Administrative

1. Homework #3 due
2. Weblink readings
   General protocol info: http://www.protocols.com
   General protocol info: http://www.decodes.com
   ATM: http://cell-relay.indiana.edu for more information
   TCP/IP tools: http://www.private.org.il/mini-faq.html
   SSH: http://www.faqs.org/faqs/computer-security/ssh-faq/index.html
   DNS: http://www.intac.com/~cdp/cptd-faq/
   FTP: http://war.jgaa.com:8080/ftp/
   General TCP/IP resources: http://www.faqs.org/faqs/internet/tcp-ip/resource-list/
3. Project drafts due next week
4. IEEE meeting and lan lab usage
5. ATM speaker
6. Voice/data center tour

V. WAN Technologies [continued]

   G. X.25, Frame Relay, ATM

      3. Asynchronous Transfer Mode (ATM)

         Goal is combine the performance guarantees of a circuit switched
         network like the telephone network with the flexibility of a packet
         switched network like that of the Internet.  Three primary concepts
         for ATM are:

         i.   virtual circuits
         ii.  fixed size packets (cells)
         iii. small packet (cell) size
         iv.  statistical multiplexing
         v.   integrated services

         Synchronous transfer mode versus asynchronous transfer mode

           timeslots, non addressing information, receiver knows where data
           goes based on the "time" - that is, the sender and receiver are
           synchronized.

         Review virtual circuits
          - connection oriented
          - circuit id as opposed to full source/destination address required
          - VCI's (virtual circuit id's), VCI swapping in switch
          - switch stores info (state) for connections (VCI, quality, etc.)

                 Input              VCI      |          Output        VCI
             Host1->Switch1          1       |     Switch1->Switch2    1
             Host2->Switch1          1       |     Switch1->Switch2    2
             Host3->Switch1          2       |     Switch1->Switch2    3

         a. Cell format (in bits)

            Generic Flow control (4)
              -Often not used or used as an extension to VPI
            Virtual Path ID (8)
            Virtual Channel ID (16)
	      -Virtual Channel versus Virtual Path
               -both have local significant
            Payload type (3)
              -User data, AAL info, network info, etc.
            Cell Loss Priority (1)
              -similar to DE in frame relay
            Header Error Check (4)
            Cell Payload/Data (48 bytes)

            b. Service characterizations

               CBR      Constant bit rate
               VBR-NRT  Variable bit rate - non-real time
               VBR-RT   Variable bit rate - real time
               ABR      Available bit rate
               UBR      Unspecified bit rate

         c. LANE and MPOA

            Overview: Backwards compatibility of ATM nodes with LANs
                      such as Token Ring and Ethernet.  Must support the
                      broadcast nature of LANs with the virtual circuit
                      nature of ATM.

            LAN Emulcation Client (LEC)
              - Provides abstraction for LAN protocols to ATM network
            LAN Emulation Server (LES)
              - Manages and supports LECs
            LAN Emulation Configuration Server (LECS)
              - Maintains emulated LANs (ELANs) and supports LECs
            Broadcast and Unknown Server (BUS)
              - Distributes broadcasts/multicasts

            1. LEC - Implemented at each client (bridge listens to all)
            2. LEC contacts LECS to going a ELAN via a preconfigured SVC or
               discovered dynamically via intergrated local management
               interface (ILMI)
            3. LECS assign LEC to a ELAN and direct them to a LES
            4. LEC setups up connection to LES and registers addresses
            5. LES assigns a BUS to the LEC
            6. LEC queries LES for a MAC address to ATM address translation
            7. LECS responds directly or forwards query to another LEC
            8. MAC broadcasts are sent to BUS so that an associated ATM
               broadcast can be sent to all stations in the ELAN.

            The use of SVCs for LAN based protocols (i.e. TCP/IP).

         d. ATM Adaptation Layers (AAL)

            The highest layers in the ATM protocol stack which corresponds
            to different services ATM supports.  Intended to interface with
            applications.  AAL1 and AAL5 only used today.  Perhaps only AAL5
            will exist in the future?

            AAL1 - CBR (circuit emulation)
            AAL2
            AAL3/4
            AAL5 - VBR  (data)

         http://www.atmforum.com for more
         ATM Theory and Applications, McDysan and Spohn, ISBN: 0-07-045346-2

VI. Applications

    A. DNS
    B. SNMP
       Network management stations and network elements
       Version 1: RFC 1157
       MIB RFCs 1155 and 1156
       communities (read only and read-write)

       Object id's in the ASN.1 notation:

          iso org dod internet mgmt mib system sysDescr
           1   3   6     1      2    1    1       1

         Hence, the object type, x, would be 1.3.6.1.2.1.1.1 to which is
         appended an instance sub-identifier of 0.  That is, 1.3.6.1.2.1.1.1.0
         identifies the one and only instance of sysDescr.

         get-request
         get-next-request
         get-response
         set-request
         trap

       Security issues
       snmpwalk example with test router

    C. TELNET

       Plain text transmission for virtual terminal

    D. FTP

       Plain text

    E. SMTP
       1. POP
       2. IMAP

    F. WWW
       1. HTTP
       2. HTML
       3. URL

    G. Also: X-windows, finger, talk, gopher, archie, tftp, ntp, nfs, etc...

Possible topis next week:
Remote access, modems (56K), ISDN BRI/PRI, PPP, etc.
Network Security
VoIP
Network Design
DePaul Network