Transporting Voice by Using IP
Chapter 2
Internet Overview


A collection of networks


The private networks






The public networks





LANs, MANs, WA...
Internet Overview


Interconnecting networks


Routers provides the connectivity

3

Internet Telephony
Overview of the IP Protocol Suite


IP





A routing protocol for the passing of data packets
Must work in cooperatio...
OSI seven-layer stack

5

Internet Telephony
OSI seven-layer model


Physical layer





Data link layer





The physical media
Coding and modulation schemes f...


Transport layer






Ensure error-free, omission-free and in-sequence
delivery
Support multiple streams from the so...


Presentation layer




Specify the language, the encoding (e.g. ASCII or
binary)

Application layer



Provide an i...
The IP suite and the OSI stack


TCP




Reliable, error-free, in-sequence delivery

UDP


No sequencing, no retransmi...
Internet Standards and the Process


The Internet Society






A non-profit organization
Keep the Internet alive and...


IAB






The Internet Architecture Board
The technical advisory group
Technical guidance, oversee the Internet
sta...


IESG







The Internet Engineering Steering Group
Manage the IETF’s activities
Approve an official standard
Can ...
The Internet Standards Process


The process




RFC 2026

First, Internet Draft






The early version of spec.
C...


RFC





Proposed standard






Request for Comments
An RFC number
A stable, complete, and well-understood spec...


A standard







The IESG is satisfied
The spec. is stable and mature
Significant operational experience
A standa...
IP


RFC 791





Amendments, RFCs 950, 919, and 920
Requirements for Internet hosts, RFCs 1122, 1123
Requirements fo...
IP Header


Version







4

Header Length
Type of Service
Total Length
Identification, Flags, and Fragment Offset
...


Protocol





The higher-layer protocol
TCP, 6; UDP, 17

Source and Destination IP Addresses

18

Internet Telephony
IP Routing



Based on the destination address
Routers





Can contain a range of different interfaces
Determine the...
Populating routing tables


Issues






The correct information in the first place
Keep the information current in a...
TCP


TCP









In sequence, without omissions and without errors
End-to-end confirmation, packet retransmissio...


The TCP header

22

Internet Telephony
The TCP Header


TCP Port Numbers





Identifying a specific instance of a given
application
A unique port number for...


Sequence and acknowledge numbers




Identify individual segments
Actually count data octets transmitted
A given seg...





RST: reset; an error and abort a session
SYN: Synchronize; the initial messages
FIN: Finish; close a session
Wind...


Urgent Pointer




An offset to the first segment after the urgent data
Indicates the length of the urgent data
Crit...
TCP Connections



An examples
After receiving





100, 200, 300
ACK 400

Closing a connection




> FIN
< ACK, F...
UDP


UDP





Pass individual pieces of data from an application
to IP
No ACK, inherently unreliable
Applications

...


UDP header

29

Internet Telephony
Voice over UDP, not TCP


Speech




Small packets, 10 – 40 ms
Occasional packet loss is not a catastrophe
Delay-sensi...
The Real-Time Transport Protocol


RTP: A Transport Protocol for Real-Time
Applications






UDP




RFC 1889
RTP ...


RTCP






A companion protocol
Exchange messages between session users
# of lost packets, delay and inter-arrival...
RTP Payload Formats


RTP carries the actual digitally encoded voice





RTP header + a payload of voice samples
UDP ...


Separate signaling systems




Capability negotiation during the call setup
SIP and SDP
A dynamic payload type may b...
RTP Header Format

35

Internet Telephony
The RTP Header


Version (V)




Padding (P)






2
The padding octets at the end of the payload
The payload needs...


CSRC Count (CC)




Marker (M)





The number of contributing source indentifiers
RFC 1890
The first packet of a ...


Timestamp




32-bit
The instant at which the first sample
The receiver




Synchronized play-out
Calculate the j...


Synchronization Source (SSRC)










32-bit identifier
The entity setting the sequence number and
timestamp
Ch...


