prof. younghee lee 1 1 computer networks u lecture 5: ip addressing-route lookup younghee lee

1Prof. Younghee Lee1

Computer Networks Lecture 5: IP Addressing-route lookup

Younghee Lee


The Internet Protocol Identifier: A sequence number to identify a datagram uniquely. Flag: More bit(indicates the last fragment in original datagram), Don’t Fragment bit(can be

discarded at some subnet->source routing advisable) Fragment offset:: indicate where in the original datagram this fragment belongs Time to live: somewhat similar to a hop count Protocol: the next higher-level protocol


Type of Service

TOS subfield: guidance to the IP entity indicating the type or quality of service – The way in which a router learns which routes support whi

ch TOS» Domain administrator preconfigure the TOS associated with the ro

utes» A routing protocol monitor the TOS along the routes monitoring del

ays, throughputs, and dropped datagrams.(ex: OSPF)

Typically ignored now Replaced by DiffServ


IPv4 Options

Security: – Security label to be attached to a datagram

Source routing– A sequenced list of router addresses that specifies the routes to be followed.

May be strict or loose Route recording

– allocated to record the sequence of routers visited by the datagram Timestamping

– The source IP entity and some intermediate routers add a time stamp (precision to milliseconds)


Naming and Addressing Naming versus addressing

– naming is typically a high-level description– addresses refer to specific physical resources– distinction hard to define but often clear:

» icu.ac.kr» 128.9.23.93» D74A049C2384

Naming/addressing formats– structure: flat versus partitioned (hierarchical)– duration: dynamic versus static– scope: local versus global

Domain Name System (DNS) names are names of hosts DNS binds host names to interfaces Routing binds interface names to paths


Name/Address Structure

Hierarchical address space– address space has structure: sequence of fields

» fields identify autonomous organizations, geographical location, ..

– hierarchical can simplifies routing– easily supports distributed assignment of addresses– can result in inefficient use of the address space– example: IP addresses, postal address, telephone

numbers, .. Flat address space

– address has no structure: single field– easier to use full address space– lacks support for routing– example: IEEE addresses (48 bits)


IP Addressing: introduction

IP address: 32-bit identifier for host, router interface

interface: connection between host, router and physical link– router’s typically have

multiple interfaces– host may have multiple

interfaces– IP addresses

associated with interface, not host, router

223.1.1.1

223.1.1.2

223.1.1.3

223.1.1.4 223.1.2.9

223.1.2.2

223.1.2.1

223.1.3.2223.1.3.1

223.1.3.27

223.1.1.1 = 11011111 00000001 00000001 00000001

223 1 11


IP addresses: how to get one?

Hosts (host portion): hard-coded by system admin in a file DHCP: Dynamic Host Configuration Protocol: dynamically get address: “plu

g-and-play”– host broadcasts “DHCP discover” msg– DHCP server responds with “DHCP offer” msg– host requests IP address: “DHCP request” msg– DHCP server sends address: “DHCP ack” msg

Auto-configuration– IPv6 stateless autoconfiguration– MANET AUTOCONF :

» Standalone» With gateway: can be relatively simple but how to select gateway?» Stand-alone for most of the time but temporarily connected to the infrastructured network

e.g. car network connected while parked and disconnected otherwise» Strong DAD, Prophet, AROD


Hierarchical addressing: route aggregation

“Send me anythingwith addresses beginning 200.23.16.0/20”

200.23.16.0/23

200.23.18.0/23

200.23.30.0/23

Fly-By-Night-ISP

Organization 0

Organization 7Internet

Organization 1

ISPs-R-Us“Send me anythingwith addresses beginning 199.31.0.0/16”

200.23.20.0/23Organization 2

...

...

Hierarchical addressing allows efficient advertisement of routing information:


IP addressing: the last word...

Q: How does an ISP get block of addresses?

A: ICANN: Internet Corporation for Assigned

Names and Numbers– allocates addresses– manages DNS– assigns domain names, resolves disputes


Addressing in IP v4 Addresses are hierarchical.

– address contains hint about location Original design: 4 classes of subnets.: classful Total IP address size: 4 billion

– Class A: 128 networks, 16M hosts– Class B: 16K networks, 64K hosts– Class C: 2M networks, 256 hosts– Class D: for multicast– Class E: 1111, for experiment

127.0.0.1: local host (a.k.a. the loopback address) Host bits all set to 0: network address Host bits all set to 1: broadcast address

typetype networknetwork hosthost

A 0 7 24B 10 14 16C 110 21 8D 1110 28


Subnetting

Hierarchy can be extended to more than two layers.

