TCP/IP ????

1
TCP/IP ????
2? ?? ??
2
? ?

• 2.1 Introduction
• 2.2 Ethernet and IEEE 802 Encapsulation
• 2.3 Trailer Encapsulation
• 2.4 SLIP Serial Line IP
• 2.5 Compressed SLIP
• 2.6 PPP Point-to-Point Protocol
• 2.7 Loopback Interface
• 2.8 MTU (maximum transmission unit)
• 2.9 Path MTU
• 2.10 Serial Line Throughput Calculations
• 2.11 ??

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2.1 Introduction

• ????? ??
• IP module? ?? IP datagram? send/receive
• ARP module? ?? ARP request? reply
• RARP module? ?? RARP request? reply
• TCP/IP? ?? ?? Link Layer? ????
• ?, TCP/IP ????? ?? ??? ??? ???? ???? ??? ? ???
  ???? ??.
• Ethernet, token ring, FDDI, RS-232 serial line,
  etc.

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2.2 Ethernet and IEEE 802 Encapsulation

• Ethernet
• ????? DEC, Intel, Xerox?? 1982?? ??? ??? ????
  CSMA/CD (Carrier Sense, Multiple Access with
  Collision Detection) ?? ?? access method? ??
• ???? 10Mbps, 48-bit address
• IEEE 802 ???
• 802.2 LLC(Logical Link Control)
• 802.3 CSMA/CD
• 802.4 token bus
• 802.5 token ring

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2.2 Ethernet and IEEE 802 Encapsulation (Contd)

• IP datagram encapsulation define
• Ethernet? ?? RFC 894
• IEEE 802 network? ?? RFC 1042

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2.2 Ethernet and IEEE 802 Encapsulation (Contd)

• Host Requirement RFC
• RFC 894(Ethernet) encapsulation? ???? packet?
  ???? ? ??? ??
• RFC 894 packet? ??? RFC 1042(IEEE 802) packet?
  ??? ? ??? ??
• RFC 1042 encapsulation? ??? packet? ??? ?? ???
  ??. ???? ? ??? packet? ??? ? ??? ??? packet? ???
  ??? ? ??? ?? ?? ??? RFC 894? ??? ??.
• RFC 894 encapsulation? ?? ????? ???? ??.

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IEEE 802.2/802.3 ???(RFC 1042)? ??? ???(RFC 894)
type
IP datagram
0800
2
46-1500
type
ARP request/reply
PAD
0806
2
28
18
type
RARP request/reply
PAD
0835
28
18
2
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2.3 Trailer Encapsulation

• RFC 893? trailer encapsulation??? ?? ? ?? ???
  Ethernet encapsulation? ??
• ??? IP datagram? ?? ??? ????? ?? ??? ?? ????
  ?????
• ?, IP? TCP header? data ??? ??? ????? data?
  kernel?? ??? ? memory to memory copy? ?????
  ?????? ? ??
• ??? ???? ??

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2.4 SLIP Serial Line IP

• RFC 1055
• RS-232 serial port? ?? Internet? ??? ? ??
• framing rule
• IP datagram? ??? special character END(0xc0)? ??.
  ?? ?? line noise? ???? ???? ?? ?? ??.
• IP datagram ?? 0xc0? 0xdb, 0xdc? ???? ??(0xdb?
  SLIP ESC character? ?)
• IP datagram ?? 0xdb? 0xdb, 0xdd? ???? ??

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2.4 SLIP Serial Line IP(Contd)

• SLIP? ??
• ? end system? ??? IP address? ?? ??? ??. ?, IP
  address? ?? ? ??? ??.
• Ethernet? type field? ??? type field? ??. ??
  serial line? SLIP? ???? ??? ??? ?? protocol? ???
  ? ??.
• SLIP? Ethernet? CRC? ?? ??? checksum? ?? ???.
  SLIP? ?? ???? ?? datagram? ???? ?? ??? ? ??, ??
  ?? ??? ???? ??. ??? IP? header checksum, TCP?
  header? data checksum, UDP? header?
  data(optional) checksum? ?? ????.

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2.5 Compressed SLIP

• RFC 1144 Jacobson 1990a
• SLIP line? ??(19200bits/sec or below)??
  interactive traffic(TCP? ???? Telnet or Rlogin)?
  ??? ?? 1 byte? ???? ?? 40bytes(TCP 20, IP20)?
  overhead? ??.
• ??? ???? ??? ???? ?? CSLIP? ??
• ????? ?? ??? ???? ? header? ?? field? ??? ????
  ??? ???? 40 bytes? header? 3 or 5 bytes? ??? ??.
  ??? ??? ?? header? interactive response time? ??
  ????.

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2.6 PPP Point-to-Point Protocol

• PPP? SLIP? ?? ??? ???? ??? ?? 3?? ??? ????.
• Serial link?? IP datagram? encapsulation?? ??.
  PPP? 8 bits data, no parity? ???? asynchronous
  link? bit-oriented synchronous link? ?? ????.
• Data-link connection? ??, ??, ??? ?? ?? LCP(Link
  Control Protocols). ??? ? end system? ??? option?
  ??? ? ??.
• NCP (Network Control Protocols)? ?? ???? ??? ????
  ??. ?? IP, OSI network layer, DECnet, AppleTalk?
  ?? RFC? ??.