RTP Header Extensions




Accommodate the common requirements of most
media streams
For payload formats that requires...
Mixers and Translators


Mixers




Enable multiple media streams from different
sources to be combined
An audio confer...
The RTP Control Protocol (RTCP)


RTCP



A companion control protocol of RTP
Periodic exchange of control information
...


Source Description (SDES)



One or more
Must contain a canonical name







BYE




Separate from SSRC which ...


Two or more RTCP packets will be combined







SRs and RRs should be sent as often as possible
New receivers in ...
RTCP Sender Report


SR





Header Info
Sender Info
Receiver report blocks
Option


Profile-specific extension

45
...


Resemble to a RTP packet


Version




Padding bit




2
Padding octets?

RC, report count



The number of rece...


NTP Timestamp


Network Time Protocol Timestamp





The time elapsed in seconds since 00:00, 1/1/1900 (GMT)
64-bit...


RTP Timestamp







Sender’s packet count




Corresponding to the NTP timestamp
Use the same units and has the ...
RR blocks


SSRC_n




Fraction lost






Fraction of packets lost since the last report issued by
this participant...


Interarrival jitter




Last SR Timestamp (LSR)






An estimate of the variance in RTP packet arrival
The middle...
RTCP Receiver Report


RR




Issued by a participant who receives RTP packets
but does not send, or has not yet sent
I...
RTCP Source Description Packet


Provides identification and information regarding
session participants




Header


...


RTCP BYE Packet




Indicate one or more media sources are no longer
active

Application-Defined RTCP Packet



For...
Calculating Round-Trip Time



Use SRs and RRs
E.g.






Report A: A, T1 → B, T2
Report B: B, T3 → A, T4
RTT = T4-...
Calculation Jitter


The mean deviation of the difference in
packet spacing at the receiver



Ri = the time of arrival...
Timing of RTCP Packets


RTCP provides useful feedback




Regarding the quality of an RTP session
Delay, jitter, pack...
IP Multicast


An IP diagram sent to multiple hosts





Conference
To a single address associated with all listeners
...


IPv4








Multicast addresses: 224.0.0.0 – 239.255.255.255
224.0.0.1
all hosts on a local subnet
224.0.0.2
all...
IP Version 6


The explosive growth of the Internet








Expanded address space, 128 bits
Simplified header form...
IP Version 6 Header

60

Internet Telephony
IP Version 6 Header


Version




Traffic Class, 8-bit




6
For the quality of service

Flow Label, 20-bit





L...


Payload Length, 16-bit unsigned integer





The length of payload in octets
Header extensions are part of the paylo...
IP version 6 addresses


XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XX
XX




E.g., 1511:1:0:0:0:FA22:45:11





Leading zer...
IP version 6 special addresses


The all-zeros address, ::




The loopback address, ::1




On a virtual internal in...
IP Version 6 Header Extensions


Extension Headers


Are not acted upon by intermediate nodes




With one exception

...
Header extension


Use the next header field

66

Internet Telephony
Hop-by-hop extension


The exception header extension







Next header
Length




Examined and processed by ever...


Hop-by-hop header extension

68

Internet Telephony


Type[0:1]








00 skip this option and continue processing the header
01 discard the packet
10 discard the pack...


Destination options extension






Has the same format as the hop-by-hop extension
Only the destination node exami...


Routing Extension

71

Internet Telephony



Routing type
Segments Left





The number of nodes that still need to be visited

A list of IP addresses needs to...
Interoperation IPv4 and IPv6


IPv4 and IPv6 will coexist for a long time






IPv4 nodes  IPv6 nodes
IPv6 nodes  ...
Interoperation IPv4 and IPv6


IPv4-compatible nodes with IPv4-compatible
addresses at the boundaries of IPv6 networks

...
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Transporting voice by using IP