Makes it possible to break up a network in multiple subnets.– provides flexibility to manage

networks– packet forwarding between

subnets is also done using routers, I.e. same as in Internet

Provides autonomy.– subnets inside network are not

visible outside the network

1 0

Network Host

Network HostSubNet

Subnet 1Subnet 3

Subnet 2


IP Addressing: Issues

Running out of IP address space: short term solutions.– Classless inter-domain routing– Dynamic address assignment– Network address translation

Longer term solution for IP address shortage: IPv6.– Move to longer addresses: IPv6


IP Address Utilization (‘98)

http://www.caida.org/outreach/resources/learn/ipv4space/


Problems with Simple Address Structure Address space is not used very efficiently.

– Address spaces for networks can only be 2**8, 2**16, 2**24 in size» Sizes differ by two orders of magnitude

– Organizations that do not fit in smaller network (e.g. 257 hosts) need to use a size that is significantly larger

Running out of addresses.– Especially true for mid-sized networks– Class B – greatest problem

» Sparsely populated – but people refuse to give it back

– Class C too small for most domains– Very few class A – IANA (Internet Assigned Numbers Authority) very

careful about giving

Routing tables are becoming too big.– 100 of thousands of entries


Ideas Behind Classless Inter-Domain Routing

Use address space more efficiently by relaxing the strict address structure.– length of network address is variable– generalization of subnetting idea– makes network use more efficient

Have Internet service providers hand out blocks of addresses to their customers.– customers of ISPs appear like subnets of the ISP to other

ISPs– reduces size of the routing tables


CIDR Addressing

Length of network address is variable and specified using a netmask.– Can make the address space ju

st large enough

Can merge a group of adjacent class C addresses to form a larger network address.

Network Hosts0

Network Hosts1

1 0

Network Hosts

1 0


CIDR Address Allocation: Example

ISP: 128.5.X.X

Customer 1: 128.5.010xxxxx.XCustomer 2: 128.5.110xxxxx.XCustomer 3: 128.5.011xxxxx.X

ISP 4ISP 4

ISPISP

Customer1

Customer1

HostHost

Customer2

Customer2

HostHost

Customer3

Customer3

HostHost

ISP 5ISP 5ISP 3ISP 3

ISP 2ISP 2 HostHostHostHost

HostHost

Single route entry: 128.5/16


Route Lookup with CIDR Need to store a netmask with each en

try to indicate the size of the network identifier.– can no longer rely on type field

Problem: with CIDR there can be multiple matches when looking up an address.– Can for example happen when a custo

mer switches ISPs but keeps addresses

Solution: lookup is based on longest prefix match.– when there are multiple matches, the

match with the most bits (longest netmask) wins

– Complicates route lookup!

10110110

10110110 010

10110110 010 0100011

Ex-ISP

MyEntry

-> ISP 1

-> ISP 2


Shortcomings of CIDR

CIDR does not help with the large number of addresses that were already assigned before CIDR was introduced.

Many exceptions to CIDR addresses.– Customer receives a block of addresses and then moves

to a different ISP» Typically keeps the same addresses

– Many customers subscribe with several ISPs for redundancy

» Example: 45 Mbs with a primary ISP, and 5 Mbs with two backup ISPs

» Can only have one set of addresses


B IPB IP

NATs NAT maps (private source IP, source port) onto (public

source IP, unique source port)– reverse mapping on the way back– destination host does not know that is process is happening

Very simple working solution.– NAT functionality fits well with firewalls

Publ A IPPubl A IP

B IPB IP

A Port’A Port’ B PortB Port

Priv A IPPriv A IP

B IPB IP

A PortA Port B PortB Port

Publ A IPPubl A IP

B PortB Port

B IPB IP

Priv A IPPriv A IP

B PortB Port A PortA Port

A Port’A Port’

A

B


NAT Considerations NAT has to be consistent during a session.

– Set up mapping at the beginning of a session and maintain it during the session

– Recycle the mapping that the end of the session» May be hard to detect

NAT only work for certain applications.– Some applications (e.g. ftp) pass IP information in payload– Need application level gateways to do a matching translation

NAT has to be consistent with other protocols.– ICMP, routing, …

Many flavors of NAT exist.– Basic, network address port translation (NAPT), bi-directional,..


