1. Chapters 13 and 16 (sections 1-3 only)
Dr. Clincy
Lecture

2. (1) Transport Layer Protocols
Simple Protocol
Stop-and-Wait Protocol
Go-Back-N Protocol
Selective-Repeat Protocol
Bidirectional Protocols: Piggybacking
(2) SCTP – Stream Control Transmission
Dr. Clincy
Lecture

3. Simple protocol FSMs for simple protocol
Simple Protocol has no Error Control or Flow Control
The both the Tx and Rx are always in the “Ready” state
Tx can’t send a message until the Sending Application layer has a message to send
When the message is ready to be sent, it is then encapsulated in a packet and sent to the Rx
The Rx is in the “Ready” state until it receives a packet from the Tx, then Rx decapsulates the message out of the packet and send it to the receiving process.
FSMs for simple protocol
Dr. Clincy
Lecture

4. Stop-and-wait Protocol
Stop-and-Wait Protocol is a connection-oriented protocol with Error Control and Flow Control
Both the Tx and Rx uses a sliding window of size 1
Tx sends one packet at a time and waits for an acknowledgement
A checksum is used in the packet for the Rx to detect errors.
Tx uses a timer every time it sends a packet
If Tx receives an ACK before the timer counts down, it sends the NEXT packet
If Tx doesn’t receive an ACK before the timer counts down, it resends the previous packet
If Tx doesn’t receive an ACK before the timer counts down because the ACK itself is lost or corrupted, the Tx will resend the previous packet – creating a duplicate at the Rx side – the Rx will know it has duplicates because both packets will have the SAME sequence number
Therefore, the Tx holds the packets until it receives an ACK
If Rx detects an error, the packet is dropped and no acknowledgment is sent
FLOW CONTROL is achieved by Tx waiting for an ACK before sending
ERROR CONTROL is achieved by the Rx dropping bad packets and allowing the Tx to re-send
Dr. Clincy
Lecture

5. FSMs for stop-and-wait protocol
If time out event occurs, resend packet and remain in blocking state
If corrupted ACK received or ACK not related to packet, drop ACK and remain in blocking state until time-out occurs –then resend packet
Send packet, go into blocking state
While in blocking state, if error-free ACK received, go to ready state
If good packet received with the expected sequence number, send an ACK about the packet and remain in the ready state expecting the next packet
If corrupted packet received, drop it and remain in ready state
If good packet received without the expected sequence number, drop the packet because it is a duplicate, send an ACK about the packet and remain in the ready state expecting the next packet
Dr. Clincy
Lecture

6. Stop-and-wait Protocol Example
(2) Packet0 arrives and ACK pointing to the next packet is sent back
(1) Packet created with Seq# 0 and sent and time starts
(3) ACK comes back and match next Seq#, so sent packet is removed out of storage
(5) Packet lost and doesn’t arrive before time out
(4) Packet created with with next Seq# 1 and sent and time starts
(7) Packet1 arrives and ACK pointing to the next packet is sent back
(6) Try resending packet 1
(8) ACK comes back and match next Seq#, so sent packet is removed out of storage
(10) Packet0 arrives and ACK pointing to the next packet is sent back but lost enroute
(9) Packet created with with next Seq# 0 and sent and time starts
(11) ACK not received in time, so Packet0 is resent
(12) Packet0 arrives AGAIN, so duplicate occurs because Rx was expecting packet1 (and not packet0)
(13) ACK comes back and match next Seq#, so sent packet is removed out of storage
Dr. Clincy
Lecture

7. Stop-and-wait Protocol
Bandwidth-Delay-Product
The data-rate (or bandwidth) TIMES the length of the pipe (or round-trip delay), tells the volume of the pipe in bits
A small pipe with a low data rate with have LESS VOLUME of bits than a large/fat pipe with a high data rate
For Stop-and-wait, not many bits are being sent at once because it is done sequentially – therefore, the stop-and-wait protocol is inefficient when it comes to the bandwidth-delay-product
Pipelining
Pipelining is starting new tasks before the previous task (or tasks) is completed
Pipelining improves the efficiency of transmission by increasing the number of bits in transition with respect to the bandwidth-delay-product
Stop-and-wait protocol doesn’t use pipelining because the previous task must be acknowledged before the next starts
Dr. Clincy
Lecture

