Chapter Objectives After completing this chapter you will
Chapter Objectives After completing this chapter you will be able to: l Identify the characteristics and features of IP l Describe IP addressing l Explain the purpose and operation of different protocols in the TCP/IP suite, including DNS, ARP, ICMP, TCP, UDP and DHCP l Understand IPv 6
Internet Protocol (IP) l Provides logical 32 -bit network addresses l Routes data packets l Connectionless protocol – No session is established l “Best effort” delivery l Reliability is responsibility of higher-layer protocols and applications l Fragments and reassembles packets
Internet Protocol (IP) Host A Host B Reliability & Sequencing Router IP Fires & Forgets Network Interface IP IP Routes If Possible Delivers as Received Network Interface PACKET Fragmented Packet
IP Packet Structure 32 bits (4 Bytes) Version Type of Service IHL Identification Time to Live Protocol Total Length Flags Fragment Offset Header Checksum Source Address Destination address Options (variable) DATA (variable) Padding IP header is normally 20 bytes long
Type of Service (TOS) 3 PRECEDENCE 1 1 1 D T R D = Delay T = Throughput R = Reliability 2 UNUSED
Fragmentation IP Header Original IP Packet data area IP Hdr 1 Data 1 FDDI IP Hdr 2 Data 2 IP Hdr 3 Data 3 FDDI ETHERNET Router 1 MTU =1500 Router 2 bytes MTU = 4500 bytes
The IP Address 193. 160. 1. 0 193. 160. 1. 1 193. 160. 2. 0 193. 160. 2. 1 193. 160. 1. 5 193. 160. 2. 83 Binary Format 11000001 10100000001 00000101 Dotted Decimal Notation 193. 160. 1. 5
Converting from Binary to Decimal Binary Value Decimal Value 1 1 1 1 27 26 25 24 23 22 21 20 128 64 32 16 8 4 2 1 If all bits are set to 1 then the decimal value is 255 i. e. 1+2+4+8+16+32+64+128=255
Traditional IP Address Classes NET ID CLASS A HOST ID 0 NET ID CLASS B 10 NET ID CLASS C HOST ID 110 HOST ID
Traditional IP Address Classes (Contd) l Class D – Used for multicast group usage - first 4 high-order bits are 1110 – 1 st Octet between 224 and 239 1 1 10 Group Identification l Class E – Reserved for future use - first 5 high-order bits are 11110
Addressing Guidelines l Network ID cannot be 127 – 127 is reserved for loop-back function l Network ID and host ID cannot be 255 (all bits set to 1) – 255 is a broadcast address l Network ID and host ID cannot be 0 (all bits set to 0) – O means “this network only” l Host ID must be unique to the network
Private IP Address Space 10. 0 - 10. 255 1 “Class A” network 172. 16. 0. 0 - 172. 31. 255 16 “Class B” networks 192. 168. 0. 0 - 192. 168. 255 256 “Class C” networks
Subnet Mask l Blocks out a portion of the IP address to distinguish the Network ID from the host ID l Specifies whether the destination’s host IP address is located on a local network or on a remote network l The source’s IP address is ANDed with its subnet mask. The destination’s IP address is ANDed with the same subnet mask. If the result of both ANDing operations match, the destination is local to the source, that is, it is on the same subnet.
