31W6 Lectures Spring 2001

Introductory Material

Lecture 1 16 February 2001

Basic communications model: source/transmitter/transmission system/receiver/destination
Historical communications systems
Concept of networking
Circuit switching, packet switching, frame relay concepts

Reference material: Stallings pp1-11,
Tanenbaum, pp1-16
Peterson and Davie pp4-20

Lecture 2 19 February 2001

ISDN
Protocols: basic concept as agreement on transferring of information
Key elements: syntax (data format, signal levels etc.), semantics, timing
Simple 3 layer protocol stack. Application layer, Comms service layer,, Network access layer
Protocol Data Units (PDU), and how they get used by different layers.

Reference material: Stallings pp 12-18,
Tanenbaum pp 16-22,
Peterson and Davie 29-36.

Lecture 3 20 February 2001

Basic concepts of TCP/IP
OSI layers: issues and what's omitted in TCP/IP
Standards and standardisation organisations

Reference Material: Stallings pp 19-29
Tanenbaum pp 28-43, 66-72
Peterson and Davie pp 29-40

There are PDFs of my powerpoint slides for the first three lectures. These are based on Chapter 1.zip in those produced by Adrian Pullin.

Protocols

Lecture 4 23 February 2001

Characteristics of protocols: Direct/Indirect, Monolithic/Structured, Symmetric/Asymmetric, Standard/Special-purpose.
Basic functions of protocols: Encapsulation (adding control information to the header/trailer of the data to form PDUs), Segmentation (Maximal sizes of PDUs, error effects, equitable access to network resources), Connection Control (Connection oriented circuits or Datagrams).

Reference Material: Stallings pp 31-38, Tanenbaum pp 21-28, Peterson & Davie 170 185 (more detailed)

Lecture 5 26 February 2001

Protocol characteristics continued:
Flow control: stop and wait, basic windowing concepts, requirement at different protocol levels
Error control: Checksum concept, retransmission. Bit error rate.
Addressing: addressing level: TCP/IP host address and port no, OSI NSAP and SAP
addressing scope: globality, Connection identifiers and circuits
Unicast, broadcast and multicast messages.
Multiplexing: upward and downward

Reference Material: Stallings pp39-44, Tanenbaum: 183,202-206, 489-492, Peterson and Davie: 92-116 (too detailed).

Lecture 6 27 February 2001

Protocol characteristics concluded:
Transmission services: Priority, quality of service, Security.
Open systems interconnections (OSI) concepts
Seven layer model: application, presentation, session, transport, network, datalink, physical levels
Brief discussion of each level.

(Actually in 2 March 2001 lecture)
Basic Concepts of TCP/IP protocol suite
PDUs and actual protocols contained in TCP/IP

Reference Material: Stallings pp44-54, Tanenbaum pp 28-35, Peterson and Davie pp 36-39

There are PDFs of my powerpoint slides for lectures 4 to 6. These are based on Chapter 2.zip in those produced by Adrian Pullin.

Physical and Datalink Levels of Protocol

Lecture 7 2 March 2001

Concepts in data transmission
Guided and unguided media
Direct and indirect links
Simplex, half-duplex and duplex
Concepts of frequency, wavelength, spectrum, bandwidth
Analogue transmission of digital data. Noise
Data rate and bandwidth
Actual transmission media: twisted pair...

Reference material: Stallings Chapters 3 and 4 (too detailed), Tanenbaum, pp77-100 (also too detailed)

Lecture 8 5 March 2001

...coaxial cable and fiber optic links
Wireless concpets: point-to-point and broadcast
Infrared links

The data communications interface
Asynchronous and synchronous data transmission
Asynchronous: start, stop bits, data frame, clocking
Synchronous: blocks, use of SYN, clocking problems.
V24/RS232: linking host to modem, levels of this iterface
Mechanical specification, electrical specification, procedural specification
Operation of a dial-up line
RS449: RS423 (single-ended) and RS423 (Balanced) lines

Reference Material: Stallings pp173-188, Tanenbaum 114-115

Lecture 9 6 March 2001

Data Link: for point to point control and data transfer.
Transparency: ability to send any byte. Character stuffing and bit stuffing.
Error detection: Cyclic redundancy checksum
Error control: Automatic request for repeat.
Flow control: preventing buffer overflow. Stop and Wait, Sliding Window techniques.
Dealing with frame errors in sliding window: Go Back N, for damaged and lost frames, Selective reject.