8. Go-Back-N protocol
Go-Back-N protocol improves efficiency (filling of the pipe) by allowing multiple packets to be in transition while the Tx is waiting for acknowledgments
Several packets can be sent before the Tx receives an ACK, however the Rx can only buffer one packet at a time
Tx keeps copies of the sent packets until ACK is received
Sequence number is modulo 2m , where m is the number of bits in the sequence number field
The ACK number is cumulative – it keeps track of the next packet expected – if ACK#=4, that means all packets up to 3 have arrive successfully
Dr. Clincy
Lecture

9. Go-Back-N protocol
Sf is the first outstanding packet to be sent that has not been ACK
Sn is the next packet to be sent
Ssize is the send window size
Rn is the sequence number of the next packet to be received at the Rx
Tx keeps copies of the sent packets until ACK is received
SENT Window - Four possible cases for sequence number
The send window can slide one or more slots when an error-free ACK with ackNo between Sf and Sn arrives.
Sequence numbers that can’t be used until the window slides
Dr. Clincy
Lecture

10. Sliding the Go-Back-N send window
Receive window for Go-Back-N
The Rx is always looking for the arrival of a specific packet –all other packets received are discarded
A timer is only used for the FIRST outstanding packet (packets that have not been ACK)
If the timer expires, ALL outstanding packets must be resent
Suppose the Tx has already sent packet 5, so the next packet to be sent is 6 (Sn=6) – and lets say packet 2 was the initial outstanding packet to be sent (Sn=2) – if the timer expired, packets 2, 3, 4, and 5 will all have to be resent – this is the reason this protocol is called Go-Back-N
Dr. Clincy
Lecture

11. Go-Back-N protocol Example
Initialization
Packet0 sent and ACK1 comes back
So packet0 is moved from storage
Packet1 is sent and ACK2 is lost – in the meanwhile, packet2 and packet3 are sent
ACK3 comes back before ACK2, because ACK2 was lost
Because the ACK are cumulative, ACK3 coming back means both packets 1 and 2 were successfully received – so packets 1 and 2 are moved from storage
Dr. Clincy
Lecture

12. Selective-Repeat Protocol
Go-Back-N simplifies the process at the Rx however, it is inefficient because if one packet is out-of-order or corrupted, it could resend other packets that are NOT corrupted. This protocol could cause traffic to increase greatly, causing the network to collapse.
Selective-Repeat Protocol only resends the individual packets that are corrupted or lost.
For Selective-Repeat, the receiver window is larger than 1 and is the same size as the Tx window
Dr. Clincy
Lecture

13. Send window for Selective-Repeat protocol
Receive window for Selective-Repeat protocol
The ACK sent from the Rx is for each individual packet successfully received
Dr. Clincy
Lecture

14. Selective-Repeat Protocol Example
Not pointing to next packet – but rather current packet received
Dr. Clincy
Lecture

15. Design of piggybacking for Go-Back-N
The protocols thus far were all presented as being “unidirectional” – data packets flow in only one direction (from Tx to Rx) – and ACK packets flow in only one direction (Rx to Tx)
In real life for client-server, data packets flow in both directions – therefore, ACK packets need to flow in both directions.
Piggypacking is when the data packets also carry the ACK
For example, when a packet is carrying data from Tx to Rx, it can also carry an ACK about a data packet sent from the Rx to Tx
Piggybacking improves efficiency of the bidirectional protocols
Dr. Clincy
Lecture

