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CCNA semestr 1. Podstawy działania sieci. Ethernet.
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  1. Historia Ethernetu

    2. Ethernet was developed at Xerox PARC between 1973 and 1974. It was inspired by ALOHAnet, which Robert Metcalfe had studied as part of his PhD dissertation. The idea was first documented in a memo that Metcalfe wrote on May 22, 1973, where he named it after the disproven luminiferous ether as an "omnipresent, completely-passive medium for the propagation of electromagnetic waves". In 1975, Xerox filed a patent application listing Metcalfe, David Boggs, Chuck Thacker, and Butler Lampson as inventors. In 1976, after the system was deployed at PARC, Metcalfe and Boggs published a seminal paper.

    Metcalfe left Xerox in June 1979 to form 3Com. He convinced Digital Equipment Corporation (DEC), Intel, and Xerox to work together to promote Ethernet as a standard. The so-called "DIX" standard, for "Digital/Intel/Xerox", specified 10 Mbit/s Ethernet, with 48-bit destination and source addresses and a global 16-bit Ethertype-type field. It was published on September 30, 1980 as "The Ethernet, A Local Area Network. Data Link Layer and Physical Layer Specifications". Version 2 was published in November, 1982 and defines what has become known as Ethernet II. Formal standardization efforts proceeded at the same time.

    Ethernet initially competed with two largely proprietary systems, Token Ring and Token Bus. Because Ethernet was able to adapt to market realities and shift to inexpensive and ubiquitous twisted pair wiring, these proprietary protocols soon found themselves competing in a market inundated by Ethernet products, and, by the end of the 1980s, Ethernet was clearly the dominant network technology. In the process, 3Com became a major company. 3Com shipped its first 10 Mbit/s Ethernet 3C100 transceiver in March 1981, and that year started selling adapters for PDP-11s and VAXes, as well as Multibus-based Intel and Sun Microsystems computers. This was followed quickly by DEC's Unibus to Ethernet adapter, which DEC sold and used internally to build its own corporate network, which reached over 10,000 nodes by 1986, making it one of the largest computer networks in the world at that time. An Ethernet adapter card for the IBM PC was released in 1982, and, by 1985, 3Com had sold 100,000.

  2. Standardy IEEE Ethernet

    3. In February 1980, the Institute of Electrical and Electronics Engineers (IEEE) started project 802 to standardize local area networks (LAN). The "DIX-group" with Gary Robinson (DEC), Phil Arst (Intel), and Bob Printis (Xerox) submitted the so-called "Blue Book" CSMA/CD specification as a candidate for the LAN specification. In addition to CSMA/CD, Token Ring (supported by IBM) and Token Bus (selected and henceforward supported by General Motors) were also considered as candidates for a LAN standard. Competing proposals and broad interest in the initiative led to strong disagreement over which technology to standardize. In December 1980, the group was split into three subgroups (today known as 802.3 for CSMA/CD, 802.4 for Token Bus and 802.5 for Token Ring), and standardization proceeded separately for each proposal.

    The IEEE 802.3 CSMA/CD standard was approved in December 1982, published as a draft in 1983 and as a standard in 1985.

    Generally speaking IEEE 802 refers to a family of IEEE standards, maintained by the IEEE 802 LAN/MAN Standards Committee (LMSC), dealing with local area networks and metropolitan area networks. More specifically, the IEEE 802 standards are restricted to networks carrying variable-size packets. (By contrast, in cell relay networks data is transmitted in short, uniformly sized units called cells.) The number 802 was simply the next free number IEEE could assign, though “802” is sometimes associated with the date the first meeting was held - February 1980. The services and protocols specified in IEEE 802 map to the lower two layers (Data Link and Physical) of the seven-layer OSI networking reference model. In fact, IEEE 802 splits the OSI Data Link Layer into two sub-layers named Logical Link Control (LLC) and Media Access Control (MAC).