  1. 1. Transporting Voice by Using IP Chapter 2
  2. 2. Internet Overview  A collection of networks  The private networks     The public networks    LANs, MANs, WANs Institutions, corporations, business and government May use various communication protocols ISP: Internet Service Providers Using Internet Protocol To connect to the Internet  Using IP 2 Internet Telephony
  3. 3. Internet Overview  Interconnecting networks  Routers provides the connectivity 3 Internet Telephony
  4. 4. Overview of the IP Protocol Suite  IP    A routing protocol for the passing of data packets Must work in cooperation with higher layer protocols The OSI seven-layer model   The top layer: usable information passed The information must be    Packaged appropriately Routed correctly And it must traverse some physical medium 4 Internet Telephony
  5. 5. OSI seven-layer stack 5 Internet Telephony
  6. 6. OSI seven-layer model  Physical layer    Data link layer    The physical media Coding and modulation schemes for 1s and 0s Transport the information over a single link Frame packaging, error detection/correction and retransmission Network layer   Routing traffic through a network Passing through intermediate points 6 Internet Telephony
  7. 7.  Transport layer    Ensure error-free, omission-free and in-sequence delivery Support multiple streams from the source to destination for applications Session layer   The commencement (e.g., login) and completion Establish the dialogue  One way at a time or both ways at the same time 7 Internet Telephony
  8. 8.  Presentation layer   Specify the language, the encoding (e.g. ASCII or binary) Application layer   Provide an interface to the user FTP, Web browsers 8 Internet Telephony
  9. 9. The IP suite and the OSI stack  TCP   Reliable, error-free, in-sequence delivery UDP  No sequencing, no retransmission 9 Internet Telephony
  10. 10. Internet Standards and the Process  The Internet Society     A non-profit organization Keep the Internet alive and growing “to assure the open development, evolution, and the use of Internet for the benefit of all people throughout the world” The tasks     Support the development and dissemination of Internet standards Support the RD related to the Internet and internetworking Assists developing countries Form a liaison for Internet development 10 Internet Telephony
  11. 11.  IAB     The Internet Architecture Board The technical advisory group Technical guidance, oversee the Internet standards process IETF     Comprises a huge number of volunteers Develop Internet standards Detailed technical work Working groups  avt, megaco, iptel, sip, sigtran 11 Internet Telephony
  12. 12.  IESG      The Internet Engineering Steering Group Manage the IETF’s activities Approve an official standard Can a standard advance? IANA  The Internet Assigned Numbers Authority   Unique numbers and parameters used in Internet standards Be registered with the IANA 12 Internet Telephony
  13. 13. The Internet Standards Process  The process   RFC 2026 First, Internet Draft     The early version of spec. Can be updated, replaced, or made obsolete by another document at any time IETF’s Internet Drafts directory Six-month life-time 13 Internet Telephony
  14. 14.  RFC    Proposed standard     Request for Comments An RFC number A stable, complete, and well-understood spec. Has garnered significant interest May be required to implement for critical protocols Draft standard    Two independently successful implementations Interoperability be demonstrated Requirements not met be removed 14 Internet Telephony
  15. 15.  A standard      The IESG is satisfied The spec. is stable and mature Significant operational experience A standard (STD) number Not all RFCs are standards  Some document Best Current Practices (BCPs)   Others applicability statements   Processes, policies, or operational considerations How a spec be used, or different specs work together STD1 list the various RFCs 15 Internet Telephony
  16. 16. IP  RFC 791     Amendments, RFCs 950, 919, and 920 Requirements for Internet hosts, RFCs 1122, 1123 Requirements for IP routers, RFC 1812 IP datagram   Data packet with an IP header Best-effort protocol 16 Internet Telephony