Subnet Mask Example l For example 160. 30. 20. 10 is on the same subnet as 160. 30. 20. 100 if the mask is 255. 0 – Note: 1 AND 1 = 1. Other combinations = 0. IP Address Subnet Mask Result 160. 30. 20. 10 255. 0 160. 30. 20. 0 10100000 00011110 00010100 00001010 11111111 0000 10100000 00011110 00010100 0000 IP Address Subnet Mask Result 160. 30. 20. 100 255. 0 160. 30. 20. 0 10100000 00011110 11001000 01100100 11111111 0000 10100000 00011110 00010100 0000
Subnetting Routing Advertisement 160. 30. 0. 0/16 INTERNET • Before subnetting: 1 network with approx. . 65 thousand hosts • After subnetting: 256 networks with 254 hosts per subnet PRIVATE NETWORK 160. 30. 0. 0/24 160. 30. 1. 0/24 160. 30. 2. 0/24 ……………. 160. 30. 254. 0/24 160. 30. 255. 0/24
Example: Network with Customised Mask Allocated IP address space 160. 30. 0. 0/16 3 -octet mask 255. 0 8 bits available for subnets and 8 bits available for host 255 255 1111 1111 Network No. of Subnets 0 0000 Host 160. 30. 0. x 1010 0001 1110 0000 xxxx 160. 30. 255. x 1010 0001 1110 1111 xxxx Maximum of 256 subnets (28)
Example: Network with Customised Mask (continued) Allocated IP address space 160. 30. 0. 0/16 3 -octet mask 255. 0 8 bits available for subnets and 8 bits available for host 255 1111 255 1111 Network No. of hosts 0 0000 Host 160. 30. x. 1 1010 0001 1110 xxxx 0000 0001 160. 30. x. 254 1010 0001 1110 xxxx 1111 1110 Maximum of 254 hosts (28 - 2)
Subnetting Example Network Address Subnet Mask 200. 0 255. 0 Allocated IP address space 200. 0/24 200. 64 62 hosts per network 200. 0 200. 128 200. 192 Note: Subnet mask for each subnet = 255. 192
Example Network with VLSM Allocated IP address space 200. 0/24 Required: 2 subnets with 50 hosts and 8 subnets with 10 hosts 200. 0 /26 (max. of 62 hosts) 200. 64 /26 (max. of 62 hosts) 200. 0 Note: Subnet masks /26 = 255. 192 /28 = 255. 240 200. 128 /28 (max. of 14 hosts) 200. 144 /28 200. 160 /28 200. 176 /28 200. 192 /28 (max. of 14 hosts) 200. 208 /28 200. 224 /28 200. 240 /28
Example Network with VLSM Site C Site B 160. 40. 140. 0 255. 252. 0 LAN 1 160. 40. 156. 0 255. 0 160. 40. 156. 1 160. 40. 157. 13 160. 40. 157. 5 LAN 3 160. 40. 152. 1 LAN 2 160. 40. 152. 0 255. 252. 0 160. 40. 157. 14 160. 40. 157. 12 255. 252 160. 40. 157. 4 255. 252 160. 40. 148. 1 160. 40. 148. 0 255. 252. 0 Site A 160. 40. 144. 1 160. 40. 157. 6 160. 40. 144. 0 255. 252. 0
Variable Length Subnets from 1 to 16 CIDR Prefix-length /1 /2 /3 /4 /5 /6 /7 /8 /9 /10 /11 /12 /13 /14 /15 /16 Subnet Mask # Individual Addresses # Classful Networks 128. 0. 0. 0 192. 0. 0. 0 224. 0. 0. 0 240. 0 248. 0. 0. 0 252. 0. 0. 0 254. 0. 0. 0 255. 128. 0. 0 255. 192. 0. 0 255. 224. 0. 0 255. 240. 0. 0 255. 248. 0. 0 255. 252. 0. 0 255. 254. 0. 0 255. 0. 0 2048 M 1024 M 512 M 256 M 128 M 64 M 32 M 16 M 8 M 4 M 2 M 1 M 524, 286 262, 142 131, 070 65, 534 128 A 64 A 32 A 16 A 8 A 4 A 2 A 1 A or 256 Bs 128 B 64 B 32 B 16 B 8 B 4 B 2 B 1 B or 256 Cs
Variable Length Subnets from 17 to 30 CIDR Prefix-length /17 /18 /19 /20 /21 /22 /23 /24 /25 /26 /27 /28 /29 /30 Subnet Mask # Individual Addresses # Classful Networks 255. 128. 0 255. 192. 0 255. 224. 0 255. 240. 0 255. 248. 0 255. 252. 0 255. 254. 0 255. 128 255. 192 255. 224 255. 240 255. 248 255. 252 32, 766 16, 382 8, 190 4, 094 2, 046 1, 022 510 254 126 62 30 14 6 2 128 Cs 64 Cs 32 Cs 16 Cs 8 Cs 4 Cs 2 Cs 1 C 1/2 C 1/4 C 1/8 C 1/16 C 1/32 C 1/64 C
CIDR Route Aggregation ISP The INTERNET 200. 25. 0. 0/16 200. 25. 16. 0/20 200. 25. 16. 0/21 200. 25. 16. 0/24 200. 25. 17. 0/24 200. 25. 18. 0/24 200. 25. 19. 0/24 200. 25. 20. 0/24 200. 25. 21. 0/24 200. 25. 22. 0/24 200. 25. 23. 0/24 Company A 200. 25. 28. 0/23 200. 25. 24. 0/22 200. 25. 24. 0/24 200. 25. 26. 0/24 200. 25. 27. 0/24 Company B 200. 25. 30. 0/23 200. 25. 28. 0/24 200. 25. 29. 0/24 200. 25. 30. 0/24 200. 25. 31. 0/24 Company C Company D
