Trends in Networks

Trends in Networks Varaiya - Walrand UC Berkeley 4/1998 • Networking Principles • LANs: Gigabit Ethernet vs. ATM • WAN: SONET/SDH • QoS: Policy-Based Routing • Middleware: Caching, Pricing, Load Balancing • Multicasting: MBONE, Reliable • Applications: Voice over IP • Technology: ADSL, WDM, Switches • Active Networks • Security

Networking Principles • Driving Forces: Digital, Packets, Economies of Scale & Integration • Internetworking: How do we connect different networks? • Scalability: Hierarchical naming and addressing • Error, Flow, and Congestion Control • End-to-end Principle: Religion or Science?

Driving Forces Packets Economies Utility Cost Penetration Critical Networking Principles Digital Text Picture Video Audio Touch Smell Transmission 01001 Processing (Editing, Compression, Encryption) Storage Retrieval Statistical Multiplexing Error Control Rate adaptation Differentiated Service

Internetworking B|A| P b | w | B A R a b v w v | a | Networking Principles B|A| P B|A| P Decoupling of protocols, packet formats, timing Requires global addressing scheme + routing tables Fragmentation may be needed

Scalability N’ 1 N 2 1 N’ 1 N 2 N” 2 N’ 3 N 1 N” 2 N.S’ 3 1 3 2 2 N.S N.S.H’ N’ 3 N” 3 N.S’ 1 N.S 2 N.S.H N” Networking Principles Addressing: Subnetting

Scalability Root IP = R edu: NS = E com: NS = C Local NS edu? Ibm.com: IP = I .... X E berkeley.edu: NS = A stanford.edu: NS = A’ berkeley.edu? edu IP = E A eecs.berkeley.edu? eecs: NS = B cs: NS = B’ berkeley.edu IP = A B V X V Diva: IP = V Eclair: IP = V’ eecs.berkeley.edu IP = B Networking Principles Naming: Domain Name System X: diva.eecs.berkeley.edu?

Control: Errors Objective: Retransmit lost packets A B Lost or corrupted Networking Principles B|A| # 27 | data | crc B|A| # 27 | data | crc Timeout A|B| # 27 | ack | crc B|A| # 28 | data | crc

Control: Errors Objective: Retransmit lost packets more efficiently A B 1 2 3 4 5 4 Timeout Networking Principles Window size = Max. # of outstanding packets

Control: Flow Objective: Don’t overwhelm the receiver A B W W W’ W’ Networking Principles W = receiver-advertised window

Control: Congestion Objective: Efficient and Fair Share of Resources Max Min 20 30 10 10 Networking Principles 20 Algorithm: If ACKs are delayed, reduce window size; Else, increase. Note: Current algorithms are not very good. Could be improved with router measurements.

Networking Principles End-to-End Principle: Religion or Science? Principle: Don’t ask the network to do what hosts can do “Keep the network as simple as possible” Motivation: Scalability: As more hosts are added, they can do more Upgradability: If most functions are in hosts, can upgrade Flexibility: Different hosts need different functions Examples: Datagram Transmission in IP (no connection state in routers) Error/Flow/Congestion Control in TCP Compression, Encryption Soft-States (need to be refreshed) for multicast groups, RSVP

Networking Principles End-to-End Principle: Religion or Science? Limitations of End-to-End Principle: Reservation of resources for QoS? Billing? Effective congestion control? Persistent connections for slow links? Active networks may be a compromise?

