COMP3122 Network Management

1. COMP3122 Network Management Richard Henson February 2011

2. Week 1: Technical Issues, People Issues • Learning Objectives: • Explain the relative merits and problems involved in linking computers together • Analyse the knowledge and skills needed to manage the technology of a network • Analyse the range of protocols developed to manage users and resources so they can get what need from the network

3. This is NOT just another technical networks module… • Question for you • in groups of 3-4… • What does it take to be a good network manager?

4. Some of the Qualities needed • knowledge of network technologies • understanding of institutional ICT strategy/policy • patience and liking people • ability to explain consequences of actions (or inactions…) in non-technical terms to non-technical people (like senior managers)

5. “Network Manager” is a fulfilling job • Easy to say… • Whether this is true depends on many things that are not necessarily to do with technology • Factors? Over to you again…

6. Some Factors that affect the demands on a Network Manager • the size of the organisation • The number of sites within the organisation • how much an organisation values its data • how much an organisations values its employees • The structure of the organisation

7. How much do network managers get paid? • Estimates?

8. “Network Manager” is often a well-paid job… • Average salary (last 3 months): • £47000 approx • High salary (large network) • typically £65000 • Min salary (small network) • typically £20000 • Vacancies & salaries … currently increasing • Ref: • http://www.itjobswatch.co.uk/default.aspx?page=1&sortby=0&orderby=0&q=network+manager&id=0&lid=2618

9. More Questions, 1… • “Why link an organisation’s computers or other digital devices together anyway?

10. Question 2… • “What are the challenges of linking multiple devices together?

11. Question 3… • “What background knowledge and skills does anyone even thinking about administering, maintaining and provisioning a network need to have?”

12. Technical aspects of Network Management (1) • Making sure computers can “talk” to one another very, very quickly and accurately: • knowledge and configuration of communications protocols • management of IP addressing • management of other naming systems

13. Technical aspects of Network Management (2) • management of hardware devices and media connecting them • management of network services • management of login/transfer of data/access to services as appropriate across different networks • anticipating/troubleshooting network problems including backup/recovery

14. Communications Protocols • A Protocol is a set of rules/procedures • Computer protocol: • rules programmed into software, carried out by a CPU • Communications protocol • therefore software that allows “intelligent” hardware devices to use digital data to communicate rapidly & accurately • Intelligent? The device must have… • CPU • storage capability

15. Types of Communications Protocol • Many, many protocols have been developed! • rules/procedures depend on the network… • number of devices • issues involved in controlling the devices and data • degree of control required • speed of response required • many other factors…

16. Specification of a Protocol • Written as “psuedo code” • Can then be translated into an implementation in a variety of languages • Most network protocols written in “C” then compiled • code executes very fast…

17. Familiarity with LAN hardware is ESSENTIAL… • Repeaters • control up to OSI level 1 (i.e. no software)) • Bridges • control up to OSI level 2 • Routers & Switches • control up to level 3 • Gateways • control at least up to level 4 • could be right up to level 7

18. Hubs and Control • A variety of hubs available. All need a power supply: • simplest (unmanaged or passive) just cleans up and splits the signal • managed hub or “switch” can either read: • frames & MAC addresses (level 2) - bridging • packets and IP addresses (level 3) - routing • either can manage traffic to optimise use of network media • some switches can read even higher up the protocol stack • e.g. transport layer ports (level 4) • loading based on TCP data

19. Software Development for Network Protocols • Must include: • a naming/addressing system including all network devices • communication of addresses of sending and receiving computers • a method of error checking and confirming complete delivery • resolution of other network-related issues… • Examples of protocol stacks (OSI): • TCP/IP (LAN or WAN) • IPX/SPX (LAN only)

20. IETF • The International organisation responsible for assessing and agreeing network management protocols • established in 1984 • after OSI model became an International Standard • IETF and system of “peer review” of new protocols evolved from the small group of computer scientists that developed the Internet (1969) • draft protocol circulated • if assessment panel of peer agrees, the draft becomes an RFC • 5759 RFCs have been issued to date…

21. Example of an early Communications Protocol • FTP: Original Spec offered by (Bhushan, 1971) • documented in RFC 114 • http://community.roxen.com/developers/idocs/rfc/rfc114.html • comments on spec in RFC 141 • became part of the Internet infrastructure via RFC 238 • final improved version RFC 959 (in 1985)

22. The OSI seven layer software model • Agreed in the late 1970s • based loosely on TCP/IP & IBM protocol models • Took until the late 1990s for most network software developers accepted it as a standard • Layers together make up a protocol stack • below layer 1, communications sent/received as digital signals • above level 7, visual communications reach the human eye

23. Application Layer Presentation Layer Session layer Transport Layer Network Layer Data link Layer Physical Layer The OSI Layers Screen display e.g. TCP e.g. IP Network medium

24. Practical Exercise • Use the IETF website to locate RFCs covering the following level 7 communication protocols. Make a note of the level 4 TCP or UDP port in each case: • SMTP (Simple Message Transfer Protocol) • DNS (Domain Name System protocol) • HTTP (hypertext transfer protocol) • HTTP-s (secure http) • POP3 (multiple message download to client)

25. IETF Network Management software model • Based on IETF Network Management Components, defined as: • Network elements • Agents • Managed object Management Information Base (MIB) • Syntax notation • Structure of Management Information (SMI) • Network management stations (NMSs) • Management protocol • “Parties”

26. Network Elements • Hardware devices such as computers, routers, and terminal servers that are connected to networks • Sometimes called “managed devices”