16. Chapters 16 (SCTP) Stream Control Transport Protocol
Dr. Clincy
Lecture

17. OBJECTIVES:
To introduce SCTP as a new transport-layer protocol.
To discuss SCTP services and compare them with TCP.
Outline
16.1 Introduction
16.2 SCTP Services
16.3 SCTP Features
Dr. Clincy
Lecture

18. SCTP - INTRODUCTION
Stream Control Transmission Protocol (SCTP) is a new reliable, message-oriented transport-layer protocol. SCTP lies between the application layer and the network layer and serves between the application programs and the network operations.
SCTP is designed for recently introduced Internet apps like ISDN-over-IP, telephony signaling, media gateway control, and IP telephony
SCTP provides more enhanced performance and reliability than TCP.
Dr. Clincy
Lecture

19. SCTP - INTRODUCTION
UDP is a “message-oriented” protocol because UDP encapsulates the message into the datagram and sent over the network – each message is independent from any other message – this is a desirable feature for “real-time data” type apps – the problem with UDP is, it is unreliable and packets can be lost and it doesn’t have flow or congestion control
TCP is a “byte-oriented” protocol because it receives a message (or messages) and stores them as a stream of bytes and sends them in segments. TCP doesn’t preserve the message boundaries. However, TCP is reliable with congestion and flow control - it can detect duplicates, lost packets are resent and bytes are delivered in order.
SCTP combines the best features from UDP and TCP with some additional features – it preserves the message boundaries and able to detect duplicates, resend lost packets and deliver packets in order. It also has congestion and flow control mechanisms.
Dr. Clincy
Lecture

20. SCTP Services provided to Application Layer Processes
Process-to-Process Communication
Multiple Streams
Multihoming
Full-Duplex Communication
Connection-Oriented Service
Reliable Service
Process-to-Process Communications
SCTP uses well-known ports
Dr. Clincy
Lecture

21. Multiple-stream concept
TCP uses streams – each connection between a client and server involves streams being sent – the problem is, if there is a lost, multiple data is lost – not acceptable for real-time data type apps.
SCTP allows multiple streams for a connection at the same time – so if one stream has a problem and is blocked, some other stream will get the data to the process – this is called “association” in SCTP terminology.
Dr. Clincy
Lecture

22. Multihoming concept
A TCP connection involves only two IP addresses – one for the Tx and another for the Rx
In implementing an “SCTP association” or “multiple streams”, multiple connections must be made – therefore both the Tx and Rx must multiple IP addresses on both ends – this is called “multihoming”
Typically SCTP will have a single “main” connection and an “alternative” connection if the main connection fails
SCTP does not use the multiple connections for “load sharing” between Tx and Rx
Server connected to two local networks with two IP addresses
Client connected to two local networks with two IP addresses
Dr. Clincy
Lecture

23. More SCTP Services provided to Application Layer Processes
FULL-DUPLEX COMMUNICATION - data can flow in both directions – therefore buffers are used at both ends
CONNECTION-ORIENTED SERVICE – like TCP, SCTP establishes a relationship upfront before the sending and receiving occurs – the only difference is, SCTP establishes an “association” upfront.
RELIABLE SERVICE – like TCP, SCTP uses ACK for error control
Dr. Clincy
Lecture

24. SCTP Features
NOTE: For SCTP, a stream could consists of multiple sequences of messages (or multiple ordered sets of messages). For TCP, a segment consisted of a “sequence of bytes” and a message could have multiple segments
TRANSMISSION SEQUENCE NUMBER (TSN) - The unit of data for TCP is the byte and recall that TCP numbers bytes using the sequence numbers. SCTP’s unit of data is the “chunk” and may or may not have a one-to-one relationship with the “message” due to fragmentation. If a message is very large, it could consists of multiple chunks. SCTP uses a transmission-sequence-number in numbering data chunks. TSNs are 32 bits and are randomly initialized. Each chunk carries a TSN in its header.
STREAM IDENTIFIER (SI) – for TCP, there is only one stream. For SCTP, there could be multiple streams. Each stream is identified by a stream identifier (SI) – the SI is also in the chuck’s header. The SI is 16 bits starting from 0. Think of this “stream” as the connection or path.
STREAM SEQUENCE NUMBER (SSN) – there could be multiple “chunks” associated with a message and multiple messages associated with a stream. Each data chunks uses the stream sequence number to associate with the appropriate stream (or group of messages) on the Rx side. SSN use tp distinguish between different data chunks belonging to the same stream. Think of this “stream” as a collection of chunks belonging to the same group at the Rx side.
Dr. Clincy
Lecture