NAT/firewall traversal of VoIP Types of NAT functionality.

– Full Cone If a host behind a NAT sends a packet from address:port {A:B}, the NAT process translates the address:port {A:B} to {X:Y} and causes a binding of {A:B} to {X:Y}. Any incoming packets (from any address) destined for {X:Y} are translated to {A:B}.

– Partial/Restricted Cone full cone, However, once that first packet comes inward, the bindings are turned into complete four-component bindings. This enforces only packets from that source to be accepted and NATed from

now onward.· – Symmetric Cone If a host behind a NAT sends a packet from address:po

rt {A:B} to {C:D}, the NAT process translates the source address:port {A:B} to {X:Y} and causes a binding of {A:B} to {C:D} to {X:Y}. Only packets from {C:D} to {X:Y} are accepted in the reverse direction and these are NATed to {A:B}.


NAT/firewall traversal of VoIP


NAT/firewall traversal of VoIP NAT problem

– ‘Bindings’ can only be initiated by outgoing traffic.– Unsolicited incoming calls cannot be supported.

» Like incoming call of PABX can’t be translated without attendant.



Solutions to NAT problem– Universal Plug and Play (UPnP)

» limited to small installations.

– Simple Traversal of UDP Through Network Address Translation devices (STUN)

» STUN does not work with the type most commonly found in corporate networks - the symmetric NAT.

– TURN– ICE– Application Layer Gateway – Manual Configuration – Tunnel Techniques



STUN– The STUN protocol enables a SI

P client to discover whether it is behind a NAT, and to determine the type of NAT.

» STUN server: “This is what I see as the source address and port”

TURN– Server that is inserted in the medi

a and signalling path. This TURN server is located either in the customers DMZ or in the Service Provider network.

» Increase latency and packet loss


Skype : From the KaZaA community

A peer-to-peer VoIP client developed by KaZaa in 2003 : P2P – SIP

It has better voice quality than the MSN and Yahoo IM applications

It encrypts calls end-to-end, and stores user information in a decentralized fashion

Auto-detect NAT/firewall settings– STUN and TURN

Allows searching a user (e.g., kun*) Promote to super node

– Based on availability, capacity Conferencing


Kazaa FastTrack (aka Kazaa)

– Modifies the Gnutella protocol into two-level hierarchy» Hybrid of Gnutella and Napster

– Group leader» Nodes that have better connection to Internet» Act as temporary directory servers for other nodes in group» Maintains database, mapping names of content to IP address of its group member» Not a dedicated server; an ordinary server

– Bootstrapping node» A peer wants to join the network contacts this node.» This node can designate this peer as new bootstrapping node.

– Standard nodes» Connect to super nodes and report list of files» Allows slower nodes to participate

– Broadcast (Gnutella-style) search across Group leader peer; Query flooding– Drawbacks

» Fairly complex protocol to construct and maintain the overlay network» Group leader have more responsibility. Not truly decentralized » Still not purely serverless(Bootstrapping node is on “always up server”)

Overlay peer

Group leader peer

Neighboring relationshipsIn overlay network


IPv6

Initial motivation: 32-bit address space completely allocated by 2008.– => 128 bit address

Additional motivation:– header format helps speed processing/forwarding– header changes to facilitate QoS – new “anycast” address: route to “best” of several repli

cated servers

IPv6 datagram format: – fixed-length 40 byte header– no fragmentation allowed


IPv6 Header (Cont)

Priority: identify priority among datagrams in flowFlow Label: identify datagrams in same “flow.” (concept of“flow” not well defined).Next header: identify upper layer protocol for data


IPv6 Header: Flow Label

A flow: – A sequence of packets sent from a particular source to a

particular (unicast or multicast) destination for which the source desires special handling by the intervening routers.

» A flow may comprise multiple TCP connections: file transfer application» A single application may generate multiple flow: multimedia conferencing

one flow for audio, one for graphic window, .. With different requirements

Rules applied to the flow label– The source assigns a flow label to a flow. Chosen randomly in range 1

to 224-1.* a table with 224 (16 million) entries: memory burden.* on entry in the table per active flow: search the entire table=> hash table approach, CAM?