Subnet ID Tables No. of Bits in Mask 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Subnet Mask Subnet IDs 255. 0. 0 255. 128. 0 255. 192. 0 255. 224. 0 255. 240. 0 255. 248. 0 255. 252. 0 255. 254. 0 255. 128 255. 192 255. 224 255. 240 255. 248 255. 252 0 0, 128 0, 64, 128, 192 0, 32, 64, 96, 128, 160, 192, 224 0, 16, 32, 48, 64, 80, 96, 112, 128, 144, 160, 176, 192, 208, 224, 240 0, 8, 16, 24, 32, 40, 48, 56, 64……………. , 216, 224, 232, 240, 248 0, 4, 8, 12, 16, 20, 24, 28, 32, ……………. 236, 240, 244, 248, 252 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, ……………. 246, 248, 250, 252, 254 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, ……………. 251, 252, 253, 254, 255 0, 128 0, 64, 128, 192 0, 32, 64, 96, 128, 160, 192, 224 0, 16, 32, 48, 64, 80, 96, 112, 128, 144, 160, 176, 192, 208, 224, 240 0, 8, 16, 24, 32, 40, 48, 56, 64……………. , 216, 224, 232, 240, 248 0, 4, 8, 12, 16, 20, 24, 28, 32, ……………. 236, 240, 244, 248, 252 3 rd Octet 4 th Octet
DNS - Domain Name System Protocol software Humans 185. 26. 69. 125 ? Kiss. val. com l Internet addresses are hard for humans to remember - Easy for protocol software to work with. l Symbolic names are more natural for humans - Hard for protocol software to work with.
Internet Domain Name Space Generic int com edu gov Countries mil org net us ie se Pizza ericsson Oxford eng CS eng ai Linda robot cookie Krusty Burger 4 Star
Domain Name Resolution . com Juniper Ericsson eng sales ACC research
Domain Name Resolution Root Name Server Iterative query 2 3 4 Com Name Server 5 Local Name Server 6 7 Recursive query 1 10 DNS Client ericsson. com 8 9 eng. ericsson. com
DNS Caching l Internet name servers use name caching to reduce the traffic on the Internet and improve performance l Servers report cached information to clients, but mark it as a nonauthoritative binding l If efficiency is important, the client will choose to accept the nonauthoritative answer and proceed l If accuracy is important the client will choose to contact the authority and verify that the binding between name and address is still valid l Whenever an authority responds to a request, it includes a Time To Live (TTL) value in the response that specifies how long it guarantees the binding to remain
Address Resolution Protocol (ARP) l A source must know a destination’s hardware address before it can send an IP packet directly to it l ARP is the mechanism that maps IP to hardware addresses l ARP uses a local broadcast to obtain a hardware address dynamically l ARP stores mappings in cache for future use l Static entries can be manually entered into the ARP cache
Address Resolution Protocol (ARP) “If your IP address is 160. 30. 10 please send me a reply stating your hardware address” Source 160. 30. 100. 20 00 -AA-00 -12 -34 -56 Broadcast Unicast Remote Networks Destination 160. 30. 10 00 -A 0 -C 9 -78 -9 A-BC That’s me and my Hardware address is 00 -A 0 -C 9 -78 -9 A-BC
ARP Packet Structure 32 bits (4 Bytes) Hardware Type HLEN Protocol Type Operation code Sender’s Hardware Address (Octets 0 -3) Sender HA (Octets 4 -5) Sender IP (Octets 0 -1) Sender IP (Octets 2 -3) Target HA (Octets 0 -1) Target HA (octets 2 - 5) Target IP (octets 0 - 3) Variable Length
Reverse Address Resolution Protocol l Reverse ARP is the mechanism that maps hardware addresses to the IP address l RARP protocol allows a newly booted machine to broadcast its Ethernet address l The RARP server sees this request and sends back the corresponding IP address
Internet Control Message Protocol (ICMP) l Reports errors and sends control messages on behalf of IP l ICMP messages are encapsulated within an IP packet l One of the most frequently used debugging tools uses ICMP l ICMP Message Format IP Header. . . Type Code Identifier Checksum Sequence Number Optional Data
ICMP Message Types TYPE FIELD 0 3 4 5 8 11 12 13 14 15 16 17 18 ICMP Message Types Echo Reply Destination Unreachable Source Quench Redirect (change a route) Echo Request Time exceeded for a packet Parameter problem on a packet Timestamp request Timestamp reply Information request (obsolete) Information reply (obsolete) Address mask request Address mask reply
Echo Request and Reply Message Format IP Header. . . Type = 8 (or 0) Code = 0 Checksum Identifier Sequence Number Optional Data These messages test whether a destination is reachable and responding, by sending ICMP echo requests and receiving back ICMP echo replies. This test is carried out by using the “PING” command.
