024-49151), and the Dynamic and/or Private Ports (49152-65535); the difference uses of these ranges is described in [RFC6335]. System Ports are assigned by IETF
process for standards-track protocols, as per [RFC6335]. User Ports are assigned by IANA using the “IETF Review” process, the “IESG Approval” process, or the “Expert Review” process, as per [RFC6335]. Dynamic Ports are not assigned.
The registration procedures for service names and port numbers are described in [RFC6335].
Assigned ports both System and User ports SHOULD NOT be used without or prior to IANA registration.
