Networking For the Future

By

Dr. Junaid Ahmed Zubairi

Sigma Xi Brown Bag SeminarOct 3rd, 2003 at 12 Noon

Overview of Presentation The Evolution of Internet The Types of Traffic on the Internet Performance Issues in Packet Switching The World Wide Web Changing Traffic on the Internet The Birth of ATM!! ATM’s Service Classes and Layers Intserv, Diffserv, MPLS, TE GMPLS Future Network

Fig 1: The Evolution of Internet: Past and PresFu

Seminar References

Computer Networking: A Top Down Approach Featuring the Internet by Kurose and Ross, Addison Wesley 2001

ATM With X-Cell, XYLAN Course 701, XYLAN Inc.

Computer Networks: A Systems Approach Peterson and Davie, Morgan Kaufmann 2000

Computer Networks Andrew Tanenbaum Prentice Hall 1996

The Evolution of Internet

DARPA (Defense Advanced Projects Research Agency) funded the development of the Internet.

The first working network was ARPAnet that was started in 1969 between four nodes

The emphasis was on developing a robust network that would continue to function even if some of its parts were bombed out

The Evolution of Internet

email, usenet, file transfer and remote login were the main

Internet applications

Types of Traffic on the Internet

These applications generated almost identical traffic stream on the Internet

This traffic required “reliability”. The protocols were expected to

deliver all the data no matter how long it took

Performance Issues in Packet Switching The TCP/IP suite of protocols breaks the

data into datagrams or packets and routes each packet through an independently selected path

Packets may arrive at the destination out of sequence but due to buffering and re-ordering, the actual data can be recovered easily

Message Text

Dear John I agree with your suggestions. I think we

may want to include Mike in the discussion. I am forwarding this message to him as well. He is an expert in this area and we should wait for his comments before proceeding forward on this project.

Junaid

Message Broken Down

Dear John

I agree with your suggestions. I think we may want to include Mike in the discussion. I am forwarding this message to him as

well. He is an expert in this area and we should wait for his comments before proceeding forward on this project.

Junaid

Packet # 1

Packet # 2

Fig 2: Packets may follow longer paths and arrive

later than expected

Pkt#1

Pkt#2

Fig 2: Packets may follow longer paths and arrive

later than expected

Pkt#1

Pkt#2

Fig 2: Packets may follow longer paths and arrive

later than expected

Pkt#1

Pkt#2

Performance Issues in Packet Switching

Selecting a path is called routing and the intermediate nodes from source to destination are called routers

Each router builds up a routing table to keep track of reachable destinations

If more than one path is open to destination, the router may select the “best” path

Performance Issues in Packet Switching Path selection criterion is usually shortest

path first If the shortest path is congested or

unreliable, the router can choose another path

The traffic is bursty and it can increase or decrease abruptly based on the way the Internet is used

Performance Issues in Packet Switching Given this scenario, a router may find itself

overwhelmed with a lot more packets than it can handle

Usually routers would use simple FIFO scheme to select the next packet to be transmitted from a queue of packets

Router Exposed

Performance Issues in Packet Switching If the queue is full, the newly arrived packets must

be dropped (or discarded) Thus increase in traffic may increase time-outs,

retransmissions and decrease in efficiency Usually, congestion in the network results in

delay and loss penalties Congestion builds up due to bursty users, no

active resource allocation and selfish users trying to monopolize the bandwidth

Performance Issues in Packet Switching Traditional TCP/IP based Internet can be

described as– “Best Effort”– “One Size Fits All”– “Hardly Any Service”– “World Wide Wait”

The World Wide Web

Web deployment is flexible and easy Due to the web technologies, the Internet has

been put to use in almost all areas of human knowledge

For example, water distribution monitoring, real-time traffic maps of big cities, free long distance calling, distance learning with lecture videos, buying and selling shares, online shopping etc., the list appears endless

The Changing Traffic on the Internet Due to the web enabled applications on the

Internet, there has been a tremendous change in the types of traffic

Now we have to deal with a significant amount of traffic that is time-sensitive

For example, consider the case of an audio based application that needs to transmit the data across the Internet

The Changing Traffic on the Internet

The Changing Traffic on the Internet

The Birth of ATM!!