Reports of Unreachable Destinations Code Value 0 1 2 3 4 5 6 7 8 9 10 11 12 Meaning Network unreachable Host unreachable Protocol unreachable Port unreachable Fragmentation needed and DF set Source route failed Destination network unknown Destination host unknown Source host isolated Communication with destination network administratively prohibited Communication with destination host administratively prohibited Network unreachable for type of service Host unreachable for type of service
Traceroute l Traceroute uses ICMP and the TTL field in the IP header, to let us see the route that IP packets follow from one host to another. l Source sends packet with TTL set to 1 l First router sends back “time exceeded” message l Source increments TTL counter by 1 l Second router on path sends back “time exceeded” message l Process continues until ultimate destination send back “port unreachable” message. l Source uses the responses to display the route to the destination
Transmission Control Protocol (TCP) l Connection-oriented l Provides logical connections between a pair of processes: – These are uniquely identified using sockets – Socket = IP address & port number, e. g. FTP is port 21 l End-to-End reliable delivery l Implements Flow Control
Transmission Control Protocol (TCP) l Units of data transferred between two devices running TCP software called “segments” l Segments are exchanged to do the following: – Establish a connection – Agree window size – Transfer data – Send acknowledgements – Close connection
TCP Packet Structure 32 bits (4 Bytes) Source Port Destination Port Sequence Number Acknowledgement Number OFF Reserved SET Flags Checksum Window Urgent Pointer Options DATA Padding
Well-known Port Numbers Port Number 7 20 21 23 25 53 79 80 104 139 160 -223 Description Echo File Transfer Protocol (FTP) data File Transfer Protocol (FTP) control Telnet Simple Mail Transfer Protocol (SMTP) Domain name server (DNS) Finger World Wide Web (WWW) X 400 Mail Sending Net. BIOS session service Reserved
Establishing a TCP Connection Client Server SYN SEQ # 1, 000 Window 8, 760 bytes Max. segment 1, 460 bytes SYN SEQ # 3, 000 ACK # 1, 001 Window 8, 760 bytes Max. segment 1, 460 bytes SEQ # 1001 ACK # 3001 ACK
Positive Acknowledgement with Retransmit Events at Sender Site Send Packet 1 Start Timer Network Messages Events at Receiver Site Packet lost Packet should arrive ACK should be sent ACK would normally arrive at this time Timer Expires Retransmit Packet 1 Start Timer Receive ACK 2 Cancel Timer Receive Packet 1 Send ACK 2
Sliding Window Protocol Initial window Segments 1, 2 and 3 acknowledged Window Slides
Sliding Window Protocol Send Segment 1 Send Segment 2 Data, SE Q#2, 000 Data, SE Q#2, 100 Data, SE Send Segment 3 length=1 0 20 , 2 # 00 3 , #2 K AC 00 Receive Segment 1 Q#2, 200 l K AC length=1 00 00 Receive Segment 2 Send ACK 3 for next segment expected Receive Segment 3 Send ACK 4 for next segment expected
Slow Start Algorithm l Slow Start adds another window to the sender's TCP: the congestion window, called "cwnd" l When a new connection is established with a host on another network, the congestion window is initialised to one segment l Each time an ACK is received, the congestion window is increased by one segment l The sender can transmit up to the minimum of the congestion window and the advertised window l Slow Start provides an exponential growth (send one segment, then two, then four, and so on) l The congestion window is flow control imposed by the sender, while the advertised window is flow control imposed by the receiver
Congestion Avoidance and Slow Start algorithm l Initialisation for a given connection sets cwnd to one segment and Slow Start threshold to 65535 bytes l The TCP output routine never sends more than the minimum of cwnd and the receiver's advertised window l When congestion occurs (indicated by a timeout or the reception of duplicate ACKs), one-half of the current window size is saved in ssthresh. Additionally, if the congestion is indicated by a timeout, cwnd is set to one segment (i. e. , Slow Start) l When new data is acknowledged by the other end, increase cwnd