25. SCTP Features continue
FLOW CONTROL - Like TCP, SCTP implements flow control
ERROR CONTROL – Like TCP, SCTP implements error control.
CONGESTION CONTROL – Like TCP, SCTP implements congestion control to determine how many data chunks can be injected into the network.
Dr. Clincy
Lecture

26. Comparison between a TCP segment and an SCTP packet
In TCP, a user datagram carried both data and control information – the form of bytes
SCTP is different – data is carried in chunks and control info is carried in chunks
For SCTP, several data and control chunks can be packaged in a packet
A “packet” for SCTP is the same as a “segment or user-datagram” for TCP
Dr. Clincy
Lecture

27. TCP segment Versus SCTP packet
For TCP, control info is in the header; For SCTP, control info is in a chuck – and there can be different types of control chunks
For TCP, the datagram is treated as one entity; For SCTP, the packet can carry several chunks – and each chunk can belong to a different stream
For TCP, options can be a part of the segment; For SCTP, options are in chunks – and new option chunks can be defined
TCP minimum header size is 20 bytes; SCTP header is 12 bytes – some of the info is located in other chunks
TCP checksum is 16 bits; SCTP checksum is 32 bits
TCP uses socket addresses; SCTP uses the “verification tag” to id the “association”
TCP uses the sequence number; SCTP uses the TSN, IS and SSN
Dr. Clincy
Lecture

28. SCTP Packets, Data chunks, and Streams
An association may send many packets
A packet may contain several chunks
Chunks may belong to different streams
If a message is very long, it can be carried by several chunks.
But typically, a message can fit into a single chunk
Dr. Clincy
Lecture

29. Packet, data chunks, and streams
In better understanding this, lets assume an application process delivers 11 messages to SCTP, where each message is earmarked for an appropriate stream
It delivers all messages belonging to the first stream first, then all messages belonging to the second stream second, and finally, all messages belonging to the last stream last. (keep in mind it could have been mixed).
If the network can only handle 3 data chunks per packet, we will need 4 packets (because 11/3 = 3.66 = 4)
Data chunks for stream 0 are carried in the 1st and 2nd packet; data chunks for stream 1 are carried in the 2nd and 3rd packet; data chunks for stream 2 are carried in the 3rd and 4th packets
TSN is a cumulative number and used for flow and error control; SI defines the stream to which the chunk belongs; SSN defines the chunk’s order in a particular stream (SSN starts from 0 for each stream)
Dr. Clincy
Lecture

30. SCTP Acknowledgments TCP’s acknowledgment number is byte-oriented
SCTP’s acknowledgment number is chunk-oriented
Dr. Clincy
Lecture

31. Next Generation: IPv6 and ICMPv6
Also called , IPng – “IP next generation”
Next Generation:
IPv6 and ICMPv6
Recall IPv4 provides host-to-host or hop-to-hop communication
Recall UDP/TCP provide end-to-end or process-to-process communication
Dr. Clincy

32. Why IPv6 ? 3 major reasons
Recall that (1) subnetting, (2) classless addressing, (3) DHCP (dynamic address allocation) and (4) NAT all contributed to better utilization of the 32-bit address space
- despite these solutions, address depletion is still an issue
There are numerous applications on the rise that require streaming real-time audio and video – and real-time transmission requires minimum delay and reservation-of-resources strategies – and IPv4 isn’t designed for these strategies
Over the last few years, there has been a much greater demand for security and for the Internet to accommodate encryption and authentication of data for some applications – and IPv4 doesn’t provide encryption or authentication
Dr. Clincy

