• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.3B
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• pp.65-71
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• 2005

The primary function of the Internet routers is to forward incoming packets toward their final destinations. IP address lookup is one of the most important functions in evaluating router performance since IP address lookup should be performed in wire-speed for the hundred-millions of incoming packets per second. With CIDR, the IP prefixes of routing table have arbitrary lengths, and hence address lookup by exact match is no longer valid. As a result, when packets arrive, routers compare the destination IP addresses of input packets with all prefixes in its routing table and determine the most specific entry among matching entries, and this is called the longest prefix matching. In this paper, based on parallel multiple hashing and prefix grouping, we have proposed a hardware architecture which performs an address lookup with a single memory access.

• Proceedings of the Korean Information Science Society Conference
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• 1998.10a
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• pp.386-388
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• 1998

Multiprotocol Label Switching(MPLS)는 기존 인터넷 라우팅에서 사용하는 longest prefix match 방식 대신에 short label exact match 방식을 사용함으로써 더 단순한 고속 포워딩 기술을 제공한다. 또한, 동일한 Forwarding Equivalence Class(FEC)에속하는 플로우들을 합성하여 하나의 레이블을 사용하는 방법 즉, Multipoint-to-point Tree(MPT)를 형성함으로써 확장설을 향상시켰다. 본 논문에선 현재 이슈가 괴고 있는 "IP address prefix"와 "host LSP"의 FEC타입과는 전송방식이 다른 브로드캐스팅을 위한"broadcast"FEC 타입을 제안하였으며, 브로드캐스트 패킷을 전송하는데 있어서 각각의Label Switched Path(LSP)제어 방식을 사용할 경우의 문제점을 분석하고, 유니캐스팅과 브로드캐스팅의 서로 다른 레이블 할당방식으로 인한 레이블 충돌을 해결하기 위해서 레이블 범위를 분류하여 사용하는 방식을 제안한다.해서 레이블 범위를 분류하여 사용하는 방식을 제안한다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1998.11a
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• pp.354-357
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• 1998

MPLS (Multiprotocol Label Switching)는 인터넷에서 속도, 확장성 그리고 서비스 제공 능력을 향상시키기 위한 백본 네트웍으로 이용하기 위하여 Internet Engineering Task Force (IETF) standard로 급속하게 성장하고 있다. MPLS는 기존의 인터넷 라우팅에서 사용하는 longest prefix match 방식을 이용하는 라우팅 방법 대신에 short label exact match 방식과 L3 forwarding 방법을 사용함으로써 고속 인터넷 서비스 기술을 제공한다. 한편, 기존 인터넷의 IP format을 보면 Host Id, (Address prefix, Host Id), Broadcasting, Multicasting의 네 가지 종류의 구조를 가지고 있다. 그러나 아직 MPLS에서의 멀티캐스트 서비스에 대한 방식이 아직 표준화되고 있지 않고 있는 상황에서, MPLS 서비스 도메인 내에서 멀티캐스트 패킷은 기존의 멀티캐스트 라우팅 프로토콜과 연계되어 MPLS상에서 멀티캐스트 서비스가 이루어져야 한다. 본 논문에서는 기존의 인터넷상에서 제공되어지는 멀티캐스트 IP 플로우들을 MPLS 상에서 수용하기 위한 방식을 제안한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.2B
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• pp.138-143
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• 2003

One of the important design issues for IP routers responsible for packet forwarding in computer networks is the route-lookup mechanism. For each incoming packet, IP routing requires that a router performs a longest-prefix-match address lookup in order to determine the next hop that the incoming packet should be forwarded to. In this paper, we present a new scheme which applies the hashing function for IP address lookup. In the proposed scheme, the forwarding table is composed of multiple SRAMs, and each SRAM represents an address lookup table in each prefix. Hashing function is applied in order to find out the matching entries from the address lookup tables in parallel, and the entry with the longest prefix match among them is selected. Simulation using the MAE-WEST router example shows that a large routing table with 37000 entries can be compacted to a forwarding table of 300 Kbytes in the proposed scheme. It is also shown that the proposed scheme achieves one route lookup every 1.93 memory accesses in average.