As the users started to use the web for time-sensitive applications, they did not get what they wanted--- a consistent acceptable performance

On some occasions, the network would give the best performance and on other occasions, it would be horrible in terms of delays and lost packets

The Birth of ATM!!

In this scenario, ATM offered a great promise to the users

ATM standards started taking shape in mid-1980’s as telcos pushed for integrating voice, video and data networks

ATM was developed with the right targets and in mid-1990’s, it offered the much awaited performance assurance

What is ATM?

ATM:

Is a cell-switching and multiplexing

technology that combines the benefits

of Circuit Switching (consistent

transmission delay and guaranteed

bandwidth) with those of Packet

Switching (flexibility and efficiency for

intermittent traffic).

Why is ATM needed?

Need to mix data, voice, and video traffic. We cannot just throw more bandwidth at the

problem

Switch

Why is ATM needed?

All data packets are fragmented into fixed size cells Segmentation & re-assembly only occurs at end stations Time critical traffic on segment “A” only has to wait for the

current cell of “B”s data packet to be sent before it can get the wire and be transmitted

The ability to interleave cells from different messages is instrumental to the operation of ATMs QoS.

“A”

“B”

“C”Switch

ATM Cell

Small Cells - 53 bytes long– 5 byte header

– 48 byte payload

Fixed Length = Fast Switching Fixed Length = Contracts can be established and QoS

maintained

Header Payload

5 bytes 48 bytes

AAL TypesAAL Types

AAL1 is for circuit emulation

– Class A - constant bit rate and time sensitive trafficAAL5 is for compressed video and data (used in IP over ATM)

– Class B - variable bit rate and time sensitive traffic

– Class C - variable bit rate (e.g., Frame Relay)

– Class D - variable bit rate, connectionless

ATM Adaptation layer

ATM layer

Physical layer

User Traffic: Voice, video and data

Service Categories

Categories are based on type of traffic and type of service– CBR Constant Bit Rate -Voice

– rt-VBR Real-Time Variable Bit Rate -Video

– nrt-VBR Non-Real Time Variable Bit Rate -Frame Relay

– ABR Available Bit Rate -Data

– UBR Unspecified Bit Rate -Data

Traffic ManagementTraffic Management

Traffic Management

Two opposing views– Enforce several rules in order to regulate the

traffic and adapt to the available bandwidth– Add more bandwidth

For example, highways enforce HOV rule, speed limits, traffic light controlled ramps to enter the highway etc. OR autobahns with no such rules

CACCAC

Can I support this reliably without

jeopardizing other contracts

ATM Network

No oror Yes,Agree to a

Traffic Contract

Guaranteed QoS request

• If CAC passes, network and user agree on a traffic contracttraffic contract

I want to send traffic of this

type, and want this QoS

VPIs and VCIs

Virtual Path Identifier (VPI) Virtual Circuit Identifier (VCI)

OC-3 155 MbpsVPI-10, 50 Mbps

VPI-20, 60 Mbps

Remaining 45 Mbps is in VPI-0

VCI-100VCI-101

VCI-100VCI-101

Traffic Shaping and Policing

In order to meet the QoS contract obligations, ATM network enforces traffic shaping and policing

Shaping involves techniques such as “Leaky Bucket Algorithm” to regulate bursty traffic

Policing means marking CLP (Cell Loss Priority) on the offending cells that violate the maximum rates agreed

Leaky Bucket Algorithm

Why ATM Failed!!

ATM failed because of several factors– ATM is too complex (From packets to cells to SONET

frames, using AAL’s, emulating LAN)

– ATM is expensive

– Ethernet has evolved into much faster 100Mbps and 1000Mbps services

– All popular and established network applications are packet based

ATM is down but not out. It is used in the telco cores

Life after ATM

IETF (Internet Engineering Task Force) is a very large organization with thousands of members

IETF identified the problems with the traditional Internet and engaged in a long and continuing effort to improve the services and management

Quality of Service

New applications need performance and resource assurance

Service differentiation is also needed so that the traffic from different applications is treated in service-appropriate way

Resource assurance and service differentiation means QoS (Quality of Service)