Congestion Avoidance and Slow Start algorithm (Contd) l The way that the cwnd is increased depends on whether TCP is performing Slow Start or Congestion Avoidance l If cwnd is less than or equal to ssthresh, TCP is in Slow Start; otherwise TCP is performing Congestion Avoidance l Slow Start continues until TCP is halfway to where it was when congestion occurred, and then Congestion Avoidance takes over l Slow Start sends one segment, then two, then four, and so on l Congestion Avoidance dictates that cwnd be incremented by segsize*segsize/cwnd each time an ACK is received l This is a linear growth of cwnd, compared to Slow Start's exponential growth
Fast Retransmit l TCP may generate an immediate acknowledgement (a duplicate ACK) when an out-of-order segment is received l The purpose of this duplicate ACK is to let the other end know that a segment was received out of order, and to tell it what sequence number is expected l Since TCP does not know whether a duplicate ACK is caused by a lost segment or just a reordering of segments, it waits for a small number of duplicate ACKs to be received l If three or more duplicate ACKs are received in a row, it is a strong indication that a segment has been lost l TCP then performs a retransmission of what appears to be the missing segment, without waiting for a retransmission timer to expire
Fast Recovery Algorithm l After Fast Retransmit sends what appears to be the missing segment, Congestion Avoidance, but not Slow Start is performed l The reason for not performing Slow Start in this case is that the receipt of the duplicate ACKs tells TCP that there is still data flowing between the two ends l TCP can thus avoid reducing the flow abruptly by not going into Slow Start l The Fast Retransmit and Fast Recovery algorithms are usually implemented together
User Datagram Protocol l Connectionless – No session is established l Does not guarantee delivery – No sequence numbers – No acknowledgements l Reliability is the responsibility of the application l Uses port numbers as end points to communicate
User Datagram Protocol l UDP Packet Format Source Port Destination Port Length UDP Checksum DATA l Checksum performed on Pseudo-Header
BOOTP (BOOTstrap Protocol) l A newly booted device may use BOOTP to obtain an IP address, a bootable file address, and configuration information. – The client initiates a BOOTP request with a broadcast address to all stations on the local network – The BOOTP server monitors for BOOTP requests (on UDP port 67). – The server looks up the assigned IP address and puts it in the response message. – It also adds the name of the BOOTP server and the name of the appropriate load file that may be executed. – It may also add other configuration parameters such as the subnet mask and default gateway. – The client receives the reply (on UDP port 68). – it uses the information supplied by the server to initiate a TFTP get message to the server specified. – The response to the TFTP get message is an executable load file. l DHCP is an enhanced version of BOOTP
BOOTP Message Format 0 8 16 OP 24 HTYPE HLEN TRANSACTION ID SECONDS 31 HOPS UNUSED CLIENT IP ADDRESS YOUR IP ADDRESS SERVER IP ADDRESS ROUTER IP ADDRESS CLIENT HARDWARE ADDRESS (16 OCTETS) SERVER HOST NAME (64 OCTETS) BOOT FILE NAME (128 OCTETS 0 VENDOR-SPECIFIC AREA (64 OCTETS)
Dynamic Host Configuration Protocol - DHCP Non-DHCP client IP Address 1 IP Address 2 DHCP client 1. Find a DHCP server 2. Offer an address 3. Accept an address 4. Confirmation DHCP server DHCP Database IP Address 1 IP Address 2 IP Address 3
DHCP l DHCP supports three mechanisms for IP address allocation: – Manual allocation – Automatic allocation – Dynamic allocation
DHCP Operation DHCPDISCOVER Source IP address = 0. 0 Dest. IP address = 255 Hardware address = 00 -80 -37 -12 -34 -56 DHCPOFFER Source IP address = 160. 30. 20. 10 Dest. IP address = 255 Offered IP address = 160. 30. 20. 150 Client Hardware address = 00 -80 -37 -12 -34 -56 Subnet mask = 255. 0 Length of lease = 72 hours Server identifier = 160. 30. 20. 10
DHCP Operation DHCPREQUEST Source IP address = 0. 0 Dest. IP address = 255 Hardware address = 00 -80 -37 -12 -34 -56 Requested IP address = 160. 30. 20. 150 Server Identifier = 160. 30. 20. 10 DHCPACK Source IP address = 160. 30. 20. 10 Dest. IP address = 255 Offered IP address = 160. 30. 20. 150 Client Hardware address 00. 80. 37. 12. 34. 56 Subnet mask = 255. 0 Length of lease = 72 hours Server Identifier = 160. 30. 20. 10 DHCP option: router = 160. 30. 20. 1