    • 802.1 Bridging & Management. Higher layer LAN protocols. Zarządzanie sieciami LAN i funkcje kontrolne.
      • 802.1D Spanning Tree Protocol - Protokół drzewa rozpinającego.
      • 802.1Q Virtual Local Area Networks (VLAN).
    • 802.2 Logical Link Control. Funkcje wspólne dla kilku typów sieci LAN (pierwotnie dla 802.3, 802.4 i 802.5).
    • 802.3 Ethernet. Sieć Ethernet LAN.
    • 802.4 Sieć Token Bus LAN (Disbanded).
    • 802.5 Sieć Token Ring LAN (Inactive).
    • 802.6 Metropolitan Area Networks (Disbanded).
    • 802.11 Wireless LANs
    • 802.15 Wireless PANs
    • 802.16 Broadband Wireless MANs
    • 802.17 Resilient Packet Rings
    • 802.20 Mobile Broadband Wireless Access
    • 802.21 Media Independent Handover Services
    • 802.22 Wireless Regional Area Networks

    Praca na zajęciach: uzupełnić informacje o 802.11 - podać datę wydania, przepustowość, zasięg.

    Warstwa łacza danychPodwarstwa LLC (sterowania łaczem logicznym)
    Podwarstwa MAC 802.3 (kontrola dostępu do nośnika)
    Warstwa fizyczna 10BASE510BASE210BASE-T10BASE-F100BASE-T100BASE-TX100BASE-FX1000BASE-T1000BASE-SX1000BASE-LX1000BASE-ZX 10GBASE-**10GBASE-T100GBASE-**
    802.3
    10Mbit/s
    500m
    1980
    Thicknet    		 802.3a
    10Mbit/s
    185m
    1985
    Thinnet    		 802.3i
    10Mbit/s
    100m
    1990
    UTP    		 802.3j
    10Mbit/s
    2000m
    1993
    światłowód    		 100BASE-T 802.3u
    100m
    UTP    		 228-412m (duplex), 2000m (full duplex)
    1995
    światłowód wielomodowy    		 1999
    100m
    UTP    		 220-550m
    światłowód wielomodowy    		 550-5000m
    światłowód wielomodowy    		 802.3z
    70km
    światłowód ???    		 802.3ae 2003 10 Gbit/s (1,250 MB/s) Ethernet over fiber; 10GBASE-SR, 10GBASE-LR, 10GBASE-ER, 10GBASE-SW, 10GBASE-LW, 10GBASE-EW 802.3an 2006 10GBASE-T 10 Gbit/s (1,250 MB/s) Ethernet over unshielded twisted pair (UTP) 802.3ba 2010 40 Gbit/s and 100 Gbit/s Ethernet. 40 Gbit/s over 1m backplane, 10 m Cu cable assembly (4x25 Gbit or 10x10 Gbit lanes) and 100 m of MMF and 100 Gbit/s up to 10 m of Cu cable assembly, 100 m of MMF or 40 km of SMF respectively
    Tabela: Standardy IEEE Ethernet a warstwy modelu OSI

    Praca na zajęciach: uzupełnić informacje o 802.3 z tabeli powyżej - podać datę wydania, przepustowość, zasięg, rodzaj nośnika.

  3. Ramka sieci Ethernet

    4. Ethernet II frame (or Ethernet Version 2, or DIX frame) is the most common type in use today, as it is often used directly by the Internet Protocol. 

                         1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 2 3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                             PREAMBLE                        =>|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|<=                                             |     SFD       |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                         ETH DEST ADDRESS                    =>|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|=>                               |                           <=|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|<=                       ETH SRC ADDRESS                       |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|    TYPE CODE/LENGTH             |                           =>|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|<=                        DATA (PAYLOAD)                     =>|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                          ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|<=                        DATA (PAYLOAD)                       |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                            ETH CHECKSUM                       |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    where
    • PREAMBLE Preamble is a sequence of 1-0 of 7 bytes length of the form 
      10101010101010101010101010101010101010101010101010101010

0xAA 0xAA 0xAA 0xAA 0xAA 0xAA 0xAA

Since octets are transmitted least-significant bit first the corresponding hexadecimal representation is 

0x55 0x55 0x55 0x55 0x55 0x55 0x55.
    • SFD Start of frame delimiter - predefined sequence of bits of the form 
      10101011

