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13 Cards in this Set
- Front
- Back
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Version
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Version of the IP protocol. Most networks use IPv4 today, with IPv6 becoming more popular. The header format reflects IPv4.
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Header Length
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Defines the length of the IP header, including optional fields. Because the length of the IP header must always be a multiple of 4, the IP header length (IHL) is multiplied by 4 to give the actual number of bytes.
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DS Field
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Differentiated Services Field. This byte was orignially called the Type of Service (ToS) byte, but was redefined by RFC 2474 as the DS Field. It is used for marking packets for the purpose of applying different quality of service (QoS) levels to different packets.
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Packet Length
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Identifies the entire length of the IP packet, including the data.
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Identification
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Used by the IP packet fragmentation process. If a single packet is fragmented into multiple packets, all fragments of the original packet contain the same identifier, so that the original packet can be reassembled.
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Flags
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3 bits used by the IP packet fragmentation process.
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Fragment Offset
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A number set in a fragment of a larger packet that identifies the fragment's location in the larger original packet.
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Time to Live (TTL)
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A value used to prevent routing loops. Routers decrement this field by 1each time the packet is forwarded; once it decrements to 0, the packet is discarded.
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Protocol
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A field that identifies the contents of the data portion of the IP packet. For example, protocol 6 implies a TCP header is the first thing in the IP packet data field.
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Header Checksum
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A value used to store a frame check sequence (FCS) value, whose purpose is to determine if any bit errors occurred in the IP header (not the data) during transmission.
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Source IP Address
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The 32-bit IP address of the sender of the packet.
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Destination IP address
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The 32-bit IP address of the intended recipient of the packet.
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Optional Header Fields and Padding
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IP supports additional header fields for future expansion via optional header. Also, if these optional headers do not use a multiple of 4 bytes, padding bytes are added, comprimised of all binary 0s, so that the header is a multiple of 4 bytes in length.
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