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8/2/2019 Ipv6 Header Main Projects
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Understanding IPv6 Slide: 1
Lesson 4
The IPV4 AND IPv6Header
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Understanding IPv6 Slide: 2
Internet layer
Internet layer is responsible for source todestination delivery of a packet across differentnetworks.
Internet layer is not reliable transmission Examples of Network layer Routed protocols
are:
IP
IPX (internetwork packet exchange)
AppleTalk
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Understanding IPv6 Slide: 3
Internet layer
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Understanding IPv6 Slide: 44
IPv4 Header
Octet +0 Octet +1 Octet +2 Octet +3
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
VER(4) HLEN TOS(QOS) TOTAL LENGTH(16)
IDENTIFICATION(Sequential no.) D
F
M
FFRAGMENT OFFSET
TIME TOLIVE(8) PROTOCOL HEADER CHECKSUM
SOURCE ADDRESS OF HOST(32)
DESTINATION ADDRESS OF HOST(32)
OPTIONS and PADDING
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DSCP (Differentiated service code point)
Total 8 bits are available
First 6 bits are used for DSCP
ds5,ds4,ds3,ds2,ds1,ds0 ds5,ds4,ds3 are used for classes, Total
four classes are available
In each class there are 3 drop levels Low ,medium, high
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IPv4 packet processing
1. Verify the header checksum2. Verify the version field
3. Decrement the TTL value by 1
4. Check the DA and check the localrouting table
5. If no entry in the routing table sendICMP message
6. Recalculate the header checksumand place its new value in theheader checksum
7. Forward the packet on interface
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IPV6 Header
NextHeader(8)
Hop Limit(8)
Flow Label(20)Traffic
Class(8)
Destination Address(128)
Source Address(128)
Payload Length(16)
Version(4)
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IPv6 Header Format
IPv6
20 Bytes + Options
Fragment
OffsetFlags
Total LengthType ofService
IHL
PaddingOptions
Destination Address
Source Address
Header ChecksumProtocolTime to Live
Identification
Version
IPv4 Header
NextHeader
Hop Limit
Flow LabelTrafficClass
Destination Address
Source Address
Payload Length
Version
IPv6 Header
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Flow Label
This field indicates this packet belongsto a specific sequence of packetsbetween source to destination , which
requires special handling byintermediate routers.
Ex: voice and video
Note; flow label 0 means no flow label.
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IPv6 packet processing
1. Verify the version field2. Decrement the hop limit value by 1
3. Check the DA and check the local
routing table4. If no entry in the routing table send
ICMP message
5. Forward the packet on interface.
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Comparing the IPv4 and IPv6 Headers
IPv4 Header Field Change in IPv6
Version New value of 6Internet Header Length Removed (Header length is fixed)
Type of Service Traffic Class field
Total Length Payload Length field
Identification Removed to Fragment headerFragmentation Flags Removed to Fragment header
Fragment Offset Removed to Fragment header
Time to Live Hop Limit field
Protocol Next Header field
Header Checksum Removed
Source Address Same, new 128-bit length
Destination Address Same, new 128-bit length
Options Removed (extension headers)
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IPv6 HeaderNext Header = 6(TCP)
TCP Segment
IPv6 HeaderNext Header = 43(Routing)
TCP SegmentRouting HeaderNext Header = 6(TCP)
Authentication Header
Next Header = 6(TCP)
IPv6 HeaderNext Header = 43(Routing)
Routing HeaderNext Header = 51(AH)
TCP Segment
The Chain of Pointers Formed by the Next Header field
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Extension Headers Order
1. Hop-by-Hop Options header2. Destination Options header (for
intermediate destinations when the Routingheader is present)
3. Routing header
4. Fragment header
5. Authentication header
6. Encapsulating Security Payload header
7. Destination Options header (for the finaldestination)
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Values of the Next Header Field
Value Header
0 Hop-by-Hop Options Header6 TCP
17 UDP
41 Encapsulated IPv6 Header
43 Routing Header
44 Fragment Header
50 Encapsulating Security Payload
51 Authentication Header58 ICMPv6
59 No next header
60 Destination Options Header
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Thank you