VCI MAC addresses a 1 a | d | 5+48 bytes 640-1.5 kB b 1 b | d | c a | d | 1 d 2 b | d | PVC or SVC S&F or cut-through ATM Gigabit Ethernet LANs: Gigabit Ethernet vs. ATM

MAC LANE AAL ATM A V IP LANE AAL ATM C S Z LANE Server LANE B W AAL ATM D LANs: Gigabit Ethernet vs. ATM LAN Emulation A -> B: A -> V: P = [b|a|…] V -> S: b = ? S -> V: b on W V -> W: P / AAL5 W -> B: P Applications/IP do not take direct advantage of QoS of ATM

Gigabit Ethernet ATM Compatibility Yes With LANE Setup Easy Define VCs QoS Coming Yes Cost Small Medium MAN Gigabit Mesh Router or ATM WAN Router (DS or OS) Router or ATM Predicted for many backbones some LAN backbones (between 10/100 LAN switches) LANs: Gigabit Ethernet vs. ATM

payload R SONET “PATH ” R’ (Sync. to master clock) Note: R’ may not be synchronized! control header a b a b a b a b a cbc bc bcbc ADM c c c a a a Byte interleaving (synchronized) Add-Drop Multiplexer WANs: SONET / SDH OC-3 = 155 Mbps, OC-12 = 622 Mbps, OC-48 = 2.4 Gbps OC-96 = 4.8 Gbps, OC-192 = 9.6 Gbps

IP packet PAD + CRC ATM cells AAL5 Last SONET PATH IP/ATM/SONET WANs: SONET / SDH ATM located in Path by using HEC of cells (no additional framing bits required)

SONET Paths SONET ring Case for IP / PHY WANs: SONET / SDH • TDM not ideal • Synchronization not needed if SM used instead of TDM Proposal: Straight IP / PHY

Switch Premium HP w = 6 R bps Regular LP w = 4 QoS: Policy-Based Switching Scheduling guarantees a fraction of bandwidth to user small delays for premium service Note: Should prevent excessive load (RSVP?)

Caching of web pages • Billing for usage of link • Load balancing across servers ISP Intranet Middleware: Caching, Pricing, Load Balancing Where (in router or a special server?) Static or dynamic? Standards? • Pricing examples: • time/parameters • measured resource utilization • congestion pricing • auction pricing

Multicasting Replication by routers to link toward at least one multicast “group member”

Previous multicast router replicates packets Non-Multicast Router MBONE: Multicast using also non-multicast routers. Multicasting [Tunneling between multicast routers and hosts]

NACK implosion => NACK merging Possibly: Caching in “Designated Receivers” NACKs Errors How to make multicast reliable? Multicasting Note: Multiscale?

D R Voice Samples Size R (kbps) IP Header (20 bytes) D (ms) Voice over IP Tradeoff between delay D and total rate R

Voice over IP Inside company: Single network Integration of services: voice mail, forwarding, call back, listen to email, read voice mail, translation, voice commands, encryption, integration with video, ... -> New products: PBX-IP, Phone-Ethernet In Central Office: Switch-IP, Routing, Billing

384 kbps 1.5 Mbps (example) Questions: Pricing of services? ADSL Technology Voice + IP Access Competition with cable modems

A A B B C C WDM Technology • Laser spectra should be disjoint and • fit in low-loss window around 1.5 mm • Multiplies capacity of existing fiber

IP Switching D = net.host of destination Must search in table => Limits throughput D net output port Routing Table TAG Switching T = Tag placed by host or edge router Smaller table (fast) Policy-based tag T D T T’ output port Routing Table Switches Technology

Policy-based Scheduler (Linked lists) Switches Technology Input/Output Buffering Compromise Complexity of Scheduling / Throughput Multicasting possible Easier with fixed-size cells (e.g.., ATM core)

Active Networks General ideas: Network nodes programmable (by user or manager) Node interprets a program that specifies how session packet should be handled Examples: Compression Filtering (firewall) Scheduling Caching Challenges: Protection mechanisms Standards

P = D(C; K) C = E(P; K) P Alice C Bob Eve ? Security Standards for E(.; K) and D(.; K) - Example: DES Distributing K: Public Key (e.g., RSA) Trusted Certificate: Bob trusts Alice (trusted K, identity) Alice certifies: Jim’s Key = ...

Summary • Future networks will probably see a larger role for • Gigabit Ethernet • DSL or cable modem • WDM • Hybrid (in/out buffer) Switches • The following features will be implemented • QoS • Billing • Reliability • Multicasting Voice over IP and other real-time applications may become important. See references and web page for more details.

Trends in Networks