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2.6 PPP Point-to-Point Protocol (Contd)

• RFC 1331 encapsulation method and link control
  protocol
• RFC 1332 network control protocol for IP

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2.6 PPP Point-to-Point Protocol(Contd)

• information field? 0x7e? ??? ??
• ??? ??? ?? bit stuffing
• ???? ??? ?? escape character(0x7d) ???? escape
  character? PPP frame? ??? ??(? ?? ???? 6?? bit?
  ??? ??)
• 0x7e? 0x7d, 0x5e
• 0x7d? 0x7d, 0x5d
• 0x20?? ?? ?? ??? ???? ??? ?? ??. ?? ?? 0x01?
  0x7d, 0x21? ??? ??. ?? ???? ???? serial driver?
  ASCII control character? ???? ?? ?? ??.

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2.6 PPP Point-to-Point Protocol(Contd)

• SLIP? ????? constant(flag, address)? ????
  protocol? 1 byte? ?? ??? ? ??. ??? ? ???? 3
  byte(CRC 2, protocol 1)? overhead? ??. ?? CSLIP?
  ????? IP, TCP header? ??? ??? ??? ? ??.
• SLIP?? PPP? ?? ??
• ? serial line? multiple protocol? ??
• ? frame? cyclic redundancy check
• IP network control protocol? ???? IP address? ??
  ?? ??
• CSLIP? ??? TCP, IP header compression
• link control protocol? ?? ??? data-link option ??
• ????? ??? ??? 3 byte? overhead, link? ??? ? ???
  ?? ?? ? ?? frame, ?? ? ??? ??? ?? ????.

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2.7 Loopback Interface

• ?? ????? client? server? TCP/IP? ???? ???? ?? ???
  loopback interface? ??
• ??? localhost, IP address? 127.0.0.1

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2.7 Loopback Interface (contd)

• Key points
• loopback address? ??? ?? ?? IP input? ????.
• broadcast or multicast address? ??? datagram?
  loopback interface? ???? Ethernet?? ????. ??
  broadcasting? multicasting? ??? sending host?
  ???? ????.
• ??? IP address ? ??? ??? ?? ?? loopback
  interface? ????.
• ?? transport? IP layer? loopback data? ???? ??
  ?????? ???? ????? ?? network layer?? loopback
  interface? ?? ?? link layer? ??? ??? ??? ??? ???.
• ?? ??? IP address ? ??? ??? IP datagram? ???? ??
  ??? ??? ?? ??? ?? ????.

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2.8 MTU

• frame? ??? ???? link layer? ??? MTU (maximum
  transmission unit)? ??.
• IP datagram? link layer? MTU?? ?? fragmentation?
  ???? ? fragment? MTU?? ??? ??.
• ? ? Point-to-Point? ?? MTU? network media? ???
  ??? ?? ?? ??? ??? ??? ??? response? ???? ?? ????
  ??.

MTU(bytes)
Network
Hyperchannel
65535
16 Mbits/sec token ring(IBM)
17914
4 Mbits/sec token ring(IEEE 802.5)
4464
FDDI
4352
Ethernet
1500
IEEE 802.3/802.2
1492
X.25
576
Point-to-Point(low delay)
296
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2.9 Path MTU

• ? ???? ?? network ??? ??? ?? MTU? ??? factor??.
• ??? ? ??? ??? multiple network? ???? ?? ?? ? ????
  ??? network? MTU ??? ?? network? ?? ?? MTU? ?
  ???? ?? path MTU? ??.
• Path MTU? ???? ??? ?? ?? ??? ??? ??? ???? ????.
• ?? routing? ??? ???. ?, A?? B? ?? ??? B?? A? ??
  ??? ?? ? ?? ????. ??? path MTU? ? ??? ?? ?? ? ??.
• RFC 1191?? path MTU? ???? ?? ??(path MTU
  discovery mechanism)? ???? ??.

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2.10 Serial Line Throughput Calculations

• line speed 9600bps, data 8 bits, start 1 bit,
  stop 1bit? ?? 960 byte/sec?? 1024 byte packet ???
  1066ms? ????.
• ??? ???? SLIP link ??? 1024 byte frame? ???
  application? interactive application? ???? ??
  interactive packet? ???? ?? 1066/2 533ms? ????
  ??.
• Interactive traffic? 100-200ms? ???? ?? ?? ???
  ????Jacobson 1990a(?? ?? ??)
• MTU? 256? ?? 266ms(256/960) ???? ?? wait?
  133ms??. 133? ??? throughput? ??? 64? 128???
  utilization? ??.

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2.10 Serial Line Throughput Calculations(Contd)

• Point-to-Point link?? MTU? 296?? ?? ??
• 25640(TCP IP header)296??. ??? CSLIP? ???? ??
  40? 5? ??? ??? 261byte frame? ?? 261 ???
  98.1(256/261)? data, 1.9(5/261)? header??? ??
  utilization ??? ? ? ??.

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2.11 ??

• ???? IEEE 802.2/802.3???? ???
• SLIP? PPP ??? ???
• SLIP? PPP? ? ? ?? ???? ???? ??? ?? ??? ?? ???
  ???? ????
• ??? ?????
• MTU? path MTU