DHCP Interaction through Routers PC DHCP Server DHCP D iscover DHCP D i scover DHCP Offer DHCP Request Router DHCP Request K DHCP AC
DHCP Message Format 0 8 16 OP 24 HTYPE HLEN TRANSACTION ID SECONDS HOPS FLAGS CLIENT IP ADDRESS YOUR IP ADDRESS SERVER IP ADDRESS ROUTER IP ADDRESS CLIENT HARDWARE ADDRESS (16 OCTETS) SERVER HOST NAME (64 OCTETS) BOOT FILE NAME (128 OCTETS 0 OPTIONS (VARIABLE) 31
IPv 4 and IPv 6 l If IPv 4 works so well then why change? – Dramatically increase the number of IP addresses – Provide better support for real-time applications – Security features 8/038 13 LZUBB 108 101/2
New features of IPv 6 l Address size – 128 -bit addresses l Improved option mechanism – simplifies and speeds up router processing of IPv 6 packets l Address autoconfiguration – dynamic assignment of IPv 6 addresses l Increased addressing flexibility – anycast address l Support for resource allocation – labelling of packets to handle specialised traffic l Security capabilities – authentication and privacy 8/038 13 LZUBB 108 101/3
The IPv 6 Packet Format 40 bytes Base Header Optional Extension Header 1 …. . . Extension Header N Data area
IPv 4 Header Version IHL 32 bits (4 Bytes) Type of Service Identification Time to Live Protocol Total Length Flags Fragment Offset Header Checksum Source Address Destination address Options (variable) DATA (variable) Padding IP header is normally 20 bytes long
IPv 6 Base Header 4 Version 8 Priority Payload Length 16 24 32 Flow Label Next Header Source Address Destination Address Hop Limit 10 x 32 bits = 40 octets 0
IPv 6 Extension Header Extension header Description Hop-by-hop options Miscellaneous information for routers Destination options -1 Information for 1 st destination Routing Full or partial route to follow Fragmentation Management of datagram fragments Authentication Verification of the sender’s identity Encrypted security payload Information about the encrypted contents Destination options -2 Additional information for the final destination only
Hop-by-hop Options & Destination Options Headers l Hop-by-hop Options Header – Read by all routers along the path – useful for transmitting management information or debugging commands to routers l Destination Options Header – 2 types l one for 1 st destination l one for final destination
Routing Header l Specifies a list of IP addresses that dictate what path a packet will traverse l Type zero routing headers indicate how intermediate nodes may forward a packet to the next address in the routing header – strict forwarding, packets only visit routers listed in the routing header – loose forwarding, unlisted routers can be visited by a packet
Routing Header Format Next Header Reserved Type Number of Addresses Strict/loose Bit Map 1 - 24 Addresses Next address
Fragment Header 8 Next Header 8 13 2 1 Reserved Fragment Offset Res M Identification 32
Authentication Header l The authentication header provides authentication and integrity l the authentication header extension to IPv 6 ensures that a packet is actually coming from the host indicated in its source address
ESP- Encrypted Security Payload Transport Mode Unencrypted IPv 6 Header Encrypted Extension Headers ESP Header Transport Header and Payload Tunnel Mode Encrypted Unencrypted IPv 6 Header Extension Headers ESP Header IPv 6 Header Extension Headers Transport Header and Payload
IPv 6 Addressing l Like IPv 4, IPv 6 assigns a unique address for each connection between a computer and a physical network l There are three types of IPv 6 addresses: – Unicast – Multicast – Anycast
IPv 6 Colon Hexadecimal Notation l Consider a 128 -bit number written in dotted decimal notation: – 105. 220. 136. 100. 255. 0. 0. 18. 128. 140. 10. 255 l This number written in hex notation – 69 DC: 8864: FFFF: 0: 1280: 8 C 0 A: FFFF l Leading zeros within a group can be omitted l One or more groups of 16 zeros can be replaced by a pair of colons – for example: FF 0 C: 0: 0: 0: B 1 can be written as: – FF 0 C: : B 1
Transition to IPv 6 l Tunnelling – Configured l manually configuration of IPv 6/IPv 4 mappings l whole IPv 6 address space can be used – Automatic l compatible address space l no advantage of the extended address space
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