The Technology Behind Distance Working

1. The Technology Behind Distance Working

2. Overview • The modern enterprise may well have: • A data centre with multiple branch offices • Mobile workers either working from home or ‘on the road’ working at customer sites

3. Overview - 2 • Increasing dependence on IP networks causes problems in three key areas: • User access to data centre resources (application, storage, etc) • Backup strategy (if multiple remote servers exist) • Communication (audio and visual) • We will look at each of these in turn

4. Remote User Access

5. Limited Bandwidth • The problems here are obvious: • Much slower file access • Remote offices may well now access the company phone network using VoIP • User experience will be different from those at the HQ • But not the whole picture!

6. High Latency • Often overlooked • TCP requires packet acknowledgements – high latency means time is wasted waiting for acknowledgements • Layer 7 protocols (e.g. CIFS) are even more chatty! Many round trips across the WAN results in even more time being wasted • Adding more bandwidth will not solve this problem

7. The Problem with Latency WAN

8. This is even worse for Satellite Networks Diameter of the Earth = 13,000 Km (approx) Speed of light, C = 300,000 Km/s Average round trip (very approx) = 150,000 Km Equates to ~500ms (0.5s) of latency!

9. Possible Solutions Storage Tape Backup Tape Backup Filers WAN Branch Office Data Center File Servers Mail Servers Filers Mail Servers Web Servers File Servers • Local servers • Places applications and storage where the users are • BUT: • Expensive • Creates pools of storage – issues for backup and management

10. Possible Solutions - 2 100 Mbps • Install a high bandwidth link • An obvious, simple solution • BUT: • Expensive • Doesn’t solve latency issues

11. Possible solutions - 3 • Install a WAN Acceleration device – e.g. Riverbed • Riverbed tackles the problem in three key areas: • Bandwidth • Latency issues associated with TCP • Latency issues associated with layer 7 protocols

12. How does Riverbed accelerate the bandwidth? Reconstructed Files & Data Data Files & Data WAN Data Center Branch Office References New data

13. How does Riverbed deal with TCP latency? Data Make TCP payload bigger 16KB to 100KB+ Repack payload with references References From 100KB+ to Virtual 1MB+ New data • Window Scaling (RFC 1323) • Virtual Window Expansion • High-Speed and Maximum TCP

14. How does Riverbed deal with latency issues at layer 7? Optimized WAN Transfer WAN BRANCH OFFICE DATA CENTER Steelhead completes transaction locally Steelhead completes transaction locally • The Steelheads understand certain application layer protocols and are able to perform certain transactions ahead of time, saving unnecessary WAN round trips – Transaction Prediction

15. But what about users on the move? WAN Steelhead Mobile Controller Engineers at home Planners on-site Data Center Mobile Executives Branch Offices Small Offices • Riverbed Steelhead Mobile enables Mobile Client software to be installed which effectively creates a Virtual Steelhead which travels with the user

16. Possible Solutions - 4 FTP (40%) Total bandwidth (100%) Web (30%) VoIP (30%) • Implement Quality of Service (QoS) • Can prioritise key traffic and clients/servers to guarantee bandwidth and/or delay • Does not give any extra bandwidth but is used to ensure that bandwidth or delay sensitive traffic (e.g. VoIP) is not suppressed by other traffic • Riverbed Steelheads can mark traffic for other QoS devices or can implement QoS enforcement directly

17. Backup Strategy • For a consolidated environment not an issue • Data will be backed up centrally • If you have local servers then these will need backing up • How will this fit into any existing backup strategy? • Where and how will be data be backed up? • How will backup media be managed?

18. Televaulting Data Centre Vault Branch office 2 Branch office 1 • A scenario where data from remote sites are backed up over the WAN to a central server – the vault • Simplifies backup strategy by removing the need for removable media at remote sites

19. Example - Asigra DS-User Windows DS-Client Web Portal DS-Operator WAN DS-System BLM Archiver Linux DS-Client • Incremental forever backups • WAN data is compressed and encrypted • Common File Elimination Local servers

20. Audio / Visual Communication • Remote office communications are no longer just about data • The use of networks has changed due to media with a resulting adaptation of the underlying technology • Historically, media has been transferred using a ‘Store and Forward’ approach • There is now an ever increasing use and demand for media to be transported in Real-Time

21. Voice over IP (VoIP) • Increasingly, companies are starting to replace their analogue phone systems with VoIP technology • Why? • Cost - Voice conversations require a relatively low bandwidth, comfortably carried on existing data networks • Flexibility – VoIP systems enable easy relocation of handsets should employees move or change location • Management Services – Can use control tools providing facilities such as security, forwarding, conferencing and storing data, often over a web-browser • Reporting – Can easily obtain and generate usage reports

22. How do you transfer audio packets over a network? • Analogue sound, e.g. human speech needs converting into a digital signal and then coding into a format suitable for transport across a network • This process will need reversing at the far end • This process is the same for both audio and video

23. Analogue to Digital Conversion Codewords (G.729 etc.) or ADPCM Sending Codec 8-bit samples V t fc fs>2fc Sample & hold LPF A/D compression Data network 8-bit samples (no jitter) 8-bit samples (jitter) V t Decoder De-jitter buffer D/A Receiving Codec LPF = Low Pass Filter Fc = cutoff frequency Fs = sampling frequency A/D = Analogue to Digital Converter D/A = Digital to Analogue Converter

24. But what about session setup? • In legacy, analogue telephone networks a dedicated session or circuit was established - circuit switching • IP is a packet switched protocol, therefore there needs to be a mechanism to setup and configure a session between users having a phone conversation. • Two alternate protocols exist to accomplish this: • H.323 • SIP

25. H.323 - Overview • ITU-T standard • Key goals • Discovery and registration • Admission • Call set-up (H.225 -> Q.931) • Capability (H.245) • Availability • Location / addressing • Call Control • Services

26. H.323 Architectural Overview H.323 zone Terminal Gateway Terminal Terminal Gatekeeper Terminal Terminal Terminal Router MCU Terminal Terminal Router Router Terminal MCU Source: ITU H.323 Recommendation

27. SIP Overview • SIP stands for Session Initiation Protocol • Based on HTTP/1.1 • More lightweight than H.323 • Supports personal mobility • Handles • User location • User capability • User availability • Call setup • Call handling

28. SIP Architecture Location Server Registrar DNS UAC UAS Redirect Gateway Proxy

29. Example System - Videoconferencing ISDN Gatekeeper Internet MCU Gateway / Networker Call Manager LifeSize Codec Paris Toronto Leeds Berlin