  17. 17. IP Header  Version      4 Header Length Type of Service Total Length Identification, Flags, and Fragment Offset    A datagram can be split into fragments Identify data fragments Flags    a datagram can be fragmented or not Indicate the last fragment TTL  A number of hops (not a number of seconds) 17 Internet Telephony
  18. 18.  Protocol    The higher-layer protocol TCP, 6; UDP, 17 Source and Destination IP Addresses 18 Internet Telephony
  19. 19. IP Routing   Based on the destination address Routers    Can contain a range of different interfaces Determine the best outgoing interface for a given IP datagram Routing table    Destination IP route mask the longest match 19 Internet Telephony
  20. 20. Populating routing tables  Issues     The correct information in the first place Keep the information current in a dynamic environ The best path? Protocols     RIP, Routing Information Protocol IGRP, Internet Gateway Routing Protocol OSPF, Open Short Path First BGP, Border Gateway Protocol, RFC 1771 20 Internet Telephony
  21. 21. TCP  TCP        In sequence, without omissions and without errors End-to-end confirmation, packet retransmission, Flow control RFC 793 Break up a data stream in segments Attach a TCP header Sent down the stack to IP At the destination, checks the header for errors   Send back an ack The source retransmits if no ack within a given period 21 Internet Telephony
  22. 22.  The TCP header 22 Internet Telephony
  23. 23. The TCP Header  TCP Port Numbers    Identifying a specific instance of a given application A unique port number for a particular session Well-known port numbers    IANA, 0-1023 23, telnet; 25, SMTP Many clients and a server    TCP/IP Source address and port number + Destination address and port number A socket address 23 Internet Telephony
  24. 24.  Sequence and acknowledge numbers    Identify individual segments Actually count data octets transmitted A given segment with a SN of 100 and contains 150 octets of data    The ack number will be 250 The SN of the next segment is 250 Other header fields     Data offset: header length (in 32-bit words) URG: 1 if urgent data is included, use urgent pointer field ACK: 1, an ACK PSH: a push function, be delivered promptly 24 Internet Telephony
  25. 25.     RST: reset; an error and abort a session SYN: Synchronize; the initial messages FIN: Finish; close a session Window   The amount of buffer space available for receiving data Checksum  1's complement of 1's complement sum of all 16-bit words in the TCP header, the data, and a pseudo header 25 Internet Telephony
  26. 26.  Urgent Pointer    An offset to the first segment after the urgent data Indicates the length of the urgent data Critical information to be sent to the user application ASAP. 26 Internet Telephony
  27. 27. TCP Connections   An examples After receiving    100, 200, 300 ACK 400 Closing a connection    > FIN < ACK, FIN > ACK 27 Internet Telephony
  28. 28. UDP  UDP    Pass individual pieces of data from an application to IP No ACK, inherently unreliable Applications       A quick, one-shot transmission of data, request/response DNS If no response, the AP retransmit the request The AP includes a request identifier The source port number is optional Checksum  The header, the data and the pseudo header 28 Internet Telephony
  29. 29.  UDP header 29 Internet Telephony
  30. 30. Voice over UDP, not TCP  Speech    Small packets, 10 – 40 ms Occasional packet loss is not a catastrophe Delay-sensitive   5 % packet loss is acceptable if evenly spaced    Resource management and reservation techniques A managed IP network In-sequence delivery   TCP: connection set-up, ack, retransmit → delays Mostly yes UDP was not designed for voice traffic 30 Internet Telephony
  31. 31. The Real-Time Transport Protocol  RTP: A Transport Protocol for Real-Time Applications     UDP   RFC 1889 RTP – Real-Time Transport Protocol RTCP – RTP Control Protocol Packets may be lost or out-of-sequence RTP over UDP    A sequence number A time stamp for synchronized play-out Does not solve the problems; simply provides additional information 31 Internet Telephony