33. Why IPv6 ? IPv6 was proposed in overcoming IPv4’s deficiencies
IPv6 has these advantages over IPv4: 1. larger address space – 128 bits
2. better header format – options can be inserted or not
3. new options – additional functionalities 4. allowance for extension – protocol can be extended for newer technologies 5. support for resource allocation – enables the Tx to request special handling 6. support for more security – provides encryption and authentication
Related protocols were either modified or dropped for IPv6
- ICMP was modified (ICMPv6)
- ARP and IGMP in version 4 were combined in ICMPv6
- RARP was dropped
- RIP and OSPF were slightly modified
Dr. Clincy

34. IPv6 Address Abbreviated address
Uses hexadecimal colon notation, a 296 address increase over IPv4
Abbreviated address
Leading zeros can be omitted
If consecutive sections consist of zeros only, the zeros can be removed altogether and replaced with double semicolon
Only allowed once per address – if there were two runs of zero sections, only one can be abbreviated
Dr. Clincy

35. IPv6 Address 3 Categories of IPv6 Addresses
Like IPv4, IPv6 can use CIDR notation
3 Categories of IPv6 Addresses
Unicast Address – packet sent to a specific computer
Anycast Address – group of computers with addresses that have the same prefix (ie. all belong to the same physical network)
Multicast Address – packet sent to a group of computers with different address prefixes
Dr. Clincy

36. IPv6 Address Address structure Type prefixes for IPv6 addresses
Means 1/8 of the entire address spaces uses type prefix 010
The address space has many purposes
The address space is divided into 2 parts
The first part, called “type prefix”, is variable length, defines the purpose by using unique codes
Type prefixes for IPv6 addresses
Dr. Clincy

37. IPv6 Address Provider-based address structure
Type prefix 010 or provider-based address is generally used by a host as a unicast address
Provider-based address structure
Variable-length field identifies the provider for Internet access (ie ISP) – recommends this field be 16 bits
The provider (ISP) assigns a 24-bit subscriber id to the organization
Identifies one of many subnets under the subscriber’s control – recommends using 32-bits
Identifies the node connected to the subnet – recommends 48-bits (the same as the 48-bit physical Ethernet address)
Defines the address as a provider-based address
Indicates one of the three agencies that has registered the address.
INTERNIC – North America
RIPNIC – Europe
APNIC – Asia & Pacific
Dr. Clincy

38. IPv6 Address Address hierarchy
Can think of the provider-based address as a hierarchical identity with several prefixes
Address hierarchy
Dr. Clincy

39. IPv6 Address Unspecified address Loopback address
When the non-prefix part of the address is also zeros – this is called an Unspecified Address – this address is used when the host doesn’t know its own address and sends an inquiry and uses the Unspecified Address to represent itself – the address can not be used as a destination address
Loopback address
Recall the purpose of the loopback address – an address used by a host to test itself without going into the network.
Dr. Clincy

40. IPv6 Address Compatible address
During transition from IPv4 to IPv6, hosts can use their IPv4 addresses embedded in IPv6 addresses. Two formats have been designed for this – (1) compatible and (2) mapped
Compatible address
96 bits of zeros followed by 32 bits of IPv4 address
Compatible Address is used when a IPv6 Tx wants to send a message to an IPv6 Rx, but needs to pass through a region using IPv4 – the Tx must them use the compatible address while passing through the Ipv4 region
Binary
D E
Hexidecimal
Dr. Clincy
Decimal