Other Changes from IPv4 Checksum: removed entirely to reduce processing time at each

hop Options: allowed, but outside of header, indicated by “Next

Header” field ICMPv6: new version of ICMP

– additional message types, e.g. “Packet Too Big”– multicast group management functions

IPv6 eliminates fragmentation Easy configuration

– Provides stateless auto-configuration using hardware MAC address to provide unique base

Additional requirements– Support for security– Support for mobility


Migration from IPv4 to IPv6

Interoperability with IPv4 is necessary for gradual deployment.

Two mechanisms:– dual stack operation: IPv6 nodes support both address types– tunneling: tunnel IPv6 packets through IPv4 clouds

Unfortunately there is little motivation for any one organization to move to IPv6.– the challenge is the existing hosts (using IPv4 addresses)– little benefit unless one can consistently use IPv6

» can no longer talk to IPv4 nodes

– stretching address space through address translation seems to work reasonably well


Dual Stack Approach


Tunneling

IPv6 inside IPv4 where needed


IPv6 Addresses A interface may have multiple unicast addresses.

– Allow subscriber that uses multiple access providers across the same interface to have separate addresses aggregated under each provider’s address space Longer Internet addresses allow for aggregating addresses by hierarchies of network, access provider, geography, corporation…

– smaller routing tables, faster table lookups Address types

– Unicast: an identifier for a single interface– Anycast: an identifier for a set of interface. Delivered to one of the interface(the “nearest” one for example)– Multicast: an identifier for a set of interfaces. Delivered to all interface.


IPv6 Stateless Autoconfiguration Local communication with no intervention

– Generate link-local address» corresponds to installed Ethernet network adapters. The last 64 bits of th

e IPv6 address is known as the interface identifier. It is derived from the 48-bit MAC address of the network adapter.

» Perform Duplicate Address Detection

– This looks like this:» FE80:0:0:0:XXXX:XXXX:XXXX:XXXX: prefix of FE80::/64» The X’s are the EUI-64 address.(extended unique identifier; 24 for company id)» They could be a random 64 bit address also.» The only requirement is that the address be unique.

– Start sending data Global communication with no stateful server Adds devices with no user configuration Stateful configuration: DHCP


Routing : source routing Source routing

– List entire path in packet Router processing

– Examine first step in directions– Strip first step from packet– Forward to step just stripped off

Advantages– Switches can be very simple and fast

Disadvantages– Variable (unbounded) header size– Sources must know or discover topology (e.g., failures)

Typical use– Ad-hoc networks (DSR)– Machine room networks (Myrinet)


Routing : Virtual Circuits/Tag Switching Connection setup phase

– Each router allocates flow ID on local link– VC connection id

Each packet carries connection ID Router processing

– Lookup flow ID – simple table lookup– Replace flow ID with outgoing flow ID– Forward to output port

Advantages– More efficient lookup (simple table lookup)– More flexible (different path for each flow)– QoS: reserve bandwidth at connection setup– Easier for hardware implementations

Disadvantages– Complex signalling to route connection setup request : stateful– More complex failure recovery – must recreate connection state

Typical uses– ATM – combined with fix sized cells– MPLS – tag switching for IP networks


Routing : IP routing Each switch has forwarding table of destination next hop Distributed routing algorithm for calculating forwarding tables Routing table size

– One entry for every host on the Internet» 100M entries,doubling every year

– One entry for every LAN» Every host on LAN shares prefix» Still too many, doubling every year

– One entry for every organization» Every host in organization shares prefix» Requires careful address allocation

Advantages– Stateless – simple error recovery

Disadvantages– Every switch knows about every destination

» Potentially large tables

– All packets to destination take same route


Longest Prefix Match: is Harder than Exact Match

The destination address of an arriving packet does not carry with it the information to determine the length of the longest matching prefix

Hence, one needs to search among the space of all prefix lengths; as well as the space of all prefixes of a given length

Metrics for Lookup Algorithms– Speed (= number of memory accesses)– Storage requirements (= amount of memory)– Low update time (support ~5K updates/s)– Scalability

» With length of prefix: IPv4 unicast (32b), Ethernet (48b), IPv4 multicast (64b), IPv6 unicast (128b)

» With size of routing table: (sweetspot for today’s designs = 1 million) – Flexibility in implementation– Low preprocessing time


Longest Prefix Match

LPM in IPv4Use 32 exact match algorithms for LPM!