  32. 32.  RTCP      A companion protocol Exchange messages between session users # of lost packets, delay and inter-arrival jitter Quality feedback RTCP is implicitly open when an RTP session is open   Not mandatory E.g., RTP/RTCP uses UDP port 5004/5005 32 Internet Telephony
  33. 33. RTP Payload Formats  RTP carries the actual digitally encoded voice    RTP header + a payload of voice samples UDP and IP headers are attached Many voice- and video-coding standards  A payload type identifier in the RTP header     Specified in RFC 1890 New coding schemes have become available See table 2-1 A sender has no idea what coding schemes a receiver could handle 33 Internet Telephony
  34. 34.  Separate signaling systems    Capability negotiation during the call setup SIP and SDP A dynamic payload type may be used   Also support new coding scheme in the future The encoding name is also significant    Unambiguously refer to a particular payload specification Should be registered with the IANA RED, Redundant payload type    Voice samples + previous samples May use different encoding schemes Cope with packet loss 34 Internet Telephony
  35. 35. RTP Header Format 35 Internet Telephony
  36. 36. The RTP Header  Version (V)   Padding (P)     2 The padding octets at the end of the payload The payload needs to align with 32-bit boundary The last octet of the payload contains the count Extension (X)  1, contains a header extension 36 Internet Telephony
  37. 37.  CSRC Count (CC)   Marker (M)    The number of contributing source indentifiers RFC 1890 The first packet of a talkspurt, after a silence period Payload Type (PT)  RED is an exception   RFC 2198, the addition of headers Sequence number   A random number at the beginning Incremented by one for each RTP packet 37 Internet Telephony
  38. 38.  Timestamp    32-bit The instant at which the first sample The receiver    Synchronized play-out Calculate the jitter The clock freq depends on the encoding    E.g., 8000Hz, TS=1/10 samples; TS=11 Support silence suppression The initial timestamp is a random number 38 Internet Telephony
  39. 39.  Synchronization Source (SSRC)       32-bit identifier The entity setting the sequence number and timestamp Chosen randomly, independent of the network address Meant to be globally unique within the session May be a sender or a mixer Contributing Source (CSRC)   An SSRC value for a contributor 0-15 CSRC entries 39 Internet Telephony
  40. 40.  RTP Header Extensions   Accommodate the common requirements of most media streams For payload formats that requires 40 Internet Telephony
  41. 41. Mixers and Translators  Mixers   Enable multiple media streams from different sources to be combined An audio conference    Could also change the data format The SSRC is the mixer   If the capacity or bandwidth of a participant is limited More than one CSRC values A translator   Manage communications between entities that does not support the same coding scheme The SSRC is the participant, not the translator 41 Internet Telephony
  42. 42. The RTP Control Protocol (RTCP)  RTCP   A companion control protocol of RTP Periodic exchange of control information   A third party can also monitor session quality   For quality-related feedback Using RTCP and IP multicast Five type of RTCP packets   Sender Report: transmission and reception statistics Receiver Report: reception statistics 42 Internet Telephony
  43. 43.  Source Description (SDES)   One or more Must contain a canonical name     BYE   Separate from SSRC which might change When both audio and video streams exist  Have different SSRCs  Have the same CNAME for synchronized play-out Regular names, such as email address or phone number The end of participation APP  Convey application-specific functions 43 Internet Telephony
  44. 44.  Two or more RTCP packets will be combined      SRs and RRs should be sent as often as possible New receivers in a session must receive CNAME An SR/RR must contain an SDES packet A SDES packet is sent with an SR/RR even if no data to report An example RTP compound packet 44 Internet Telephony
  45. 45. RTCP Sender Report  SR     Header Info Sender Info Receiver report blocks Option  Profile-specific extension 45 Internet Telephony