41. IPv6 Address Mapped address
During transition from IPv4 to IPv6, hosts can use their IPv4 addresses embedded in IPv6 addresses. Two formats have been designed for this – (1) compatible and (2) mapped
Mapped address
80 bits of zeros followed by 16 bits of ones followed by 32 bits of IPv4 address
Mapped Address is used when a IPv6 Tx wants to send a message to an IPv4 Rx. The packet will mostly travel through an IPv6 region with a final destination of IPv4.
NOTE: when calculating the CHECKSUM, either the embedded address or total address can be used because the extra 0s or 1s (in multiples of 16) DO NOT have an effect on the checksum calculation.
Dr. Clincy

42. IPv6 Address Link local address Site local address
Addresses that use the reserved prefix ( ) are local addresses
Link local address
Used if the LAN uses the Internet protocols but is not connected to the Internet for security reasons – these addresses do not have a global effect
Site local address
Used if a site with several networks uses the Internet protocols but is not connected to the Internet for security reasons – these addresses do not have a global effect
Dr. Clincy

43. IPv6 Address Multicast address
Addresses used to define a group of hosts instead of just one.
Multicast address
Defines the group address as either permanent or transient
Permanent Address – defined by the Internet authorities and can be accessed at all time
Transient Address – is temporary
Defines the scope of the group address
Dr. Clincy

44. Next Generation: IPv6 and ICMPv6
.. Continuing …
Dr. Clincy

45. IPv6 Packet
Dr. Clincy

46. Format of an IPv6 datagram
Defines the priority of the packet with respect to traffic congestion (discuss later)
24-bit field that provide special handling for a particular flow of data (discuss later)
Defines the version (IPv6 = 6)
8-bit field defining the header that follows the base header (discuss later)
8-bit field serves as the Time-To-Live (TTL)
2-byte field defines the length of the data excluding the base header
Source address
Usually identifies the destination address – if Source Routing is used, identifies the address of the next router
Dr. Clincy

47. Format of an IPv6 datagram
Next Header
The next header is either one of the optional extension headers used by IPv6 or the header of an encapsulated packet such as UDP or TCP.
Each extension header also contains the next header field.
For version 4, this field was called the protocol.
Next header codes
Dr. Clincy

48. Format of an IPv6 datagram
Priority
Defines the priority of each packet with respect to other packets from the same source.
IPv6 divides traffic into two categories: congestion-control and non-congestion-control
Priorities for congestion-controlled traffic
Process does not define a priority
If a source adapts itself to traffic slowdown when there is congestion, the traffic is called congestion-control traffic – example, TCP sliding window protocol
Defines data delivered in the background
User is not waiting for the data (ie. )
Protocol that transfer data while the user is waiting to receive the data (ie FTP, HTTP)
User interaction is needed (ie. TELNET)
Dr. Clincy
Protocols that control traffic (ie. OSPF, RIP, SNMP)

49. Format of an IPv6 datagram
Priority
Defines the priority of each packet with respect to other packets from the same source.
IPv6 divides traffic into two categories: congestion-control and non-congestion-control
Priorities for non congestion-controlled traffic
Refers to traffic that expects minimum delay – dropping packets is not desired – retransmission is impossible. Examples would be realtime audio and video
Dr. Clincy

50. IPv6 Packet
Flow Label
Recall how a routing-algorithm table lookup is performed for a packet using a router.
Sequence of packets sent from a Tx to Rx needing “special handling” is called a flow
Combo of the Tx address and a flow label uniquely identifies a flow of packets
The flow label is assigned to the packet by the Tx – randomly generated number
From a router perspective, a flow is a sequence of packets sharing the characteristics (using same resources, same security, , etc)
If the packet has a flow number, the router consults it flow label table for the next hop
This speeds up the process – much faster than going through the routing algorithm approach
Flow label approach is good for apps needing to reserve bandwidth and buffer space beforehand in minimizing delays (ie. realtime audio and video)
Dr. Clincy

51. Comparison between IPv4 and IPv6 packet header
Dr. Clincy

52. IPv6 Packet Extension header format
The base header is 40 bytes – in providing the IPv6 datagram more functionality, up to 6 extension headers can be added
There are 6 different extension header types
Dr. Clincy

