Ağ yönlendiricileri için çoklu eşik kullanan geçişsiz öncelikli zamanlayıcı

Bilgisayar ağları için mevcut ve geliştirilmekte olan çok çeşitli uygulamaların farklı hizmet kalitesi gereksinimleri vardır. Uygulamaların ihtiyaçlarını karşılamanın en önemli yollarından birisi ağ yönlendiricileri tarafından kullanlan paket zamanlama algoritmalarıdır. Uygulamalara yönlendirici kaynaklarını ayırarak, paket zamanlayıcıları uygulamaların hizmet kalitesi ihtiyaçlarını artırmaya çalışır. Bu nedenle, gecikmeler azaltılabilir ya da uygulamaların güvenilirliği paket kayıplarını azaltmak suretiyle arttırılabilir. Öncelikli zamanlayıcılar, yüksek öncelikli uygulamaların gecikme ve kayıplarını azaltabilirler. Öte yandan, düşük öncelikli uygulamalar için açlık problemi getirirler. Düşük öncelikli uygulama paketleri aşırı gecikmeler ve kayıplarla karşılaşabilirler. Bu makalede çoklu eşik kullanan geçişsiz öncelikli zamanlayıcı (PRMT) önerilmektedir. PRMT zamanlayıcı farklı öncelikli uygulamalar için önceden tanımlanmış eşik seviyeleri kullanan tek bir kuyruk ihtiyacı duyar. PRMT zamanlayıcı yüksek öncelikli uygulamaların üzerinde önemli bir etkiye yol açmadan, düşük öncelikli uygulamalardaki açlık sorunu ortadan kaldırır.

Anahtar Kelimeler:

Ağ yönlendiricileri, Servis kalitesi, Öncelikli zamanlayıcı, Çoklu eşik

Non-preemptive priority scheduler with multiple thresholds for network routers

The vast variety of applications available and being developed for computer networks have different quality of service requirements. One of the most significant ways to satisfy the needs of the applications is the packet scheduling algorithms employed by the network routers. By allocating router resources to the applications, packet schedulers try to improve the quality of service needs of the applications. Thus, the delays can be reduced or the reliability of the applications can be increased by reducing packet losses. Priority schedulers are able reduce the delay and losses for high priority applications. On the other hand, for low priority applications they introduce the starvation problem. Low priority application packets can face excessive delays and losses. In this paper, a non-preemptive priority scheduler with multiple thresholds (PRMT) is proposed. The PRMT scheduler needs only a single queue with predefined threshold levels for different priority applications. The PRMT scheduler eliminates the starvation problem of low priority applications without a significant impact on the high priority applications.

Keywords:

Network routers, Quality of service, Priority scheduler, Multiple threshold,

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