Exact matchagainst prefixes

of length 1


of length 2


of length 32

Network Address PortPriorityEncodeand pick


Patricia Tries Trie: Use binary tree paths to encode prefixes

Advantage: simple to implement Disadvantage: one lookup may take O(m), where

m is number of bits (32 in the case of IPv4)

001xx 2 0100x 310xxx 101100 5

0 1

0

1 0

1

1

0

0

0

0

2

3

5

1


Skip Count vs. Path Compression

Removing one way branches ensures # of trie nodes is at most twice # of prefixes; (case: trie containing a small number of very long strings)– Patricia tries

Using a skip count requires exact match at end and backtracking on failure path compression simpler

P1

P2

P3 P4

0

0

0 1

1

1

1

P1

P2

P3 P4

0

0

0 1

(Skip count) Skip 2

or

11 (path compressed)

1


Fast Longest Prefix Match

Lulea’s Routing Lookup Algorithm (Sigcomm’97)– use a three-level data structure

Multi-bit Tries Controlled Prefix Expansion [Sri98] Binary Search on Prefix Intervals [Lampson98] Binary search on prefixes : Waldvogel – Sigcomm 97 Longest prefix matching using bloom filters Route caches

– Temporal locality– Many packets to same destination


Fast Longest Prefix Match

Content addressable memory (CAM)– Hardware based route lookup– Input = tag, output = value associated with tag– Requires exact match with tag

» Multiple cycles (1 per prefix searched) with single CAM

» Multiple CAMs (1 per prefix) searched in parallel

– Ternary CAM» 0,1,don’t care values in tag match

» Priority (I.e. longest prefix) by order of entries in CAM


Performance Comparison: Complexity

Algorithm Lookup Storage Update

Binary trie W NW W

Patricia W2 N W

Path-compressed trie W N W

Multi-ary trie W/k N*2k -

LC trie W N -

Lulea - - -

Binary search on trie levels logW NlogW -

Binary search on intervals log(2N) N -

TCAM 1 N W


Performance Comparison

Algorithm Lookup (ns) Storage (KB)

Patricia (BSD) 2500 3262

Multi-way fixed-stride optimal trie (3-levels) 298 1930

Multi-way fixed-stride optimal trie (5-levels) 428 660

LC trie - 700

Lulea 409 160

Binary search on trie levels 650 1600

6-way search on intervals 490 950

Lookups with direct access 15-60 9-33 * 1000

TCAM 15-20 512


Packet classification

Packet classification – The process of categorizing packets into “flows” in an In

ternet router– All packets belonging to the same flow obey a predefine

d rule and are processed in a similar manner by the router

Flow-aware router: keeps track of flows and perform similar processing on packets in a flow– Non best effort services, firewalls, QoS

Flow-unaware router (packet-by-packet router): treats each incoming packet individually


Example of Classification Rules Access-control in firewalls

– Deny all e-mail traffic from ISP-X to Y Policy-based routing

– Route IP telephony traffic from X to Y via ATM Differentiate quality of service

– Ensure that no more than 50 Mbps are injected from ISP-X Committed Access Rate (rate limiting)

– Rate limit WWW traffic from sub interface#739 to 10Mbps


Complexity: Hard Problem

N rules and k header fields for k > 2– O(log Nk-1) time and O(N) space– O(log N) time and O(Nk) space

How many rules?– Largest for firewalls & similar 1700– Diffserv/QoS much larger 100k (?)


Multi-field Packet Classification

Given a classifier with N rules, find the action associated with the highest priority rule matching an incoming packet.

Example: packet (5.168.3.32, 152.133.171.71, …, TCP)

Field 1 Field 2 … Field k ActionRule 1 5.3.90/21 2.13.8.11/32 … UDP A1

Rule 2 5.168.3/24 152.133/16 … TCP A2

… … … … … …

Rule N 5.168/16 152/8 … ANY AN


Special processing

Control

Datapath:per-packet processing

Routing lookup

Flow-aware Router: Basic Architectural Components

Routing, resource reservation, admission control, SLAs

Packet classification

Switching

Scheduling


Packet Classification: Problem Definition

Given a classifier C with N rules, Rj, 1 j N, where Rj consists of three entities:

1) A regular expression Rj[i], 1 i d, on each of the d header fields, 2) A number, pri(Rj), indicating the priority of the rule in the classifier, a

nd3) An action, referred to as action(Rj).