53. Hop-by-hop option header format
Option used when the Tx needs to pass info to every router visited by the datagram (ie mgmt, debugging or control functions)
The various options for the Hop-by-Hop option are (1) Pad1, (2) PadN and (3) Jumbo payload.
The general format is
Dr. Clincy

54. Pad1
1 byte long and used for alignment or padding – some options need to start at specific bit. Pad1 doesn’t contain the option length field nor the data field – simply consists of the code field with all bits set to zeros. The Pad1 option can be inserted anywhere.
Action is 00 (skip over this option)
Change bit is 0 (does not change in transit)
Type is (Pad1)
Dr. Clincy

55. PadN
Similar to Pad1 however, PadN is used when 2 or bytes are needed for alignment or padding. Length contains the number of padding bytes
Data contains the zero padding bytes
Action is 00 (skip over this option)
Change bit is 0 (does not change in transit)
Type is (PadN)
Dr. Clincy

56. Jumbo payload
Maximum size of an IP payload is 65,535 bytes – but suppose a longer payload is needed – use the Jumbo Payload to define the longer payload
Action is 11 , change bit is 0, type is  Code =
Contains the size-in-bytes of this field (static 4 bytes)
Contains the size of the payload – can be a max size of because it can be a max of 32 bits (4x8)
Dr. Clincy

57. Source Routing
Recall the concepts of strict source routing and loose source routing for IPv4 – IPv6 combines the two.
Indicates the # hops needed to reach destination
Defines Source routing
Defines Strict (must follow exactly) or Loose (in addition to the routers in the header, can visit other routers)
For this option, the destination address is the next hop (versus the Rx) and it is not constant
Dr. Clincy

58. Fragmentation
Recall the concept of fragmentation for IPv4 – IPv6 fragmentation is similar however, ONLY the Tx can fragment – the TX uses Path MTU Discovery technique in finding the smallest MTU across the path – then it fragment based on this
If the Tx does not use the Path MTU Discovery technique, it fragments to 576 bytes or smaller – the minimum size MTU
Dr. Clincy

59. Authentication
Authentication extension header (1) validates the Tx and (2) ensures the integrity of the data – making sure the Tx is genuine and making sure the data sent wasn’t altered.
Identifies which authentication algorithm is used
Contains the data generated from the algorithm
The way the authentication data is generated by the TX is by passing the key first, then the IP datagram with the changing and authentication fields removed, and them passing the key again
Using the secret key, the RX performs the same operation and if there is a match, fine, if there is no match, the datagram is discarded.
Dr. Clincy

60. Encrypted Security Payload
ESP extension header provides confidentiality and guards against eavesdropping.
32-bit word that defines the type of encryption/decryption used
Encrypted data with any extra parameters needed by the algorithm
Encryption can be implemented in 2 ways: transport mode or tunnel mode
For the transport mode, a TCP segment or UDP datagram is first encrypted and then encapsulated in the IPv6 packet – typically used to encrypt from host to host
For the tunnel mode, entire datagram with base header and extension header is encrypted and then encapsulated into a NEW datagram – most used by security gateways
Dr. Clincy

61. Destination option
Option used when the Tx needs to pass info to the Rx only
Dr. Clincy

62. Comparison between IPv4 options and IPv6 extension headers
Dr. Clincy

63. Next Generation: IPv6 and ICMPv6 final …
Dr. Clincy

64. Comparison of network layers in version 4 and version 6
Recall that ICMP is used for:
Error reporting
Host and management queries
Related protocols were either modified or dropped for IPv6
- ICMP was modified (ICMPv6)
- ARP and IGMP in version 4 were combined in ICMPv6
- RARP was dropped
- RIP and OSPF were slightly modified
Dr. Clincy

65. Categories of ICMPv6 messages
- Still divided into 2 categories
Report problems that a router or a host (destination) may encounter when it processes an IP packet.
Help a host or network manager get specific info from a router or another host.
New
New
Dr. Clincy

