Communication Networks

Week 1: Introduction

Introduction, description of the goals and requirements of the course. Motivations for the course.

Introduction of networks and systems through examples; history, foundations, and architecture of the Internet and long-distance communication. Applications and services, examples. Requirements related to the network. Packet loss and delay.

Week 2: Protocol architectures

Protocol architectures, reference models: the ISO OSI reference model, TCP/IP protocol architecture, circuit switching, packet switching, addressing.

Week 3: Physical and data link layer

Transmission media and their properties. The physical foundations of radio communication.

Ethernet. Overview, versions. Structure of the Ethernet frame. Ethernet switches: operation, properties, management. Comparison of switching and routing. Virtual Local Area Networks (VLAN).

Wireless Local Area Networks (WLAN). Overview. Characteristics of wireless connections. Wireless local networks based on recommendation IEEE 802.11: architecture, frequency allocation, medium access. The problem of hidden terminals. Organization of frames. Outlook: Bluetooth and Zigbee.

Week 4: Routing basics

Interpretation of the task, routing tables, distance vector method, link state method. Hierarchical routing, autonomous systems.

Week 5:

Multicast routing.

Internet Protocol: Tasks, characteristics, and addressing (address classes, private address domains, Classless Inter-Domain Routing, exhaustion of the IPv4 address domain) of IP, IP packet structure.

Week 6:

IP routing (RIP, EIGRP, OSPF, IS-IS, BGP), Address Resolution Protocol, IP fragmentation, signaling and management messages of IP (ICMP and IGMP).

MultiProtocol Label Switching (MPLS).

Week 7:

Traffic control: desirable characteristics of traffic control and its types. Transport layer: the concept of socket, socket types, User Datagram Protocol (port management, header, application).

Week 8:

Transmission Control Protocol (main characteristics, segment format, call structure, use of sequence numbers and acknowledgment numbers, cases of retransmission, fast retransmit). Traffic control, congestion control, AIMD, Slow Start, some common applications and the transport protocols used, practical examples of calculation.

Week 9:

Network applications.

Services of the infrastructure: DNS (role and requirements of name resolution, name space, zone and name servers, name resolution process, DNS messages), Dynamic Host Configuration Protocol.

Mail systems: Simple Mail Transfer Protocol, Post Office Protocol, Internet Message Access Protocol.

Web systems: HyperText Transfer Protocol, persistent and non-persistent connection, message formats, commands, headers.

Week 10:

Wireless and mobile networks. Mobile phone systems. Overview, the cellular principle. Characteristics and operation of mobile phone systems. Media access, network architecture, services, identifiers, location registration, call forwarding.

Generations of mobile phone networks.

Week 11:

4G mobile networks: LTE: Long Term Evolution: requirements, media access, resource blocks. Cell capacity. LTE architecture, main protocols. Voice transmission over LTE. VoLTE. VoWiFi.

5G mobile networks. Requirements. 5G architecture, access and backbone networks. CUPS (Control and User Plane Separation).

Week 12:

Analog and digital voice transmission. Characteristics of the speech signal. Digitization of the speech signal: the PCM encoder. Examples of application: voice transmission via telephone, hi-fi-quality digital audio coding. Outlook: other speech encoders. Overview of Next Generation Networks (NGN).

Week 13:

Voice over IP, VoIP. Best effort forwarding and IP Quality of Service (QoS). Real-time Transport Protocol (RTP): structure, operation and limitations. Overview of Session Initiation Protocol (SIP).

Week 14:

Multimedia networks. Characteristics of motion pictures. Types of multimedia network applications. Streaming over UDP and HTTP. Content distribution networks. IP television (IPTV). IPTV and Internet TV: similarities and differences. IPTV: structure of the head station, details of the media stream. MPEG-2 Transport Stream. Structure of an H.264-encoded data stream. IPTV Quality of Service: measurement, important influencing factors, opportunities of quality improvement.

Detailed topics of the labs:

Lab 1: Analysis of the TCP/IP protocol stack, presence lab.

Getting to know Wireshark (the program itself, capture filter, display filter; Ethernet, IP, ICMP, TCP, UDP headers at an overview level). Getting to know ARP: Request, Reply, Probe and Announcement. Getting to know DHCP: returning an address (Release, Ack), the process of requesting an address (Discover, Offer, Request, Ack). Getting to know ping and traceroute. Establishing and terminating a TCP connection. Counting TCP connections when downloading a complex webpage. Analyzing TCP congestion control. Analyzing TCP options.

Lab 2: Examining application, presence lab.

DNS: Analysis of "A", "PTR" and "AAAA" record request and response. SMTP: sending mails "by hand" using the commands of the SMTP protocol, distinguishing the envelope sender/recipient and the header fields of the mail. POP3: mailbox management (USER, PASS, STAT, LIST, RETR, DELE, RSET, QUIT commands). FTP: data transfer with a client application, and in the meantime:

a) analysis of active and passive modes with Wireshark: from where to where is the data connection established?

b) analysis of BIN and ASCII transmission modes, what happens with a text file, what happens with a jpg file?

Analysis of data transfer in FTP PASV mode using telnet.

HTTP: GET command versions 1.0 and 1.1 (Host: specification, virtual webservers). Analysis of ssh and scp: key generation, login with key-based authentication, file copying with scp.

Lab 3: Analysis of IPv6 operation and IPv6 transition technologies, presence lab.

Analysis of the stateless address autoconfiguration (SLAAC) process (studying neighbor solicitation, router solicitation, router advertisement messages, checking the correctness of link-local and global unicast addresses, modified EUI-64 calculation). DNS64: setting a common DNS64 server as a name server, then name resolution: analysis of an IPv4-embedded IPv6 address. Configuring and using a DNS64 server under Linux (checking what passes before and after the DNS64 server). Accessing IPv4-only servers via a common NAT64 gateway: first with HTTP, then with FTP, in passive and in mode. Testing additional applications (SMTP, POP3). What IPv4 routers (with IPv4-embedded IPv6 address) look like in the output of traceroute. Using a NAT64 gateway on local Linux (TAYGA + IPTABLES preconfigured) and using Wireshark to check what passes before and after the NAT64 gateway.

Lab 4: Voice over IP (VoIP), remote lab.

During the lab session, the student learns about Voice over IP. The student gains experience in the following topics: IP-based desktop and software phones, telephone services, computer virtualization and network packet analysis. Each student can also try out his/her own virtualized IP telephone center.

Lab 5: IP television (IPTV), remote lab.

The purpose of the lab session is for the students to familiarize themselves with the network context of the Internet Protocol Television (IPTV) technology, with special emphasis on multicast-based IP packet transmission and on the network aspects of Quality of Service guarantees. The students learn about multicast IP transmission, the methods and protocols used to transmit IPTV video streams, and perform measurements to determine the main network parameters of the service and the Quality of Service.

Lab 6: Local networks: Ethernet and WiFi, remote lab.

The purpose of the lab session is for the students to familiarize themselves with the basic operating characteristics of Ethernet (IEEE 802.3) wired and WiFi (IEEE 802.11) wireless local networks in practice through traffic. After studying the Ethernet protocol with a protocol analyzer, the students have the opportunity to configure dedicated WiFi base stations, to monitor the effect of settings and parameters on operation, while also using their own devices (e.g., mobile phone) to check connection characteristics and transmission quality.