Lecture 10 9 March 2001

High Level Data Link Protocol (HDLC): station types and link transfer modes (NRM, ABM, ARM)
Frame structure: flag fields, Address field, control fields
Information, Supervisory and unnumbered frme types. P/F bit. Frame checksum
Operation of HDLC: setup, data transfer, busy, reject, timeout.
Other datalink techniques: Frame relay and ATM.

Reference Material for lectures 9, 10: Stallings chapter 7, Tanenbaum pp 176-219 (too detailed), 225-228

There are PDF's of slides for Lecture 7 and for Lecture 8. And for lectures 9-10. Again, these are (loosely) based on Adrian Pullin's slides.

Network level issues and protocols

Lecture 11 12 March 2001

Issues at the network level for wide area networks
Circuit vs Packet switching: resource issues, data rate, differences in behaviour under heavy load
Datagrams and Virtual circuits. differences in routing strategy, and in error correction and flow control facilities
Mode of operation of a virtual circuit: setup, data transfer and close phases.
External and internal datagrams and virtual circuits
Routing issues: desirable properties of routing systems
Basic costing issues: link speed, link latency, link queue size
When and where routing decisions are taken: distributed and centralised routing.

Reference material: Stallings pp 303-315, Tanenbaum 339-346.

Lecture 12 13 March 2001

Routing continued: Fixed routing (and its shortcomings),
flooding, (and how to bound packet numbers, and where it can be useful),
adaptive routing (its overheads, advantages. local and distributed adaptive routing)
ARPANET routing strategies
X25 protocol: virtual calls, reset and restart
ATM protocol: ATM and AAL. Basic concepts: Virtual channel connections (VCCs) and Virtual Path Connections (VPCs)
Quality of Service concept. Control signalling. ATM cell.

Reference Material: Stallings: 315-338, 348-355, Tanenbaum pp351-374 (too detailed), 59-66, 449-452.

Lecture 13 16 March 2001 (described as "fierce" by one student)

ATM continued. Basic format of cells (not in detail): 53 octet fixed length
ATM service categories and concept of convergence between audio, video and data transfer
Constant bit rate (CBR), real-time variable bit rate (rt-VBR), non-realtime variable bit rate (nrt-VBR), Available bit rate (ABR), Unspecified bit rate (UBR)
ATM Adaptation Layer (AAL) function and concept. Convergence through different adaptation layers.
AAL5 and IP over ATM
Frame Relay (very brief description)
Congestion: what it is, and why it comes about.
Queues at nodes
Congestion effects: increased delay and packet discards.
Ideal and practical performance.
Controlling congestion: backpressure, choke packet, implicit and explicit congestion signalling.
Virtual private networks (VPNs) why there is interest, and the concept itself

References:Stallings 354-356, 364-369, 373-376, 384-394 Tanenbaum: 449-455, 458-460, 467-471.

There are PDFs of slides for lecture 11, for lecture 12, and for lecture 13, again based on Adrian Pullin's.

Local Area Networks

Lecture 14 19 March 2001

LANs and WANs. Connecting LANs and WANs, Bridge concept.
LAN applications: functionally distributed systems
LAN protocol architecture: IEEE 802 series protocols
Media access layer (MAC), Logical Link Control (LLC), how they inter-relate
LAN topologies: Bus/Tree, Ring and Star
Media access control: synchronous vs asynchronous. MAC frame format
LLC services. Multiplexing.
Bus LAN basics: signal constraints, transmission media.

References: Stallings 424-432, 434-443, Tanenbaum: 84, 275-281.