For an incoming packet P with the header considered as a d-tuple of points (P1, P2, …, Pd), the d-dimensional packet classification problem is to find the rule Rm with the highest priority among all the rules Rj matching the d-tuple; i.e., pri(Rm) > pri(Rj), j m, 1 j N, such that Pi matches Rj[i], 1 i d. We call rule Rm the best matching rule for packet P.


Example 4D classifier

Rule L3-DA L3-SA L4-DP L4-PROT Action

R1 152.163.190.69/255.255.255.255

152.163.80.11/255.255.255.255

* * Deny

R2 152.168.3/255.255.255

152.163.200.157/255.255.255.255

eq www udp Deny

R3 152.168.3/255.255.255

152.163.200.157/255.255.255.255

range 20-21 udp Permit

R4 152.168.3/255.255.255

152.163.200.157/255.255.255.255

eq www tcp Deny

R5 * * * * Deny


Example Classification Results

Pkt Hdr

L3-DA L3-SA L4-DP L4-PROT Rule, Action

P1 152.163.190.69 152.163.80.11 www tcp R1, Deny

P2 152.168.3.21 152.163.200.157 www udp R2, Deny


Classification is a Generalization of Lookup

Classifier = routing table One-dimension (destination address) Rule = routing table entry Regular expression = prefix Action = (next-hop-address, port) Priority = prefix-length


Example Two-dimension space, i.e., classification based on two fields Complexity depends on the layout, i.e., how many distinct

regions are created


Classification algorithm

Linear search– The simplest data structure is a linked list of rules

stored in order of decreasing priority


Recursive Flow Classification [Gupta99]

Difficult to achieve both high classification rate and reasonable storage in the worst case

Real classifiers exhibit structure and redundancy

A practical scheme could exploit this structure and redundancy

Observations:


RFC: Classifier Dataset

793 classifiers from 101 ISP and enterprise networks with a total of 41505 rules.– Classifier (policy database)

40 classifiers: more than 100 rules. Biggest classifier had 1733 rules.

Maximum of 4 fields per rule: source IP address, destination IP address, protocol and destination port number.


RFC: Problem formulation:

– Map S bits (i.e., the bits of all the F fields) to T bits (i.e., the class identifier) Main idea:

– Create a 2S size table with pre-computed values; each entry contains the class identifier

» Only one memory access needed

– …but this is impractical require huge memory– Use recursion: trade speed (number of memory accesses) for memory footprint


The RFC Algorithm

At each stage the algorithm maps one set of values to a smaller set– A set of memories return a value shorter than the index of

the memory access

Split the F fields in chunks1. Use the value of each chunk to index into a table

Indexing is done in parallel

2. Combine results from previous phase, and repeat

3. In the final phase we obtain only one value that is action


Chunking of a Packet

Source L3 Address

Destination L3 Address

L4 protocol and flags

Source L4 port

Destination L4 port

Type of Service

Packet Header

Chunk #0

Chunk #7


The RFC Algorithm


Complete Example

indx=c02*6+c03*3+c05

indx=c10*5+c11


Choice of Reduction Tree

3

2

1

0

5

4

Number of phases = P = 310 memory accesses

3

2

1

0

5

4

Number of phases = P = 411 memory acceses


RFC: Classification Time

Pipelined hardware: 30 Mpps (worst case OC192) using two 4Mb SRAMs and two 64Mb SDRAMs at 125MHz.

Software: (3 phases) 1 Mpps in the worst case and 1.4-1.7 Mpps in the average case. (average case OC48) [performance measured using Intel Vtune simulator on a windows NT platform]


RFC: Pros and Cons

Advantages

Exploits structure of real-life classifiersSuitable for multiple fieldsSupports non-contiguous masksFast accesses

Disadvantages

Depends on structure of classifiersLarge pre-processing timeIncremental updates slowLarge worst-case storage requirements


Summary of classification schemes


Lookup/Classification Chip Vendors – Switch-on– Fastchip– Agere– Solidum– Siliconaccess– TCAM vendors: Netlogic, Lara, Sibercore, Mosaid, Kl

si etc.

Packet classification still an area of active research

Summary of classification schemes

prof. younghee lee 1 1 computer networks u lecture 5: ip addressing-route lookup younghee lee

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