IETF’s Models

Targets:– Internet should be run in a way that there is no

congestion– Applications should be able to reserve or obtain

network resources at a given QoS IETF has been working on developing new

models and protocols for the Internet During the last decade, Intserv and Diffserv

models have been developed

Integrated Services

Intserv stands for “Integrated Services” and requires reservations before transmission

To receive resource reservation, an application describes its requirements

The network determines a path based on the request

Reservations, Reservations, Reservations

Intserv

A reservation protocol is used to install the reservation state along the selected path

The reservation setup protocol in the Intserv model is the RSVP (Resource ReSerVation Protocol)

RSVP’s Services

RSVP offers two types of services CONTROLLED LOAD service means that

the service offered to a flow in an overloaded network is the same as it would get in a lightly loaded network

GUARANTEED SERVICE is when a flow gets hard guarantees on the delay it will suffer

RSVP Problems

RSVP relies on extensive signaling for obtaining flow reservations along a path.It also entails soft state overhead and therefore does not scale well to the Internet

Most of the Internet traffic consists of short-lived web transactions. It will be unwise to go through reservations for such traffic

RSVP may be successfully deployed in a campus network but not on the global network

IETF’s DiffServ Model Intserv’s problems prevented its deployment IETF started developing a new model in 1997 to

provide differing levels of service to different applications without the overhead of signaling and state maintenance

The DiffServ model uses the TOS field in IPv4 header to affix labels on packets belonging to different service levels

DiffServ has the potential to offer QoS on the Internet, at last!!

IETF’s DiffServ Model

Consider a gas station, you can buy regular, super or premium gasoline from the same pump

DiffServ offers various service levels to the customer from the same network with SLA

DiffServ adopts techniques used in ATM for traffic management, in a simplified way

No Reservations Ever!!

VIP

Diffserv Outline

Diffserv works on the basis of dividing the traffic into a small number of forwarding classes

For each FEC, the amount of traffic entering the network is controlled at the edge of the Diffserv network

FEC’s are prioritized, with each one coded into the IP header’s TOS byte. Core routers offer priority treatment based on the coding

Diffserv Edge Router Functions

Per-Hop Behaviors

IETF has defined two DS services that are visible as PHB (per-hop-behavior) of an intermediate router for the marked packet

EF (Expedited Forwarding)– EF is the premium service offered. It can

appear as a virtual leased line for the customer. It offers low loss/latency and assured bandwidth

http://www.ietf.org/rfc/rfc2598.txt

Per-Hop Behaviors

AF (Assured Forwarding)– The AF PHB group provides delivery of IP

packets in four independently forwarded AF classes. Within each AF class, an IP packet can be assigned one of three different levels of drop precedence. A DS node does not reorder IP packets of the same microflow if they belong to the same AF class.

http://www.ietf.org/rfc/rfc2597.txt

Hybrid Approach

MPLS

MPLS was developed to map IP over ATM because the core routers use ATM. MPLS has additional features that are too exciting to ignore

In MPLS, a short fixed length label is encoded into the packet

The intermediate LSR (Label Switched Router) finds the next hop from a table, using the label as an index

MPLS

If the LSR is an ATM switch, label is just the VPI/VCI identifier

If the LSR is an IP router, the label eliminates the destination based routing and reduces the router to a label switch

A label switched path (LSP) must be set up prior to the start of transmission

LSP Hierarchy

LSP’s in an MPLS Network

MPLS & TE

Instead of routing, now the routers do label switching, a much faster job

Network manager can decide LSP’s (label switched paths) based on load distribution and other administrative goals

Directing traffic on paths not determined by traditional IGP’s provides flexibility and load balancing. It is known as TE (Traffic Engineering)

MPLS AND TE

MPLS runs constrained routing to determine an LSP within an MPLS domain.

LSP may have some QoS features, based on the algorithm used

The path could be strictly specified or loosely outlined and backup paths may be specified for handling link failures

Automated Provisioning

The networks are growing bigger!! The protocols are becoming more complex With Diffserv, MPLS, RSVP-TE, CR-LDP,

COPS and associated protocols, it is impossible to allow manual provisioning

Therefore, there is a need for automated TE-based path selection algorithms

QoS Traffic Considerations

If only the available bandwidth is considered, the class of service may not be taken into consideration

Thus, the best effort traffic may intersect the QoS traffic at several points within the domain

In Diffserv, this may be a recipe for disaster!!