0xAB

0xD5
    • ETH DEST ADDRESS Ethernet destination address - a destination network address in the form of media access control address (MAC address).
    • ETH SRC ADDRESS Ethernet source address - a source network address in the form of media access control address (MAC address).
    • TYPE CODE/LENGTH Ethertype (for Ethernet II) or length (for IEEE 802.3) This two-octet field can be used for two different purposes. Values of 1500 (0x05DC) and below indicate that it is used as the size of the payload in octets while values of 1536 (0x0600) and above indicate that it is used to represent EtherType. EtherType is used to indicate which protocol is encapsulated in the payload of an Ethernet Frame.
    • DATA (PAYLOAD) The minimum payload is 42 octets when an 802.1Q tag is present (see below) and 46 octets when absent. The maximum payload is 1500 octets. Non-standard jumbo frames allow for larger maximum payload size.
    • ETH CHECKSUM The frame check sequence is a 4-octet cyclic redundancy check which allows detection of corrupted data within the entire frame.

    With the above frame in the Ethernet also coegzists two other frames

    • IEEE 802.2 Logical Link Control (LLC) frame 
                           1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 2 3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                             PREAMBLE                        =>|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|<=                                             |     SFD       |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                         ETH DEST ADDRESS                    =>|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|=>                               |                           <=|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|<=                       ETH SRC ADDRESS                       |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|    TYPE CODE/LENGTH             |     DSAP    |     SSAP      |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|     CONTROL   |                 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|<=                        DATA (PAYLOAD)                     =>|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                          ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|<=                        DATA (PAYLOAD)                       |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                            ETH CHECKSUM                       |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      • DSAP
      • SSAP
      • CONTROL
      All three fields belongs to IEEE 802.2 header; other belongs to 802.3 header.
    • IEEE 802.2 Subnetwork Access Protocol (SNAP) frame 
                           1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 2 3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                             PREAMBLE                        =>|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|<=                                             |     SFD       |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                         ETH DEST ADDRESS                    =>|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|=>                               |                           <=|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|<=                       ETH SRC ADDRESS                       |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|    TYPE CODE/LENGTH             |


DSAP, SSAP, CONTROL (IEEE 802.2)

OUI, TYPE (IEEE SNAP)

                                                              =>|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|<=                        DATA (PAYLOAD)                     =>|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                          ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|<=                        DATA (PAYLOAD)                       |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                            ETH CHECKSUM                       |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    In all cases (for all three headers) an optional 802.1Q tag can be used. The IEEE 802.1Q tag, placed after ETH SRC ADDRESS, is an optional 4-octet field that indicates Virtual LAN (VLAN) membership and IEEE 802.1p priority.

    Praca na zajęciach: kodowanie ramek Ethernet.

  4. EUI / MAC address
    5. Praca na zajęciach: poznajemy format adresu EUI.
    MAC address on Wiki
    IAB
    Interesting information, among others: prices
    Praca na zajęciach: podać OUI dla Cisco.
  5. Podstawowe mechanizmy działania sieci Ethernet
    1. Problem kolizji
    2. Algorytm CSMA/CD
      3. CSMA CD - A Clay Animation About Computer Networking
      topology bus csma cd 2
      topology token
    3. Dupleks, półdupleks
    4. Domeny kolizji
      5. zapobieganie kolizjom przez przełączniki (buforowanie), pełny dupleks
  6. Przełączanie w sieciach Ethernet
    1. Działanie mostów i przełączników
    2. Tablice CAM
    3. Przekazywanie nietypowych ramek
      4. nieznane ramki jednostkowe, ramki rozgłoszeniowe, ramki grupowe Praca na zajęciach: ramki grupowe.
    4. Wewnętrzne przetwarzanie w przełączniku
    5. Protokół drzewa rozpinającego (STP)
      6. Spanning Tree Protocol (STP) Introduction By Edward Tetz from Cisco Networking All-in-One For Dummies
      STP
      protokół stp
      Introduction to Spanning Tree Protocol (STP) Part 1
      Introduction to Spanning Tree Protocol (STP) Part 2