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TCP/IP 47 Figure 3.8: The IP header • Version (V): field of 4 bits that represents the IP version. • IHL: field of 4 bits that represents the length of the header (in bytes) • Type of service: reserved/priority of the required service • Total length: the total length in bytes of the complete IP packet • Identification: if an IP packet has to be divided, then each packet gets a unique identification so that all packets can be merged back correctly on the receiving side. • Flags: the flags are used to follow-up the fragmentation of the packets • Fragment offset : when a data packet is divided then the position of the fragment in the entire packet is a 8-bit unit. • Time to live (TTL): every time an IP packet passes a router, this value is reduced by 1. If this number is 0 then the relevant router will reject this message. This avoids that a message can exist forever. • Protocol: the higher level protocol is represented here 01h 06h 11h ICMP TCP UDP • Header Checksum: a check value for the IP header. Every router will recalculate this header checksum. • Source IP address: IP address of the sending participant • Destination IP address: IP address of the receiving participant • Options : other network information can be included in the IP header. If the options data do not end with a 32-bit word, then the rest is filled with padding zeroes.
TCP/IP 48 3.2.8 IPv6 General The most recent IP protocol that is discussed in this chapter has version number 4 (IPv4). The great success of the IP protocol results in the need for a new version. There is a pressing shortage of IP addresses and furthermore it is also important that new functionalities can be integrated in a simple way. Moreover, a new version of the IP protocol has to be able to guarantee a higher performance. With the introduction of IPv6, there is also a practical problem: how will the publicly accessible Internet that functions on Ipv4 switch to Ipv6? The easiest way is the so-called dual-stack approach. This means the implementation of IPv6 and IPv4 on the nodes. These nodes can process IPv4 as well as IPv6 datagrams. Currently, the automation world is not interested in the integration of IPv6. Some features of the IPv6 are discussed below. However, as many IPv4 design features as possible are retained as these have made this version so successful. IP address IPv6 uses IP addresses of 128 bits. This creates extensive addressing options. Hexadecimal notation with double dots, addresses become 128 bits long: 8 groups of 4 hexadecimal digits 2000:0000:0000:0FED:CBA9:8765:4321 2000::FED:CBA9:8765:4321 IPv4 addresses ::192.32.20.46 The new addressing has to result in smaller routing tables. IPv6 header Figure 3.9: IPv6 header The IP header is completely changed. A simpler basic header in combination with the option to integrate optional headers has to ensure that the header-processing time for the router is greatly reduced. A number of IPv4 fields are deleted or are only still available as option. The fields in the IPv6 header: • Flow label: a 20-bit identification number to distinguish a packet in a data stream
Page 1 and 2: Ethernet Basics Rev. 02
Page 3 and 4: Contents ii 2.8.7 Parallel Redundan
Page 5 and 6: Contents iv 8 VPN 97 8.1 Introducti
Page 7 and 8: Introduction 2 The OSI model consis
Page 9 and 10: Introduction 4 • IEEE802.2 Logica
Page 11 and 12: Ethernet 6 • 1999: IEEE802.3ab; G
Page 13 and 14: Ethernet 8 Figure 2.1: The MAU for
Page 15 and 16: Ethernet 10 • Data transmission a
Page 17 and 18: Ethernet 12 Figure 2.4: Physical im
Page 19 and 20: Ethernet 14 Figure 2.6: The 5GHz ba
Page 21 and 22: Ethernet 16 2.3 The data link layer
Page 23 and 24: Ethernet 18 • TYPE: for the field
Page 25 and 26: Ethernet 20 a complete data frame s
Page 27 and 28: Ethernet 22 glass cabling are alway
Page 29 and 30: Ethernet 24 2.5 IEEE802.1Q tagged f
Page 31 and 32: Ethernet 26 According to the norm,
Page 33 and 34: Ethernet 28 2.7 VLAN A VLAN or Virt
Page 35 and 36: Ethernet 30 2.8 Network redundancy
Page 37 and 38: Ethernet 32 To create a network wit
Page 39 and 40: Ethernet 34 2.9.3 Link Aggregation
Page 41 and 42: Ethernet 36 Table 2.5: Environmenta
Page 43 and 44: TCP/IP 38 The second part of the an
Page 45 and 46: TCP/IP 40 Figure 3.4: Building of t
Page 47 and 48: TCP/IP 42 Table 3.2: IP addresses f
Page 49 and 50: TCP/IP 44 Table 3.4: Subnetting and
Page 51: TCP/IP 46 3.2.7 The IP packet The d
Page 55 and 56: TCP/IP 50 3.3.3 How reliability is
Page 57 and 58: TCP/IP 52 - the FIN bit that is use
Page 59 and 60: TCP/IP 54 Figure 3.14: Real time au
Page 61 and 62: TCP/IP 56 3.6 Communication over TC
Page 63 and 64: TCP/IP 58 number. This combination
Page 65 and 66: TCP/IP 60 3.6.5 Status of a socket
Page 67 and 68: Extension protocols and network app
Page 85 and 86: Chapter 5 The switch 5.1 General Th
Page 87 and 88: The switch 82 • mounted on DIN ra
Page 89 and 90: The switch 84 is indicated in the V
Page 91 and 92: Chapter 6 The router 6.1 Introducti
Page 93 and 94: The router 88 6.3 Types of routers
Page 95 and 96: The router 90 Figure 6.4: Adaptatio
Page 97 and 98: The router 92 Figure 6.6: Port forw
Page 99 and 100: The router 94 Figure 6.8: Principle
Page 101 and 102: The firewall 96 Packet filters are
Page 103 and 104:
VPN 98 • Confidentiality: the pro
Page 105 and 106:
VPN 100 Figure 8.4: Host to host ga
Page 107 and 108:
Automation networks & Security 102
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