66. General format of ICMP messages
First 4 bytes are common to all
Type – type of message
Code – reason for the particular message type
Checksum
For error messages, this carries info for finding the original packet that had the error
For query messages, this carries extra info based on the type of the query
Dr. Clincy

67. Comparison of error-reporting messages in ICMPv4 and ICMPv6
Dr. Clincy

68. Destination-unreachable message format
Same as in version 4
Used when a router cannot route a datagram or a host cannot deliver a datagram
So the datagram is dropped and the host or router sends this message
Dr. Clincy

69. Packet-too-big message format
New in version 6
Router receives a datagram larger than the MTU
So the datagram is dropped and the host or router sends this message to the source
Dr. Clincy

70. Time-exceeded message format
Same as in version 4
When the hop limit is violated
So the datagram is dropped and the host or router sends this message to the source
The only difference is that the type is 3
Dr. Clincy

71. Parameter-problem message format
Same as in version 4
When a router or host discovers ambiguous or missing value in any field
Datagram is dropped and this error message is sent
The only differences are that the type is 4 and the size of the offset was increased to 4 bytes
Dr. Clincy

72. Redirection message format
Same as in version 4
When a host sends a datagram to the wrong router
The datagram IS NOT dropped – but rather “redirected” to the correct router
The only differences are:
It accommodates the larger IPv6 addresses
Has an option to let the host know the physical address of the target router
Dr. Clincy

73. Comparison of query messages in ICMPv4 and ICMPv6
Dr. Clincy

74. Echo request and reply messages
Same as in version 4
Used to identify network problems
The only difference is that the type was changed to 128 or 129
Dr. Clincy

75. Router-solicitation and advertisement message formats
Same as in version 4
Used by host to determine if routers are alive and functioning
The only differences are: (1) it can announce its physical address, (2) router can announce the MTU size, and (3) allows the router to define valid lifetime
Dr. Clincy

76. Neighbor-solicitation and advertisement message formats
New in version 6
Performs IPv4’s ARP function
Used to find the physical address of the Rx (given the network address of the Rx)
The only option announces the sender physical address for convenience of the Rx
Dr. Clincy

77. Four situations of group-membership operation
Group-membership message formats
New in version 6
Performs IPv4’s IGMP function
Four situations of group-membership operation
Dr. Clincy

78. TRANSITION FROM IPv4 TO IPv6
Three strategies have been devised by the IETF to provide for a smooth transition from IPv4 to IPv6.
1. Dual Stack
2. Tunneling
3. Header Translation
Dr. Clincy

79. Dual stack All host have both IPv4 and IPv6 protocols running
The host would query the DNS in determining the type of address (ie IPv4 or IPv6)
Depending on the type of address, the host would invoke the corresponding IP version
Dr. Clincy

80. Tunneling Automatic Tunneling Configured tunneling
Given an IPv6 Tx wants to send a packet to an IPv6 but needs to traverse across an IPv4 network – the IPv6 packet can be encapsulated into the IPv4 packet in traversing across the IPv4 network and “unpackaged” after reaching across the IPv4
Automatic Tunneling
If the Rx is IPv6, automatic tunneling is perform and the “compatible IPv6” address is used (recall this)
Configured tunneling
If the Rx doesn’t support a compatible IPv6 address, the initial IPv4 router uses it address as the source address
And the final IPv4 router address is used as the destination address
The final IPv4 router performs the decap and send the packet on the IPv6 Rx
Dr. Clincy

81. Header translation
Header Translation will be used when the majority of the Internet is IPv6 with some systems still using IPv4.
When the final destination is IPv4, tunneling will not work because the Rx only understands IPv4
Therefore, the IPv6 header must be translated to an IPv4 header
Header translation uses the “mapped address” (recall) to translate IPv6 address to a IPv4 address
Some of the rules used in the translation are:
Dr. Clincy