About this interactive
The lesson's comparison:
- **Both:** a version field; DSCP and ECN bits (IPv6 calls them Traffic Class); a protocol field (IPv6's Next Header); a hop counter lowered at each router (TTL, IPv6's Hop Limit); source and destination addresses.
- **IPv4 only:** a variable-length header (IHL, options inside it); a header checksum recomputed at every router; identification, flags and fragment offset; routers that fragment; 32-bit addresses.
- **IPv6 only:** a fixed 40-byte main header, with extension headers after it; no header checksum; a flow label; a payload length that leaves out the main header; 128-bit addresses.
Routers never fragment IPv6 packets. The video says IPv6 has no way to fragment at all; the sending host still can, with a fragment extension header.
What you'll learn
- Decide whether a header feature belongs to the IPv4 header, the IPv6 header or both
- Use the differences the lesson names: IPv6's fixed 40-byte header, no header checksum, no router fragmentation, the flow label and 128-bit addresses
Aligned to
CompTIA Network+
1.4
Explain common networking ports, protocols, services, and traffic types
Cisco CyberOps Associate
4.8
Interpret the fields in protocol headers as related to intrusion analysis
Key terms
- IPv6 Header
- A fixed-length 40-byte header used in IPv6 packets, containing fields such as version, traffic class, flow label, payload length, next header, hop limit, and source and destination addresses.
- IP Packet Header
- The portion of an IP packet that contains control information, including the source and destination IP addresses, prepended to the payload.
- Hop Limit
- A field in the IPv6 header that starts at a value set by the sender and is decremented by one at each router; when the value reaches zero the packet is discarded and an ICMPv6 error is sent to the source. The hop limit serves the same loop-prevention purpose as the TTL field in IPv4.
- Flow Label
- A 20-bit field in the IPv6 header used to identify and group related packets that belong to the same traffic flow.
- Next Header
- An IPv6 header field that identifies the type of header immediately following the IPv6 header, typically indicating the Layer 4 protocol such as TCP or UDP.
- Traffic Class
- An 8-bit IPv6 header field used for quality of service and congestion notification, equivalent to the DSCP and ECN fields in IPv4.
- Internet Header Length
IHL
- A 4-bit field in the IPv4 header that specifies the total length of the IP header in 32-bit words, indicating where the payload begins.
Topics
Ipv4
Ipv6
Ip Header
Ipv6 Header
Interactive
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