NetForecast ® Quality of Service for IP Telephony and Video John Bartlett NetForecast, Inc....

NetForecast ®

Quality of Service for IP Telephony and Video

John Bartlett

NetForecast, Inc.

[email protected]

Slide 2©2004, NetForecast, all rights reserved.

NetForecast ®Four Major Tasks

Network QoS Implementation

Classification

Bandwidth Management

Testing, Measuring and Monitoring


NetForecast ®Enterprise QoS Implementations

Enterprises use a broad variety of QoS implementations Over Provision

Point to Point

Using meshed service provider

Full network implementation

Overlay network

Lets take a look at each one and see how they compare


NetForecast ®Over Provision

Adding bandwidth allows real-time traffic and data traffic to coexist

Simple solution

Inexpensive in the LAN, expensive in the WAN

Works most of the time …


NetForecast ®Point to Point

Leased line or Frame Relay link has contention due to limited bandwidth

Deploy edge box on both ends (Allot, Packeteer, Sitara, etc)

Simple, manageable, works well


NetForecast ®Meshed Service Provider

Corp

Now have a more complex problem

QoS box on edge can manage traffic flowing towards ISP

Traffic from ISP flowing toward enterprisecan become congested at the boundary with the access link

Now need ISP to provide QoS capabilities as well

Corp

Corp

ServiceProvider


NetForecast ®Full Network Implementation

Whole corporate network has QoS implementation

Requires careful design

Adds significant complexity


NetForecast ®Overlay Network

Overlays are a compromise implementation

Traffic in constrained areas (WAN) are separated

LAN uses over provisioning

Real-Time

Data


NetForecast ®Is QoS Easy to Implement?

Easy Simple point to point setup, supporting interactive or real-time traffic Traffic shaping can manage bursts Primary focus, consistency of performance, support interactive traffic

responsiveness, maintain quality of real-time traffic

More Difficult Full network implementation is complex Managing priority traffic volumes is vital, and complex Set up failure paths, allocating bandwidth during failure Testing, finding micro event problems, isolation

Impossible (or not yet possible) Across the Internet, using multiple carriers Primarily a business issue Need arbitration, common terms, contract negotiations, etc. Whole business model needed to make this work


NetForecast ®Classification

This is the job of deciding which traffic is high priority traffic, and which is not

End point vs. network Multimedia clients/servers can mark their traffic with DiffServ code

point to identify it as high priority Endpoint is the best place to distinguish between real-time and other

traffic, because it is close to the application Network may not want to trust the endpoint to determine priority

– Has a more global point of view– Distrust of end user (gamer? hacker?)– Network has to manage total amount of high priority traffic

Who gets to decide?

Semantic problem Organizational high priority and application requirements should not

be confused


NetForecast ®Bandwidth Management

Priority mechanisms only work if the prioritized traffic is a low percentage of overall traffic


NetForecast ®Bandwidth Management

Priority mechanisms only work if the prioritized traffic is a low percentage of overall traffic


NetForecast ®More Bandwidth Management

The good news is: Voice and video have very predictable bandwidth consumption Voice and video understand the concept of a busy signal, and/or can

be rerouted through the PSTN

The bad news is: Data traffic does not have predictable bandwidth Data applications need significant overhead to perform properly Data traffic must be always connected, no busy signal

ATM – has built-in bandwidth management functionsMPLS – must have bandwidth management system

associated with it IP – has some features in some routers ….


NetForecast ®Yet More Bandwidth Management

Bandwidth management can be done by the voice/video infrastructure

Telecommunications & Video organization vs. IP Network Organization Must have an agreement on bandwidth usage Telecom/Video must stick to their allocation Need a process to negotiate growth

Growth over time is natural Real-time will encroach on data, and vice versa


NetForecast ®The Testing Problem

The TCP/IP Way TCP covers up most low level network problems

TCP/IP UDP/IP

The real-time problemUDP covers up nothing When network problems exist, applications fail rapidly


NetForecast ®Brave New World

Network congestion causes TCP-based applications to gracefully degrade their functionality (e.g. slow down)

Network often self-heals after a short time Long term traffic volume is managed by listening to user

grumbles, or monitoring average link usage. Time constants are long.

UDP-based applications fail in a more binary way (works, doesn’t work)

Real-time applications have an additional disadvantage, user expectations are high: Voice over IP is compared to the toll quality voice we get on the PSTN Videoconferencing is often used by high level execs, hence high visibility

Yikes! We better test this network constantly!


NetForecast ®Testing, Testing, Testing

We have to test the network and monitor the call quality to know what is going on Are we delivering the quality voice/video service we want to? Is the problem with the voice equipment, or the transport? Where and when is the network causing problems?

Must test as close to end-to-end as possible Voice is subject to very local problems (echo, local connection, poor

equipment) as well as network problems

Must isolate problems in the network So this call had poor quality, which part of this complex network caused the

problem?

Must find problems in time domain Micro-outages cause momentary burst packet loss Testing or sniffing after the fact has little value

Monitoring tools, NetIQ, RADCom, Telchemy and more


NetForecast ®Does this stuff really work?

The priority mechanism works well for low volume high priority traffic

What happens when we have higher volumes of high priority traffic?

What happens to the applications that fall to the bottom of the priority stack?


NetForecast ®

Ban

dwid

th

Time

Priority


NetForecast ®

Ban

dwid

th

Time

Priority


NetForecast ®

Ban

dwid

th

Time

Priority


NetForecast ®More Issues!

In a link failure situation, if a back-up link has less BW, what gets dropped?

Convergence: How quickly will the new network routing configuration resolve after failure?

Marking of traffic is more difficult as more end-points come on-line, soft phones, from peering points, etc.

Also, how to distinguish traffic that is in-service or out of service (rogues, illegally marked traffic, etc.)

Why would we willingly put ourselves in this complex situation?


NetForecast ®Conclusions

QoS Mechanisms exist, and work for low volumes of high priority traffic

Simple network configurations are simple to implement

Whole network convergence is still very complex, difficult to implement and more difficult to manage


NetForecast ®Net Forecast

Nature abhors leaving money on the table

New technologies to aid convergence will arise in the next few years

Many folks will separate real-time and data traffic in the low-bandwidth high cost areas (WAN) until new technologies simplify the problem considerably

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