TELIC

An efficient dynamic traffic engineering algorithm is developed for selecting paths across an MPLS-Diffserv domain

TELIC (Traffic Engineering with Link Coloring) works with a set of traffic requests present at an ingress router of such a domain

It allocates paths to an egress node using Dijkstra’s shortest path algorithm

TELIC

Each request specifies the amount of bandwidth requested followed by the Diffserv class of service (EF,AF,DF)

While processing a request, TELIC partitions the network into several monochromatic subgraphs and makes an effort to match the request with an appropriate subgraph

TELIC

In case a subgraph has no path to the egress node, TELIC merges it with another subgraph as per rules carefully built-in and starts the search all over again

In case a search is exhausted, rules are available to deallocate a best effort class LSP and start the search again

TELIC is written as a flexible tool in C++

Router 0

Router 2

Router 8

Router 7Router 1

Router 6

Router 10

Router 9

Router 3

Router 5

Router 4

BL16=20BL11=100

BL13=60

Silver

White

Green

Yellow

Red

All possible pathsP0: 0 1 3 10P1: 0 1 4 7 10P2: 0 1 4 8 10P3: 0 2 9 8 10P4: 0 2 9 10P5: 0 5 4 7 10P6: 0 5 4 8 10P7: 0 5 8 10P8: 0 6 9 8 10P9: 0 6 9 10

Figure 6: An MPLS domain

GMPLS The Internet backbone must use optical switching

instead of electronic switching to handle the projected huge bandwidth

MPLS cannot handle non-packet switching Recently the industry has gravitated towards

GMPLS (Generalized MPLS) as the control plane solution for automatic lightpath setup and teardown in optical networks

GMPLS is an extension of MPLS GMPLS allows control and provisioning of non-

packet devices

Why Optical Networking?

(Courtesy Prof. Raj Jain Ohio State University)

GMPLS Layers (Courtesy Prof. Raj Jain Ohio State University)

GMPLS

Using GMPLS, it is possible to perform switching based on:– Wavelengths– Wavebands– Timeslots– Ports– And Labels

GMPLS

For example, in an all-optical switch, there may be thousands of tiny mirrors that can be moved by miniature motors

Switching can be done by adjusting a mirror so that light entering from one fiber can be reflected (switched) to the desired path forward

LMP A link management protocol has been developed

for GMPLS. It provides link provisioning, fault isolation and link aggregation

Selection of label in MPLS Selection of wavelength and OXC port in GMPLS

MPLS LSP GMPLS lightpath Before GMPLS, control and provisioning of

optical network could take weeks!! Vendors were also reluctant to de-provision due to

any changes

End to End Provisioning

Ubiquitous Networking

The future of networking is being defined today. It is planned as a global network with no breaks or bumps

Users may roam around with notebooks and remain connected wherever they go!!

The realization of this goal calls for a global wireless network, global wired network and an interface between the wired and wireless networks

Mobile Networking

Mobile networking is developed rapidly with IEEE 802.11and Bluetooth standards

Let us take a look at the various configurations possible with IEEE 802.11

Wireless LAN with access point under IEEE 802.11

Ad-hoc network

Issues

Several issues are being investigated for improving Wireless LAN functionality

For example, how to perform transparent handoff ?

How to perform routing in an ad-hoc network?

How to shape and mark the traffic to esnure good QoS?

Bluetooth

Bluetooth is more focused on connecting electronic gadgets like digital cameras, mobile phones, printers, mouse etc. with each other and with the computer

It replaces infrared line-of-sight type of connection

It faces tough competition from UWB (ultra wideband), a similar technology but much faster than Bluetooth

Future Network We envision a global ubiquitous network with

instant access to email and the web from anywhere in the world

With tremendous capacity, the network would offer the desired quality of service to our multimedia applications

Traditional phone network will become a tiny section of the overall Internet

Videophone over the Internet is expected to be the next killer app

Privacy?? Huh