Lecture 15 20 March 2001

Ethernet. IEEE 802.3 MAC.
CSME, CSMA/CD concepts. Collision detection, and performance under heavy load
Star LANs, and Ethernet based hubs
Wireless LAN concept
Repeaters and Bridges.
Multiple LANs and basic concept of spanning tree
ATM LANs

References: Stallings: pp 448-451, 457-462, 470-475. Tanenbaum: 250-254, 275-283, 304-313 (too detailed)

There are some PDFs of slides for Lecture 14 and for lecture 15, again based on Adrian Pullin's.

The internet protocols: IP and TCP

Lecture 16 23 March 2001

Some internetworking terms: an internet and the Internet, Intranets, End Systems and Intermediate Systems
Repeaters, Bridges and Routers
Network architecture features
Connection-oriented vs connectionless operation at the network level
IP: a connectionless network protocol.
Design inssues: datagram lifetime, fragmentation and reassembly, error and flow control
Parameters of the IP Send and DEliver elements
Basic contents of the IP header: version, header length, type of service, total length, identification, flags, frag offset, time to live, protocol
IP addresses (v4): class A, B, C addresses
ICMP concept

References: Stallings 528-536, 538-546, Tanenbaum 396-399, 402-403, 406-409, 412-419

Lecture 17 26 March 2001

The internet Protocol version 6 (IPv6)
The need for update: address space exhaustion, rapid growth, limitations of single address/host
What's new in IPv6: 128 bit addressing, better option mechanism, address autoconfguration, anycast, resource allocation
IPv6 header structure, address types, mixing addresses with v4
Multicasting and IGMP (v4): IPv6 multicasting (brief) The transport level: Transmission Control Protocol (TCP) and Unconfirmed Datagram Protocol (UDP)
What a transport protocol needs to do with a reliable network protocol: addressing issues
Tasget address is host||port (socket): how does the TCP entity learn the socket address
Basic concept of Domain Naming System, name server

References: Stallings 549-554, 556, 560, 564-566, 608-611. Tanenbaum 437-449 479-480, 489-492

Lecture 18 27 March 2001

Transport protocols continued:
Transport over reliable Network layer ctd: multiplexing (downward and upward)
Flow control at the transport layer: why (because the transport layer, or higher layers, can't keep pace), and how (do nothing, refuse all segments, sliding window, credit scheme.
Credit scheme details: decoupled from ACK, sequenced octet numbering.
Connection establishment and termination: FSM diagram, and how this system deals with establishment and termination problems
Transport layer over unreliable detagram service (as provided by IP)
out-of-order delivery (sequence numbering)
Retransmission on non-delivery: timer issues.
Duplicate detection, and possible problems with octet sequencing wraparound
Flow control: possible problems when credit limit packet is lost
Connection establishment: probels with simple two-way synchronisation:
obsolete data segment, obsolete SYN

References: Stallings: pp611-624, Tanenbaum 483-486, 493-496, 502-508

Lecture 19 30 March 2001

TCP concluded
3-way handshaking as a mechanism for overcoming unreliable underlying network service
Graceful close, crash recovery
TCP header format
TCP implementation policy options on send, deliver (push), accept (in/out of order) retransmission and acknowledgement.
UDP protocol basics and uses
Overview of the self-study required for week of 2 April, for tutorial week starting 16 April (see below)

References: Stallings 624-635, 644-646. Tanenbaum 521-536.

Another useful reference is to be found on Ip and on TCP, courtesy of IBM.

Higher Level Protocols and Issues

Lectures due on 2, 3, 6 and 17 April

These have had to be cancelled. Instead, I have produced some information for self-study, on HTTP and SMTP/MIME. There will be a tutorial on this material in the week after mid-semestet, starting on 16 April 2001

Lecture 20 21 April 2001

SNMP and ASN1:
Simple network management protocol: networks are complex, need managed
Agents, Management Information Base
Basic commands: get, set, notify
Probelm of differing representations of data types
Abstract Syntax Notation 1: abstract and transfer syntax
Basic types, tagged data, extensibility

References: Stallings: pp688-702 (much too detailed), 702-707. Tanenbaum: 630-642 (also too detailed).

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Last updated, 20 April 2001 LSS