• Proceedings of the Korean Information Science Society Conference
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• 2001.10c
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• pp.361-363
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• 2001

본 논문은 IPv6 헤더의 플로우 레이블 필드를 이용한 레이블 포워딩 방법을 제안하고 이 방법을 기반으로 리눅스 운영체제에서 멀티캐스팅 라우팅 레몬과 유니 캐스팅 데몬과 구현하여 레이블 포워딩에 의한 유니 캐스트 및 멀티캐스트 전송을 구현하였다. 레이블을 이용한 포워딩은 라우팅 엔트리를 결정하기 위해 If주소 중 가장 많은 부분이 일치되는 엔트리를 찾는 방법(longest prefix match) 을 기본으로 하는 IP주소정색 방법에 비해, 짧은 레이블 값 전체가 일치하는 엔트리를 찾는 방법 (short label exact match)을 원칙으로 하고있어 상대적으로 빠른 속도로 라우팅 테이블을 검색할 수 있으며, 쉽게 QoS를 제공할 수 있는 구조를 제공한다. 실험을 통해 구현된 레이블 포워딩을 이용한 유니캐스트 및 멀티캐스트 전송이 잘 동작함을 확인하였고, 성능비교 실험을 통해 레이불 포워딩이 일반 IP 검색 포워딩 방법보다 더 좋은 성능을 발휘함을 확인할 수 있다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.1B
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• pp.18-28
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• 2004

Efficient hardware implementation of address lookup is one of the most important design issues of internet routers. Address lookup significantly impacts router performance since routers need to process tens-to-hundred millions of packets per second in real time. In this paper, we propose a practical IP address lookup structure based on the binary tree of prefixes of different lengths. The proposed structure produces multiple balanced trees, and hence it solve the issues due to the unbalanced binary prefix tree of the existing scheme. The proposed structure is implemented using pipelined binary search combined with a small size TCAM. Performance evaluation results show that the proposed architecture requires a 2000-entry TCAM and total 245 kbyte SRAMs to store about 30,000 prefix samples from MAE-WEST router, and an address lookup is achieved by a single memory access. The proposed scheme scales very well with both of large databases and longer addresses as in IPv6.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.8B
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• pp.691-700
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• 2006

Based on the destination IP address of incoming packets, the Internet routers determine next hops and forward packets toward final destinations through If address lookup. The bandwidth of communication links increases exponentially fast as well as the routing table size grows significant as the number of single host networks attached to the Internet increases. Since packets should be processed at wire-speed, the increased link speed reduces the processing time of a packet in routers, and hence more efficient and fast IP address lookup algorithms and architectures are required in the next generation routers. Most of the previous IP lookup schemes compare routing prefixes of shorter length first with a given input IP address. Since IP address lookup needs to find the most specific route of the given input, search continues until the longest matched prefix is found while it keeps remembering the current test matching prefix. In this paper, based on binary search on prefix length, we proposed a new IP address lookup algorithm which compares longer prefixes first. The proposed scheme is consisted of multiple tries with prefixes on leaves only. The trie composed of the longest prefixes is primarily searched whether there is a match with the given input. This processing is repeated for the trio of the next longer prefixes until there finds a match. Hence the proposed algorithm provides the fast search speed. The proposed algorithm also provides the incremental update of prefixes while the previous binary search on length scheme does not provide the incremental update because of pre-processing requirement. In this paper, we performed extensive simulations and showed the performance comparisons with related works.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.2B
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• pp.158-166
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• 2004

Address lookup is one of the most essential functions of the Internet routers and a very important feature in evaluating router performance. Due to the facts that the Internet traffic keeps growing and the number of routing table entries is continuously growing, efficient address-lookup mechanism is indispensable. In recent years, various fast address-lookup schemes have been proposed, but most of those schemes are not practical in terms of the memory size required for routing table and the complexity required in table update In this paper, we have proposed a parallel IP address lookup architecture based on multiple hashing. The proposed scheme has advantages in required memory size, the number of memory accesses, and table update. We have evaluated the performance of the proposed scheme through simulation using data from MAE-WEST router. The simulation result shows that the proposed scheme requires a single memory access for the address lookup of each route when 203kbytes of memory and a few-hundred-entry TCAM are used.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.12B
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• pp.1103-1111
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• 2008

Internet routers forward an incoming packet to an output port toward its final destination through IP address lookup. Since each incoming packet should be forwarded in wire-speed, it is essential to provide the high-speed search performance. In this paper, IP address lookup algorithms using binary search are studied. Most of the binary search algorithms do not provide a balanced search, and hence the required number of memory access is excessive so that the search performance is poor. On the other hand, binary-search-on-range algorithm provides high-speed search performance, but it requires a large amount of memory. This paper shows an optimized binary-search-on-range structure which reduces the memory requirement by deleting unnecessary entries and an entry field. By this optimization, it is shown that the binary-search-on-range can be performed in a routing table with a similar or lesser number of entries than the number of prefixes. Using real backbone routing data, the optimized structure is compared with the original binary-search-on-range algorithm in terms of search performance. The performance comparison with various binary search algorithms is also provided.