  46. 46.  Resemble to a RTP packet  Version   Padding bit   2 Padding octets? RC, report count   The number of reception report blocks 5-bit    If more than 31 reports, an RR is added PT, payload type SSRC of sender 46 Internet Telephony
  47. 47.  NTP Timestamp  Network Time Protocol Timestamp    The time elapsed in seconds since 00:00, 1/1/1900 (GMT) 64-bit  32 MSB: the number of seconds  32 LSB: the fraction of a seconds (200 ps) A primary time server    NTP, RFC 1305 Station WWV, Fort Collins, Colorado, by NIST Station WWVB, Boulder, Colorado, by NIST 47 Internet Telephony
  48. 48.  RTP Timestamp     Sender’s packet count   Corresponding to the NTP timestamp Use the same units and has the same offset as used for RTP timestamps For better synchronization Cumulative within a session Sender’s octet count  Cumulative 48 Internet Telephony
  49. 49. RR blocks  SSRC_n   Fraction lost    Fraction of packets lost since the last report issued by this participant By examining the sequence numbers in the RTP header Cumulative number of packets lost   The source identifier Since the beginning of the RTP session Extended highest sequence number received    The sequence number of the last RTP packet received 16 lsb, the last sequence number 16 msb, the number of sequence number cycles 49 Internet Telephony
  50. 50.  Interarrival jitter   Last SR Timestamp (LSR)    An estimate of the variance in RTP packet arrival The middle 32 bits of the NTP timestamp used in the last SR received from the source in question Used to check if the last SR has been received Delay Since Last SR (DLSR)  The duration in units of 1/65,536 seconds 50 Internet Telephony
  51. 51. RTCP Receiver Report  RR   Issued by a participant who receives RTP packets but does not send, or has not yet sent Is almost identical to an SR   PT = 201 No sender information 51 Internet Telephony
  52. 52. RTCP Source Description Packet  Provides identification and information regarding session participants   Header   Must exist in every RTCP compound packet V, P, SC, PT=202, Length Zero or more chunks of information   An SSRC or CSRC value One or more identifiers and pieces of information    Email address, phone number, name Defined in RFC 1889 A unique CNAME  E.g., user@host 52 Internet Telephony
  53. 53.  RTCP BYE Packet   Indicate one or more media sources are no longer active Application-Defined RTCP Packet   For application-specific data For non-standardized application 53 Internet Telephony
  54. 54. Calculating Round-Trip Time   Use SRs and RRs E.g.      Report A: A, T1 → B, T2 Report B: B, T3 → A, T4 RTT = T4-T3+T2-T1 RTT = T4-(T3-T2)-T1 Report B   LSR = T1 DLSR = T3-T2 54 Internet Telephony
  55. 55. Calculation Jitter  The mean deviation of the difference in packet spacing at the receiver   Ri = the time of arrival   Si = the RTP timestamp for packet I D(i,j) = (Rj-Sj) - (Ri- Si) The Jitter is calculated continuously  J(i) = J(i-1) + (| D(i-1,i) | - J(i-1))/16 55 Internet Telephony
  56. 56. Timing of RTCP Packets  RTCP provides useful feedback    Regarding the quality of an RTP session Delay, jitter, packet loss Be sent as often as possible    Consume the bandwidth Should be fixed at 5% An algorithm, RFC 1889     Senders are collectively allowed at least 25% of the control traffic bandwidth The interval > 5 seconds 0.5 – 1.5 times the calculated interval A dynamic estimate the avg RTCP packet size 56 Internet Telephony
  57. 57. IP Multicast  An IP diagram sent to multiple hosts    Conference To a single address associated with all listeners Multicast groups   Multicast address Join a multicast group   Inform local routers Routing protocols   Support propagation of routing information for multicast addresses Minimize the number of diagrams sent 57 Internet Telephony
  58. 58.  IPv4       Multicast addresses: 224.0.0.0 – 239.255.255.255 224.0.0.1 all hosts on a local subnet 224.0.0.2 all routers on a local subnet 224.0.0.5 all routers supporting OSPF 224.0.0.9 all routers supporting RIP v.2 IGMP, Internet Group Message Protocol   Advertise membership in a group to routers RFC 1112, 2236 58 Internet Telephony
  59. 59. IP Version 6  The explosive growth of the Internet       Expanded address space, 128 bits Simplified header format Improved support for headers and extensions Flow-labeling capability   IPv4 address space, 32-bit Real-time and interactive applications Better support at the IP level for real-time ap Authentication and privacy  At the IP level 59 Internet Telephony