27. Agents • Software modules • reside in network elements • Collect and store management information e.g. • number of error packets received by a network element

28. Managed Objects • Anything that can be managed… • e.g.: • list of currently active TCP circuits in a particular host computer • differ from variables (particular object instances) • e.g. a single active TCP circuit in a particular host computer • Can be scalar • defining a single object instance • or tabular • defining multiple, related instances

29. Management information Base (MIB) module • A Collection of related managed objects residing in a virtual information store

30. Syntax notation (MIB managed objects) • Language used to describe these objects in a machine-independent format • Allows different types of computers to share information • Internet management systems use ASN.1 • a subset of the International Organization for Standardization's (ISO's) Open System Interconnection (OSI) Abstract Syntax Notation • to define • packets exchanged by the management protocol • objects that are to be managed

31. SMI (Structured Management Information) • Defines the rules for describing management information • SMI itself defined using ASN.1

32. Network management stations (NMSs) • Physically, NMSs are usually engineering workstation-calibre computers • fast CPUs • mega pixel colour displays • substantial memory • abundant disk space • Also called consoles… • Execute management applications that monitor and control network elements • At least one NMS must be present in each managed environment

33. Management Protocol • SNMP - the Internet community's de facto standard management protocol • Used to convey management information between agents and NMSs • Originally developed as a series of RFCs • architectural Model for SNMP • RFC 1065: Rose & McCloghrie, 1988 • MIB for SNMP • RFC 1066: Rose & McCloghrie, 1988 • The SNMP protocol • RFC 1067: Case et al, 1988 • Rationalised in RFC 1157, agreed 1990

34. Further Development of SNMP • Evolved into SNMP v2 (RFC 1901, agreed 1996) • two new operations • GetBulk - used to efficiently retrieve large blocks of data • Inform - allows one NMS to send trap information to another NMS and to then receive a response • Later, SNMP v3 (RFC 2570, agreed 1999) • adds security and remote configuration capabilities

35. “Parties” (SNMP v2) • Defined in SNMPv2 as logical SNMPv2 entities that can initiate or receive SNMPv2 communication. Components: • a single, unique party identity • a logical network location • a single authentication protocol • a single privacy protocol • SNMPv2 messages communicated between two parties • SNMPv2 entity can define multiple parties, each with different parameters • e.g. different parties can use different authentication and/or privacy protocols

36. Controlling Flow of Data sink source • Data flow management built into protocol • Two main types: SYNCHRONOUS or ASYNCHRONOUS • Synchronous: • sent as a continuous flow • uses time signals to control flow • Asynchronous: • sent as packets • next packet not sent until acknowledgement from receiver

37. Data Routing Technologies • Connection-Oriented (e.g. TCP use for confirming receipt of a packet): • source, destination, and network topology all stored in a database • single connection channel calculated from available data using a routing algorithm • all data sent along that channel • Connectionless (e.g. IP): • data sent in discrete units called packets • each packet finds its own way through the network with the aid of routers

38. Connection-Oriented • All data follows the same route

39. Connectionless • Each packet follows its own route

40. Many other Technical Issues resolved and became RFCs… • Network Managers today don’t need to worry about developing their own protocols • so many have been developed… • They do need to know what is out there, and what it does… • RFC’s provide an exhaustive list of any “open source” protocols proposed for Internet use since 1969 • RFCs therefore hugely influential… in most cases implementations available for popular operating systems

41. Less Technical Aspects of Network Management • Less technical because management is done at the desktop using “wizards”: • Fault Tolerance • User Management • Control of user access to files & services • Server Management • LAN management • Multiple-site management • Virtual Desktop Management

42. Fault Tolerance • ALL network hardware and software should have a backup!! • In case things go wrong...

43. User Management • More associated with “administration” • can also be technical • Involves: • putting new users on the system • allocating users to groups • Making sure groups have appropriate network rights and privileges

44. User Access Control • At least 2 level access e.g. username/password • Usernames & passwords stored in an authentication database • sensible use of passwords (fixed rules) • Username linked to level of privilege • System must use a file system that includes file/folder level access control

45. File Security • No file security at all by default with DOS & Windows, until Vista arrived… • General principle not to allow users access to files/folders they should not need to use • Number of types of access: • e.g. read, execute, write, change, full control • Files can also be remotely accessed through shares or a network directory

46. Server(s) Management • Active Directory on a Windows network • Controlling user login • Controlling network assets • Controlling access to server resources • Managing primary storage • memory…. (largely automatic) • Secondary storage • especially hard disk

47. LAN Management • Active Directory (Windows) manages a domain • includes servers, clients, users, and connections between all of these • includes a range of other network services : • printing • applications • web access • file access • A Client uses services PROVIDED the current user is given authority by active directory

48. Client-Server Networks on Multiple Sites • Multiple domains • Trust relationships between domains • Inter-domain link: • via telecoms line (expensive) • via Internet (v. cheap!) • also needs a router • if domains use different protocols, and/or NOSs, gateway needed

49. Operating Systems serving Virtual Desktops • A case of “back to the future” • Before the PC (“fat client”), network users didn’t have local processing • everything was centralised on the server(s) • The current trend is for “thin clients” where a whole desktop environment provided by the server fits into an actual desktop • Increased centralisation again on the server • Why? Suggestions? In groups….

50. Issues in client-server networking • Which NOS? • Which protocol? • How server security? • Which Internet connectivity method/partner? • Communications within client-server applications • Thick or thin clients? • Network naming system? etc…