  60. 60. IP Version 6 Header 60 Internet Telephony
  61. 61. IP Version 6 Header  Version   Traffic Class, 8-bit   6 For the quality of service Flow Label, 20-bit    Label sequences of packets A flow := source address, destination address, flow label 0, no special handling 61 Internet Telephony
  62. 62.  Payload Length, 16-bit unsigned integer    The length of payload in octets Header extensions are part of the payload Next Header, 8-bit  The next higher-layer protocol    The existence of IPv6 header extensions Hop Limit, 8-bit unsigned integer   Same as the IPv4 The TTL field of the IPv4 header Source and Destination Addresses, 128-bit 62 Internet Telephony
  63. 63. IP version 6 addresses  XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XX XX   E.g., 1511:1:0:0:0:FA22:45:11    Leading zeros are omitted = 1511:1::FA22:45:11 0:0:0:0:AA11:50:22:F77 = ::AA11:50:22:F77   X is a hexadecimal character “::” can appears only once Should not generally require significant changes to up-layer protocols  But the checksum calculation in UDP and TCP includes a pseudo header 63 Internet Telephony
  64. 64. IP version 6 special addresses  The all-zeros address, ::   The loopback address, ::1   On a virtual internal interface IPv6 address with embedded IPv4 address (type 1)    An unspecified address; a node does not yet know its address 96-bit zeros + 32-bit IPv4 address ::140.113.17.5 IPv6 address with embedded IPv4 address (type 2)    80-bit zeros + FFFF + 32-bit IPv4 address 0:0:0:0:0:FFFF:140.113.17.5 ::FFFF:140.113.17.5 64 Internet Telephony
  65. 65. IP Version 6 Header Extensions  Extension Headers  Are not acted upon by intermediate nodes   With one exception Next Header     The type of payload carried in the IP datagram The type of header extension Each extension has its own next header field An example 65 Internet Telephony
  66. 66. Header extension  Use the next header field 66 Internet Telephony
  67. 67. Hop-by-hop extension  The exception header extension      Next header Length   Examined and processed by every intermediate node If present, must immediately follow the IP header Of variable length in units of eight octets, not including the first eight octets Options  TLV (Type-Length-Value) format   8-bit, 8-bit (in units of octets), variable length Type [0:2] of special significance 67 Internet Telephony
  68. 68.  Hop-by-hop header extension 68 Internet Telephony
  69. 69.  Type[0:1]      00 skip this option and continue processing the header 01 discard the packet 10 discard the packet and send an ICMP Parameter Problem, Code 2 message to the originator of the packet 11 do above only if the destination address in the IP header is not a multicast address Type[2]   1, the option data can be changed 0, cannot 69 Internet Telephony
  70. 70.  Destination options extension     Has the same format as the hop-by-hop extension Only the destination node examine the extension Header type = 60 Routing Extension      A routing type field to enable various routing options Only routing type 0 is defined for now Specify the nodes that should be visited Next header Length 70 Internet Telephony
  71. 71.  Routing Extension 71 Internet Telephony
  72. 72.   Routing type Segments Left    The number of nodes that still need to be visited A list of IP addresses needs to be visited Is this type of header analyzed by intermediate node?       Yes or no A->Z, 3, (B,C,D) A->B, 3, (C,D,Z) A->C, 2, (B,D,Z) by B A->D, 1, (B,C,Z) by C A->Z, 0, (B,C,D) by D 72 Internet Telephony
  73. 73. Interoperation IPv4 and IPv6  IPv4 and IPv6 will coexist for a long time     IPv4 nodes  IPv6 nodes IPv6 nodes  IPv6 nodes via IPv4 networks IPv4 nodes  IPv4 nodes via IPv6 networks IPv4-compatible nodes with IPv4-compatible addresses at the boundaries of IPv6 networks  IPv6 in IPv4 packets 73 Internet Telephony
  74. 74. Interoperation IPv4 and IPv6  IPv4-compatible nodes with IPv4-compatible addresses at the boundaries of IPv6 networks  IPv6 in IPv4 packets 74 Internet Telephony

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